Papers for Tuesday, Sep 30 2025

Background diffuse X-ray emission is contributed in large part by the emission of point sources not individually resolved. While this is established since decades for the contribution of quasars to the diffuse emission above 1 keV energies, the possible contribution of undetected stars in the Milky Way to the softer band (0.5-1 keV) background emission is still poorly constrained. The overall unresolved X-ray flux from the stars is the product between the stellar spatial distribution in the Milky Way and the underlying X-ray luminosity function (XLF). In this work, we build the XLF of the stars and study its structure with respect to a set of main-sequence spectral types (F, G, K, M) and evolutionary stages (giants and white dwarfs). We build the XLF in volume-limited subsamples of increasing maximum distance and corresponding minimum X-ray luminosity using the HamStar catalog of X-ray emitting stars detected in the Western Galactic hemisphere with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spectrum-Roentgen-Gamma (SRG) space observatory. We build an extinction-corrected Gaia color-magnitude diagram and decompose the XLF into the relative contribution of different groups of stars. We provide an empirical polynomial description of the XLF for the total sample and for the different stellar subgroups that can be used to estimate the unresolved contribution from the stars to the soft X-ray background of the Milky Way in a flux-limited survey.

The formation of the Universe's first luminous stellar structures depends on the unique conditions at "Cosmic Dawn," which are set by the underlying cosmological model and early baryonic physics. Observations suggest that high-$z$ star clusters reached stellar surface densities above $10^5 M_\odot$ pc$^{-2}$, suggesting scenarios where models predict that the ability of stellar feedback to counter gravitational collapse is severely limited. We investigate the first star clusters in a suite of AREPO simulations, which explore the capacity for $\Lambda$CDM halos to maximally form high-density systems without feedback. We include the effects of the supersonic baryon-dark matter streaming velocity, an effect that impacts gas density and distribution in early minihalos. We show that early star clusters can reach high densities even in regions of strong supersonic streaming, provided feedback is weak. We analyze the interplay of the stream velocity and the dynamical processes of structure formation, finding that JWST has the opportunity to detect the brightest, most massive objects in our computational box. The detection of individual $z\geq12$ Pop III star clusters below $10^7M_\odot$ is challenging, although lensing could reveal these objects in rare configurations, especially if a top-heavy IMF is present. We find that accounting for baryonic clusters separately from dark matter halos complicates predictions for the faint-end of the high-$z$ UVLF, with competing effects from the stream velocity and low-mass clusters outside of halos. Finally, we explore clustering of star clusters as a promising probe of the stream velocity in these systems.

We present follow-up observations of the day-long, repeating GRB 250702B with the Near Infrared Spectrograph (NIRSpec) on board the James Webb Space Telescope (JWST). Through the identification of narrow hydrogen emission lines at a consistent redshift of $z = 1.036 \pm 0.004$, we calibrate the distance scale, and therefore the energetics, of this unique extragalactic transient. At this distance, the resulting $\gamma$-ray energy release is at least $E_{\gamma,\rm iso} = 2.2 \times 10^{54}$\,erg. We find no evidence for ongoing transient emission at the GRB position, and exclude any accompanying supernova with a luminosity comparable to the Type Ic broad-line SN 2023lcr, though we are unable to constrain fainter events. The inferred rate of such events, assuming at most one in the lifetime of {\em Fermi}, suggests that such bursts are very rare, with volumetric rates $>1,000$ times lower than normal high luminosity long GRBs and $> 10^5$ times lower than core collapse supernovae when corrected for beaming. Furthermore, we find that the host galaxy is unique amongst GRB host galaxies, and extremely rare in the general galaxy population, being extremely large, dusty and with high stellar mass. The identification of such an exotic GRB in such an unusual galaxy raises the possibility that the environment was important in the progenitor channel for this event.

Ultra-long gamma-ray bursts (ULGRBs), a rare class of high-energy transients with durations $>10^3$,s, remain poorly understood. GRB,250702B ($z=1.04$) is notable for its multi-hour prompt emission, an X-ray precursor $\sim$1 day earlier, off-nuclear host position, and hard, rapidly variable gamma-rays. This combination is difficult to explain with standard ULGRB progenitors such as blue-supergiant collapsars, magnetar engines, or white-dwarf tidal disruptions by intermediate-mass black holes. We interpret the event as a micro-tidal disruption event ($\mu$TDE), where a stellar-mass black hole or neutron star partially or fully disrupts a main-sequence star. Three $\mu$TDE pathways can reproduce the observed precursor-main flare delay: (i) a \emph{dynamical (partial/repeating)} disruption, in which a grazing passage yields a faint precursor and the core returns after $\sim$day for a deeper encounter; (ii) a \emph{natal-kick} disruption, where the delay reflects the ballistic motion of a newborn compact object relative to its companion, leading to full disruption; and (iii) a \emph{hybrid natal-kick + partial} case, in which the kick seeds the close encounter but the first passage is only partial, with the core returning on the day-scale period. Cross-section scalings imply comparable rates for partial and full outcomes in both dynamical and natal-kick scenarios. The highly variable, hard $\gamma$-ray emission supports association with a stellar-mass compact object. Fallback and viscous accretion naturally explain the ultra-long duration, energetics, and ks-scale X-ray variability. We outline observational discriminants between the three channels and argue that $\mu$TDEs offer a compelling framework for ULGRBs such as GRB 250702B.

We investigate a splashback-like feature in the outer region of central galaxies (CGs) in clusters. This feature is detected as a "dip" in the radial slope of the CG surface brightness, derived through the stacking of Dark Energy Survey data of over four thousand galaxy clusters in the redshift range of 0.2 to 0.5 with richness 20 and above. The local minimum of the dip occurs between 40 to 60 kpc from the CG center, with a mild dependence on cluster richness. This feature resembles the density transition caused by the splashback effect at the outskirts of galaxy clusters, when accreted matter reaches the apocenter for the first time. We turn to the IllustrisTNG hydro-dynamic simulation to gain theoretical insights. Density bumps, shells and accretion streaks are identified in the diffuse stellar content of the CGs and intra-cluster light which relate to the recent history of disruption and accretion. These features occur at the outskirts of the CGs, up to several hundred kiloparsecs from the cluster center. Thus, the location of the splashback-like dip in the data potentially marks the edge of the CG and the beginning of a region with the cluster diffuse light undergoing active or recent accretion.

To investigate the population of massive black holes in dwarf galaxies, we conduct a systematic search for active galactic nuclei (AGNs) using data from the first data release of the eROSITA All-Sky Survey (eRASS1). We crossmatch dwarf galaxy positions in the NASA-Sloan Atlas with X-ray sources from eRASS and apply rigorous criteria to remove contaminants such as background sources, galaxies with dubious stellar masses, and X-ray binaries. Potential contamination from ultraluminous X-ray sources is also assessed. We ultimately assemble a sample of 27 X-ray-selected AGN candidates in dwarf galaxies with stellar masses $M_{*} = 10^{7.5-9.5} M_{\odot}$ and redshifts $z<0.15$. An analysis of the host galaxy properties reveals that the AGN candidates are predominantly situated in systems with $g-r$ colors, star formation rates, and concentrations typical of the broader dwarf galaxy population. Detailed examination of the X-ray sources indicates that most AGN candidates in our sample are consistent with being located in the nuclear regions of their host galaxies and exhibit Eddington ratios ranging between $\lambda_{Edd} \sim 10^{-3}-10^{-1}$, with a few radiating at/above their Eddington limit. Notably, our methodology identifies 15 previously unreported AGNs candidates, highlighting the complementary nature of our approach to the existing literature.

GRB 250702B was the longest gamma-ray burst ever observed, with a duration that challenges standard collapsar models and suggests an exotic progenitor. We collected a rich set of optical and infrared follow-up observations of its rapidly fading afterglow using a suite of telescopes including the W. M. Keck Observatory, the Gemini telescopes, the Magellan Baade Telescope, the Victor M. Blanco 4-meter telescope, and the Fraunhofer Telescope at Wendelstein Observatory. Our analysis reveals that the afterglow emission is well described by forward shock emission from a highly obscured relativistic jet. Deep photometric observations of the host galaxy reveal a massive 10^10.66 solar masses, dusty, and extremely asymmetric system that is consistent with two galaxies undergoing a major merger. The galactocentric offset, host galaxy properties, and jet characteristics do not definitively distinguish between competing progenitor scenarios. We find that the afterglow and host are consistent with a range of progenitors including a collapsar, a merger between a helium star and a stellar mass black hole, the disruption of a star by a stellar mass compact object, and the tidal disruption of a star by an off-nuclear intermediate mass black hole.

Giant impacts, the collisions between planetary embryos, play a crucial role in sculpting the planets and their orbital architectures. Numerical simulations have advanced our understanding of these events, enabling estimations of mass and atmospheric loss during the primary impacts. However, high computational costs have restricted investigations to the immediate aftermath, limiting our understanding of the longer-term consequences. In this study, we investigate the effect of re-accretion of giant impact debris, a process previously overlooked, on the atmospheres of terrestrial planets. Following the collisional and dynamical evolution of the debris ejected during the primary impacts, we quantify the amount of debris that would be re-accreted by the progenitor. We find that $\sim 0.003\ M_{\oplus}$ would be re-accreted over a wide range of Earth-like planet properties, assuming $1\%$ of their mass is ejected as non-vaporised debris. Over a prolonged period, the secondary impacts during re-accretion drive enhanced atmospheric loss. Notably, the impacts from the debris of the canonical Moon-forming impact would have gradually eroded an atmosphere similar to present-day Earth's in $\sim 30$ Myr. More generally, any planet growing via giant impacts within $2$ au is likely to experience significant post-impact atmospheric erosion unless the initial atmosphere was at least $5$ times more massive than Earth's. Our results highlight the crucial role secondary impacts from giant-impact ejecta could have in driving the long-term atmospheric evolution of Earth-like planets, and demonstrate that giant impacts can be significantly more effective at eroding such atmospheres than previously thought, when re-accretion of debris is considered.

We combine more than 40 years of eclipse timings of the intermediate polar FO Aqr and derive new orbital ephemerides. The eclipse times are best fit with a second order polynomial, implying an $8\sigma$ detection of a period derivative. The results show that the orbital period of FO Aqr is currently increasing, with a derivative of $\dot{P}=6.65\pm0.81\times10^{-11}$.

GRB 250702B is an exceptional transient that produced multiple episodes of luminous gamma-ray radiation lasting for $>25$ ks, placing it among the class of ultra-long gamma-ray bursts (GRBs). However, unlike any known GRB, a soft X-ray precursor was discovered by the Einstein Probe up to 24 hours before the gamma-ray triggers. We present comprehensive X-ray observations of the transient's afterglow obtained with the Neil Gehrels Swift Observatory, the Nuclear Spectroscopic Telescope Array, and the Chandra X-ray Observatory between 0.5 to 65 days (observer frame) after the initial high-energy trigger. The X-ray emission decays steeply as $\sim t^{-1.9}$, and shows short timescale X-ray variability ($\Delta T/T < 0.03$) in both Swift and NuSTAR, consistent with flares superposed on an external shock continuum. Serendipitous detections by the Swift Burst Alert Telescope (BAT) out to $\sim$0.3 days and continued NuSTAR variability to $\sim$2 days imply sustained central engine activity; including the precursor, the required engine duration is $\gtrsim 3$ days. Afterglow modeling favors the combination of forward and reverse shock emission in a wind-like ($k \approx 2$) environment. These properties, especially the long-lived engine and soft X-ray precursor, are difficult to reconcile with a collapsar origin, and GRB 250702B does not fit neatly with canonical ultra-long GRBs or relativistic tidal disruption events (TDEs). A hybrid scenario in which a star is disrupted by a stellar-mass black hole (a micro-TDE) provides a plausible explanation, although a relativistic TDE from an intermediate-mass black hole remains viable. Decisive discrimination between progenitors will require sensitive late-time X-ray observations.

Gamma-ray bursts are the most luminous electromagnetic events in the universe. Their prompt gamma-ray emission has typical durations between a fraction of a second and several minutes. A rare subset of these events have durations in excess of a thousand seconds, referred to as ultra-long gamma-ray bursts. Here, we report the discovery of the longest gamma-ray burst ever seen with a ~25,000 s gamma-ray duration, GRB 250702B, and characterize this event using data from four instruments in the InterPlanetary Network and the Monitor of All-sky X-ray Image. We find a hard spectrum, subsecond variability, and high total energy, which are only known to arise from ultrarelativistic jets powered by a rapidly-spinning stellar-mass central engine. These properties and the extreme duration are together incompatible with all confirmed gamma-ray burst progenitors and nearly all models in the literature. This burst is naturally explained with the helium merger model, where a field binary ends when a black hole falls into a stripped star and proceeds to consume and explode it from within. Under this paradigm, GRB 250702B adds to the growing evidence that helium stars expand and that some ultra-long GRBs have similar evolutionary pathways as collapsars, stellar-mass gravitational wave sources, and potentially rare types of supernovae.

We perform milliarcsecond X-ray astrometry of the quadruply lensed radio-quiet quasar GraL J065904.1+162909 (J0659). This z = 3.083 quasar is lensed into four images and was discovered with the second Data Release of the Gaia Space Observatory (Gaia DR2). The methodology of using gravitational lenses as high resolution telescopes has been applied, so far, to five lensed quasars (including J0659) and shows potential to elucidate the spatial origin of the X-ray and optical emitting regions in distant quasars. We use Gaia DR3 and HST observations of J0659 and infer a mass model for the deflector that reproduces the positions of the quasar lensed images to milliarcsecond precision. Next, we apply archival Chandra observations of J0659, together with our lens model, to conduct a Bayesian test evaluating whether the X-ray emitting region coincides with the optical source position predicted by our mass model. We constrain the origin of the X-ray emission to be within a 0.''030 x 0.''020 ellipse at the 99.7% level, finding the maximum possible distance between the X-ray and optical source is 44.7 milliarcseconds. Our methodology enhances Chandra's spatial resolution at high-z by a factor of 6. We provide a novel approach that extends the methodology towards investigating the origin of the soft and hard X-ray emitting regions in lensed quasars. We elaborate on the potential of upcoming broadband and spectrally resolved X-ray astrometric studies to probe complex quasar morphology at high-z and to identify dual and binary AGN candidates.

Stephan's Quintet (SQ) is a local compact galaxy group system that exhibits significant star formation activity. A history of tidal interactions between its four member galaxies and a recent collision between an intruder galaxy and the original group are associated with active star formation, particularly in many shocked regions in the intra-group medium. Using an existing star cluster candidate (SCC) catalog constructed from HST UV/optical images, we integrate flux measurements from five near-infrared filters (F090W, F150W, F200W, F277W, F356W) obtained from JWST NIRCam observations in 2022. Leveraging the extended photometric baseline from HST and JWST, spanning ~300 nm to ~3500 nm, we perform spectral energy distribution (SED) fitting using the CIGALE code to derive reliable estimates of age, mass, and extinction for the 1,588 high-confidence SCCs. We confirm earlier results that very young SCCs (~a few Myr) are predominantly located along previously identified shock regions near the merging galaxies, while older (>100 Myr) and globular clusters are more widely distributed. Our analysis shows that NIR photometry helps break the age-extinction degeneracy, reclassifying many SCCs from older to younger, moderately dust-extincted clusters when added to HST-based SED fits. We also observe a strong spatial correlation between young clusters and CO-traced molecular gas, although active star formation is present in several regions with no detectable CO. We find that the two prominent epochs of star formation, around 5 Myr and 200 Myr, correspond to the two major interaction events in SQ that gave rise to the observed extended tidal features.

We investigate the formation of tidal features, such as tidal tails, streams, and shell-like structures, composed of stars stripped from satellites within galaxy clusters. For this, we use multiresolution cosmological $N-$body simulations with the ``galaxy replacement technique". We find that the fraction of satellites with tidal features increases with the mass of the host clusters but is not related to the dynamical state of the clusters. Although the strong tidal field in the cluster environment accelerates the mass loss of the satellites, only 20\% of tidal-featured galaxies form their tidal features purely due to tidal perturbation in the cluster environment, without any interactions with other galaxies before falling into the cluster. In contrast, the majority (80\%) is affected by the preprocessing, as they experienced merging events with other galaxies before infalling into the cluster. Among this preprocessing population, 45\% of all tidal-featured galaxies form their tidal features after passing the pericenter of the cluster, affected by both preprocessing and the tidal field of the cluster, whereas 35\% of all tidal-featured galaxies form their tidal features before reaching the pericenter, primarily due to preprocessing. Notably, this fraction increases from 35\% to 40-50\% when we focus only on galaxies with brighter surface brightness limits or higher stellar mass. Therefore, our results highlight that preprocessing is an important channel for forming tidal features within clusters. However, the importance of preprocessing may be further amplified in observations, since more massive galaxies, which are commonly associated with preprocessing, are preferentially detected.

Ross 458c is a widely separated planetary mass companion at a distance of 1100 AU from its host binary, Ross 458AB. It is a member of a class of very low-mass companions at distances of hundreds to thousands of AU from their host stars. We aim to constrain Ross 458c's formation history by fitting its near-IR spectrum to models to constrain its composition. If its composition is similar to its host star, we infer that it likely formed through turbulent fragmentation of the same molecular cloud that formed the host. If its composition is enhanced in heavy elements relative to the host, this lends evidence to formation in the disk and subsequent migration to its current separation. Here, we present high-resolution (R$\sim$2700) emission spectra of Ross 458c with JWST NIRSpec Fixed Slit in the F070LP, F100LP, and F170LP filters from 0.8 to 3.1 $\mu$m. We fit these spectra using both grids of forward models (Sonora Bobcat, Sonora Elf Owl, and ExoREM) and atmospheric retrievals (POSEIDON). We also constrain the composition of Ross 458AB by fitting an archival SpeX spectrum with PHOENIX forward models. The forward model grids prefer an enhanced atmospheric metallicity for Ross 458c relative to the host, but our retrievals return a metallicity consistent with the host within 1$\sigma$. Our results offer new insights into the formation history of Ross 458c, as well as the efficacy of fitting forward model grids versus retrievals to derive atmospheric properties of directly imaged companions.

The streaming of neutrinos in an inhomogeneous medium is known to affect the physics of flavor conversion. We employ an ensemble of single-crossed angular distributions and explore the physics of flavor conversion, while neutrinos propagate across a one-dimensional inhomogeneous medium. The advective term in the neutrino equations of motion is responsible for the cascade of flavor waves towards ever smaller spatial and angular scales. However, as the system evolves, perturbations with large wavenumbers are damped, with a resulting smearing of the flavor configuration. We provide a simple recipe that allows to forecast the steady-state flavor configuration achieved by neutrinos without solving their kinetic equations. In particular, we find that flavor equipartition on one side of the angular spectrum and the cancellation of the spectral crossing in the lepton number distributions, proposed in the literature as generic flavor outcome, is a special solution depending on the degree of neutrino-antineutrino asymmetry. This work constitutes a step forward towards the development of semi-analytic schemes to account for flavor conversion physics in hydrodynamic simulations of core-collapse supernovae and neutron-star merger remnants.

