Papers for Tuesday, Aug 26 2025

The problem of local (e.g., interplanetary) Hubble expansion is studied for a long time but remains a controversial subject till now; and of particular interest is a plausible value of the local Hubble parameter at the scale of the Solar system. Here, we tried to estimate the corresponding quantity by the analysis of surface temperatures on the Earth and Mars, which are formed by a competition between a variable luminosity of the Sun and increasing radii of the planetary orbits. Our work employs paleochemical and paleobiological data on the temperature of the ancient Earth, on the one hand, and geological data on the existence of an ocean of liquid water on the ancient Mars, on the other hand. As follows from our analysis, the martian data impose only a weak constraint on the admissible values of the Hubble parameter because of the unknown salinity - and, therefore, the freezing point - of the martian water. On the other hand, the terrestrial data turn out to be much more valuable, especially, for the Precambrian period, when temperature variation was sufficiently smooth and monotonic. For example, in the framework of standard LambdaCDM model with 70% of dark energy, contemporary value of the local Hubble parameter was found to be 70-90 km/s/Mpc under assumption that the Earth's surface temperature in the end of Precambrian equaled 45 C. This is in reasonable agreement both with the intergalactic data and with an independent estimate of the local Hubble parameter from tidal evolution of the Earth-Moon system.

Grouping stars by chemical similarity has the potential to reveal the Milky Way's evolutionary history. The APOGEE stellar spectroscopic survey has the resolution and sensitivity for this task. However, APOGEE lacks access to strong lines of neutron-capture elements ($Z > 28$) which have nucleosynthetic origins that are distinct from those of the lighter elements. We assess whether APOGEE abundances are sufficient for selecting chemically similar disk stars by identifying 25 pairs of chemical ``doppelgangers'' in APOGEE DR17 and following them up with the Tull spectrograph, an optical, $R \sim 60{,}000$ echelle on the McDonald Observatory 2.7-m telescope. Line-by-line differential analyses of pairs' optical spectra reveals neutron-capture (Y, Zr, Ba, La, Ce, Nd, and Eu) elemental abundance differences of $\Delta$[X/Fe] $\rm \sim 0.020 \pm 0.015$ to $0.380 \pm 0.15$ dex (4--140%), and up to 0.05 dex (12%) on average, a factor of 1--2 times higher than intra-cluster pairs. This is despite the pairs sharing nearly identical APOGEE-reported abundances and [C/N] ratios, a tracer of giant-star age. This work illustrates that even when APOGEE abundances derived from SNR $> 300$ spectra are available, optically-measured neutron-capture element abundances contain critical information about composition similarity. These results hold implications for the chemical dimensionality of the disk, mixing within the interstellar medium, and chemical tagging with the neutron-capture elements.

Ab initio free energy calculations are employed to derive the entropy of liquid and superionic water over a wide range of conditions in the interiors of Uranus and Neptune. The resulting adiabats are much shallower in pressure-temperature space than those adopted for earlier models of Uranus and Neptune. Our models for their interiors are thus much colder, increasing the likelihood that diamond rain or the recently predicted phase separation of planetary ices has occurred in the mantles of ice giant planets. Based on our ab initio data, we construct interior models for Uranus and Neptune with the Concentric MacLaurin Spheroid method that match the existing gravity measurements. We compare fully convective models with models that include a convective boundary between liquid and superionic water. We also share a code to characterize giant planet atmospheres where para and ortho hydrogen as well as helium are present.

We present detailed radio observations of the mid-infrared (MIR) tidal disruption event (TDE) WTP14adeqka. We detect rising radio emission starting $\approx 4$ years after the discovery of the MIR emission (and about 2 years after its peak), peaking at $\approx 6.5$ years and declining thereafter, reminiscent of the delayed radio emission recently identified in optically discovered TDEs. The peak radio luminosity, $\nu L_\nu\approx 2\times 10^{39}$ erg s$^{-1}$, is comparable to the brightest radio emission in optical TDEs. Multi-frequency radio observations at 8.9 and 9.7 years reveal a non-relativistic outflow with a mean expansion velocity of $\approx 0.021c$ (for an assumed launch at the time of disruption) and an energy of $\approx 10^{50.7}$ erg, about an order of magnitude larger than in typical optical TDEs. More importantly, Very Long Baseline Array (VLBA) observations at the same epochs directly resolve the radio source and reveal an increase in size from approximately 0.11 pc to 0.13 pc (with no apparent astrometric shift), corresponding to an expansion velocity of $\approx 0.05c$, and a likely delayed launch by about 2 years. The VLBA size measurements rule out an off-axis jet launched at the time of disruption, which would have an expected size of $\gtrsim {\rm pc}$ on these timescales; the possibility of a delayed jet can be evaluated with future VLBA observations. We conclude that MIR TDEs can launch energetic, delayed outflows. Ongoing radio observations of the full MIR TDE sample will reveal whether this behavior is ubiquitous.

Observations reveal a striking diversity in dwarf galaxy structures, spanning a wide range of masses, inner density slopes, shapes, and sizes. Tidal stripping may play a crucial role in shaping the evolution of these galaxies, yet the underlying physical mechanisms remain poorly understood. Using idealized N-body simulations, we investigate the tidal evolution of two-component systems -- stellar and dark matter -- embedded in a host potential. We find that in terms of energy distributions, both stellar and dark matter particles are stripped identically, regardless of their initial profiles. This surprising result suggests that the energy distribution of stripped stars can provide direct constraints on the underlying dark matter structure. Furthermore, we show that systems with cored dark matter and cuspy stellar profiles naturally evolve into dark matter-deficient (DMD) galaxies, supporting tidal stripping as a viable DMD formation pathway. This energy-space analysis of multi-component systems offers new insights into the dynamical evolution of tidally stripped galaxies.