The dominant site(s) of the $r$-process are a subject of current debate. Ejecta from $r$-process enrichment events like kilonovae are difficult to directly measure, so we must instead probe abundances in metal-poor stars to constrain $r$-process models. This requires state-of-the-art Non-Local Thermodynamic Equilibrium (NLTE) modeling, as LTE is a poor approximation for the low-opacity atmospheres of metal-poor giants. Neodymium (Nd) is a prominent $r$-process element detected in both near-infrared kilonovae spectra and spectra of metal-poor stars, so precise Nd stellar abundances are particularly needed to model kilonovae and constrain $r$-process sites. We thus constructed a Nd I / Nd II model atom to compute NLTE abundances in FGK metal-poor stars. We obtain $\mathrm{A(Nd)}_\odot = 1.44\pm0.05$, in agreement with the meteoritic value, when calibrating the model atom with a Drawin hydrogen collision factor of $S_H=0.1$. For a sample of metal-poor $r$-process enhanced stars with observed optical and near-infrared Nd II lines, we find NLTE Nd corrections in the range $-0.3$ to $0.3$ dex. Optical and UV lines have positive NLTE corrections, whereas H band lines have negative corrections. Additionally, we compute a large grid of NLTE corrections for 122 Nd II spectral lines ranging from the UV to the H band, for stellar parameters of typical metal-poor FGK dwarfs and giants with $-3.00\le\mbox{[Fe/H]}\le-1.00$ and $-2.0\le\mathrm{A(Nd)}\le2.0$. Within this grid, we find NLTE corrections ranging from $-0.3$ to $+0.5$ dex. Deviations from LTE are found to be strongest for blue lines with low excitation potentials in the most metal-poor giants.

Dynamical interactions between planets and debris discs can excite the orbits of embedded planetesimals to such a degree that a collisional cascade is triggered, generating detectable amounts of dust. Millimetre wavelength observations are sensitive to emission from large and cold dust grains, which are unperturbed by radiation forces and act as a proxy for the location of the planetesimals. The influence of unseen planetary companions on debris discs can be inferred with high-resolution imaging observations at millimetre wavelengths, tracing the radial and vertical structure of these belts. Here we present a set of dynamical $N$-body simulations modelling ALMA millimetre-wavelength observations of the HD 16743 debris disc system. In these simulations, we consider a range of relative contributions from either a single planetary companion and/or a set of embedded massive planetesimals to reproduce the disc's observed radial and vertical structure. We compare our dynamical results for the limiting cases of planet-stirring and self-stirring, finding them to be consistent with theoretical expectations for each scenario. For the case of HD 16743, we find that a set of massive planetesimals on mildly eccentric orbits, confined to a relatively narrow range of semimajor axes (compared to the observed belt width), offers the best results to reproduce the vertical and radial extent of the observed emission.

In this work, we present the development of the Tonalli code: a simplified multi-species (HI, HII, H-, and e) magnetohydrodynamics (MHD) model in Non-local Thermodynamic Equilibrium (NLTE) focused on solar chromospheric conditions. This new model integrates two well established models, Newtonian CAFE (MHD) and PakalMPI (NLTE), through a self-convergence system that links the state equations used by both codes to calculate density, pressure and temperature, with the mean molecular weight ($\mu$) serving as a proxy. Newtonian CAFE computes the plasma variables using the ideal MHD while PakalMPI calculates the species densities of neutral Hydrogen (HI), protons (HII), negative Hydrogen (H-), and electrons (ne) under the NLTE approximation. We used Tonalli to test the stability of the hydrostatic C7 model, covering 3000 km of the solar chromosphere with a vertical constant field of 30 Gauss and a vertical constant gravity field of 274.0 ms-2. As a result, Tonalli generates 3D cubes of densities, temperature, pressure, mean molecular weight, and the departure coefficient of Hydrogen in its first energy level b1, providing a detailed representation of the ionization states of the plasma at chromosphere altitudes. Despite the fact that MHD conditions can lead to numerical diffusion of the plasma, we demonstrate robustness and consistency, and self-convergence of the model with the relative error of electron density reaching values of $3.7x10^{-7}$.

GRB 250702B is a unique astrophysical transient characterised by its nature as a repeating gamma-ray trigger. Its properties include possible periodicity in its gamma-ray light curve, an X-ray counterpart that rose prior to the gamma-ray outbursts and faded quickly, and radio and infrared counterparts. These features are difficult to reconcile with most models of high energy transients but we show that they are compatible with a white dwarf bound to an intermediate mass black hole that is tidally stripped over multiple pericentre passages before being fully disrupted. Accretion onto the black hole powers a mildly relativistic jet that produces the X-rays through internal processes and the infrared and radio counterparts through thermal emission and external shocks respectively but is unable to produce the gamma-ray emission on its own. We propose that chaotic debris streams from the multiple stripping episodes can collide with a period roughly the same as the orbital period of the star. These shocks produce hard X-ray photons that are upscattered by the jet to produce the observed gamma-ray emission. Future analysis of the jet properties will allow us to place firmer constraints on our model.

The Main Sequence of Star-Forming Galaxies (SFGMS or MS) is a fundamental scaling relation that provides a global framework for studying galaxy formation and evolution, as well as insight into the complex star formation histories (SFHs) of individual galaxies. In this work, we combine large-area pre-JWST surveys (COSMOS2020, CANDELS), which probe high-$M_\star$ sources (${>10^9\,M_\odot}$), with SHARDS/CANDELS FAINT and JWST data from CANUCS, CEERS, JADES, and UNCOVER, to obtain a high-$z$, star formation rate (SFR) and stellar mass ($M_\star$) complete sample spanning both high- and low-$M_\star$ regimes. Completeness in both $M_\star$ and SFR is key to avoiding biases introduced by low-mass, highly star-forming objects. Our combined data set is 80% complete down to $10^{7.6}\,M_\odot$ at $z\sim1$ ($10^{8.8}\,M_\odot$ at $z\sim9$). The overall intrinsic MS slope (based on the SFR$_{100}$ and $M_\star$ derived with Dense Basis and nonparametric SFHs) shows little evolution up to $z\sim5$, with values $\sim0.7 - 0.8$. The slope in the low-$M_\star$ regime becomes steeper than that in the high-$M_\star$ end at least up to $z\sim5$, but the strength of this change is highly dependent on the assumptions made on the symmetry of the uncertainties in $M_\star$ and SFR. If real, the steepening suggests reduced star formation efficiency or declining gas content with decreasing $M_\star$. The transition between the low-$M_\star$ regime and the canonical MS occurs around $10^{9.5}\,M_\odot$, independent of $z$. This critical value may coincide with the assembly of galaxies' disks, which can provide a mechanism for self-regulation that stabilizes them against feedback. The intrinsic scatter is compatible with canonical estimates, also at low-$M_\star$, ranging from $0.2-0.3$ dex. This is indicative of rapid variations in star formation being averaged out over $\lesssim100$ Myr.

Applying a principle of "radical mundanity", this paper examines explanations for the lack of strong evidence for the presence of technology-using extraterrestrial civilizations (ETCs) in the Galaxy - the Fermi paradox. With this principle, the prospect that the Galaxy contains a modest number of civilizations is preferred, where none have achieved technology levels sufficient to accomplish large-scale astro-engineering or lack the desire to do so. This consideration also leads to the expectation that no ETC will colonize a large fraction of the Galaxy, even using robotic probes, and that there are no long-duration high-power beacons. However, there is a reasonable chance that we may make contact on a short, by historical standards, timescale. This event would be momentous, but could still leave us slightly disappointed. Such a Universe would be less terrifying than either of the two possibilities in the quote generally attributed to Arthur C. Clarke on whether we are alone or not. Also, if there is a modest number of ETCs in the Galaxy, that would suggest that there is a large number of planets with some form of life.

The ``sub-Jovian desert" ($2{\lesssim}R_{\rm p}{\lesssim}10 \ R_{\oplus}$, periods $\lesssim$3 days) is sparsely populated but no longer empty. Recent surveys have revealed that planets residing in the desert are dense (${\rho}{\gtrsim}1$ g/cm$^{3}$), massive ($\sim$10${-}$50 $M_{\oplus}$), and orbit metal-rich stars that are indistinguishable from those hosting hot Jupiters. However, their origins remain mysterious. In this work we adopt and test the hypothesis that tidal destruction of hot Jupiters can populate the sub-Jovian desert with stripped remnant planets. We first show that stars hosting desert dwellers exhibit Galactic kinematics indicative of an older population descended from those hosting hot Jupiters. We highlight that tidally-driven Roche lobe overflow (RLO) can indeed populate the desert with planets similar to those observed, but only if angular momentum transfer during RLO is inefficient (``lossy" RLO). The entire width of the sub-Jovian desert can be backfilled with the remnants of hot Jupiters that possessed their empirically inferred spread in entropy. In this picture, current desert dwellers such as LTT 9779b should be tidally decaying at an observationally testable rate of ${\sim}0.5$ ms/yr. Our theory also predicts that desert dweller host stars may rotate up to an order of magnitude more rapidly than field stars; rotation period differences may persist ${\sim}$Gyr after RLO. Lossy RLO may also manifest as a burst of IR excess that could outshine the host star for up to ${\sim}10^{3}$ yr. If these predictions are confirmed by observations, our theory indicates that desert dwellers can be leveraged to study the interiors of giant planets in exquisite detail.

In this work, we test whether gradient-boosting algorithms, trained on broadband photometric data from traditional Lyman-$\alpha$ emitting (LAE) surveys, can efficiently and accurately identify LAE candidates from typical star-forming galaxies at similar redshifts and brightness levels. Using galaxy samples at $z \in [2,6]$ derived from the COSMOS2020 and SC4K catalogs, we trained gradient-boosting machine-learning algorithms (LGBM, XGBoost, and CatBoost) using optical and near-infrared broadband photometry. To ensure balanced performance, the models were trained on carefully selected datasets with similar redshift and i-band magnitude distributions. Additionally, the models were tested for robustness by perturbing the photometric data using the associated observational uncertainties. Our classification models achieved F1-scores of $\sim 87\%$ and successfully identified about $7,000$ objects with an unanimous agreement across all models. This more than doubles the number of LAEs identified in the COSMOS field compared with the SC4K dataset. We managed to spectroscopically confirm 60 of these LAE candidates using the publicly available catalogs in the COSMOS field. These results highlight the potential of machine learning in efficiently identifying LAEs candidates. This lays the foundations for applications to larger photometric surveys, such as Euclid and LSST. By complementing traditional approaches and providing robust preselection capabilities, our models facilitate the analysis of these objects. This is crucial to increase our knowledge of the overall LAE population.

The empirical underabundance of close-in planets with radii 1.5-2.0 times that of the Earth, referred to as the radius irradiation valley, may be linked to the inability of gas dwarfs under certain conditions to retain their volatile envelopes due to photoevaporation or core-powered mass loss. In either case, the extent to which a planet can preserve its atmosphere critically depends on poorly understood planetary magnetism. An effective probe of planetary magnetic fields is the interaction between a star and its close-in planet, where the planet magnetically interacts with its host, inducing flares as it moves near its periastron within the Alfvén surface of its host star. We construct a pipeline, \textsc{ardor}, to detect and characterize potentially planet-induced flares in time-series photometric data using a physically motivated forward model of star-planet interactions, with a focus on recovering flares located near the noise floor. We perform extensive injection-recovery simulations to determine our sensitivity to flares correlating with the planetary phase over a range of stellar types and orbital architectures. We identify one close-in, eccentric ($e=0.18$) system, TOI-1062\,b, which exhibits flaring during periastron consistent with being induced with $p_{KS}=2.2\times10^{-5}$ and a $5.1\sigma$ detection through unbinned likelihood analysis and goodness-of-fit tests. We also identify an additional eccentric ($e=0.363$) candidate, Gliese 49b, which exhibits moderately significant ($2.5\sigma$) flare clustering at periastron, requiring additional photometric observations to confirm its significance. TOI-1062b and Gliese 49b are promising candidates for induced flares, underscoring the need for radio and UV follow-up observations.

We present a new planetary structure/thermal evolution model, designed for use in problems that couple orbital dynamics with planetary structure. We first benchmark our structural/thermal evolution calculations against the \texttt{MESA} stellar evolution code, finding excellent agreement across a wide range of planet mass, equilibrium temperature, entropy, and extra heating deposited at various depths in the planet. We then apply our method to study the tidal migration histories of Neptunes in the recently identified ``ridge" (periods ${\sim}3{-}6$ days), a feature that has been suggested to be populated via high eccentricity migration (HEM) of more distant Neptunes. We find that it is difficult to form a circularized Neptune in the ridge without instigating runaway tidal inflation and likely atmospheric destruction; low eccentricity Neptunes in the ridge can only be emplaced by HEM if they are metal-rich and exhibit finely-tuned tidal quality factors. If follow-up observations confirm that low eccentricity Neptunes in the ridge did arrive via HEM and are not strongly enriched in metals, our calculations indicate that their tidal heating mechanism must operate in the upper reaches of the planet to avoid runaway inflation. Gravity modes excited in upper radiative layers are a possible candidate mechanism, while friction in the core or turbulent dissipation in convective zones could be ruled out.

We publish the first NIR spectra of grain particulate mixtures of water ice, epsomite, and halite at cryogenic temperatures. Furthermore, we perform a quantitative assessment of the ability of both intimately- and linearly-mixed models to reproduce laboratory data of different grain mixtures of water ice, as well as water ice mixed with epsomite. We find that smaller grains of water ice impart a stronger influence than larger grains of water ice on the 2.0 {\mu}m spectral feature in epsomite, and grain size signatures for both halite and epsomite are challenging to discern for larger grain sizes as a result of the saturated absorption features. These findings may indicate that an observation bias toward smaller grain sizes of ice could exist, and that quantitative assessments provided by spectral mixture analyses will be the most reliable method for determining compositions and abundances of materials. We also find that the linearly-mixed and intimately-mixed models of water ice appear to match the laboratory spectra as expected, though still display some inconsistencies, often either in the continuum or the absorption features. When modeling pure water ice and water ice mixed with epsomite, no discernible difference is observed between the fits of the linearly- and intimately-mixed models. Future spectral mixture analyses that use epsomite should be aware of a potential error in the published epsomite optical constant data, in which the cryogenic data appear to be taken at ambient conditions.

I provide two short derivations for the Shklovskii effect, which describes the apparent secular period drift of a periodic source due to its motion on the sky. These derivations use easily visualizable geometry and calculus, and might be useful for those who wish to gain intuition for the subject.

While many hot Jupiter systems have a measured obliquity, few warm Jupiter systems do. The longer orbital periods and transit durations of warm Jupiters make it more difficult to measure the obliquities of their host stars. However, the longer periods also mean any misalignments persist due to the longer tidal realignment timescales. As a result, measuring these obliquities is necessary to understand how these types of planets form and how their formation and evolution differ from that of hot Jupiters. Here, we report the measurement of the Rossiter-McLaughlin effect for the TOI-4127 system using the HARPS-N spectrograph. We model the system using our new HARPS-N radial velocity measurements in addition to archival TESS photometry and NEID and SOPHIE radial velocities. We find that the host star is well-aligned with the highly eccentric (e=0.75) warm Jupiter TOI-4127 b, with a sky-projected obliquity ${\lambda} = {4^\circ}^{+17^\circ}_{-16^\circ}$. This makes TOI-4127 one of the most eccentric well-aligned systems to date and one of the longest period systems with a measured obliquity. Conclusions. The origin of its highly eccentric yet well-aligned orbit remains a mystery, however, and we investigate possible scenarios that could explain it. While typical in-situ formation and disk migration scenarios cannot explain this system, certain scenarios involving resonant interactions between the planet and protoplanetary disc could. Similarly, specific cases of planet-planet scattering or Kozai-Lidov oscillations can result in a highly-eccentric and well-aligned orbit. Coplanar high-eccentricity migration could also explain this system. However, both this mechanism and Kozai-Lidov oscillations require an additional planet in the system that has not yet been detected.

Luminous Blue Variables (LBVs) are a class of massive blue supergiants exhibiting irregular and eruptive instability, sometimes accompanied by extreme mass loss. While they have often been considered to be a brief but very important transitional phase in the evolution of massive single stars, mounting evidence suggests that LBVs are actually a phenomenon associated with binary star evolution by way of mass gainers and mergers. If true, this would leave single massive stars without a way to shed their H envelopes and become Wolf-Rayet (WR) stars, requiring a revision of our most basic paradigm of massive star evolution. Understanding their properties and role in evolution is therefore extremely important. The eruptive mass loss of LBVs is also invoked to account for some of the most extraordinary supernovae (SNe) with dense circumstellar material (CSM), which again contradicts the standard single star scenario where LBVs are massive stars in transition to the WR phase. This chapter reviews many aspects of LBVs including terminology and classification, the physical properties of the stars, their mass loss, and their variability, as well as their observed companion stars, implications of their surrounding stellar populations, and their circumstellar nebulae. These are put into context with proposed evolutionary scenarios and possible mechanisms that drive their eruptive variability.

We present dynamical masses for 23 pre-main sequence K- and M-type stars in the Upper Scorpius star-forming region. These masses were derived from the Keplerian rotation of CO disk gas using the MCMC radiative-transfer package pdspy and a flared-disk model with 15 free parameters. We compare our dynamical masses to those derived from five pre-main sequence evolutionary models, and find that most models consistently underestimate stellar mass by $\gtrsim$25%. Models with updated treatment of stellar magnetic fields are a notable exception $-$ they consistently return stellar masses in good agreement with the dynamical results. We find that the magnetic models' performance is valid even at low masses, in contrast with some literature results suggesting they may overestimate stellar mass for M$_{\star}$ $\lesssim$ 0.6 M$_{\odot}$. Our results are consistent with dynamical versus isochronal evaluations for younger samples (e.g. Taurus, 1-3 Myr), and extend the systematic evaluation of stellar evolutionary models up to stars $\sim$11 Myr in age. Finally, we derive disk dust masses to evaluate whether using dynamical masses versus isochronal masses changes the slope of the log(M$_{dust}$)$-$log(M$_{\star}$) relation. We derive a slightly shallower relation using dynamical masses versus isochronal masses, but the slopes of these relations agree within uncertainties. In all cases, we derive a steeper-than-linear relation for log(M$_{dust}$)$-$log(M$_{\star}$), consistent with previous literature results for Upper Sco.

We present a comparative analysis of interstellar hydrogen (HI) and potassium (KI) absorption from the radio and optical surveys, GASKAP and GALAH, to study the physical and kinematic properties of the cold interstellar medium (ISM) in the Milky Way foreground towards the Magellanic Clouds. By comparing GASKAP HI absorption with interstellar KI absorption detected in GALAH spectra of nearby stars (within 12 arcmin angular distance or a spatial separation of ~0.75 pc), we reveal a strong kinematic correlation between these two tracers of the cold neutral ISM. The velocity offsets between matched HI and KI absorption components are small, with a mean (median) offset of -1.3 (-1.2) km s-1 and a standard deviation of 2.3 km s-1. The high degree of kinematic consistency suggests a close spatial association between Ki and cold HI gas. Correlation analyses reveal a moderate positive relationship between HI and KI line-of-sight properties, such as KI column density with HI column density or HI brightness temperature. We observe a ~63% overlap in the detection of both species towards 290 (out of 462) GASKAP HI absorption lines of sight, and estimate a median KI/HI abundance ratio of ~2.3 x 10^(-10), in excellent agreement with previous findings. Our work opens up an exciting avenue of Galactic research that uses large-scale surveys in the radio and optical wavelengths to probe the neutral interstellar medium through its diverse tracers.

Inflation generates correlated temperature ($T$) and polarization ($E$-mode) fluctuations in the cosmic microwave background (CMB), which differ only by their transfer functions. Following Philcox et al. (2025), we investigate a scenario with a massive partner to the inflaton ($\mathcal{O}(100)$ times the inflationary Hubble scale), in which particles are produced during a narrow time period, leaving characteristic hot- or cold-spots in the CMB. Using tools developed for thermal Sunyaev-Zel'dovich cluster-finding, we search component-separated $\textit{Planck}$ PR4 $E$-mode maps for these hotspots, and compare to analogous results in $T$. Our analysis pipeline is validated on simulated observations and gives unbiased constraints for sufficiently large and bright hotspots. We find no strong evidence for primordial hotspots and thereby place novel bounds on the marginal and relevant coupling between the inflaton and massive scalars during inflation, probing physics at energies many orders of magnitude above any feasible terrestrial collider. Due to the large noise in $\textit{Planck}$ polarization, the temperature data dominate constraints for small hotspots, but for sufficiently large hotspots, our bounds improve on those of Philcox et al. (2025) by $\sim 25\%$. We also forecast the inferred bounds on inflationary physics for a search using Atacama Cosmology Telescope (ACT) data, and from an optimistic cosmic-variance-limited experiment (CV), for which $E$-mode data provide stronger constraints than $T$ on nearly all scales. ACT should improve on the $\textit{Planck}$ constraints by $\gtrsim25\%$, nearing the CV limit on intermediate scales. Finally, we compare the constraining power of localized searches to that of a power spectrum analysis, and demonstrate that for sufficiently few produced particles the localized search performed herein is dominant.

The {\it Dark Energy Spectroscopic Instrument} (DESI) provides a comprehensive survey of {\it Baryon Acoustic Oscillation} (BAO) in the {\it Large Scale Structure} (LSS), {in stratified data covering a finite redshift range.} Extracting cosmological parameters in a joint analysis of LSS-CMB data is hereby inherently a nonlinear problem. In particular, this nonlinearity may concern the unknown equation of state of dark energy $w(a)$, defined in the general $w(a)$CDM framework. Nevertheless, a common approach is the linearized approximation hereto notably $w_0w_a$CDM, also applied by DESI. Here, we consider a potential source of a systematic uncertainty in this linearization due to non-commutativity between $w_0w_a$CDM and {\it a posteriori} linearization of $w(a)$CDM, identified with a symmetry in the latter, which is violated in the former. We shall refer to these as early and late linearization, respectively. We demonstrate this in the analysis of the Hubble expansion in the Local Distance Ladder (LDL). Strikingly, opposite results are found for the evolution of dark energy by early versus late linearization, indicating a thawing or respectively, increasing dark energy. It is unlikely that the DESI pipeline is immune to the same contradiction. Our results show rather than thawing, claimed by DESI, dark energy may in fact be increasing. Further confirmation is expected from {\it Euclid}.

We propose a next-generation ground-based gravitational-wave detector, the Cryogenic sub-Hz cROss torsion-bar detector with quantum NOn-demolition Speed meter (CHRONOS), optimized for the unexplored 0.1-10Hz band bridging the gap between the space-based LISA and future ground-based detectors such as Cosmic Explorer and the Einstein Telescope. CHRONOS combines a ring-cavity Sagnac interferometer with torsion-bar test masses to realize the first quantum nondemolition (QND) measurement of angular momentum in a macroscopic system. By implementing a speed-meter readout in the rotational degree of freedom, CHRONOS coherently cancels quantum radiation-pressure noise and enables sub-Hz observations. We show that detuned power recycling and cavity-length optimization can simultaneously relax technical requirements on both torsion bars and speed meters. Assuming a realistic optical design with a 1m torsion bar, we estimate strain sensitivities of $h \simeq 1 \times 10^{-18}\mathrm{Hz}^{-1/2}$ at 1Hz for detectors with arm lengths of 2.5m, 40m, and 300m. These sensitivities enable (i) direct detection of intermediate-mass black hole binaries up to 380Mpc with ${\rm SNR}=3$, (ii) probing stochastic gravitational-wave backgrounds down to $\Omega_{\rm GW} \sim 3.2 \times 10^{-9}$ at 0.2Hz with 5yr accumulation. Furthermore, CHRONOS enables prompt detection of gravity-gradient signals from magnitude-5.5 earthquakes even with a 2.5m prototype. CHRONOS thus opens new opportunities for quantum-limited geophysical observation and multi-band, multi-messenger gravitational-wave astronomy.

Fuzzy dark matter (FDM), composed of ultralight bosons, exhibits intricate wave phenomena on galactic scales. Compared to cold dark matter, FDM simulations are significantly more computationally demanding due to the need to resolve the de Broglie wavelength and its rapid oscillations. In this review, we first outline the governing equations and distinctive features of FDM. We then present a range of numerical algorithms for both wave- and fluid-based simulations, discuss their respective advantages and limitations, and highlight representative test problems. To facilitate code comparison, we also provide publicly available initial condition files for both isolated-halo and cosmological simulations.

Photometric analysis of KIC 9272276 (K9272), a low-mass contact binary system, is presented. We find it to be an example of an extreme low mass ratio system that satisfies the current theoretical criteria for a potential red-nova progenitor. V band photometry of the system was modelled using the Wilson-Devenney code and we find the system to be in marginal contact with a mass ratio of 0.081. The estimated mass of the primary component is one solar mass and the theoretical instability mass ratio range, accounting for both metallicity and age, is well above the modelled mass ratio at 0.09- 0.101. We find no evidence of a potential third light contamination and discuss other findings confirming our analysis.

We report the discovery of fullerene in the circumstellar environment of WRAY~16-232, a strong candidate luminous blue variable. Multiple pointings of archival \textit{Spitzer} IRS spectra reveal, for the first time, the presence of prominent vibrational bands of C$_{60}$ at 17.4 and 18.9~$\mu$m in an LBV envelope, along with the strong polycyclic aromatic hydrocarbon features. These observations suggest that, despite the harsh radiative conditions, large carbonaceous molecules can form, process and survive in the ejecta of massive stars. Complementary optical spectroscopy with SALT HRS shows multiple P\,Cygni profiles in H$\alpha$, He\,\textsc{i}, and Fe\,\textsc{ii} lines, which are indicative of a dense, expanding wind and substantial mass loss. Furthermore, analysis of decade long photometric data shows short-term brightness variations of $\sim$ 0.5~mag. These results not only reinforce the classification of WRAY~16-232 as a strong LBV candidate but also provide new insights into the mechanisms of dust formation and the chemical enrichment of the interstellar medium by massive stars. We discuss various scenarios for fullerene formation in such environments, and find that shock processing due to wind-wind interactions could be playing a vital this http URL shell of WRAY~16-232 has an ideal UV field strength and the time scales appears to match with shock processing timescales. The results highlight the need for further high spatial/spectral resolution and temporal observations to confirm the formation and survival scenario of C$_{60}$ in its shell.

Multi-band photometric analysis of the contact binary V717 Andromedae (V717 And) is presented. The system is found to be an extreme low mass ratio system (q = 0.197) with high inclination (i = 84.5 deg), moderate degree of contact (27%) and near equal temperatures of the components. Period analysis of survey photometry spanning over 6300 days reveals no significant change. Although the system does not demonstrate a significant O'Connell effect there are a number of other markers strongly suggesting the system is chromospherically active. Orbital analysis indicates that the system is stable and not a merger candidate.

We investigate the turbulent structures in the Tycho supernova remnant (SNR) by applying two-point autocorrelation and power spectral analyses to high-resolution X-ray and radio images. Using cleaned Chandra and VLA data, we derive two-dimensional (2D) and one-dimensional (1D) autocorrelation functions and power spectra, revealing that the fluctuations in both X-ray brightness (approximately tracing plasma density) and radio brightness (tracing magnetic field strength) follow the power-law distributions consistent with Kolmogorov-type turbulence. Specifically, power spectra exhibit a slope $8/3$ in 2D and $5/3$ in 1D analyses, indicating fully developed turbulence across a broad range of spatial scales. The structure functions and spectral slopes remain robust with and without correction for line-of-sight integration effects, suggesting the presence of Kolmogorov-like turbulence locally throughout the remnant's volume. Anisotropies in the 2D autocorrelation function are aligned with known density and magnetic field gradients. Analysis of the 1D radial properties of turbulence confirms Kolmogorov scaling and indicates that modes in the power spectra may be related either to periodicity in the fluctuations or to the physical sizes of bright or dim features in the surface brightness. Our results demonstrate that the Tycho SNR hosts a spatially and temporally developed turbulent cascade, providing insight into the physics of turbulence in SNRs.

We select 36 double-peaked narrow emission-line galaxies (DPGs) from 10,010 unique galaxies in MaNGA survey. These DPGs show double-peaked Balmer lines and forbidden lines in the spectra. We use a double Gaussian model to separate the double-peaked profiles of each emission line into blue and red components ($\lambda_\text{blue}$ < $\lambda_\text{red}$), and analyze the spatially resolved kinematics and ionization mechanisms of each component. We find that in 35 out of 36 DPGs, the flux ratio between the blue and red components varies systematically along the major axes, while it keeps roughly a constant along the minor axes. The blue and red components of these DPGs exhibit similar distributions in both the value of line-of-sight velocity and the velocity dispersion. Additionally, 83.3% DPGs have both blue and red components located in the same ionization region in the [SII]-BPT diagram. Combining all these observational results, we suggest that the double-peaked emission line profiles in these 35 DPGs primarily originate from rotating discs. The remaining one galaxy shows clear outflow features. 8 out of 35 DPGs show symmetric line profiles that indicate undisturbed rotating discs, and the other 27 DPGs exhibit asymmetric profiles, suggesting dynamic disturbances in the rotating discs. Furthermore, we find that 58.3% DPGs experienced external processes, characterized by tidal features, companion galaxies, as well as gas-star misalignments. This fraction is about twice as much as that of the control sample, suggesting the origin of double-peaked emission line profiles is associated with external processes.

Synchrotron radiation from the reverse- and forward-shock regions typically describes the evolution of temporal and spectral features given by the closure relations (CRs) during the late and long-/short-lasting emission in the afterglow phase of Gamma-ray bursts (GRBs). Although synchrotron photons are restricted to keV and a few MeV energies, the synchrotron self-Compton (SSC) mechanism can disperse them above hundreds of MeV energies. We present the CRs of the SSC process radiated from the reverse-shock region for the case of a thick and thin shell, considering that the reverse shock lies in the adiabatic regime and evolves in an environment with a homogeneous and stratified medium. We analyze these CRs with the spectral and temporal characteristics of the bursts described in the second \textit{Fermi}-LAT GRB catalog (2FLGC) and found that i) the thin shell case is preferred over a thick shell and a constant-density medium over a stellar-wind environment, ii) bursts with an atypical and hard spectral index could be successfully described by this scenario in different cooling conditions, iii) the early optical flash and GeV emission exhibited in GRB 160625B and 180720B were generated from the same accelerated region and electron population, concluding that LAT emission originated during the early afterglow, and iv) the maximum synchrotron energy radiated from the reverse-shock scenario could explain only a few photons with the exception of a pair of bursts, so that scattered photons by the SSC process must be required.

Close-in warm Jupiters orbiting M-dwarf stars are expected to exhibit diverse atmospheric chemistry, with clouds playing a key role in shaping their albedo, heat distribution, and spectral properties. We study WASP-80b, a warm Jupiter orbiting an M-dwarf star, using the latest JWST panchromatic emission and transmission spectra to comprehensively characterize its atmosphere, including cloud coverage, chemical composition, and particle sizes, and compare the observations with predictions from general circulation models (GCMs). We use a General Circulation Model (GCM), ADAM (ADvanced Atmospheric MITgcm, formerly known as SPARC/MITgcm), combined with the latest JWST data to study the atmosphere of WASP-80b. A cloud module with radiatively active, tracer-based clouds is integrated with the GCM to study the effects on the atmosphere and the spectrum. Our results indicate that both emission and transmission spectra are well fit by cloudless GCMs. The data appear to be compatible with large cloud particles of any cloud species or KCl clouds of all particle sizes. The Na$_2$S condensates of radii 0.1 and 1 $\mu$m can be ruled out due to the strength of their radiative feedback. This showcases the unique insights that can be obtained from global modelling of exoplanet atmospheres.

Low-temperature systems play a vital role in a variety of scientific research applications, including the next generation of cosmology and astrophysics telescopes. More ambitious cryogenic applications require precise estimates of the thermal conductivity of materials and thermal joints to meet project goals. We present the development of the Cryogenic Material Repository (CMR), a public GitHub repository of cryogenic material properties data created to support and enable researchers across scientific disciplines to accurately and efficiently design and assess cryogenic systems. We also present updated sub-Kelvin thermal conductivity results for select carbon fiber reinforced polymer and aluminum alloy samples.

The Terzina payload, onboard the NUSES space mission is being built in collaboration with TAS-I by GSSI, INFN and the University of Geneva. It is a Cherenkov Schmidt-Cassegrain compact telescope with an effective focal length of 925~mm and a camera focal assembly composed of 640 pixels (16 vertically and 40 horizontally) organized in $8\times 8$ tiles produced by FBK with sensitive area $2.73 \times 2.64$~mm$^2$. We will illustrate the performance for the signal of cosmic rays beyond a threshold of few hundreds of PeV. Understanding the operation of SiPMs in space with almost direct exposure to solar and trapped protons and electrons, defining the mitigation strategy for the increase of DCR of exposed silicon, the characterisation of the luminous backgrounds, the data acquisition strategy for this payload, the maximization of the effective exposure to the atmospheric showers induced by the signal of neutrinos and cosmic rays are the challenges. At this conference, we describe how they are being addressed.

Context. Bars are elongated structures developed by a large fraction of disk galaxies in their central few kiloparsecs. However, the bar formation process is still not fully understood, particularly the role played by the galaxy environment in the formation and evolution of these structures. Aims. The aim of this work is to establish how the galaxy environment affects the evolution of bars by analyzing the bar structural parameters in a sample of galaxies located in three different galaxy environments: in the Virgo cluster, in filaments in the Cosmic Web around it, and in the field. Methods. We performed structural analysis using optical imaging from the DESI Legacy survey, measuring bar radii and disk scale lengths through Fourier analysis and surface brightness fitting techniques. Results. After defining a homogeneous sample of barred galaxies across the three different galaxy environments in terms of color and magnitude, the median bar radii were found to be 2.54 +/- 0.34 kpc, 3.29 +/- 0.38 kpc, and 4.44 +/- 0.81 kpc in the cluster, filaments, and field environments, respectively. In addition, the median bar radii scaled by the disk scale lengths was found to be 1.26 +/- 0.09, 1.72 +/- 0.11, and 2.57 +/- 0.21 in the cluster, filaments, and field environments, respectively. These results indicate that the galaxy environment has a significant influence on the structural parameters of bars, with bars in high-density environments being shorter and less prominent than those in the field. Conclusions. Our findings can be interpreted in terms of a slowing of the secular evolution of bars in dense galaxy environments. Barred galaxies located in clusters could experience a reduced rate of bar secular evolution due to various physical processes that occur in high-density environments, such as gas stripping, strangulation, or tidal interactions.

The origin of ear-like structures with two opposite lobes extending from the shell of supernova remnants (SNRs) remains a subject of active debate, with proposed mechanisms ranging from jet-driven explosions to interactions with bipolar circumstellar media. We present a novel investigation using Particle-in-Cell (PIC) simulations to examine the dynamics of a spherical ejecta in magnetized media, revealing a different formation mechanism for these structures. Our results demonstrate that particle acceleration is significantly enhanced along the magnetic-field direction, producing substantial modifications to shock morphology. These effects naturally generate elongated protrusions bearing a remarkable similarity to the observed SNR ear structures. This magnetic alignment scenario represents a distinct mechanism from the existing jet-based and circumstellar interaction models. Our findings suggest that magnetic field orientation may serve as a crucial diagnostic for distinguishing between different ear formation mechanisms in SNRs.

We leverage the IllustrisTNG cosmological simulations to test how the large-scale cosmic web shapes galaxy morphology and to forecast the early cosmic web structure that the Nancy Grace Roman Space Telescope will reveal. In the hydrodynamic TNG50 and $N$-body TNG50-Dark runs, we reconstruct the cosmic web at redshifts $z=0$, 0.5, 1, 2, 3, and 4 with the Monte Carlo Physarum Machine density estimator and the DisPerSE structure identification framework. We confirm that dark matter halos start out predominantly prolate (elongated) and their shapes are aligned with their nearest filaments; prolate galaxies retain strong shape-alignment with their outer halos to later times. The fraction of prolate galaxies and halos increases toward lower stellar mass, higher redshift, and lower-density filaments. Oblate and spheroidal galaxies show weaker trends with filament density, but spheroidal halos preferentially reside in higher-density filaments. We also find that higher-density filaments favor extended rotationally-supported disks, whereas lower-density filaments more often host smaller dispersion-supported systems. Then, generating mock galaxy samples from TNG100 and TNG50, we predict the early cosmic web accessible to Roman. We find that the spectroscopic emission-line depth planned for the High-Latitude Wide-Area Survey (HLWAS) yields a highly incomplete galaxy sample that does not accurately trace the $z=1$ cosmic web. A survey $\geq2.5\times$ deeper over a few square degrees would enable a proper reconstruction and reveal qualitatively correct filament-galaxy morphology relationships. Nevertheless, the planned HLWAS Deep field should still identify most galaxy overdensities; targeted deeper spectroscopy of these regions would efficiently and adequately map the early filamentary structure.

We derived the inner rotation curve (RC) of the Milky Way by applying the terminal velocity method (TVM) to the longitude-velocity diagrams (LVD) made from the large-scale survey data of the Galactic plane in the HI (HI4PI whole sky survey) and CO lines (CfA-Chile 1.2-m Galactic plane survey, Nobeyama 45-m Galactic plane and Galactic Center surveys, and Mopra 22-m southern Galactic plane survey). The derived RC agrees well with the RCs derived from the astrometric measurements of the maser sources by very long baseline interferometer (VLBI) observations and the GAIA result. We combined them to construct a unified RC from $R=0$ to $\sim 25$ kpc and decomposed the curve into bulge, disc and dark halo components with high precision. The dark matter density near the Sun is estimated to be $0.107 \pm 0.003$ GeV cm$^{-3}$. We present the RC as ascii tables for the solar constants of $(R_0,V_0)=(8.178 {\rm kpc}, 235.1 {\rm km/s})$, We also obtained a detailed comparison of the eastern ($l\ge 0^\circ$) and western ($< 0^\circ$) RCs in the HI and CO lines, which allowed the creation of an E/W asymmetry curve of the velocity difference. The E/W asymmetry is fitted by a sinusoidal function of the radius with the amplitude increasing toward the Galactic Center. We consider the possibility of the origin due to a weak bar inside $\sim 4$ kpc.