LuSEE-Night is a pathfinder radio telescope on the lunar far side employing four 3-m monopole antennas arranged as two horizontal cross pseudo-dipoles on a rotational stage and sensitive to the radio sky in the 1-50 MHz frequency band. LuSEE-Night measures the corresponding 16 correlation products as a function of frequency. While each antenna combination measures radiation coming from a large area of the sky, their aggregate information as a function of phase in the lunar cycle and rotational stage position can be deconvolved into a low-resolution map of the sky. We study this deconvolution using linear map-making based on the Wiener filter algorithm. We illustrate how systematic effects can be effectively marginalised over as contributions to the noise covariance and demonstrate this technique on beam knowledge uncertainty and gain fluctuations. With reasonable assumptions about instrument performance, we show that LuSEE-Night should be able to map the sub-50 MHz sky at a ~5-degree resolution.

SwiftJ1910.2-0546 is a Galactic X-ray transient discovered during a bright outburst in 2012. We use time-series optical photometry and spectroscopy to estimate the orbital period, characterise the donor star, determine the interstellar extinction, distance, and system geometry, and constrain the component masses. Multi-site r-band and clear-filter light curves and WHT/ACAM spectra from the 2012 outburst are combined with time-series spectroscopy from GTC/OSIRIS and VLT/FORS2 in quiescence. Period searches are conducted using generalised Lomb-Scargle, phase-dispersion minimisation, and analysis-of-variance algorithms. Diffuse interstellar bands constrain E(B-V), while empirical correlations involving H$\alpha$ yield estimates of K2, q, and i. We detect a double-humped modulation with a period of $0.0941\pm0.0007$d ($2.26\pm0.02$h) during the outburst. Its morphology is consistent with an early superhump, suggesting that the true orbital period may be slightly shorter than 4.52h. The H$\alpha$ radial velocity curves do not yield a definitive orbital period. In quiescence, TiO bands indicate an M3-M3.5 donor contributing 70% of the red continuum. Diffuse interstellar bands give E(B-V)=$0.60\pm0.05$ and N_H=$(3.9\pm1.3)$x10$^{21}$cm$^{-2}$, placing the system at a distance of 2.8-4.0 kpc. The H$\alpha$ line width in quiescence (FWHM_0 =$990\pm45$km/s), via a FWHM-K_2 calibration, provides an estimate of K_2, while its double peaked profile gives q and i. Adopting the resulting K_2=$230\pm17$km/s and q=$0.032\pm0.010$, and two orbital period scenarios (2.25 and 4.50h), Monte Carlo sampling returns a compact object mass M_1=8-11M_sun and an inclination i=13-18 deg for plausible donor masses (M_2=0.25-0.35M_sun). We favour an orbital period of 4.5h. Further phase-resolved spectroscopy and photometry during quiescence are needed to better determine its fundamental parameters.

Interplanetary coronal mass ejections (ICMEs), the large-scale eruptive phenomena capable of shedding a huge amount of solar magnetic helicity and energy are potential in driving strong geomagnetic storms. They complexly evolve while preceded and followed by other large-scale structures e.g. ICMEs. Magnetic interaction among multiple ICMEs may result intense and long-lived geomagnetic storms. Our aim is to understand the reason of substantial changes in the geoeffectivity of two meso-scale separated counterparts of a complex solar wind structure through investigating their magnetic content e.g. helicity, energy and magnetic interaction among multiple ICMEs. We utilized the insitu observations of solar wind from Wind and Solar Terrestrial Relations Observatory-A (STA) spacecraft during the strongest geomagnetic storm period in past two decades on May 10-11, 2024 and heliospheric imagers onboard STA. Our investigation confirms complex interactions among five ICMEs resulting in distinct counterparts within a coalescing large-scale structure. These counterparts possess substantially different magnetic contents. We conclude that the complex counterpart resulted from the interaction among common-origin ICMEs observed by STA, favorably orientated for magnetic reconnection, had 1.6 and 2.8 times higher total magnetic energy and helicity, respectively, than the counterpart containing a left-handed filament-origin ICME observed by Wind. The left-handed ICME non-favorably oriented for magnetic reconnection with the surrounding right-handed, common-origin ICMEs. Therefore, two medium-separated counterparts despite belonging to a common solar wind structure, were potential to lead different geoeffectivity. This ultimately challenges space weather predictions based on early observations.

The high-redshift ($z>4$) compact sources with ``V-shaped" spectral energy distributions (SEDs), known as Little Red Dots (LRDs), are discovered by the James Webb Space Telescope and provide valuable clues to the physics of active galactic nuclei (AGNs) in the early universe. The nature of LRDs is controversial. Recently, several studies have investigated LRDs through variability, a characteristic feature of AGNs. These studies explore LRD variability by extrapolating empirical relationships from local quasars. Here, we adopt the Corona-heated Accretion-disk Reprocessing (CHAR) model, which is motivated by accretion physics and applicable to reproduce AGN conventional variability, to study the variability of $22$ LRDs in \citet{Tee2025}. Our results indicate that the observed variability in LRDs is dominated by measurement uncertainties. Within the CHAR model, the lack of variability in LRDs can be explained by two scenarios: either AGNs contribute $\lesssim30\%$ of the observed luminosities, or they are intrinsically luminous AGNs. We use simulations to demonstrate the observational requirements to effectively investigate LRDs via variability: first, a sample of about $200$ LRDs; second, each LRD has two observations separated by at least two years in the observed frame; third, the photometric uncertainty is $\leq 0.07$ mag. If the LRDs still lack variability under these conditions, the time-domain study would provide independent evidence that the accretion mode of LRDs differs significantly from low-redshift quasars.