The search for extraterrestrial intelligence (SETI) has historically focused on detecting electromagnetic technosignatures, implicitly assuming that alien civilisations are biological and technologically analogous to ourselves. This paper challenges that paradigm, arguing that highly advanced, potentially post-biological civilisations may undergo rapid technological acceleration, quickly progressing beyond recognisable or detectable phases. We introduce a simple model showing that the technological acceleration rate of such civilisations can compress their detectable phase to mere decades, dramatically narrowing the temporal "detection window" in which their technosignatures overlap with our current capabilities. This framework offers a plausible resolution to the "Great Silence": advanced civilisations may be abundant and long-lived, but effectively invisible to present-day SETI methods. Consequently, our efforts must include but also evolve beyond the search for narrow-band communication signals in the radio and optical domains. Instead, we require an expanded, technology-agnostic strategy focused on persistent, large-scale manifestations of intelligence, such as broadband electromagnetic leakage, waste heat from megastructures, and multi-dimensional anomaly detection across extensive, multi-wavelength and multi-messenger datasets. Leveraging advanced artificial intelligence for unsupervised anomaly discovery, recursive algorithm optimisation, and predictive modelling will be essential to uncover the subtle, non-anthropocentric traces of advanced civilisations whose technosignatures lie beyond our current technological and cognitive frameworks.

Three-dimensional magnetic reconnection is a fundamental plasma process crucial for heating the solar corona and generating the solar wind, but resolving and characterizing it on the Sun remains challenging. Using high-quality data from the Chinese New Vacuum Solar Telescope, the Solar Dynamics Observatory, and the Interface Region Imaging Spectrograph, this work presents highly suggestive direct imaging evidence of magnetic reconnection during the untangling of braided magnetic structures above a sunspot. These magnetic structures, visible as bright superpenumbral threads in extreme ultraviolet passbands, initially bridge opposite-polarity magnetic fluxes and then gradually tangle in their middle section. Magnetic extrapolation reveals the fibrils to form a small flux rope that is twisted and braided, possibly created by persistent and complex photospheric motions. During untangling, repetitive reconnection events occur inside the flux rope, accompanied by transient plasma heating, bidirectional outflowing blobs, and signatures of nanojets. Emission analysis reveals that the outflowing blobs are multi-thermal structures with temperatures well below 1 MK, undergoing rapid cooling and leaving emission imprints in H{\alpha} images. The measured reconnection angles indicate that 16%-22% of the magnetic field along each thread is anti-parallel, with the remaining field acting as a guide field. The estimated energy released during these reconnection events is comparable to nanoflares, which can be powered by up to 6% of the magnetic energy stored in the anti-parallel field. This work presents a textbook example of magnetic flux rope reconnection in the solar atmosphere, providing new insights into fine-scale energy release processes within sunspot superpenumbral fibrils.

Accurately modeling the solar magnetic field is important for understanding long-term solar activity and space weather, but it is challenging due to limited observations, especially near the poles. The Surface Flux Transport (SFT) model simulates how magnetic flux moves across the solar surface and contributes to the polar field, but it parametrizes emerged sunspots as simple symmetric bipolar regions and needs improvement by including more realistic sunspot features. In this study, we reconstruct the century-long evolution of the solar magnetic field, including the polar regions, using an improved SFT model. We incorporate cycle-dependent morphological asymmetry between leading and following sunspots, along with observationally derived tilt angles and sunspot area data for a century (1913-2016), to better represent magnetic flux transport and investigate the impact of asymmetry on polar field development. To study morphological asymmetry, we consider two cases: first, a long-term asymmetry factor calculated from the ratio of leading and following sunspot areas spanning over a century; second, the temporal asymmetry factor observed during solar cycle 23 applied to every solar cycle. Our simulated magnetic flux transport with inclusion of morphological asymmetry for both cases gets improved compared to the no asymmetry case in terms of enhanced low and mid-latitude magnetic flux and matches closely with observations. The simulated polar fields with asymmetry also show a better agreement with polar field observations for most cycles, particularly in capturing the timing of the polar field reversals and the peak amplitude during solar minima, which has severe consequences in solar cycle prediction

Simultaneous measurements of volatile and refractory elements are essential for tracing the formation and migration of ultra-hot Jupiters (UHJs). High-resolution infrared emission spectroscopy has been widely used to probe their atmospheres, covering molecules and atoms. For the hottest known planet, KELT-9b, whose dayside atmosphere is nearly fully dissociated and ionized, no molecules had been firmly detected. Here we report the first detection of OH in the dayside atmosphere of KELT-9b, based on two thermal emission observations with the SPIRou spectrograph, and confirm the presence of Fe. We performed a self-consistent retrieval under chemical equilibrium, constraining elemental abundances and metallicity. A significant thermal inversion layer is confirmed. No significant Doppler shifts were found, and the retrieved equatorial rotation matches the tidally locked value. The oxygen abundance is consistent with solar to supersolar (0.61$_{-0.58}^{+1.19}$ dex), while the C/O ratio and metallicity are subsolar to solar. The low metallicity may indicate a well-mixed envelope and interior. Constraints remain broad, and the data are consistent with supersolar C/O and subsolar O. Combined [C/O] and [O/H] are compatible with formation beyond the water snowline followed by inward migration, though other scenarios cannot be excluded. Volatile-to-refractory ratios, [O/Fe] = 1.25$_{-0.74}^{+0.99}$ dex and [C/Fe] = 0.60$_{-0.74}^{+0.62}$ dex, lie in the solar to supersolar range, but uncertainties limit firm conclusions. Results provide tentative evidence for volatile enrichment. Future high-resolution optical-to-infrared spectra with JWST will enable more precise abundance constraints and stronger insights into UHJ formation and migration. We also advocate a retrieval-guided cross-correlation strategy to reduce risk of missing marginal detections, as illustrated by tentative evidence for CO.

Tidal disruptions of stars by supermassive black holes in galactic centers (TDEs) are now being actively studied both theoretically and observationally. They are observed throughout the electromagnetic spectrum, from radio to gamma-rays. It is still unclear how the emission is produced and, in particular, what is the role of the magnetic field of the disrupted star. There are many ways how magnetic fields might affect the dynamics of a TDE. They are likely responsible for the angular momentum transfer in the accretion disk formed at later stages and thus affect the radiation associated with the disk. Magnetic fields are also an important requirement for the formation of relativistic jets, that are seen in some TDEs. The goal of our study is to connect the field within the star to the fields that develop during the fallback and disk accretion. Using the fluid-dynamic code Athena++, we perform a large-scale three-dimensional adaptive-mesh magnetohydrodynamic simulation of a tidal disruption of a magnetized star. The fallback stream returning to the black-hole vicinity after the disruption contains smooth magnetic fields aligned with the stream lines. Formation of a nozzle shock near the pericenter of the initial orbit leads to a turbulent eccentric disk-like structure where the field is amplified and entangled on the local dynamic time scales up to approximate equipartition. The resulting field is mildly anisotropic and has a typical length several times smaller than the pericenter distance. The properties of the field are consistent with the early stages of turbulent dynamo.

The active galactic nucleus (AGN) accretion disks are ideal sites for hierarchical black hole (BH) mergers. To robustly probe such a possibility, we analyze binary black hole mergers in the GWTC-4 with a flexible mixture population model for component masses, spin magnitudes, and spin tilt angles, and identify two distinct subpopulations. In the second subpopulation characterized by high spin magnitudes $\chi\sim 0.8$ as well as the broad mass distribution up to $\gtrsim 150M_\odot$, we find a pronounced preference for spins aligned with the orbital angular momentum: an isotropic tilt distribution is strongly disfavored (logarithmic Bayes factor = 4.5). The aligned events account for $\sim 0.57^{+0.23}_{-0.31}$ of the second subpopulation, corresponding to a local rate of $\sim 0.25^{+0.38}_{-0.16} ~ {\rm Gpc}^{-3} {\rm yr}^{-1}$ (all values reflect central 90\% credible intervals). These notable features naturally arise from hierarchical mergers embedded in AGN disks, where gas torques can effectively align spins. Our results identify AGN-disk hierarchical assembly as an important channel in the present gravitational-wave sample and provide concrete, testable predictions for future detection.

End-to-end deep learning models fed with multi-band galaxy images are powerful data-driven tools used to estimate galaxy physical properties in the absence of spectroscopy. However, due to a lack of interpretability and the associational nature of such models, it is difficult to understand how the information additional to integrated photometry (e.g., morphology) contributes to the estimation task. Improving our understanding in this field would enable further advances into unraveling the physical connections among galaxy properties and optimizing data exploitation. Therefore, our work is aimed at interpreting the deep learning-based estimation of stellar mass via two interpretability techniques: causal analysis and mutual information decomposition. The former reveals the causal paths between multiple variables beyond nondirectional statistical associations, while the latter quantifies the multicomponent contributions (i.e., redundant, unique, and synergistic) of different input data to the stellar mass estimation. Using data from the Sloan Digital Sky Survey (SDSS) and the Wide-field Infrared Survey Explorer (WISE), we obtained meaningful results that provide physical interpretations for image-based models. Our work demonstrates the gains from combining deep learning with interpretability techniques, and holds promise in promoting more data-driven astrophysical research (e.g., astrophysical parameter estimations and investigations on complex multivariate physical processes).

Space-weather and disturbances in the heliosphere are manifestations of the solar magnetic field, which is solely driven by the interior dynamo, and constraining the solar interior magnetic field and its oscillatory behavior is one of the major challenges in solar physics. Observationally, none of the techniques, including helioseismology, are able to provide an estimation of the interior magnetic field. We reconstruct, for the first time, the dynamics of the interior large-scale magnetic fields by assimilating observed line-of-sight photospheric magnetogram data from MDI/SOHO & HMI/SDO along with helioseismic differential rotation data for three decades (1996-2025) into a 3D dynamo model. Our data-driven model successfully reproduces key observational features such as the surface butterfly diagram, polar field evolution, and axial dipole moment. The reconstructed interior field dominated by toroidal component exhibits an equatorward migration and reproduces the realistic amplitude and modulation of cycles 23-25. The non-axisymmetric behaviour of the interior toroidal field becomes less prominent as we move deep towards the tachocline. A strong correlation between the simulated toroidal field and sunspot number/area establishes our 3D magnetogram-driven model as a robust predictive model of the solar cycle.

The orbital eccentricity distribution of exoplanets is shaped by a combination of dynamical processes, reflecting both formation conditions and long-term evolution. Probing the orbital dynamics of planets in the kinematic thin and thick Galactic disks provides insight into the degree to which stellar and Galactic environmental factors affect planet formation and evolution pathways. The classification of host stars in Galactic kinematic terms constitutes a potentially useful axis for the interpretation of orbital eccentricity, when included together with stellar metallicity and age. Leveraging the photoeccentric effect, we constrain orbital eccentricities for the sample of Kepler planets and candidates orbiting F, G, K and M dwarf stars. With Gaia astrometry, inferred Galactic phase space information, and kinematic disk criteria calibrated on stellar chemical abundances, we probabilistically associate each planet host with the kinematic thin or thick Galactic disks. We then fit the underlying eccentricity distributions for the single- and multi-transit populations. We find that for single-transiting planets, kinematic thick disk planets exhibit higher eccentricities than thin disk planets, yet we find no such difference among multis. We determine that the difference in eccentricity is unlikely to be caused solely by the effects of host stellar metallicity or giant planet occurrence. We situate these findings in the context of known eccentricity relations, including its relationships with planet multiplicity, radius and metallicity. We suggest comprehensive analyses to disentangle these results from the effects of poorly understood star-planet relationships, such as that between stellar age and planetary orbital dynamics.

Hypervelocity stars (HVSs) are stars with velocities exceeding their local escape velocities. Searching for HVSs and studying their origins can be an important way to study the properties of the Milky Way. In this paper, we utilize precise distances for RR Lyrae stars (RRLs) derived from the period-absolute magnitude-metallicity (PMZ) relation, along with proper motions from Gaia DR3, to conduct a large-volume search for HVSs. Our sample consists of a catalog with 8,172 RRLs with metallicity, distance and radial velocities estimated from SDSS and LAMOST spectroscopic data, and an extended catalog of 135,873 RRLs with metallicity and distance estimated from Gaia photometry. After careful quality cuts, 165 hypervelocity RRL candidates were found. We performed further checks on their light curves, and selected the most reliable 87 hypervelocity RRLs. All of them exceed the Milky Way's escape velocity in the tangential component. Among them, 7 stars have tangential velocity over 800 km s^-1. We identified two spatially distinct distributions of hypervelocity RRLs: one concentrated toward the Galactic Center and another localized around the Magellanic Clouds, suggesting that their origins are likely associated with these regions through the Hills or other mechanisms. Furthermore, we detected a significant number of RRLs associated with dwarf galaxies that exceed the Milky Way's escape velocity, likely ejected from their host systems. Future Gaia releases and spectroscopic follow-up observations will provide further insight into their ejection origin.

The excess of muons observed in ultra-high-energy cosmic-ray air showers relative to simulation predictions, known as the muon puzzle, provides indirect evidence of our incomplete understanding of high-energy hadronic interactions. An unambiguous resolution requires that each proposed solution be directly tested through collider experiments probing hadronic interactions. In this work, we develop a framework to assess the strangeness enhancement scenario, wherein an increased yield of kaons relative to pions boosts muon production. Using the MCEQ air-shower simulation package, we first identify the key phase-space regions of hadronic interactions that drive muon yields in this scenario. We then demonstrate that combining Pierre Auger Observatory muon measurements with forthcoming kaon-to-pion ratio data from LHC Run~3 can robustly constrain the scenario's parameters. In particular, we find that achieving 10.8% precision on the kaon-to-pion ratio at LHCb and 8.4% at FASER is sufficient to test the strangeness enhancement hypothesis over its viable parameter space. These upcoming experimental results will provide the first direct constraints on strangeness enhancement as a potential resolution of the muon puzzle.

We explore the renormalization group-based extension of the $\Lambda$CDM model as a potential solution to the current cosmological tensions. In this approach, both the cosmological constant density and Newton's constant are allowed to vary with the energy scale, as a consequence of the remnant effects of massive quantum fields in the low-energy regime. The corresponding cosmological model is consistent with the principles of quantum field theory, based on the covariance of the vacuum effective action, and is characterized by an unique extra parameter $\nu$. Our analysis yields a best-fit value of $\nu = - (2.5 \pm 1.3)\times 10^{-4}$, placing the $\Lambda$CDM limit at the $2\sigma$ region of the $\nu$ posterior. This narrow range is consistent with data from CMB (Planck), BAO (DESI), and SN Ia (DES Y5). Our result also alleviates the $H_0$ tension and is consistent with the previously established constraints from large-scale structure. In this kind of models there is a link between cosmology and particle physics. Our results point to possibility of a new physics, characterized by a mass spectrum lying below the Planck scale but above the values typically associated with Grand Unified Theories (GUTs).

Dust-lane spheroidal galaxies (DLSGs) are unique astrophysical systems that exhibit the morphology of early-type galaxies (ETGs) but are distinguished by prominent dust lanes. Recent studies propose that they form through minor mergers between ETGs and gas-rich dwarf galaxies, offering a window into the interstellar medium (ISM) of ETGs and star formation triggered by small-scale interactions. However, their rarity poses a challenge for assembling large, statistically robust samples via manual selection. To overcome this limitation, we employ GC-SWGAN, a semi-supervised learning method developed by \citet{2025ApJS..279...17L}, to systematically identify DLSGs within the DESI Legacy Imaging Surveys (DESI-LS). The methodology involves training a generative adversarial network (GAN) on unlabeled galaxy images to extract morphological features, followed by fine-tuning the model using a small dataset of labeled DLSGs. In our experiments, despite DLSGs constituting only $\sim$ 3.7\% of the test set, GC-SWGAN achieves remarkable performance, with an 87\% recall rate, 84\% accuracy, and an F1 score of 86\%, underscoring its efficacy for DLSG detection. Applying this model to $\sim$ 310,000 DESI-LS galaxies that meet the criteria $m_r < 17.0$ and $0.01 < z < 0.07$ we compile the largest catalog of DLSG candidates to date, identifying 9,482 dust-lane ETGs. A preliminary analysis reveals that these DLSGs exhibit significantly redder $g-r$ colors and higher specific star formation rates compared to non-DLSGs. This catalog enables future studies of ISM properties in ETGs and the role of minor mergers in driving star formation in the nearby universe.

Mass-modeling methods are used to infer the gravitational field of stellar systems, from globular clusters to giant elliptical galaxies. While many methods exist, most require assumptions about the form of the underlying distribution function or data binning that leads to loss of information. With only line-of-sight (LOS) data, many methods suffer from the well-known mass-anisotropy degeneracy. To overcome these limitations, we develop a new, publicly available mass-modeling method, GravSphere2. This combines individual stellar velocities from LOS and proper motion (PM) measurements to solve the Jeans equations up to fourth order, without any data binning. Using flexible functional forms for the anisotropy profiles at second and fourth order, we show how including additional constraints from a new observable - fourth-order PMs - fully closes the system of equations, breaking the mass-anisotropy degeneracy at all orders. We test our method on mock data for dwarf galaxies, showing how GravSphere2 improves on previous methods. GravSphere2 recovers the mass density, stellar velocity anisotropy, and logarithmic slope of the mass density profile within its quoted 95% confidence intervals across almost all mocks over a wide radial range (0.1 < R/Rhalf < 10). We find GravSphere2 outperforms simple mass estimators, suggesting that it is worth using even when only a few LOS velocities are available. With 1,000 tracers without PMs, GravSphere2 recovers the logarithmic density slope at Rhalf with 12% (25%) statistical errors for cuspy (cored) mock data, enabling a distinction between the two. Including PMs, this improves to 8% (12%). With just 100 tracers and no PMs, we recover slopes with ~ 30% (20%) errors. GravSphere2 will be a valuable new tool to hunt for black holes and dark matter in spherical stellar systems, from globular clusters and dwarf galaxies to giant ellipticals and galaxy clusters.

We present AstroCo, a Conformer-style encoder for irregular stellar light curves. By combining attention with depthwise convolutions and gating, AstroCo captures both global dependencies and local features. On MACHO R-band, AstroCo outperforms Astromer v1 and v2, yielding 70 percent and 61 percent lower error respectively and a relative macro-F1 gain of about 7 percent, while producing embeddings that transfer effectively to few-shot classification. These results highlight AstroCo's potential as a strong and label-efficient foundation for time-domain astronomy.

Ultra-short-period (USP) planets, defined as those with orbital periods shorter than 1 day, provide valuable insights into planetary evolution under strong stellar tidal interactions. In this work, we investigate the formation of USP planets in two-planet systems consisting of an inner terrestrial planet accompanied by an outer hot Jupiter (HJ). Our simulation results show USP planets can form through a process driven by secular perturbations from the outer companion, which induce eccentricity excitation, tidal dissipation, and subsequent orbital decay of the inner planet. The probability of USP formation is governed by key factors, including the mass ratio between two planets, their orbital eccentricities, and the tidal dissipation process. 6.7\% of our simulations form USP planets, and USP planets form most efficiently when the mass ratio is around 4 $M_{\oplus}{\rm /}M_{\rm J}$, with the inner planet less than 8 $M_{\oplus}$. Furthermore, the eccentricity of the outer HJ plays a crucial role-moderate eccentricities ($e_{\rm outer}<0.1$) favor USP formation, whereas higher eccentricities ($e_{\rm outer}>0.1$) enhance the likelihood of orbital instability, often resulting in a lonely HJ. USP planets form more efficiently when the tidal dissipation function of the inner planet is comparable to the values estimated for terrestrial planets in the solar system. Comparison with observed planetary systems reveals that systems with large mass ratios or nearly circular outer planets tend to produce short-period (SP) planets instead of USP planets. Our findings offer a potential explanation for the most commonly observed system architectures, which predominantly feature either an HJ with an inner SP planet or a lonely HJ.

Singly-ionized carbon is theorized to be the brightest emission line feature in star-forming galaxies, and hence an excellent tracer of the evolution of cosmic star formation. Archival maps from far-infrared and sub-millimeter surveys potentially contain the redshifted [CII]-158$\mu$m, hidden in the much brighter continuum emission. We present a search for aggregate [CII]-158$\mu$m line emission across the predicted peak of star formation history by tomographically stacking a high-completeness galaxy catalog on broadband deep maps of the COSMOS field and constraining residual excess emission after subtracting the continuum spectral energy distribution (SED). We obtain constraints on the sky-averaged [CII]-158$\mu$m signal from the three Herschel/SPIRE maps: $11.8\pm10.2$, $11.0\pm8.7$, $9.6\pm9.8$, and $9.2\pm6.6$ $k$Jy/sr at redshifts $z\sim 0.65$, $\sim1.3$, $\sim2.1$, and $\sim2.6$ respectively, corresponding to $1-1.4\sigma$ significance in each bin. Our $3\sigma$ upper limits are in tension with past $z\sim2.6$ results from cross-correlating SDSS-BOSS quasars with high-frequency Planck maps, and indicate a much less dramatic evolution ($\sim\times7.5$) of mean [CII] intensity across the peak of star formation history than collisional excitation models or frameworks calibrated to the tentative PlanckxBOSS measurement. We discuss this tension, particularly in the context of in-development surveys (TIM, EXCLAIM) that will map this [CII] at high redshift resolution. Having demonstrated stacking in broadband deep surveys as a complementary methodology to next-generation spectrometers for line intensity mapping, our novel methods can be extended to upcoming galaxy surveys such as Euclid, as well as to place upper limits on fainter atomic and molecular lines.

High-velocity collisions between gas-rich ultra-diffuse galaxies present a promising formation channel for baryon-dominated dwarf galaxies (BDDGs). Using hydrodynamical simulations, we show that the progenitors' baryonic binding energy, $|E_{\rm bind}|$, critically controls the outcome. Repeated potential fluctuations, e.g., from bursty feedback, inject energy and reduce $|E_{\rm bind}|$ by $\approx 15\%$, yielding fewer but substantially more massive BDDGs. By contrast, elastic self-interacting dark matter produces comparable cores without lowering $|E_{\rm bind}|$, resulting in negligible effect. This provides a novel way to distinguish between two leading galactic core formation channels, i.e., the baryon feedback and elastic dark matter self-interaction. Among 15 paired simulation runs, 13 show higher BDDG masses in the weakened-binding case, and about two thirds exhibit $>100\%$ mass enhancements. The simulations also predict systematically lower gas fractions due to sustained post-collision star formation, yielding a clean observational signature. Upcoming wide-field imaging (CSST, LSST), HI surveys (FAST), and kinematic follow-up will be crucial to test this scenario.

We present a systematic observational study of the spin alignment between galaxy groups and their central galaxies using a large spectroscopic sample from the Sloan Digital Sky Survey. Unlike previous studies based on morphology or major axis alignment, we use spin as a direct, dynamically motivated probe. To match the limitations of observational data, the group spin, central-galaxy spin, and alignment angle are defined and measured in projection on the sky plane. By applying two novel spin estimators for galaxy groups, we find strong statistical evidence for a preferential alignment, with a mean projected angle of $34.17^\circ \pm 0.29^\circ$, significantly deviating from random expectation at $37.77\sigma$. This alignment signal persists across a wide range of group and galaxy properties, but its strength is modulated by mass, morphology, and color. Specifically, we find that more massive groups and more massive central galaxies exhibit stronger alignment. Furthermore, elliptical central galaxies show stronger alignment than spirals, and bluer central galaxies are more strongly aligned than redder ones. Our results suggest a close dynamical link between the spin of central galaxies and their host groups, modulated by their physical properties and star formation history. These results provide new insights into the dynamical connection between central galaxies and their host dark matter halos.

We examine the use of a novel variant of Physics-Informed Neural Networks to predict cosmological parameters from recent supernovae and baryon acoustic oscillations (BAO) datasets. Our machine learning framework generates uncertainty estimates for target variables and the inferred unknown parameters of the underlying PDE descriptions. Built upon a hybrid of the principles of Evidential Deep Learning, Physics-Informed Neural Networks, Bayesian Neural Networks and Gaussian Processes, our model enables learning of the posterior distribution of the unknown PDE parameters through standard gradient-descent based training. We apply our model to an up-to-date BAO dataset (Bousis et al. 2024) calibrated with the CMB-inferred sound horizon, and the Pantheon$+$ Sne Ia distances (Scolnic et al. 2018), examining the relative effectiveness and mutual consistency among the standard $\Lambda$CDM, $w$CDM and $\Lambda_s$CDM models. Unlike previous results arising from the standard approach of minimizing an appropriate $\chi^2$ function, the posterior distributions for parameters in various models trained purely on Pantheon$+$ data were found to be largely contained within the $2\sigma$ contours of their counterparts trained on BAO data. Their posterior medians for $h_0$ were within about $2\sigma$ of one another, indicating that our machine learning-guided approach provides a different measure of the Hubble tension.

We investigate the feasibility of accurately determining the helium-to-metal enrichment ratio, $\Delta Y/\Delta Z$, from Gaia DR3 photometry for nearby low-mass main sequence field stars. We selected a sample of 2770 nearby MS stars from the Gaia DR3 catalogue, covering a Gaia $M_G$ absolute magnitude range of 6.0 to 6.8 mag. We computed a dense grid of isochrones, with $\Delta Y/\Delta Z$ varying from 0.4 to 3.2. These models were then used to fit the observations using the SCEPtER pipeline. The fitted values indicated that $\Delta Y/\Delta Z$ values of $1.5 \pm 0.5$ were dequate for most stars. However, several clues suggested caution ought to be taken in interpreting this result. Chief among these concerns is the trend of decreasing $\Delta Y/\Delta Z$ with increasing $M_G$ magnitude, as well as the discrepancy between the red and blue parts of the observations. This result is further supported by our additional analysis of mock data, which were sampled and fitted from the same isochrone grid. In the mock data, no such trend emerged, while the uncertainty remained as large as 0.7. The robustness of our conclusions was confirmed by repeating the estimation using isochrones with Gaia magnitudes derived from different atmospheric models and by adopting a different stellar evolution code for stellar model computation. In both cases, the results changed drastically, clustering at $\Delta Y/\Delta Z \approx 0.4$, which is at the lower end of the allowed values. Considering the current uncertainties affecting stellar model computations, it appears that adopting field stars for calibration is not a viable approach, even when adopting precise Gaia photometry.

Investigating the bubbles generated by the interaction between asymptotic giant branch stellar outflows and the interstellar medium (ISM) is pivotal for elucidating the mechanism by which evolved low- to intermediate-mass stars enrich the ISM with heavy elements. Using archival datasets from the Galactic Plane Pulsar Snapshot survey and the Galactic Arecibo L-Band Array \ion{H}{1} survey, we have identified 14 bubbles within interstellar atomic hydrogen (\ion{H}{1}) maps, each showing evidence of potential association with planetary nebulae (PNe).We pursue two primary objectives centered on the identified ISM bubbles and their association with PNe. First, leveraging the calibrated distance measurements of PNe from Gaia Data Release 3, we utilize these ISM bubbles as observational tracers to investigate and constrain the Galactic rotation curve. Second, we note that distance determinations for some PNe remain unreliable, partly because their central stars are obscured by extended nebular envelopes or are misidentified. Therefore, we develop a novel methodological framework to derive kinematic distances for PNe by leveraging the velocities of their associated ISM bubbles and constraints from the Galactic rotation curve.

The Nancy Grace Roman Space Telescope (Roman) will unveil for the first time the full architecture of planetary systems across Galactic distances through the discovery of up to 200,000 cool and hot exoplanets using microlensing and transit detection methods. Roman's huge exoplanet haul, and Galactic reach, will require new methods to leverage the full exoplanet demographic content of the combined microlensing and transit samples, given the different sensitivity bias of the techniques to planet and host properties and Galactic location. We present a framework for technique-agnostic exoplanet demography (TAED) that can allow large, multi-technique exoplanet samples to be combined for demographic studies. Our TAED forward modelling and retrieval framework uses parameterised model exoplanet demographic distributions to embed planetary systems within a stellar population synthesis model of the Galaxy, enabling internally consistent forecasts to be made for all detection methods that are based on spatio-kinematic system properties. In this paper, as a first test of the TAED framework, we apply it to simulated transit datasets based on the Kepler Data Release 25 to assess parameter recovery accuracy and method scalability for a single large homogeneous dataset. We find that optimisation using differential evolution provides a computationally scalable framework that gives a good balance between computational efficiency and accuracy of parameter recovery.

We study the analysis method to determine the cosmic-ray energy spectra of different mass groups assuming the use of the Tibet AS$\gamma$ experiment, which consists of the high-density Tibet air-shower array (Tibet-AS) and the underground muon detector (MD) array. These arrays measure the sampling air shower size $\Sigma\rho$ and the total muon number $\Sigma N_{\mu}$ of each air shower event. These parameters are known to contain information on the energy and mass of the primary particle. To reconstruct the energy spectra of individual cosmic-ray mass groups, we apply a multidimensional unfolding method based on Bayes' theorem to the two-dimensional distribution of $\Sigma\rho$ and $\Sigma N_{\mu}$ produced by Monte Carlo simulation. Simulated datasets with combinations of the EPOS-LHC, SIBYLL-2.3c, and QGSJET~II-04 high-energy hadronic interaction models and a helium-dominant composition model are analyzed while using a response matrix produced by EPOS-LHC. The unfolded spectra of the EPOS + helium-dominant composition model dataset show a deviation from the input flux within $\pm$10\% except for a few bins, meaning that the uncertainty of the technique itself and the composition model dependence is at that level. It is also shown that the deviation in the all-particle spectrum is within $\pm$10\% even when using different hadronic interaction models in the dataset and the response matrix. On the other hand, the unfolded spectra of individual mass groups have a clear dependence on the hadronic interaction model. The model dependence of the proton and helium spectra amounts to \pm25% below 10$^{6.5}$ GeV. The dependence in the carbon group is at a \pm25% level below 10$^{6}$ GeV, and for the iron spectrum, it amounts to +55% and -30% in the energy range of 10$^{5.1}$ GeV to 10$^{6.7}$ GeV.

The ASTRI Mini-Array consists of nine Cherenkov telescopes under construction at the Observatorio del Teide, with one of them already performing observations since November 2024. Given the complexity of the analysis of gamma-ray data acquired with Cherenkov telescopes, a proper evaluation of the quality of these data is important to avoid a negative impact on the high-level scientific products. There are several factors that can contribute to reducing the quality of the observations, such as clouds, high humidity or a high dust concentration in the air, among others. In order to take all these factors into account and evaluate their impact on the data, a quality check pipeline has been developed for ASTRI. This contribution describes the pipeline, from its inputs at different data levels to the production of outputs in the form of good-quality lists and diagnostic plots. We also show how setting preliminary quality cuts on the Crab Nebula data taken with the first ASTRI telescope can significantly improve the source detection.

Gamma-ray bursts (GRBs) originate from explosions at cosmological distances, generating collimated jets. GRB 221009A, exploded on 9 October 2022, has been established as the brightest GRB to date. Its bright and long emission was extensively followed up from radio to gamma rays. LHAASO firmly detected the onset of the afterglow emission at energies up to $\sim$13 TeV within about an hour after the burst, starting just a few minutes after the trigger. While this VHE emission component can be accounted for in a narrow jet scenario, such an interpretation cannot reproduce the broadband emission observed at later times, which exceeds the theoretical expectations. This discrepancy can be settled if more complex models are considered, providing the first strong evidence for a structured jet in a long GRB. Unfortunately, the VHE emission after a few hours is poorly constrained, as sensitive VHE observations by Cherenkov Telescopes were prevented due to strong moonlight conditions. The first Large-Sized Telescope (LST-1) of the future Cherenkov Telescope Array Observatory began observations about one day after the burst under high night sky background conditions. These observations are the first ones performed on GRB 221009A by a Cherenkov telescope, revealing a hint of a signal with a statistical significance of about 4$\sigma$ during the observations performed at 1.3 days after the burst. The monitoring campaign continued until the end of November 2022, making it the deepest observation campaign performed on a GRB with the LST-1. In this contribution, we will present the analysis results of the LST-1 observation campaign on GRB 221009A in October 2022.

The Gaia mission's third data release recorded low-resolution spectra for about 100 000 white dwarf candidates. A small subset of these spectra show evidence of characteristic broad Ca II absorption features, implying the accretion of rocky material by so-called polluted white dwarfs -- important probes of the composition of exoplanetary material. Several supervised and unsupervised data-intensive methods have recently been applied to identify polluted white dwarfs from the Gaia spectra. We present a comparison of these methods, along with the first application of $t$-distributed stochastic neighbour embedding ($t$SNE) to this dataset. We find that $t$SNE outperforms the similar technique Uniform Manifold Approximation and Projection (UMAP), isolating over 50% more high-confidence polluted candidates, including 39 new candidates which are not selected by any other method investigated and which have not been observed at higher resolution. Supervised methods benefit greatly from data labels provided by earlier works, selecting many known polluted white dwarfs which are missed by unsupervised methods. Our work provides a useful case study in the selection of members of rare classes from a large, sporadically labelled dataset, with applications across astronomy.

The Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based observatory for very-high-energy (VHE) gamma-ray astronomy. The Large-Sized Telescope prototype, LST-1, located on the Canary Island of La Palma, is responsible for observation of the low-energy range of the VHE gamma-ray spectrum. It is undergoing commissioning and has already observed the Crab Nebula as a standard reference source. Accurate reconstruction of shower parameters (e.g. energy, direction, and particle type) is crucial for achieving the scientific goals of the CTAO. In this work, we use CTLearn to implement deep-learning event reconstruction, as an alternative to the standard Random Forest method. CTLearn is built to be fully compatible with ctapipe, a framework for prototyping the low-level data processing algorithms for the CTAO, and can be seamlessly used for data analysis without changing the general framework. It implements convolution-neural-network based models that take the integrated charge and the relative peak time of calibrated pixels in cleaned images as an input, to infer the primary particle's properties. Using Crab Nebula observations as a validation sample, we explore two different approaches. The first is to train a model with Monte-Carlo (MC) simulations covering all possible altitude-azimuth coordinates of the Crab Nebula sample observations, resulting in a single model that can be used to reconstruct events from any Crab Nebula observations. The second approach is to train 10 models along this coordinate line, each incorporating a range of \textasciitilde10° in altitude. In this contribution, we present our investigation of the performance of CTLearn models, and highlight the potential of CTLearn for future data analysis in the CTAO.

The Cherenkov Telescope Array Observatory (CTAO) will be the next-generation major ground-based gamma-ray observatory. It will be made up of two large arrays of imaging atmospheric Cherenkov telescopes (IACTs), with one site in the Northern hemisphere (La Palma, Canary Islands) and one in the Southern (Paranal, Chile). CTAO aims to offer great improvement in energetic and angular resolution with respect to current IACT systems, spanning a photon energy range from 20 GeV to 300 TeV, as well as a significantly larger effective area and full-sky coverage. Besides a percentage of observational time available for external proposals, making it the first open gamma-ray observatory, the core observational program of CTAO is organized in several Key Science Projects. A significant amount of time will be devoted to dark matter (e.g. WIMPs, axion-like particles) and fundamental physics studies from a variety of targets, including the Milky Way's Galactic centre, dwarf spheroidal galaxies, the Large Magellanic Cloud, and extragalactic objects such as blazars. In this contribution, an overview of CTAO's main features is provided, with a focus on its capabilities to investigate these yet unanswered questions of modern physics.

Axion-like particles (ALPs) are a common prediction of several extensions of the Standard Model of particle physics and could be detected through their coupling to photons, which enables ALP-photon conversions in external magnetic fields. This conversion could lead to two distinct signatures in gamma-ray spectra of blazars: a superimposition of energy-dependent "wiggles" on the spectral shape, and a hardening at high (multi-TeV) energies, due to the ALP beam eluding absorption by the extragalactic background light (EBL). The enhanced energy resolution of the Cherenkov Telescope Array Observatory (CTAO) with respect to present ground-based gamma-ray telescopes makes it an ideal instrument to probe such phenomena. In this contribution, we explore a different approach based on the use of machine learning (ML) classifiers and compare it to the standard method. Our preliminary results suggest that both techniques yield consistent results, with the ML-based method offering comparable or even slightly broader coverage, potentially extending the CTAO sensitivity beyond existing constraints.

Understanding the origin and evolution of carbon-enhanced metal-poor (CEMP) stars is key to tracing the Galaxy's early chemical enrichment. We investigate how realistic 3D radiation-hydrodynamics (RHD) model atmospheres affect carbon abundances in CEMP stars and implications for their classification and Galactic chemical evolution (GCE). We focus on biases from traditional 1D hydrostatic models. We use the M3DIS code to compute 3D RHD model atmospheres for main-sequence and sub-giant stars over a wide range of metallicities and carbon enhancements. Synthetic spectra of the CH G-band are calculated with 3D radiative transfer and compared to spectra from classical 1D MARCS models. We derive abundance corrections and apply them to a large SAGA database sample to quantify effects on the carbon abundance distribution and CEMP classification. Our new 3D CEMP models predict cooler upper atmospheric layers than in 1D models, resulting in stronger CH absorption and lower inferred carbon abundances by up to -0.9 dex at the lowest metallicities. Carbon enhancement in the atmosphere itself increases molecular opacities and leads to radiative re-heating, partly offsetting adiabatic cooling in 3D models and reducing 3D-1D abundance corrections. Applying these corrections lowers the CEMP fraction by up to 20% below [Fe/H]=-3 and alters the relative contribution of CEMP sub-classes. The fraction of CEMP-no stars increases while the number of CEMP-r/s stars decreases, due to the downward revision of absolute carbon abundances. These changes bring the Galactic carbon distribution into better agreement with GCE models assuming a 20% contribution from faint supernovae. Realistic model atmospheres are essential to reliably reconstruct the Galaxy's early chemical enrichment history.

Context. The dynamical evolution of open clusters in the tidal field of the Milky Way and the feeding of the disc field star population depend strongly on the initial conditions at the time of gas removal. Detailed dynamical models tailored to individual clusters help us understand the role of open clusters in the Galactic disc evolution. Aims. We present a detailed dynamical model of Praesepe, which reproduces the mass profile, the stellar mass function, and the mass segregation observed with the help of Gaia EDR3 data. Based on this model, we investigate the kinematic properties of the tidal tail stars in detail. Methods. We used direct N-body simulations along the eccentric orbit of Praesepe in the tidal field of the Milky Way, where each particle represents one star. The initial mass and size of the cluster, the dynamical state, and the initial mass function were adapted to reach the best-fitting model. Based on this model and a comparison model on a circular orbit, we analysed the stars in the tidal tails in terms of density, angular momentum, and orbit shapes. Results. Praesepe can be well reproduced by a cluster model with concentrated star formation in a supervirial state after instantaneous gas expulsion, adopting a global star formation efficiency of 17%. About 75% of the initially 7500 MSol are lost in the violent relaxation phase, and the observed mass segregation can be understood by two-body relaxation. We find that the self-gravity of the tail stars is the dominant force altering the angular momentum of the tail stars. For a typical star, the total change after escaping is about 1.6 kpc km/s. This corresponds to an offset in guiding radius of 7 pc, where tail stars contribute up to 70% to the alteration. The total radial shift of the orbit of the cluster in the Galactic plane can exceed 50 pc. This effect is not a result of the eccentricity of the orbit.