We study the thermodynamic properties of a non-interacting, relativistic gas of charged scalar bosons in a uniform magnetic field, including both statistical and vacuum contributions at arbitrary field strengths. Focusing on the low-temperature regime and separating the Lowest Landau Level (LLL) from excited states provides a clearer view of the magnetic field's impact on thermodynamic quantities. We revisit Bose Einstein condensation (BEC), specific heat, magnetization, and the equation of state (EoS). A central result is the diffuse character of BEC induced by the magnetic field, reflected in the specific heat, which exhibits two plateaus: the first appears when the system becomes effectively one-dimensional through magnetic confinement, while the second-associated with the true one-particle ground state-is suppressed by the field. Consequently, no critical condensation temperature arises. For magnetization, the LLL contribution shifts from diamagnetic to paramagnetic As the field strengthen with the inclusion of the excited states, the statistical magnetization remains negative. In contrast, the vacuum contribution dominates at strong fields, driving paramagnetic. We also show that antiparticles enhance specific heat, magnetization, and total pressure. These effects are illustrated for a pion gas under neutron star conditions and compared with previous results for a neutral vector boson system.

We present the discovery of the planetary system orbiting the bright (V = 7.2), nearby (35 pc), Sun-like star HD 60779, which has a mass of 1.050 +/- 0.044 solar masses and a radius of 1.129 +/- 0.013 solar radii. We report two TESS transits and a subsequent CHEOPS transit of HD 60779 b, a sub-Neptune with a radius of 3.250 (+0.100 / -0.098) Earth radii on a 29.986175 (+0.000030 / -0.000033) day orbit. Additionally, 286 HARPS-N radial velocity measurements reveal the mass of planet b (14.7 +1.1 / -1.0 Earth masses) and the presence of an outer planet, HD 60779 c, with an orbital period of 104.25 (+0.30 / -0.29) days and a minimum mass (m sin i) of 27.7 +/- 1.6 Earth masses. Both planets' orbits are consistent with being circular, suggesting that they have a dynamically quiet history. The data are not sufficient to determine whether planet c transits. HD 60779's uniquely high systemic radial velocity (129.75 +/- 0.12 km/s) allows its Lyman-alpha emission to avoid absorption by the interstellar medium, making it a prime candidate for probing atmospheric escape from HD 60779 b. HD 60779 is also the third-brightest host of a sub-Neptune with orbital period greater than 25 days and with both mass and radius measured, distinguishing it in terms of accessibility to spectroscopic characterization.

With the discovery of the third confirmed interstellar object (ISO), 3I/ATLAS, we have entered a new phase in the exploration of these long-predicted objects. Though confirmed discovery of ISOs is quite recent, their utility as targets in the search for technosignatures (historically known as the Search for Extraterrestrial Intelligence -- SETI) has been discussed for many decades. With the upcoming NSF-DOE Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), the discovery and tracking of such objects is expected to become routine, and thus so must our examination of these objects for possible technosignatures. Here we review the literature surrounding ISOs as targets for technosignatures, which provides a well-developed motivation for such exploration. We outline four broad classes of technosignatures that are well suited for ISO follow-up, including the type of data needed and the best timing for study. Given the limitations in the current understanding of ISOs, we show that care must be taken in identifying technosignatures based primarily on comparison to objects in the Solar System. We therefore provide a roadmap for careful and consistent study of the population of ISOs in the hope of identifying technosignatures.

Magnetic effects have long been considered a possible factor in stabilizing the outer regions of active galactic nuclei (AGN) accretion disks against gravitational instability (GI). However, the computational demands of testing this hypothesis have prevented comprehensive study of this problem. Here, we present results from a suite of 6 isothermal magnetohydrodynamics (MHD) shearing box simulations, 3 initialized with strong magnetization ($\beta^{\rm{mid}}_{0} = p_{\rm{gas}} / p_{\rm{mag}} = 10^{2.5}$) and 3 initialized with weak magnetization ($\beta^{\rm mid}_{0} = 10^{4}$). For each magnetization, we performed simulations with both strong ($Q_{0} = 1.0$) and weak ($Q_{0} = 10.0$) self-gravity, where $Q_{0} = \frac{c_{\rm{s}}\Omega}{\pi G \Sigma_{0}}$ is the Toomre stability parameter; we also performed pure MHD simulations for comparison. We find that our strongly magnetized disk stabilized against GI after initialization to critical stability against GI, while our corresponding weakly magnetized disk did not. We show that the strongly magnetized, strongly self-gravitating disk became dominated by magnetic pressure, which led to its stabilization.

Spherical galaxy models with radially anisotropic velocity distributions merge faster than their isotropic counterparts. Here we investigate the effects of radially anisotropic haloes on the dynamics of disc galaxy encounters. We use stable galaxy models with isotropic bulges, thin rotating discs, and dark haloes which are either isotropic or radially anisotropic. Our simulations confirm that anisotropy can markedly accelerate orbit decay in galaxy interactions; in particular, radially anisotropic haloes transfer a good deal of orbital angular momentum to internal motions even before the galaxies reach their first pericentre. Consequently, for a given initial orbit, the anisotropic models undergo closer and more violent interactions, and their discs generate more massive tidal features. If real disc galaxies have radially anisotropic haloes, our findings may have implications for estimated merger time-scales and remnant morphology.

Binary systems surrounded by a circumbinary accretion flow can be subject to strong magnetic fields, potentially altering the character of the accretion flow itself, the evolution of the orbital dynamics, and outflow properties from the system. Here we focus on a regime where magnetic fields become so strong that the outer circumbinary flow becomes magnetically arrested, establishing a (circum)binary magnetically arrested disk ($\textit{BMAD}$) state. Such flows feature quasi-periodic magnetic flux eruptions, power jet-like magnetic tower outflows, and consequently alter the predominant contribution to angular momentum transfer inside the circumbinary disk. In this work, we provide a comprehensive analysis of the properties of these flows around equal-mass binary systems on circular orbits ultilizing massively parallel three-dimensional Newtonian magnetohydrodynamics simulations. We investigate the impact of the equation of state and of dynamical cooling, as well as that of the (large-scale) magnetic field topology. Our findings are as follows: (1) A magnetically arrested accretion flow through the cavity can generally be achieved, so long as the initial seed field is strong enough. (2) The cavity, and magnetic flux tube properties and their subsequent propagation are subject to the choice of equation of state/cooling physics. (3) We find tentative evidence that in some regimes the BMAD state, particularly during a flux eruption cycle, can aid shrinking of the binary's orbit. The regimes we explore have implications for multi-messenger transients to stars, supermassive and stellar black hole binaries and their orbital evolution in gaseous environments.