We report three epochs of polarized images of M87* at 230\,GHz using data from the Event Horizon Telescope (EHT) taken in 2017, 2018, and 2021. The baseline coverage of the 2021 observations is significantly improved through the addition of two new EHT stations: the 12\,m Kitt Peak Telescope and the Northern Extended Millimetre Array (NOEMA). All observations result in images dominated by a bright, asymmetric ring with a persistent diameter of $43.9\pm 0.6\,\muas$, consistent with expectations for lensed synchrotron emission encircling the apparent shadow of a supermassive black hole. We find that the total intensity and linear polarization of \m87 vary significantly across the three epochs. Specifically, the azimuthal brightness distribution of the total intensity images varies from year to year, as expected for a stochastic accretion flow. However, despite a gamma-ray flare erupting in M87 quasi-contemporaneously to the 2018 observations, the 2018 and 2021 images look remarkably similar. The resolved linear polarization fractions in 2018 and 2021 peak at $\sim$5\%, compared to $\sim$15\% in 2017. The spiral polarization pattern on the ring also varies from year to year, including a change in the electric vector position angle helicity in 2021 that could reflect changes in the magnetized accretion flow or an external Faraday screen. The improved 2021 coverage also provides the first EHT constraints on jet emission outside the ring, on scales of $\lesssim 1$\,mas. Overall, these observations provide strong proof of the reliability of the EHT images and probe the dynamic properties of the horizon-scale accretion flow surrounding \m87.

During the evolution of protoplanetary disks, dust grains start to grow, form larger particles, settle to the midplane, and rearrange the disk, mainly by the inward radial drift. Because of this, dust pebbles with an irregular shape usually align mechanically and thus cause polarization signatures in their thermal radiation due to dichroic emission or absorption. The goal of this paper is to evaluate the potential to trace the impact of mechanical grain alignment in protoplanetary disks on the observed degree and orientation of linear polarization at millimeter wavelengths. We combined 3D radiation hydrodynamical simulations to determine the density distribution and the velocity field of gas and dust particles, Monte Carlo dust-gas interaction simulations to calculate the mechanical alignment of dust in a gas flow, and, finally, 3D Monte Carlo polarized radiative transfer simulations to obtain synthetic polarimetric observations. We find that large grains, which contribute the most to the net polarization, are potentially mechanically aligned in the protoplanetary disk under the effect of the vertical shear instability (VSI). Thereby, the drift velocity is parallel to the rotational disk axis. Assuming oblate dust grains that are aligned with their short axis parallel to the direction of the drift velocity, the resulting polarization is usually along the major axis of the disk. This is in contrast to typical drift models that propose either a radial or azimuthal drift velocity component. If hydrodynamical instabilities, such as the VSI, dominate the kinematics in protoplanetary disks, the mechanical alignment of dust is a promising mechanism for grain alignment in these systems. In that case, the resulting millimeter polarization allows us to trace the orientation of aligned millimeter-sized grains.

Recent measurements suggest that Uranus may exhibit a higher tidal dissipation than previously assumed. This enhanced dissipation leads to a faster orbital migration of its five major moons: Miranda, Ariel, Umbriel, Titania, and Oberon. Consequently, resonant encounters that have always been discarded in previous works need to be included. In particular, Ariel's fast migration implies that the crossing of the 2:1 mean motion resonance with Umbriel is extremely likely and it could have occurred in recent times. Capture into this strong resonance would have induced significant tidal heating within Ariel, possibly explaining its resurfacing. Therefore, in this work, we aim to explore the orbital history of the Uranian moons in a context of fast tidal migration, including the crossing of the 2:1 mean motion resonance between Ariel and Umbriel. For small initial eccentricities, we confirm that the moons are always captured into this resonance. As the system is not currently involved in any mean motion resonance, we investigated possible dynamical mechanisms for exiting the 2:1 resonance. We show that the resonance could have been broken by a further resonant encounter with Titania. We analyzed the crossing of the 4:2:1 and 3:2:1 resonant chains, and looked for the parameter space where the probability of escaping the resonance is maximized. Taking a dissipative parameter of Ariel $k_{2,2}/Q_2<10^{-3}$, the passage through the 3:2:1 resonance succeeds in disrupting the 2:1 Ariel-Umbriel mean motion resonance in more than $60\%$ of our numerical experiments. A fraction of our simulations results in final low eccentricities and inclinations, which can eventually match the current orbital features of the system. As the proposed orbital history requires specific ranges of the dissipative parameters for the system, future Uranus mission data will validate (or disprove) this scenario.

The powerful combination of Gaia with other Milky Way large survey data has ushered in a deeper understanding of the assembly history of our Galaxy, which is marked by the accretion of Gaia-Enceladus/Sausage (GES). As a step towards reconstructing this significant merger, we examine the existence and destruction of its stellar metallicity gradient. We investigate 8 GES-like progenitors from the Auriga simulations and find that all have negative metallicity gradients at infall with a range of -0.09 to -0.03 dex/kpc against radius and -1.99 to -0.41 dex/$\rm 10^{-5} km^{2}s^{-2}$ against the stellar orbital energy. These gradients get blurred and become shallower when measured at $z=0$ in the Milky Way-like host. The percentage change in the radial metallicity gradient is consistently high (78-98\%), while the percentage change in the energy space varies much more (9-91\%). We also find that the most massive progenitors show the smallest changes in their energy metallicity gradients. At the same present-day galactocentric radius, lower metallicity stars originate from the outskirts of the GES progenitor. Similarly, at fixed metallicity, stars at higher galactocentric radii tend to originate from the GES outskirts. We find that the GES stellar mass, total mass, infall time, and the present-day Milky Way total mass are correlated with the percentage change in metallicity gradient, both in radius and in energy space. It is therefore vital to constrain these properties further to pin down the infall metallicity gradient of the GES progenitor and understand the onset of such ordered chemistry at cosmic noon.

We investigate the hemispherical power asymmetry observed in the CMBR by attributing it to an early inhomogeneous phase of cosmic expansion. Unlike the conventional assumption of a perfectly isotropic and homogeneous pre-inflationary Universe, we introduce a small inhomogeneous perturbation, treated within a perturbative framework. Our analysis builds on previously developed empirical models of inhomogeneous primordial power spectrum models based on dipole modulation. Using in-in formalism, we compute two-point correlations directly from the metric and demonstrate that, at leading order, this introduces a direction-dependent power spectrum that breaks rotational symmetry and naturally selects a preferred direction, relating observed violation of the cosmological principle to inflationary power spectra arising from scalar field fluctuations. Additionally, we find that this framework produces correlations between multipoles separated by $\Delta l=1$, leading to distinctive signatures in the multipole space. Furthermore, we constrain the parameters of the inhomogeneous perturbation using observed PR4 \texttt{Commander} CMB data.

SymBoltz is a new Julia package that solves the linear Einstein-Boltzmann equations. It features a symbolic-numeric interface for specifying equations, is free of approximation switching schemes and is compatible with automatic differentiation. Cosmological models are built from replaceable physical components in a way that scales well in model space. The modeler should simply write down their equations, and SymBoltz solves them and eliminates much of the friction in the process. SymBoltz enables up to 100x shorter model definitions compared to browsing equivalent files in CLASS. Symbolic knowledge enables powerful automation of tasks, such as separating computational stages like the background and perturbations, generating the Jacobian matrix and its sparsity pattern, and interpolating arbitrary expressions from the solution. Modern implicit solvers integrate the full stiff equations at all times, reducing slowdowns by taking long time steps, reusing the Jacobian and LU-factorizing it over several time steps, and using fast linear system solvers. Automatic differentiation gives exact derivatives of any output with respect to any input, which is important for gradient-based Markov chain Monte Carlo methods in large parameter spaces, training of emulators, Fisher forecasting and sensitivity analysis. These features are useful in their own rights, but also reinforce each other in a synergy. Results agree with established codes like CLASS and CAMB. With more work, SymBoltz can grow into an integrated symbolic-numeric cosmological modeling environment with a large library of models that delivers differentiable output as fast as other codes. SymBoltz is available at this https URL with single-command installation and extensive documentation, and welcomes questions, suggestions and contributions.

In situ measurements of kinetic scale current sheets in the solar wind show that they are often approximately force-free although the plasma beta is of order one. They frequently display systematic asymmetric and anti-correlated spatial variations of their particle density and temperature across the current sheet, leaving the plasma pressure essentially uniform. These observations of asymmetries have previously been modelled theoretically by adding additional terms to both the ion and electron distribution functions of self-consistent force-free collisionless current sheet models with constant density and temperature profiles. In this paper we present the results of a modification of these models in which only the electron distribution function has a term added to it, whereas the ion distribution function is kept as a thermal (Maxwellian) distribution function. In this case the nonlinear quasineutrality condition no longer has a simple analytical solution and therefore has to be solved alongside Ampère's law. We find that while the magnetic field remains approximately force-free, the non-zero quasineutral electric field gives rise to an additional spatial substructure of the plasma density inside the current sheet. We briefly discuss the potential relation between our theoretical findings and current sheet observations.

Dust growth from micron- to planet-size in protoplanetary discs involves multiple physical processes, including dust growth and fragmentation, the streaming instability, and pebble accretion. Disc turbulence and dust fragility matter at almost every stage. Previous studies typically vary one of them while fixing the other, failing to provide a complete picture. Here, we use analytical models and numerical dust evolution models DustPy to study the combinations of gas turbulence and dust fragility that can reproduce multi-wavelength ALMA observables. We find only appropriate combinations -- fragile dust (fragmentation velocity $v_\mathrm{frag}$= 1-2 m/s) in discs with viscous $\alpha=10^{-4}$ or resilient dust ($v_\mathrm{frag}$= 6-10 m/s) in discs with viscous $\alpha=10^{-3}$ -- can reproduce observations. Our result is robust to two widely used opacities (DSHARP and Ricci opacities). Regardless of the strength of disc turbulence, reproducing observations requires observed dust rings to be optically thick at $\lambda=1.3$ and $3$ mm. As only small dust can be lifted above the midplane to reach the emitting layers, SED analysis probably yields lower limits on the maximum grain sizes. We highlight the challenge of creating detectable dust rings at large radii when incorporating bouncing in models, and the need for earlier formation of dust rings at smaller radii to reproduce the decreasing ring brightness with radius observed across ALMA wavelengths.

Markov Chain Monte Carlo (MCMC) excels at sampling complex posteriors but traditionally lags behind nested sampling in accurate evidence estimation, which is crucial for model comparison in astrophysical problems. We introduce reddemcee, an Adaptive Parallel Tempering Ensemble Sampler, aiming to close this gap by simultaneously presenting next-generation automated temperature-ladder adaptation techniques and robust, low-bias evidence estimators. reddemcee couples an affine-invariant stretch move with five interchangeable ladder-adaptation objectives, Uniform Swap Acceptance Rate, Swap Mean Distance, Gaussian-Area Overlap, Small Gaussian Gap, and Equalised Thermodynamic Length, implemented through a common differential update rule. Three evidence estimators are provided: Curvature-aware Thermodynamic Integration (TI+), Geometric-Bridge Stepping Stones (SS+), and a novel Hybrid algorithm that blends both approaches (H+). Performance and accuracy are benchmarked on n-dimensional Gaussian Shells, Gaussian Egg-box, Rosenbrock Functions, and exoplanet radial-velocity time-series of HD 20794. Across Shells up to 15 dimensions, reddemcee presents roughly 7 times the effective sampling speed of the best dynamic nested sampling configuration. The TI+, SS+ and H+ estimators recover estimates under 3 percent error and supply realistic uncertainties with as few as six temperatures. In the HD 20794 case study, reddemcee reproduces literature model rankings and yields tighter yet consistent planetary parameters compared with dynesty, with evidence errors that track run-to-run dispersion. By unifying fast ladder adaptation with reliable evidence estimators, reddemcee delivers strong throughput and accurate evidence estimates, often matching, and occasionally surpassing, dynamic nested sampling, while preserving the rich posterior information which makes MCMC indispensable for modern Bayesian inference.

YSOs can display unpredictable and high-amplitude rises in brightness that can last from a few months to possibly over 100 years. These types of outbursts are explained by large changes in the mass accretion rate from the disk onto the central star. The outbursts support to a model of star formation (episodic accretion) where stars would spend most of their lifetimes accreting at low rates, and gain most of their mass through these short-lived accretion outbursts. The universality of episodic accretion, as well as its potential impact on stellar and planetary formation are still under debate. Improvement on the statistics of the members of the eruptive class is needed to better understand the episodic accretion phenomenon and its universality across different mass regimes and environments. In this paper we collect published information on the spectroscopic and photometric characteristics of 174 YSOs confirmed to belong to the eruptive variable class. We classify these objects into five different sub-classes (we find 49 FUor, 20 FUor-like, 16 EX Lupi-type, 81 Peculiar/V1647 Ori-like/MNors and 8 Periodic YSOs). The classification follows what has been done previously in the literature, and it is not an attempt to redefine these classes. In addition, we present a list of 18 embedded, and 6 massive YSOs, as additional categories of eruptive variable YSOs. Due to the complexity and/or faintness of these systems, it is hard to place them into the original classification scheme of this class of variable YSOs. Finally, we present a separate list of 355 candidate eruptive variable YSOs, which either lack spectroscopic information or the available spectroscopic data is not sufficient for an unambiguous classification. The online catalogue of confirmed and candidate eruptive YSOs will be maintained and updated in the future to serve as an important reference for the star formation community.

Using ultra-deep JWST NIRCam imaging from the GLIMPSE Survey, enhanced by gravitational lensing of the AbellS1063 cluster, we investigate the faintest galaxies ever observed in the redshift range z~9 to z~15. We identify 105 galaxy candidates within this range, spanning absolute ultraviolet (UV) magnitudes from M_UV~-18 to M_UV~-13 mag, about three magnitudes fainter, on average, than prior JWST studies. We place strong constraints on the ultra-faint end of the UV luminosity function (UVLF), finding minimal evolution in the faint-end slope, which varies from $\alpha=-2.01\pm0.20 at z=9 to \alpha=-2.10\pm0.19$ at z=13. This behaviour contrasts with the rapid evolution of the faint-end slope observed from z~0 to z~9. By integrating the UVLF down to M_UV=-16, we derive the cosmic star formation rate density (SFRD)from z=9 to z=13, revealing a best-fit redshift evolution that follows $\propto(1+z)^{-2.94^{+0.06}_{-0.10}}$. This slope is significantly shallower than predictions from most theoretical models. Extending the integration limit to M_UV=-13, we find that galaxies fainter than M_UV=-16 contribute more than 50% of the total cosmic SFR density at z~12. The observed excess in the cosmic SFRD at these high redshifts may suggest an enhancement in the star formation efficiency during the earliest phases of galaxy formation. Alternatively, this could result from other physical mechanisms, such as bursty star formation histories; minimal dust attenuation; or an evolving initial mass function. However, existing models that incorporate these scenarios fail to fully reproduce the observed redshift evolution of SFRD. Finally, we acknowledge the potential impact of low-redshift contamination and cosmic variance, as the small survey volume may not represent the broader galaxy population. Similar observations in different fields and spectroscopic confirmation are required to validate these findings

The stochastic gravitational wave background (SGWB) reveals valuable information about its origin and the Universe. The pulsar timing arrays (PTAs) are suitable indicators for detecting SGWB within the nano-Hertz frequency range. In this work, we propose a graph-based method implemented on the pulsar timing residuals (PTRs) for SGWB detection and examining uncertainties of its parameters. We construct a correlation graph with pulsars as its nodes, and analyze the graph-based summary statistics, which include topological and geometrical characteristics, for identifying SGWB in real and synthetic datasets. The effect of the number of pulsars, the observation time span, and the strength of the SGWB on the graph-based feature vector is evaluated. Our results demonstrate that the merit feature vector for common signal detection consists of the average clustering coefficient and the edge weight fluctuation. The SGWB detection conducted after the observation of a common signal and then exclusion of non-Hellings \& Downs templates is performed by the second cumulant of edge weight for angular separation thresholds $\bar{\zeta}\gtrsim 40^{\circ}$. The lowest detectable value of SGWB strain amplitude utilizing our graph-based measures at the current PTAs sensitivity is $A_{\rm SGWB}\gtrsim 1.2\times 10^{-15}$. Fisher forecasts confirmed that the uncertainty levels of $\log_{10} A_{\rm SGWB}$ and spectral index reach $2.2\%$ and $28.3\%$, respectively, at $2\sigma$ confidence interval. Evidence for an SGWB at the $3\sigma$ level is obtained by applying our graph-based method to the NANOGrav 15-year dataset.

Three-dimensional simulations of relativistic jets are a useful tool to understand the evolution of jets and radio galaxies in detail. However, computationally demanding as they are, their use is limited to a relatively small number of representative cases. When comparing to the distribution of large samples of objects in the luminosity-distance plane (P-D plane), the most efficient approach is to use analytical or semi-analytical models that reproduce the evolution of the main parameters governing the dynamics and radio luminosity of the sources. Our aim is to build a semi-analytical model that allows us to produce mock samples of radio galaxies to be compared with real populations and use this approach to constrain the general properties of active galaxies with jets in a cosmological context. In this work, we present a new model for the evolution of radio galaxies based on the resolution of ordinary differential equations and inspired both by previous experience on numerical simulations of jets across several orders of magnitude in power, and by observational evidence. Our results show remarkable agreement between the results given by the semi-analytical model and those obtained by both 2D and 3D relativistic hydrodynamics simulations of jets ranging from 1.e35 W to 1.e39 W. From the derived trajectories of powerful radio galaxies through the P-D diagram (powers greater than 1.e36 W), our model agrees with typical lifetimes of galactic activity of < 500 Myr. We also compare our results with previous models in the literature. In a follow-up paper, we use this model to generate mock populations of radio galaxies at low redshifts and compare them to the LoTSS sample.

Inferring parameters and testing hypotheses from gravitational wave signals is a computationally intensive task central to modern astrophysics. Nested sampling, a Bayesian inference technique, has become an established standard for this in the field. However, most common implementations lack the ability to fully utilize modern hardware acceleration. In this work, we demonstrate that when nested sampling is reformulated in a natively vectorized form and run on modern GPU hardware, we can perform inference in a fraction of the time of legacy nested sampling implementations whilst preserving the accuracy and robustness of the method. This scalable, GPU-accelerated approach significantly advances nested sampling for future large-scale gravitational-wave analyses.

The EXTraS project, based on data collected with the XMM-Newton observatory, provided us with a vast amount of light curves for X-ray sources. For each light curve, EXTraS also provided us with a set of features (this https URL). We extract from the EXTraS database a tabular dataset of 31,832 variable sources by 108 features. Of these, 13,851 sources were manually labeled as stellar flares or non-flares based on direct visual inspection. We employ a supervised learning approach to produce a catalog of stellar flares based on our dataset, releasing it to the community. We leverage explainable AI tools and interpretable features to better understand our classifier. We train a gradient boosting classifier on 80\% of the data for which labels are available. We compute permutation feature importance scores, visualize feature space using UMAP, and analyze some false positive and false negative data points with the help of Shapley additive explanations -- an AI explainability technique used to measure the importance of each feature in determining the classifier's prediction for each instance. On the test set made up of the remainder 20\% of our labeled data, we obtain an accuracy of 97.1\%, with a precision of 82.4\% and a recall of 73.3\%. Our classifier outperforms a simple criterion based on fitting the light curve with a flare template and significantly surpasses a gradient-boosted classifier trained only on model-independent features. False positives appear related to flaring light curves that are not associated with a stellar counterpart, while false negatives often correspond to multiple flares or otherwise peculiar or noisy curves. We apply our trained classifier to currently unlabeled sources, releasing the largest catalog of X-ray stellar flares to date. [abridged]

We present JWST/MIRI observations of the debris disk surrounding the nearby, solar analog Epsilon Eridani obtained as part of the Archetypal Debris Disk GTO program. Multi-wavelength images from 15, 18, 21, and 25.5 $\mu m$ show a smooth dust distribution with no evidence of sculpting by massive planets outside of 5 au. Maps of the color temperature and opacity constrain the dust properties while radiative transfer modeling of a warm dust component traces the interaction between the debris disk and Epsilon Eri b ($\sim$3.5 au). Dynamical and collisional modeling further shows that the disk morphology is dominated by dust produced in the outer planetesimal belt ($\sim 70 \, au$) moving inward via stellar wind drag. We confirm the presence of a disk interior to the Epsilon Eri b orbit first detected from mid-IR interferometry. Drag dominated inner disk regions have also been observed around Vega and Fomalhaut hinting at the diversity of asteroid belt analogs.

It has long been thought that nuclear star clusters (NSCs) cannot co-exist with the most massive supermassive black holes (SMBHs), since SMBH mergers - unavoidable for the most massive systems - would scatter away NSC stars. However, central concentrations of light have now been reported in up to a third of all massive ellipticals. We present a new mechanism for forming NSCs in giant elliptical galaxies, arising naturally from SMBH mergers, which could explain these observations. We call this ''black hole dragging''. After a major merger of two galaxies and their SMBHs, the newly-merged SMBH can receive a gravitational wave recoil kick. We show that recoiling SMBHs induce two competing effects on the galaxy's background stars. Firstly, some stars become bound to the SMBH and co-move with it, an effect strongest at low recoil velocities. Secondly, background stars are ejected as the recoiling SMBH falls back due to dynamical friction, an effect strongest at high recoil velocities. At intermediate recoil velocities (500-1000 km/s), both effects become important, and the density of bound stars can exceed that of the background stellar core. This yields a central dense NSC that is clearly visible in the galaxy's surface brightness profile. We show that NSCs formed in this way have realistic sizes, masses and velocity dispersions when measured similarly to observed systems. This provides a route for even giant ellipticals containing SMBHs to host an NSC. We predict such NSCs should have indistinguishable colors, ages and chemistry from non-NSC central stars, combined with low ellipticities.

Axion inflation represents an intriguing source of gravitational waves (GWs) from the early Universe. In a companion paper arXiv:2508.00798, we previously leveraged the gradient expansion formalism (GEF) to investigate pure axion inflation (PAI), i.e., axion inflaton coupled to a pure gauge sector. In this paper, we extend our analysis to fermionic axion inflation (FAI), i.e., we allow for the presence of fermions in the gauge sector. PAI predicts a strongly blue-tilted GW spectrum; in our GEF benchmark study, all parameter regions leading to observable GWs turned out to violate the upper limit on the number of extra relativistic degrees of freedom, $\Delta N_{\rm eff}$. As we demonstrate in this paper, the situation is different for FAI: Schwinger pair creation of the charged fermions results in a damping of the gauge-field production, which attenuates the GW signal. As a result, the GW signal from FAI can fall into the sensitivity reach of LISA and ET without violating the upper limit on $\Delta N_{\rm eff}$. This result notably applies to the arguably most realistic variant of Abelian axion inflation, in which the axion couples to the hypercharge sector of the Standard Model. Besides, we discuss GW emission from the fermion gas, which may further enhance the total GW signal but which also requires a more quantitative investigation in future work. Additionally, we identify a new backreaction regime in which fermion production moderates the axion--vector dynamics. In this regime, the axion velocity and all energy-density components exhibit oscillations analogous to the strong backreaction in PAI, but here, the oscillations occur around the slow-roll trajectory and are damped by the presence of charged fermions. These observations define again an interesting GEF benchmark for future lattice studies.

The CCAT Observatory's Fred Young Submillimeter Telescope (FYST) is designed to observe submillimeter astronomical signals with high precision, using receivers fielding state-of-the-art kinetic inductance detector (KID) arrays. Mod-Cam, a first-light instrument for FYST, serves as a testbed for instrument module characterization, including detailed evaluation of thermal behavior under operating conditions prior to deploying modules in the larger Prime-Cam instrument. Prime-Cam is a first generation multi-band, wide-field camera for FYST, designed to field up to seven instrument modules and provide unprecedented sensitivity across a broad frequency range. We present results from two key laboratory characterizations: an "optically open" cooldown to validate the overall thermal performance of the cryostat, and a "cold load" cooldown to measure the effect of focal plane temperature stability on detector noise. During the optically open test, we achieved stable base temperatures of 1.5 K on the 1 K stage and 85 mK at the detector stage. In the cold load configuration, we measured a detector focal plane RMS temperature stability of 3.2e-5 K. From this stability measurement, we demonstrate that the equivalent power from focal plane thermal fluctuations is only 0.0040% of a 5pW incident photon power for aluminum detectors and 0.0023% for titanium-nitride detectors, a negligible level for CCAT science goals. This highlights the success of the cryogenic system design and thermal management.

The CCAT Observatory's first-light and commissioning instrument, Mod-Cam, is nearing readiness for deployment to the Fred Young Submillimeter Telescope (FYST) in the Atacama Desert in northern Chile. In-lab testing of Mod-Cam and the first CCAT instrument module, a 280 GHz broadband camera fielding over 10,000 kinetic inductance detectors (KIDs), is currently underway. CCAT's first-generation science instrument, Prime-Cam, will field approximately 100,000 KIDs across seven instrument modules. Like Mod-Cam, it employs 46 cm long low-thermal-conductivity flexible circuits ("stripline") between 4 K and 300 K to connect large arrays of multiplexed detectors in each instrument module to readout electronics. The 280 GHz camera currently installed in Mod-Cam uses six striplines to read out its over 10,000 detectors across 18 RF chains, each individual stripline containing six traces. In-lab testing thus far has allowed us to begin optimizing the attenuation in the readout chains for each of the three detector arrays in the 280 GHz module and demonstrate simultaneous readout of all networks using CCAT's RFSoC warm readout electronics. Here we present an overview of the Mod-Cam cold readout and discuss the stripline performance by investigating how its thermal conductivity impacts Mod-Cam and Prime-Cam cryogenic performance. We also report on stripline electrical transmission and crosstalk, identifying transition printed circuit boards (PCBs) as the dominant source of crosstalk. Using this result we outline design improvements to these PCBs that enhance isolation between readout networks.

High-resolution spectra provide a powerful tool in studying the associated absorption lines (AALs) in quasars. We present a case study of the quasar J014741-030247 at $z \sim$ 4.75, which hosts complex intrinsic absorption lines revealed by the high-resolution Magellan/MIKE spectrum obtained from the HIERACHY program. We focus on one of the strongest absorption systems ($z$ $\sim$ 4.7804) and determine the column densities of multiple ionization species. We find that the Apparent Optical Depth method may significantly underestimate the column densities of high ions. Decomposing the absorption into multiple components yields a better fit and reveals clear evidence of partial coverage. The variation in covering fractions among different ions suggests that high ions are distributed more extensively in this system. We estimate electron densities of different components ($630 - 4070 \ \mathrm{cm}^{-3}$), these are based on the column densities of \ion{Si}{2}* and \ion{C}{2}*. By combining these with the hydrogen number density and ionization parameter derived from photoionization modeling, we infer that the different components are located at distances of 2.3 to 9.5 kpc from the quasar. The derived $N_{\mathrm H} / n_{\mathrm e}$ and the partial coverage observed in low ions all require cloud sizes smaller than 1 pc, even down to 0.01 pc. Finally, the low kinetic luminosity of the gas ($< 0.5\% L_\mathrm{bol}$) indicates that it is insufficient to drive significant AGN feedback and may only suppress star formation via `multistage' mechanism.

Cen X-3 is a bright, high-mass X-ray binary pulsar. We present a pulse phase-resolved X-ray spectral analysis of data from an archival XMM-Newton observation of Cen X-3 taken during the high state of the source. The observation was entirely in the out-of-eclipse part of the binary orbit. We study the pulse phase variability of the three K${\alpha}$ fluorescent emission lines from near-neutral, Helium-like and Hydrogen-like iron, along with the iron K${\beta}$ emission line. All four lines show clear modulation with the pulse phase of the neutron star, and modulation is found to be higher for the lines from highly ionised iron compared to the neutral lines. Structures within the light travel distance corresponding to the pulse period of the neutron star are likely responsible for the pulse phase modulation of the emission lines. We have also investigated the orbital phase dependence of the pulse phase variability in the iron lines by dividing the data into four segments at different orbital phases of Cen X-3. The pulse phase modulation behaviour of the four lines is quite identical at different orbital phases of Cen X-3, indicating the pulsed iron emission region is persistent in nature and probably phase aligned with respect to the observer. The accretion stream intercepting the line of sight can probably produce the observed phase dependence of the iron fluorescence emission lines.

Scale invariance is a hallmark of many natural systems, including solar flares, where energy release spans a vast range of scales. Recent computational advances, at the level of both algorithmics and hardware, have enabled high-resolution magnetohydrodynamical (MHD) simulations to span multiple scales, offering new insights into magnetic energy dissipation processes. Here, we study scale invariance of magnetic energy dissipation in two distinct MHD simulations. Current sheets are identified and analyzed over time. Results demonstrate that dissipative events exhibit scale invariance, with power-law distributions characterizing their energy dissipation and lifetimes. Remarkably, these distributions are consistent across the two simulations, despite differing numerical and physical setups, suggesting universality in the process of magnetic energy dissipation. Comparisons between the evolution of dissipation regions reveals distinct growth behaviors in high plasma-beta regions (convective zone) and low plasma-beta regions (atmosphere). The latter display spatiotemporal dynamics similar to those of avalanche models, suggesting self-organized criticality and a common universality class.

Primordial black holes (PBHs) are one of the most important tracers of cosmic history. In this work, we investigate the formation of PBHs around the time of the QCD phase transition from a broadly peaked inflationary scalar power spectrum, which naturally produces an extended PBH mass function. This scenario yields two distinct stochastic gravitational wave backgrounds (SGWB): (i) scalar-induced, second-order tensor perturbations generated at PBH formation, and (ii) a merger-driven SGWB from the subsequent PBH binary population. Using Bayesian analysis, we examine both SGWB channels with the data from the NANOGrav 15-year dataset and the first three observing runs of LVK. We also forecast continuous-wave signals from mini extreme mass ratio inspirals (mini-EMRIs) for direct comparison with NANOGrav and LVK constraints. Our parameter scans identify regions of the parameter space where the combined SGWB is detectable in future ground-based and space-based detectors. A broad PBH mass distribution naturally gives rise to mini-EMRIs, which future ground-based observatories, such as LVK A+, ET, and CE, can detect. For a large part of the PBH parameter space, the SGWB of astrophysical origin masks the primordial SGWB in the frequency band of ground-based detectors. Thus, for extended PBH mass distributions, we find that the detection of mini-EMRIs is a more robust channel for probing the PBH parameter space than the corresponding SGWB.

We study a class of Unified Dark Matter (UDM) models based on generalized K-essence, where a single scalar field with non-canonical kinetic terms accounts for dark radiation, dark matter, and dark energy. Starting from the purely kinetic Lagrangian proposed by Scherrer (2004), we extend the analysis to quadratic and exponential scalar potentials and explore their phenomenology. All models are implemented in a modified version of \texttt{Hi\_CLASS} and confronted with data from \textit{Planck} 2018, DESI DR1, and Big Bang Nucleosynthesis. The scenarios reproduce the full sequence of cosmic epochs: an early radiation-like phase, a matter-dominated era, and late-time accelerated expansion. The new models predict slightly higher values of the Hubble constant compared to $\Lambda$CDM, thereby partially alleviating the respective tensions from $\sim 4.4 \sigma$ to $\sim 3.4 \sigma$. The quadratic potential requires an ultralight mass that makes it effectively indistinguishable from the Scherrer solution. Overall, generalized K-essence provides a minimal and observationally viable realization of UDM, offering a unified description of the dark sector with distinctive signatures in both early- and late-time cosmology.

Electromagnetic induction heating has recently been proposed as an important internal heat source in the mantles of rocky exoplanets. However, its dependence on planetary interior properties remains poorly constrained. Here we construct electrical conductivity profiles for super-Earth mantles considering different temperatures and compositions, and evaluate induction heating in super-Earth mantles in both solid and partially molten states. We find that high mantle temperature, iron content, and melt fraction all suppress the overall induction heating efficiency due to increased mantle conductivity and magnetic shielding. In GJ 486b, induction heating likely exceeds both radiogenic heating and tidal heating, driving persistent surface volcanism and early volatile depletion, whereas HD 3167b and GJ 357b experience insignificant induction heating due to weak stellar magnetic fields. Our findings highlight induction heating as a critical factor in the thermal and atmospheric evolution of close-in super-Earths around magnetically active stars.

Studies of the resolved stellar populations of young massive clusters have shown that the slope of the initial mass function appears to be the same everywhere, with no dependence on stellar density or metallicity. At the same time, studies of integrated properties of galaxies usually conclude that the IMF does vary, and must be top-heavy in starburst regions. In order to investigate this, we have carried out a long-term project to characterize the massive star content of NGC 3603, the nearest giant HII region, known to have a rich population of massive stars. We used both ground-based and Hubble Space Telescope (HST) imaging to obtain photometry, and employed Gaia to establish membership. We obtained spectra of 128 stars using the Magellan 6.5~m telescope and HST, and combine these data to produce a reddening map. After analyzing the data in the same way as we have for 25 other star-forming regions in the Milky Way and the Magellanic Clouds, we find that the IMF slope of NGC 3603 is quite normal compared to other clusters, with Gamma=-0.9+/-0.1. If anything, there are fewer very high mass (>65Mo) stars than one would expect by extrapolation from lower masses. This slope is also indistinguishable from what several studies have shown for R136 in the LMC, an even richer region. We speculate that the depreciation of the highest mass bins in NGC 3603, but not in R136, may indicate that it is harder to form extremely massive stars at the higher metallicity of the Milky Way compared to that of the LMC.

Inferring cosmological parameters from Cosmic Microwave Background (CMB) data requires repeated and computationally expensive calculations of theoretical angular power spectra using Boltzmann solvers like CAMB. This creates a significant bottleneck, particularly for non-standard cosmological models and the high-accuracy demands of future surveys. While emulators based on deep neural networks can accelerate this process by several orders of magnitude, they first require large, pre-computed training datasets, which are costly to generate and model-specific. To address this challenge, we introduce gCAMB, a version of the CAMB code ported to GPUs, which preserves all the features of the original CPU-only code. By offloading the most computationally intensive modules to the GPU, gCAMB significantly accelerates the generation of power spectra, saving massive computational time, halving the power consumption in high-accuracy settings and, among other purposes, facilitating the creation of extensive training sets needed for robust cosmological analyses. We make the gCAMB software available to the community at this https URL.

The increasing volume of gamma-ray data demands new analysis approaches that can handle large-scale datasets while providing robustness for source detection. We present a Deep Learning (DL) based pipeline for detection, localization, and characterization of gamma-ray sources. We extend our AutoSourceID (ASID) method, initially tested with \textit{Fermi}-LAT simulated data and optical data (MeerLICHT), to Cherenkov Telescope Array Observatory (CTAO) simulated data. This end-to-end pipeline demonstrates a versatile framework for future application to other surveys and potentially serves as a building block for a foundational model for astrophysical source detection.

Intrinsic alignments (IA) of galaxies is one of the key secondary signals to cosmic shear measurements, and must be modeled to interpret weak lensing data and infer the correct cosmology. There are large uncertainties in the physical description of IA, and analytical calculations are often out of reach for weak lensing statistics beyond two-point functions. We present here a set of six flexible IA models infused directly into weak lensing simulations, constructed from the mass shells, the projected tidal fields and, optionally, dark matter halo catalogues. We start with the non-linear linear alignment (NLA) and progressively sophisticate the galaxy bias and the tidal coupling models, including the commonly-used extended NLA (also known as the e-NLA or $\delta$-NLA) and the tidal torque (TT) models. We validate our methods with MCMC analyses from two-point shear statistics, then compute the impact on non-Gaussian cosmic shear probes from these catalogues as well as from reconstructed convergence maps. We find that the $\delta$-NLA model has by far the largest impact on most probes, at times more than twice the strength of the NLA. We also observe large differences between the IA models in under-dense regions, which makes minima, void profiles and lensing PDF the best probes for model rejection. Furthermore, our bias models allow us to separately study the source-clustering term for each of these probes, finding good agreement with the existing literature, and extending the results to these new probes. The third-order aperture mass statistics ($M^3_{ap}$) and the integrated three-point functions are particularly sensitive to this when including low-redshift data, often exceeding a 20% impact on the data vector. Our IA models are straightforward to implement and rescale from a single simulated IA-infused galaxy catalogue, allowing for fast model exploration.

We present the first results of V\textit{z}-GAL, a high-redshift CO(\textit{J} = 1 $-$ 0) large survey with the Karl G. Jansky Very Large Array, targeting 92 \textit{Herschel}-selected, infrared-luminous, dusty star-forming galaxies (DSFGs). This flux density-limited sample includes 106 DSFGs in total, along with 14 galaxies from a recent pilot study -- altogether doubling the to-date available high-redshift \coonezero observations. These sources cover redshifts 1 to 6 with available mid/high-\textit{J} CO transitions from the Northern Extended Millimeter Array \zgal survey. We detect \coonezero emission in 90/92 targets above signal-to-noise ratio of 2, while two DSFGs remain undetected. \vzgal also covers additional \cotwoone emission lines in 10 of these sources. We find gas masses of the entire \vzgal sample to be $\rm (\alpha_{CO}/{4.0}) \mu {M}_{\rm H_2}$ = $(2-20) \times {10}^{11}~\mathrm{M_{\odot}}$, calibrated using \coonezero line luminosities. We confirm that these DSFGs -- with derived gas depletion timescales of $(50-600)$ Myr -- represent a heterogeneous population, potentially comprising both main-sequence galaxies and starbursts in the early Universe. Using \coonezero luminosities as an anchor, we robustly derive the CO brightness temperature ratios with a good statistical significance up to \textit{J} = 6. Our measurements reveal a broad range of gas excitation conditions across the \vzgal DSFGs. We also explore [CI](1$-$0)/CO(1$-$0) ratios in 23 \vzgal galaxies that have existing detections of atomic carbon ground-state emission, [CI](1$-$0), from the \zgal survey. Our results show similar [CI]/CO ratio values across cosmic time for starbursts and local star-forming galaxy populations, supporting the use of \cionezero as an alternative cold gas tracer.