Gamma-ray bursts represent some of the most energetic and complex phenomena in the universe, characterized by highly variable light curves that often contain observational gaps. Reconstructing these light curves is essential for gaining deeper insight into the physical processes driving such events. This study proposes a machine learning-based framework for the reconstruction of gamma-ray burst light curves, focusing specifically on the plateau phase observed in X-ray data. The analysis compares the performance of three sequential modeling approaches: a bidirectional recurrent neural network, a gated recurrent architecture, and a convolutional model designed for temporal data. The findings of this study indicate that the Bidirectional Gated Recurrent Unit model showed the best predictive accuracy among the evaluated models across all GRB types, as measured by Mean Absolute Error, Root Mean Square Error, and Coefficient of Determination. Notably, Bidirectional Gated Recurrent Unit exhibited enhanced capability in modeling both gradual plateau phases and abrupt transient features, including flares and breaks, particularly in complex light-curve scenarios.

The dominant mechanisms underlying high-energy $\gamma$-ray emission from galaxies vary by galaxy type. In starbursts, a major contribution comes from neutral pion decay. This is driven by interactions between interstellar gas and hadronic cosmic rays (CRs), which are accelerated in strong shocks associated star formation activity and stellar remnants. Leptonic $\gamma$-ray emission can also arise from electrons directly energized in interstellar shocks, produced via charged pion decays, or emitted by pulsars and their surrounding halos. In quiescent galaxies, pulsars and their halos can represent a major $\gamma$-ray source class, with millisecond pulsars predominantly located in globular clusters (GCs) being particularly important. Recent detections of very high-energy (VHE) emission from Galactic GCs suggests they may also contribute to the TeV $\gamma$-ray flux from evolved galaxies. We consider a scenario where this VHE emission from GCs is powered by electrons accelerated in communal stellar/pulsar wind cluster termination shocks. These electrons undergo inverse Compton scattering as they propagate into GC magnetotails. Our results show that the high-energy emission from GCs can be an important contributor to the GeV and TeV flux from massive, quiescent galaxies. The relative strength of each component depends on the global galactic properties and its evolutionary history.

I present written notes from three lectures given at the 54th Saas-Fee Advanced Course of the Swiss Society of Astrophysics and Astronomy in January 2025 entitled "Galaxies and Black Holes in the First Billion Years as seen by the JWST". I focused my lectures on progress in studies of cosmic reionisation, the properties of galaxies in the reionisation era, topics related to the redshift frontier and the search for Population III stars. The lectures were given to graduate students in astrophysics and cover both pedagogical material as well as observational results from the first two and half years of JWST science operations. The pace of discovery with JWST is, of course, rapid and so my lectures discuss long-term goals, analysis methods and their assumptions and limitations in the hope that the underlying material will retain value in the near future. In this written version, the visual material is that presented at Saas-Fee in January 2025 but I have provided updates on progress from the literature up to August 2025. The material is aimed at early career researchers and should not be considered as a scholarly review of the entire JWST literature on high redshift galaxies

We investigate the star formation histories (SFHs) of a sample of massive galaxies ($M_\star \geq 10^{10} \, M_\odot$) in the redshift range $1 < z < 4.5$. We analyze spectro-photometric data combining broadband photometry from HST and JWST with low-resolution grism spectroscopy from JWST/NIRISS, obtained as part of the MIDIS (MIRI Deep Imaging Survey) program. SFHs are derived through spectral energy distribution (SED) fitting using two independent codes, BAGPIPES and Synthesizer, under various SFH assumptions. This approach enables a comprehensive assessment of the biases introduced by different modeling choices. The inclusion of NIRISS spectroscopy, even with its low resolution, significantly improves constraints on key physical parameters, such as the mass-weighted stellar age ($t_M$) and formation redshift ($z_{\mathrm{form}}$), by narrowing their posterior distributions. The massive galaxies in our sample exhibit rapid stellar mass assembly, forming 50\% of their mass between $3 \leq z \leq 9$. The highest inferred formation redshifts are compatible with elevated star formation efficiencies ($\epsilon$) at early epochs. Non-parametric SFHs generally imply an earlier and slower mass assembly compared to parametric forms, highlighting the sensitivity of inferred formation timescales to the chosen SFH model, particularly for galaxies at $z < 2$. Quiescent galaxies are, on average, older ($t_M \sim 1.1$ Gyr) and assembled more rapidly at earlier times than their star-forming counterparts. These findings support the ``downsizing'' scenario, in which more massive and passive systems form earlier and more efficiently.

Outflows are a key part of the galactic gas cycle and crucial in shaping the star formation activity in their host galaxy. Yet, in simulations of galaxy evolution, modeling these outflows in their multi-phase nature and over the relevant timescales is an unsolved problem. We present a subgrid model for simulating multiphase galactic outflows in efficient, comparatively low-resolution simulations, designed for application in future cosmological simulations. The cold phase (T = 10000 K) is treated as pressureless, and its interaction with the hot phase is captured through source terms representing drag and mixing. These terms are obtained using analytic drag and mixing terms for single clouds and convolving them with a cloud mass distribution consistent with high-resolution simulations. Applied to a setup resembling the starburst galaxy M82, the model reproduces the velocity, density, and mass outflow rates of high-resolution simulations that resolve individual cold clouds. Cold outflows emerge naturally from interactions between the hot wind and cold interstellar clouds, with drag and mixing both contributing to the acceleration. Varying the mixing strength strongly affects outflow properties: stronger mixing enhances mass transfer from hot to cold gas, reduces the hot phase velocity, and accelerates the cold phase, while also influencing the origin and composition of the cold outflow. Weak mixing produces cold gas mostly from preexisting interstellar clouds, whereas stronger mixing leads to substantial cold gas formation from the hot phase. This framework enables efficient simulations of multiphase galactic outflows while retaining key multi-component features of the outflow dynamics.