When Carl Sagan and Ed Salpeter envisioned potential Sinkers, Floaters, and Hunters living in Jupiter's clouds in 1976 (C. Sagan & E. E. Salpeter 1976), the nature of life in Earth's atmosphere remained widely unknown. Decades later, research has revealed a remarkable variety of microorganisms in our atmosphere. However, the spectral features of airborne microbes as biomarkers for detecting atmospheric life remained a mystery. Here, we present the first reflectance spectra of biopigments of atmospheric microorganisms based on laboratory cultivars of seven microbial strains isolated from Earth's atmosphere. We show their distinct UV-resistant biosignatures and their impacts on models of diverse planetary scenarios, using Habitable Worlds Observatory (HWO) parameters. The reflectance of these biopigments from aerial bacteria creates the means to detect them on other Earth-like planets. It provides a paradigm shift that moves the search for life beyond the surface of a planet to ecosystems in atmospheres and clouds.

The cosmic dawn 21-cm signal is a highly sensitive probe of any process which injects energy into the intergalactic medium, enabling novel searches for anomalous energy injection by through dark matter interactions. In addition to modifying the global 21-cm signal, these processes would leave distinct imprints on the frequency-resolved 21-cm power spectrum with a morphology jointly set by the time- and spatial-dependence of energy emission and absorption. In this work, we extend the DM21cm code package, which models the effects of spatially inhomogeneous energy emission and deposition on 21-cm cosmology, to study three well-motivated scenarios which 21-cm measurements are particularly well-suited to probe: dark matter annihilation through $p$-wave processes, the Hawking radiation of light primordial black holes, and energetic emission from accreting solar-mass primordial black holes. We project sensitivities to each of these scenarios, demonstrating that leading or near leading sensitivity to each can be achieved through 21-cm probes. We also make public our updates to the DM21cm code package that enable it to accommodate energy injection processes for general continuum spectra with arbitrary spatial and temporal dependence in an accompanying release.

The high densities in the early Universe provide a unique laboratory to constrain couplings between feebly interacting particles, such as dark matter and neutrinos. In this article, we study how Big Bang Nucleosynthesis can constrain models of Ultra-Light Dark Matter diagonally coupled to neutrinos. We follow an adiabatic formalism which allows to average-out the rapid oscillations of the Dark Matter field and consistently take into account the feedback between the neutrino and the Dark Matter fields. This feedback alters the early Universe dynamics, causing the Dark Matter energy density to scale as radiation, while the neutrino mass scales as $a^{-1}$. These two effects modify primordial element abundances by modifying interaction rates and the expansion rate during nucleosynthesis. Then, we use primordial abundances to obtain leading cosmological bounds on the coupling in the range $m_\phi/{\rm eV}\in (10^{-22},10^{-17})$, namely $g\lesssim 0.13(m_\phi/{\rm eV})$ for $m_\phi \gtrsim 3\times 10^{-20}\,\rm eV$ and $g\lesssim 1.8\times 10^{-11}\sqrt{m_\phi/\rm eV}$ for $m_\phi \lesssim 3\times 10^{-20}\,\rm eV$. This consistent cosmological treatment emphasizes that, in the mass interval where its physical assumptions hold, neutrino masses cannot be generated refractively by a direct coupling with an Ultra-Light Dark Matter field.

The analysis of non-stationary signals in non-uniformly sampled data is a challenging task. Time-integrated methods, such as the generalised Lomb-Scargle (GLS) periodogram, provide a robust statistical assessment of persistent periodicities but are insensitive to transient events. Conversely, existing time-frequency methods often rely on fixed-duration windows or interpolation, which can be suboptimal for non-uniform data. We introduce the non-uniform Stockwell-transform (NUST), a time-frequency framework that applies a localized density adaptive spectral analysis directly to non-uniformly sampled data. NUST employs a doubly adaptive window that adjusts its width based on both frequency and local data density, providing detailed time-frequency information for both transient and persistent signals. We validate the NUST on numerous non-uniformly sampled synthetic signals, demonstrating its superior time-localization performance compared to GLS. Furthermore, we apply NUST to HARPS radial velocity data of the multi-planetary system HD 10180, successfully distinguishing coherent planetary signals from stellar activity.

On a spherically symmetric and static background, we study the existence of linearly stable black hole (BH) solutions in nonlinear electrodynamics (NED) with a Horndeski vector-tensor (HVT) coupling, with and without curvature singularities at the center ($r=0$). Incorporating the electric charge $q_E$ and the magnetic charge $q_M$, we first show that nonsingular BHs can exist only if $q_M = 0$. We then study the stability of purely electric BHs by analyzing the behavior of perturbations in the metric and the vector field. Nonsingular electric BHs are unstable due to a Laplacian instability in the vector perturbation near the regular center. In the absence of the HVT coupling ($\beta=0$), singular BHs in power-law NED theories can be consistent with all linear stability conditions, while Born-Infeld BHs encounter strong coupling due to a vanishing propagation speed as $r \to 0$. In power-law NED and Born-Infeld theories with $\beta \neq 0$, the electric fields for singular BHs are regular near $r=0$, while the metric functions behave as $\propto r^{-1}$. Nevertheless, we show that Laplacian instabilities occur for regions inside the outer horizon $r_h$, unless the HVT coupling constant $\beta$ is significantly smaller than $r_h^2$. For $\beta \neq 0$, we also reconstruct the NED Lagrangian so that one of the metric functions takes the Reissner-Nordström form. In this case, there exists a branch where all squared propagation speeds are positive, but the ghost and strong coupling problems are present around the BH center. Thus, the dominance of the HVT coupling generally leads to BH instability in the high-curvature regime.

We present a complete classification of domain wall solutions in the two-Higgs Doublet Model (2HDM) with a global $\mathbb{Z}_2$ symmetry, categorised as superconducting, CP-violating, or neither, depending on the scalar particle masses and the ratio of the two Higgs doublets' vacuum expectation values. We demonstrate that any domain wall solution can be reduced to depend on only six of the eight general field components, with further field reductions possible within different regions of the parameter space. Furthermore, we show that the superconducting solutions can be used to construct stable, current-carrying domain walls in two spatial dimensions. Similarly, the CP-violating solutions allow for two-dimensional configurations where CP symmetry is locally broken on the $\mathbb{Z}_2$-symmetric wall, which could provide an out-of-equilibrium environment for CP-violating processes to occur.

In this work, we report the experimental readout results of a {\mu}MUX device using a Direct-RF SDR prototype based on the ZCU216 Radio-Frequency System-on-Chip (RFSoC) evaluation board. First, the analog performance of the SDR system was evaluated both in loopback and coupled to the cryogenic multiplexing system. Then, the SDR system performance was optimized for {\mu}MUX readout, focusing on bolometric applications. Finally, the minimum demodulated flux noise was obtained through the optimally conditioned readout of a {\mu}MUX channel. The results presented are comparable to those obtained with traditional SDR architectures and demonstrate that the Direct-RF SDR prototype is suitable for the readout of {\mu}MUX devices. We anticipate that Direct-RF SDR technology will play a key role in enabling the next generation of SDR readout systems for frequency-multiplexed low-temperature detector arrays.

Magnetic monopoles are a long-standing prediction of Grand Unified Theories, yet their efficient production in early universe phase transitions would lead to a monopole abundance that far exceeds observational limits. The standard solution of the problem invokes inflation occurring after monopole production, diluting their density to undetectable levels and eliminating any possibility of present-day observation. Here, we propose an alternative solution based on the breaking, in the early universe prior to Big Bang Nucleosynthesis, of the Weyl conformal symmetry of the gauge kinetic sector of the Lagrangian. This mechanism enhances monopole annihilation, thereby reducing their abundance to acceptable levels without requiring inflation. This scenario also predicts a residual flux of GUT monopoles potentially within the sensitivity of current and upcoming cosmic ray detectors, making their discovery possible in the near future.

Magnetic fields in the universe potentially serve as a messenger of primordial physics. The observationally suggested intergalactic magnetic fields may be a relic of helical primordial $\mathrm{U}(1)_Y$ magnetic fields, which may also explain the origin of the baryon asymmetry of the universe. This scenario has been considered to be not viable, which we revisit as well as the baryon isocurvature problem for non-helical primordial $\mathrm{U}(1)_Y$ magnetic fields, based on the recent discussion on the hot electroweak theory. We find that maximally helical fields can be the origin of both the intergalactic magnetic fields and the baryon asymmetry of the universe and that there can be a window for non-helical fields to explain the origin of the intergalactic magnetic fields if the Higgs dynamics during the electroweak crossover compensate the helicity decay with a $\lesssim10^{-9\text{--}-10}$ precision.

Numerical simulations of core-collapse supernovae, mergers of binary neutron stars and formation of stellar black holes, which employed standard Skyrme interactions, established clear correlations between the evolution of these processes, characteristics of the hot compact objects, as well as neutrino and gravitational wave signals, and the value of effective nucleon mass at the saturation density. Unfortunately, the density dependence of the effective mass of nucleons in these models does not align with the predictions of ab initio models with three body forces. In this work, we investigate the thermal response for a set of extended Skyrme interactions that feature widely different density dependencies of the effective mass of the nucleons. Thermal contributions to the energy density and pressure are studied along with a few thermal coefficients over wide domains of density, temperature and isospin asymmetry, relevant for the physics of hot compact objects. For some of the effective interactions, the thermal pressure is negative at high densities. This results in a situation where hot compact stars can support less mass before collapsing into a black hole compared to their cold counterparts. Moreover, the higher the temperature, the lower the maximum mass that the hot star can support.

We investigate cosmological solutions for the modified gravity theory obtained from quantum relative entropy between the metric of spacetime and the metric induced by the geometry and matter fields. The vacuum equations admit inflationary solutions, hinting at an entropic origin for inflation. Equations also admit a regime of phantom like behavior. Assuming that the relation between slow roll parameters and CMB observables holds for entropic gravity, the theory predicts a viable spectrum.

In this paper, we demonstrate that a linear electromagnetic matter source can be constructed for regular black hole solutions, illustrated by the case of the Bardeen black hole. Our method relies on coupling a scalar field and its potential to General Relativity (GR) alongside electrodynamics. Both fields are minimally coupled to GR but interact with each other. We validate this approach by interpreting the Bardeen solution either as a purely magnetic or as a purely electric configuration for a spherically symmetric metric with an arbitrary electrodynamics Lagrangian $\mathcal{L}(F)$ and a coupling function $W(\varphi)$. By choosing an appropriate form of $W$, the electromagnetic Lagrangian can be rendered linear. We then analyze the behavior of the coupling function and the scalar field potential, emphasizing their relation to the magnetic or electric charge. Finally, we compare the advantages and disadvantages of this framework with the conventional formalism, in which regular charged black holes are supported solely by nonlinear electrodynamics.

Black-bounce (BB) solutions generalize the spacetimes of black holes, regular black holes, and wormholes, depending on the values of certain characteristic parameters. In this work, we investigate such solutions within the framework of General Relativity (GR), assuming spherical symmetry and static geometry. It is well established in the literature that, in order to sustain such geometries, the source of Einstein's equations in the BB context can be composed of a scalar field $\varphi$ and a nonlinear electrodynamics (NLED). In our model, in addition to the Lagrangian associated with the scalar field in the action, we also include an interaction term of the form $W(\varphi)\mathcal{L}(F)$, which introduces a nonminimal coupling between the scalar field and the electromagnetic sector. Notably, the usual minimal coupling configuration is recovered by setting $W(\varphi)=1$. In contrast to approaches where the function $W(\varphi)$ is assumed a priori, here we determine its functional form by modeling the radial dependence of the derivative of the electromagnetic Lagrangian as a power law, namely $\mathcal{L}_F(r) \sim F^n$. This approach enables us to determine $W(r)$ directly from the obtained solutions. We apply this procedure to two specific geometries: the Simpson-Visser-type BB solution and the Bardeen-type BB solution, both analyzed in the purely magnetic ($q_m \neq 0$, $q_e=0$) and purely electric ($q_m=0$, $q_e \neq 0$) cases. In all scenarios, we find that these BB spacetime solutions can be described with a linear electrodynamics, which is a noteworthy result. Furthermore, we examine the regularity of the spacetime through the Kretschmann scalar and briefly discuss the associated energy conditions for the solutions obtained.

We performed a numerical study of the dynamics of massive particles orbiting black holes and naked singularities in the Reissner-Nordström geometry. We modeled a stream of particles with a constant angular momentum and with a range of energies. We then solved the geodesic equation of motion and compared the trajectories around black holes and naked singularities by tuning the charge parameter of the metric. The setup that we used can approximate astrophysical scenarios such as tidal disruption events. We discussed differences and similarities in the orbital dynamics and deflection angles. We found that particles reflected by a black hole follow a stream-like family of orbits within a narrow range of deflection angles, whereas in case of naked singularities particles are scattered in all directions on the plain of motion. We explained this behavior as an interplay between the presence of a centrifugal barrier at the location of the unstable circular orbit and an absorbing event horizon in case of a black hole or a reflective zero-gravity sphere in case of a naked singularity. These qualitative differences are expected to impact the observable signatures of tidal disruption events.

We investigate photon, pion, and rho-meson production from proton synchrotron radiation in the presence of strong magnetic fields. The proton decay widths and the luminosities of the emitted particles are calculated within a relativistic quantum framework that incorporates Landau quantization. A scaling rule is derived for the transition probability between different Landau levels. This allows an evaluation of transitions for extremely high Landau numbers exceeding $10^{15}$. Furthermore, we calculate the momentum distribution of the emitted particles by properly including the proton recoil effect associated with particle emission. The results differ significantly from conventional semiclassical approaches.

Modelled searches for gravitational waves emitted by compact binary coalescences currently filter the data with template signals that ignore all effects related to the physics of dense-matter in neutron stars interiors, even when the masses in the template are compatible with a binary neutron star or a neutron star-black hole binary source. The leading neutron star finite-size effect is an additional phase contribution due to tidal deformations induced by the gravitational coupling between the two inspiralling objects in the binary. We show how neglecting this effect in the templates reduces the search sensitivity close to the detection threshold. This is particularly true for binary neutron stars systems, where tidal effects are larger. In this work we therefore propose a new technique for the construction of binary neutron star template banks that accounts for neutron star tidal deformabilities as degrees of freedom of the parameter space to be searched over. A first attempt in this direction was carried out by Harry & Lundgren [Physical Review D 104, 043008 (2021)], who proposed to extract randomly the tidal deformabilities of the stars over a uniform interval, regardless of the binary neutron star component masses. We show that this approach yields 33% additional templates with respect to the equivalent point-like template bank. Our proposed approach, instead, adopts a more physically motivated tidal deformability prior with a support that is informed by the value of the neutron star mass and compatible with the neutron star equation of state constraint provided by the observation of GW170817. This method significantly reduces the needed additional templates to 8.2%.

In this article we present a possibility of imposing the unimodular condition within the 5-dimensional Kaluza-Klein theory including the scalar field. Unimodular gravity became an object of increasing interest in the late 80-ties; and was recently used in primordial Universe modeling with cosmological constant, in the context of the Brans-Dicke gravity including scalar field. A generalization of the unimodularity principle to the 5-dimensional Kaluza-Klein model was discussed in our recent paper, in which variational principle is formulated in 5 dimensions first, and dimensional reduction is applied to the resulting set of equations. A cosmological model based on these equations was then presented and discussed. Here we present further developments of this approach, focussing our attention at perturbative aspects and stability of solutions.

We offer a physical interpretation of the origin of the scalar-induced gravitational wave background, showing that it is mainly produced around the peaks of the scalar perturbations. We also provide a compact expression to estimate the amount of scalar-induced gravitational waves generated by peaks.

Topological defects can have significant cosmological consequences, so their production must be examined carefully. It is usually assumed that topological defects are produced if the temperature becomes sufficiently high, but in reality their formation depends on the post-inflationary dynamics of a symmetry-breaking scalar. We analyze the dynamics of a symmetry-breaking scalar field in the early universe within models that provide an effective negative mass term at the origin, and show that the symmetry can remain broken so that topological defects are never formed. In particular, we demonstrate that nonthermally produced particles (such as the Standard Model Higgs) during preheating can generate such an effective negative mass term, allowing the scalar field to follow a time-dependent minimum even in renormalizable models with a quartic coupling. We also discuss the implications of this result for the Peccei-Quinn scalar in axion models.

We investigate a cosmological scenario in which the Peccei-Quinn (PQ) symmetry remains broken in the entire history of the Universe, thereby avoiding the formation of axion strings and domain walls. Contrary to the conventional expectation, it is demonstrated that appropriately chosen scalar interactions are able to keep the PQ symmetry broken at arbitrarily high temperatures. We carefully examine the finite-temperature effective potential in a model with two PQ breaking scalar fields. The existence of flat directions plays a vital role in suppressing axion isocurvature perturbations during inflation by stabilizing a PQ field at a large field value. The viable parameter space consistent with theoretical and observational constraints is identified. Our scenario provides a minimal path for PQ symmetry breaking that addresses both the axion domain wall and isocurvature problems while permitting arbitrarily high reheating temperatures accommodating high-scale baryogenesis scenarios such as thermal leptogenesis.

We calculate the cross section for radiative capture $^3$He$(\alpha,\gamma)^7$Be at next-to-next-to-leading order (NNLO). At this order of perturbation, momentum dependent two-body currents make their first appearance. We provide a model-independent construction of these currents from gauge and Galilean invariance, where the general framework for constructing higher-order two-body currents in low-energy effective field theories becomes evident. The $^3$He$(\alpha,\gamma)^7$Be astrophysical S-factor $S_{34}(0)= 0.564^{+0.17}_{-0.015}$ keV b is obtained from a Bayesian analysis at NNLO, with an additional nominal theoretical uncertainty $\pm0.017$ keV b of 3%.

A massive vector field is a highly promising candidate for dark matter in the universe. A salient property of dark matter is its negligible or null coupling to ordinary matter, with the exception of gravitational interaction. This poses a significant challenge in producing the requisite amount of dark particles through processes within the Standard Model. In this study, we examine the production of a vector field during inflation due to its direct interaction with the inflaton field through kinetic and axion-like couplings as well as the field-dependent mass. The gradient-expansion formalism, previously proposed for massless Abelian gauge fields, is extended to include the longitudinal polarization of a massive vector field. We derive a coupled system of equations of motion for a set of bilinear functions of the vector field. This enables us to address the nonlinear dynamics of inflationary vector field production, including backreaction on background evolution. To illustrate this point, we apply our general formalism to a low-mass vector field whose kinetic and mass terms are coupled to the inflaton via the Ratra-type exponential function. The present study investigates the production of its transverse and longitudinal polarization components in a benchmark inflationary model with a quadratic inflaton potential. It has been demonstrated that pure mass coupling is able to enhance only the longitudinal components. By turning on also the kinetic coupling, one can get different scenarios. As the coupling function decreases, the primary contribution to the energy density is derived from the transverse polarizations of the vector field. Conversely, for an increasing coupling function, the longitudinal component becomes increasingly significant and rapidly propels the system into the strong backreaction regime.

We examine gravitational entropy growth within the formalism of Clifton, Ellis and Tavakol (CET) applied to a class of spherically symmetric exact solutions whose source is a shear-free fluid with energy flux in a comoving frame. By considering these solutions as potential cosmological models, we update previous literature that considered them only as restricted toy models of radiating spheres collapsing in a Vaidya background. In the present paper we examine the integrability of the CET entropy form in connection with Einstein's equations in the fluid flow approach, proving as well that all expanding configurations comply with the growth of CET gravitational entropy. Finally, we examine the connection between the CET gravitational entropy and the notion of a gravitational ``arrow of time'' based on the ratio of Weyl to Ricci curvature. Some of the solutions also provide potentially useful and viable inhomogeneous generalizations of FLRW models, thus suggesting an appealing potential for applications to current cosmological research.