Generative models are a promising tool to produce cosmological simulations but face significant challenges in scalability, physical consistency, and adherence to domain symmetries, limiting their utility as alternatives to $N$-body simulations. To address these limitations, we introduce a score-based generative model with an equivariant graph neural network that simulates gravitational clustering of galaxies across cosmologies starting from an informed prior, respects periodic boundaries, and scales to full galaxy counts in simulations. A novel topology-aware noise schedule, crucial for large geometric graphs, is introduced. The proposed equivariant score-based model successfully generates full-scale cosmological point clouds of up to 600,000 halos, respects periodicity and a uniform prior, and outperforms existing diffusion models in capturing clustering statistics while offering significant computational advantages. This work advances cosmology by introducing a generative model designed to closely resemble the underlying gravitational clustering of structure formation, moving closer to physically realistic and efficient simulators for the evolution of large-scale structures in the universe.

The $\Lambda$CDM model faces significant challenges, including an incomplete understanding of the dark sector and persistent tensions in the Hubble constant and the clustering amplitude. To address these issues, we propose a general disformal coupling between dark energy (DE) and dark matter from a field-theoretic action which can generate a rich variety of interactions including conformal and pure-momentum coupling scenarios. Our analysis reveals that a pure disformal coupling naturally produces a unique interacting Early Dark Sector, wherein the interactions with dark matter suppress the Hubble friction on the DE scalar field leading to a kinetic-driven cosmological constant-like behavior at early times followed by its dilution as $a^{-6}$ and eventually leading to a potential-driven epoch characteristic of late-time dark energy. In contrast to existing Early Dark Energy (EDE) models that rely on finely-tuned potentials, the EDE-like behavior, in our framework, is purely a consequence of the disformal coupling paired with the dilution of dark matter, offering a more fundamental and less ad hoc solution to cosmological tensions. This framework also predicts a suppression of power in the CMB temperature spectrum on large angular scales, offering a potential physical explanation for the observed low-$\ell$ anomaly. By deriving these effects from a fundamental action, our work provides a unified, testable alternative to $\Lambda$CDM that can be constrained by next-generation cosmological surveys and gravitational wave observations.

Radio observations of the M87 jet reveal limb-brightened features that exhibit temporal variations, with the brighter limb side not remaining consistently fixed at the subparsec scales. Utilizing a force-free jet model that considers exclusively the relativistic plasma dynamics along large-scale magnetic fields attached onto the central black hole, we examine the effects of asymmetric plasmoid injections within the subparsec jet. At subparsec scales, the jet velocity is predominantly influenced by poloidal velocity, leading to distinctive characteristics in both the morphology and trajectories of the plasmoids injected within the jet. We explore the potential modifications to the limb-brightened subparsec jet images resulting from the injection of asymmetric, shearing plasma, which is traditionally considered solely under conditions of stationary and symmetric mass loading. By comparing the model jet properties with the 43 GHz observations of the M87 jet, it is suggested that the asymmetric injection of plasmoids within the jet offers a satisfactory explanation for the observed velocity variations and morphological dynamics of the M87 jet.

We consider the impact of non-power-law spectra of matter perturbations with a bump or with a blue tilt at small scales on the evolution of supermassive black holes (SMBHs) located the innermost part of galaxies. We study SMBH's mass growth rate and the epochs of their birth in four cosmological models using N-body simulations of dark matter within the box of $(100$~Mpc$/h)^3$. The simulations were populated with SMBHs using TRINITY semi-analytic model. We found that the most massive SMBHs at the redshifts $z=5-6$ are similar in all considered cosmologies, including the standard $\Lambda$CDM model. At larger $z$ the bumpy spectra can provide a tenfold increase (relative to $\Lambda$CDM model) in the masses of individual black holes without requiring super-Eddington accretion or heavy seeds. The nucleation of SMBHs starts at $z\sim 13$, which is earlier than in the standard $\Lambda$CMD model.

Kinematics of solar eruptive filaments is one of the important diagnostic parameters for predicting whether solar eruptions would induce geomagnetic storms. Particularly, some geomagnetic storms might be induced by solar filament eruptions originating from unexpected surface source regions because of non-radial ejection. The non-radial ejection of filaments has received widespread attention but remains inconclusive. We select two eruptive filaments, both of which are supported by flux ropes, as indicated by the hot channel structures seen in the 94 Å images and the hook-shaped brightenings where the filament material falls back. We measure the three-dimensional ejection trajectory of the eruptive filaments by integrating the simultaneous observations from SDO and STEREO. Furthermore, we calculate the distribution of the poloidal field along the ejection path and compare it to the ejection acceleration. It is revealed that the reinforcement of the poloidal magnetic field may lead to the suppression of the acceleration, with the acceleration resuming its increase only when the poloidal field diminishes to a certain level. Additionally, we compute the spatial distribution of the poloidal field in various directions and find that the poloidal magnetic field above the filaments is asymmetric. For both investigated events, the filaments appear to eject towards the side where the poloidal magnetic field is weaker, indicating that the eruptive filaments tend to propagate along the side with weaker strapping force. This may provide a new explanation for the inclined ejection of filaments.

Dark matter halos are fundamental cosmological structures whose properties-such as concentration, ellipticity, and mass centroid-encode information about their formation and evolution. Concentration traces collapse time and internal structure, while ellipticity and centroid offsets reflect halo shape and dynamical state. Accurate characterization of these properties improves mass estimates and tests dark matter models. Gravitational lensing, which directly probes projected mass distributions, provides a powerful means to constrain halo structure. We present a 2D weak-lensing analysis of 299 RedMaPPer clusters using shear measurements from the HSC-SSP first-year data release. By fitting elliptical NFW models with mass priors from the RedMaPPer cluster richness-mass relation, considering the priors helps us break the mass-concentration degeneracy and tighten constraints on other parameters. The derived concentration-mass relation exhibits a slightly steeper slope than traditional weak-lensing power-law or upturn models, and agrees more closely with the results from strong lensing selected halos. More massive and lower-redshift clusters tend to have lower concentrations and appear more spherical. The halo ellipticity distribution is characterized by e=1-b/a=0.530+/-0.168, with a mean of <e>=0.505+/-0.007. We also detect a bimodal distribution in the offsets between optical centers and mass centroids: some halos are well-aligned with their brightest cluster galaxy (BCG), while others show significant displacements. These results highlight the power of 2D weak-lensing modeling in probing halo morphology and in providing key inputs for understanding and modeling systematic effects in stacked lensing analyses.

We present a conditional variational autoencoder (CVAE) that generates stellar spectra covering 4000 $\le$ $T_{\mathrm{eff}$ $\le$ 11,000 K, $2.0 \le \log g \le 5.0$ dex, $-1.5 \le [\mathrm{M}/\mathrm{H}] \le +1.5$ dex, $v\sin i \le 300$ km/s, $\xi_t$ between 0 and 4 km/s, and for any instrumental resolving powers less than 115,000. The spectra can be calculated in the wavelength range 4450-5400 Å. Trained on a grid of \textsc{SYNSPEC} spectra, the network synthesizes a spectrum in around two orders of magnitude faster than line-by-line radiative transfer. We validate the CVAE on $10^4$ test spectra unseen during training. Pixel-wise statistics yield a median absolute residual of <$1.8\times10^{-3}$ flux units with no wavelength-dependent bias. A residual error map across the parameters plane shows $\langle|\Delta F|\rangle<2\times10^{-3}$ everywhere, and marginal diagnostics versus $T_{\mathrm{eff}}$, $\log g$, $v\sin i$, $\xi_t$, and $[Fe/H]$\ reveal no relevant trends. These results demonstrate that the CVAE can serve as a drop-in, physics-aware surrogate for radiative transfer codes, enabling real-time forward modeling in stellar parameter inference and offering promising tools for spectra synthesis for large astrophysical data analysis.

As the frontier of precision astronomical photometry continues to advance, correcting for time-variable atmospheric transmission becomes increasingly important. We describe an observational approach to monitoring optical attenuation due to atmospheric aerosols, using a multiband filter and disperser on the Auxiliary Telescope at the Vera C. Rubin Observatory. This configuration allows us to perform simple aperture photometry on four notched-out spectral regions, covering 347 to 618 nm. We see clear evidence of temporal variations in extinction across these bands, which we attribute to variation in the aerosol content of the atmosphere above the observatory. The observed differences in extinction between the reddest and bluest band can exceed 5 mmag/airmass, highlighting the importance of including variable aerosols in the transmission of the atmosphere. We aspire to using precise determinations of the optical transmission of the atmosphere to enable a forward-modeling approach to achieving mmag photometric precision with Rubin data.

We present observations of the mid-sized Kuiper belt objects (KBOs) Salacia-Actaea and Máni, obtained with the Near-Infrared Spectrograph on JWST. The satellite Actaea was fully blended with Salacia at the spatial resolution of the integral field unit, and we extracted the combined spectrum. The 0.7-5.1 ${\mathrm \mu}$m reflectance spectra of Salacia-Actaea and Máni display prominent water-ice absorption bands at 1.5, 2, 3, and 4-5 ${\mathrm \mu}$m. The $\nu_3$ fundamental vibrational band of carbon dioxide ice at 4.25 ${\mathrm \mu}$m is present in both spectra. From a quantitative band-depth analysis of the entire current JWST spectroscopic sample of water-ice-rich KBOs, we find strong evidence for a positive covariance between relative water-ice abundance and size, which may indicate the emergent impacts of internal differentiation and cryovolcanic production of surface water ice on mid-sized KBOs. A detailed look at the distribution of 2- and 3-${\mathrm \mu}$m band depths suggests additional sources of variability, such as different water-ice grain sizes. In addition, we report an apparent transition in the carbon dioxide band depth at diameters of roughly 300-500 km, with larger objects showing systematically weaker absorptions, although selection effects within the sample do not allow us to confidently distinguish between a size-dependent phenomenon and a correlation with dynamical class. The band shape of the carbon dioxide feature also varies with size: while small KBOs have narrow bands centered at ~4.27 ${\mathrm \mu}$m, the largest objects have broader, blue-shifted features that may include contributions from carbon dioxide in an irradiated, mixed, and/or layered state.

We examine the spatial distributions of LBV's, B[e] supergiants, and W-R stars in the LMC, to clarify their relative ages, evolutionary states, and relationships. This survey employs a reference catalog that was not available for previous work, comprising more than 3900 of the LMC's most luminous stars. Our analysis shows that LBV's, B[e] supergiants, and WR's have spatial distributions like normal stars with the same spectral types and luminosities. Most LBV's are not isolated, nor do they require binary or multiple status to explain their spatial relationship to other populations. There are two likely exceptions: one lower-luminosity LBV and one LBV candidate are relatively isolated and may have velocities that require additional acceleration. The B[e] supergiants are spatially and kinematically more dispersed than LBV's, suggesting that they belong to an older population. The most luminous early-type WN's are most closely associated with the evolved late O-type supergiants. The high luminosity late WN's, however, are highly concentrated in the 30 Dor region which biases the analysis. The less luminous WN's and WC's are associated with a mix of evolved late B, A-type, and yellow supergiants which may be in a post-red-supergiant phase. Spatial distributions of the less luminous WN, WC, and WN3/O3 stars reinforce proposed evolutionary links among those subtypes. Our analysis also demonstrates the importance of using a comprehensive census, with reference populations clearly defined by spectral type and luminosity, and how small number statistics, especially combined with spatial clustering, can invalidate some commonly-cited statistical tests.

We present the discovery of a companion to the Y-dwarf, CWISEP J193518.59-154620.3, the second Y-Y dwarf binary detected to date. Y-dwarfs are the coldest known free-floating objects ($<$ 500 K) and on average represent the lowest mass objects directly formed through turbulent fragmentation of a molecular cloud. Studying their multiplicity allows us to place strong constraints on the ability to form multiple systems of planetary masses and approaching the opacity limit of fragmentation. Due to their physical properties, Y-dwarfs also serve as analogs to gas giant planets. CWISEP J193518.59-154620.3 has been shown to have a unique methane emission feature in its near infrared spectrum at 3.326 $\mu$m, potentially indicative of auroral processes without a clear origin. CWISEP J193518.59-154620.3 was observed with JWST's MIRI in the F1000W, F1280W, and F1800W filters. We applied a point-spread function (PSF) fitting algorithm using empirically derived PSF models and resolve a companion in the F1000W and F1280W filters separated by 172 milli-arcseconds, 2.48 au assuming the distance of 14.43 pc. Using the ATMO2020 evolutionary models, we estimate a mass of 12-39 $M_{\rm Jup}$ for the primary and 7-24 $M_{\rm Jup}$ for the companion assuming an age of 1-10 Gyr for a mass ratio of 0.55-0.62, resulting in an estimated period of 16-28 years. It is unknown which component of this binary exhibits the methane emission feature. We also resolve known companions WISE J014656.66+423410.0B and WISE J171104.60+350036.8B using MIRI data and present their F1000W and F1280W photometry.

We present a foundational, scalable algorithm architecture for processing data from aperture synthesis radio telescopes. The analysis leading to the architecture is rooted in the theory of aperture synthesis, signal processing and numerical optimization keeping it scalable for variations in computing load, algorithmic complexity, and accommodate the continuing evolution of algorithms. It also adheres to scientific software design principles and use of modern performance engineering techniques providing a stable foundation for long-term scalability, performance, and development cost. We first show that algorithms for both calibration and imaging algorithms share a common mathematical foundation and can be expressed as numerical optimization problems. We then decompose the resulting mathematical framework into fundamental conceptual architectural components, and assemble calibration and imaging algorithms from these foundational components. For a physical architectural view, we used a library of algorithms implemented in the LibRA software for the various architectural components, and used the Kokkos framework in the compute-intensive components for performance portable implementation. This was deployed on hardware ranging from desktop-class computers to multiple super-computer class high-performance computing (HPC) and high-throughput computing (HTC) platforms with a variety of CPU and GPU architectures, and job schedulers (HTCondor and Slurm). As a test, we imaged archival data from the NSF's Karl G. Jansky Very Large Array (VLA) telescope in the A-array configuration for the Hubble Ultra Deep Field. Using over 100 GPUs we achieve a processing rate of ~2 Terabyte per hour to make one of the deepest images in the 2 -- 4 GHz band with an RMS noise of ~1 microJy/beam.

This article presents a publicly available, multimodal, tiered magnetic polarity inversion lines (MPILs) dataset extracted from the Solar Dynamics Observatory's (SDO) Helioseismic and Magnetic Imager (HMI) Active Region Patches (SDO/HMI HARP) between May 2010 and April 2025. The dataset comprises four distinct tiers, each generated by running our detection methodology with four different magnetic field strength thresholds to capture nuanced variations in MPIL features at multiple levels of detail. In total, we provide 6,695 HARP series mapped using the Lambert Cylindrical Equal Area (CEA) projection at a 12-minute cadence. This tiered approach ensures that each tier captures specific sensitivities to polarity changes, enabling researchers to tailor their analyses to a range of scientific and operational objectives. In each threshold tier, we offer six binary MPIL masks associated with heliophysics and space weather forecasting, including MPIL, Region of Polarity Inversion (RoPI), positive and negative polarity regions, unsigned polarity regions, and MPIL convex hulls. Furthermore, structured metadata in the form of multivariate time series is included, allowing users to track and analyze MPIL properties over time.

Both observations and models of flare-associated coronal mass ejections (CMEs) suggest that magnetic reconnection in an ejection's wake substantially increases the net, outward Lorentz force accelerating the CME. A stronger outward force can cause a feedback loop, driving further magnetic reconnection in a "reconnective instability." The flux accretion model captures this by relating reconnected flux (Delta Phi_rec) and magnetic field strength (B_CME) to increased outward Lorentz force (Delta F_r). To better understand reconnection's role in CME dynamics, we analyze two snapshots from a 2.5D, MHD simulation of a breakout eruption. Outward Lorentz forces increase substantially as reconnection proceeds, caused primarily by "flank currents," which flow just inside the boundary of the rising ejection's wake and parallel to its axis. This model's reconnection jet also alters the ejection's internal structure, an effect that could be sought in observations. Analyzing reconnection-induced Lorentz forces in 3D simulations could provide additional insights into CME dynamics.

Cosmic inflation is one of the most important paradigms in modern cosmology. In its simplest form, inflation is driven by a single inflaton field. However, multi-field inflation has become increasingly attractive because it can solve many theoretical and observational challenges. In this paper, we propose a particular model involving two axion-like fields with simply monodromy-dominated potentials. We demonstrate that this model is consistent with current cosmological observations.

DESI observations of baryon acoustic oscillations (BAOs), combined with cosmic microwave background (CMB) and type-Ia supernova (SN Ia) data, suggest that the dark energy equation of state $w_{\rm DE}$ crosses the phantom divide from $w_{\rm DE} < -1$ to $w_{\rm DE} > -1$ at low redshifts. In shift-symmetric Horndeski and generalized Proca theories with luminal gravitational-wave speed and no direct couplings to dark matter, we show that such a phantom-divide crossing is generically difficult without introducing theoretical pathologies. In Horndeski theories, however, breaking the shift symmetry allows this transition. We present an explicit model with broken shift symmetry, in which the scalar field has a potential in addition to a Galileon self-interaction and a higher-order derivative term. This model realizes the desired phantom-divide crossing at low redshifts while avoiding ghosts and Laplacian instabilities.

Recent measurements from the Atacama Cosmology Telescope (ACT), combined with Planck and DESI data, suggest a scalar spectral index $n_s$ higher than the Planck 2018 baseline, thereby placing conventional attractor-type inflationary models such as Starobinsky $R^2$ and Higgs inflation under increasing tension at the $\gtrsim 2\sigma$ level. In this work, we examine quantum-corrected $\phi^4$ inflation with a non-minimal coupling to gravity. Introducing an anomalous scaling parameter $\gamma$ to capture quantum corrections to the effective potential, we derive analytic expressions for the inflationary observables $n_s$ and $r$. Confronting these predictions with ACT, Planck, and BAO+lensing constraints, we demonstrate that modest values of $\gamma$ can raise $n_s$ into the ACT-preferred range while maintaining a strongly suppressed tensor-to-scalar ratio. For instance, with $N=60$ and $\gamma\simeq 0.006$, the model predicts $n_s\simeq 0.974$ and $r\simeq 0.007$, in excellent agreement with current bounds. We further investigate preheating dynamics, focusing on particle production via parametric resonance in quantum-corrected $\phi^4$ inflation with a non-minimal coupling to gravity. In this scenario, the inflaton $\phi$ couples to an additional scalar $\chi$ through an interaction $g^{2}\phi^{2}\chi^{2}$. In Minkowski spacetime, the resonance dynamics reduce to the Mathieu equation, and we find that broad resonance can be readily achieved, leading to efficient particle production.

Information field theory (IFT) is the application of probabilistic reasoning to fields. Physical fields are mathematical functions over continuous spaces that exhibit certain properties of regularity, such as limited variance and finite gradients. Inferring a field from an observational dataset should exploit these regularities. However, the finite number of constraints that the data provides is insufficient to determine the infinite number of degrees of freedom of a field. IFT enables us to derive optimal field inference algorithms that explicitly exploit domain knowledge. These algorithms can be implemented via Numerical Information Field Theory (NIFTy). In NIFTy, neural operator forward models can be written and inverted probabilistically. NIFTy thereby infers fields and their remaining uncertainties. This is achieved using novel variational inference schemes that scale quasi-linearly, even for ultra-high dimensional problems. This paper introduces the basic concepts of IFT and NIFTy, highlights a few of their astrophysical applications, and discusses their artificial intelligence (AI) perspective. Finally, UBIK (the Universal Bayesian Imaging Kit), an emerging customisation of NIFTy for a suite of astrophysical telescopes, is presented as a central tool to the topic of the UniversAI conference.

Wandering massive black holes (MBHs) are thought to form through gravitational recoil or galaxy mergers, but observational confirmation of their displacement in dwarf galaxies, critical laboratories for early-universe SMBH seeding, remains scarce. Using multi-epoch very long baseline interferometry (VLBI), we identify a displaced MBH in the dwarf galaxy MaNGA 12772-12704, located 0.94 kilo-parsec from its optical center. The source exhibits unambiguous signatures of an accreting MBH: a brightness temperature exceeding $10^9$K, a parsec-scale jet, and flux density variability over a 30-year baseline. This system provides the first robust evidence that dynamical black hole interactions predicted in hierarchical galaxy evolution occur even in low-mass hosts. The discovery challenges models requiring centralized gas reservoirs for MBH growth and directly informs high-redshift seeding scenarios.

The black hole low-mass X-ray binary (LMXB) candidate IGR J17091-3624 experienced a hard-state-only outburst in 2025. In this paper, we show that IXPE detected a series of intermittent X-ray dips, spanning a total interval of ~1 day. Subsequent observations with NICER, EP, NuSTAR, and Swift reveal that these dips recur with a period of 2.83$\pm$0.07 days and are accompanied by an increase in spectral hardness. This is the first time such quasi-periodic dipping behavior has been observed in this target since discovery. Our spectral analysis shows that the dips can be explained by obscuration from an ionized absorber characterized by an ionization parameter of $log{\xi}$ ~1-3 erg cm s$^{-1}$ and an equivalent hydrogen column density of $N^{\rm zxipcf}_{\rm H}$~(1-30)$\times10^{22}$ cm$^{-2}$. The periodic reappearance of the absorber is likely caused by obscuring material located in the outer accretion disk, modulated by the binary orbital period. If confirmed, this period would suggest that the donor star in IGR J17091-3624 has deviated from the standard main-sequence evolutionary path and is likely a (partially) stripped giant. In the optical band, no significant periodicity or correlation with the X-ray dips was detected, whereas the radio counterpart exhibited a flat to steep spectrum, in contrast to the inverted spectrum typically observed during the hard state of LMXBs.

We present \emph{Unified Lagrangian Perturbation Theory} (ULPT), a perturbative framework for consistently modeling galaxy density fluctuations across real space, redshift space, and post-reconstruction fields. Unlike existing approaches that treat these cases separately, ULPT provides a single theoretical structure that incorporates the three essential coordinate mappings: the Lagrangian-to-Eulerian transformation, the real-to-redshift mapping induced by peculiar velocities, and the remapping from pre to post reconstruction. A key feature of our formulation is the explicit decomposition of the density field into two physically distinct components: the \emph{Jacobian deviation}, which encodes intrinsic linear and nonlinear growth, and the \emph{displacement-mapping effect}, which captures large-scale convective distortions. This separation enables a fully analytic and infrared (IR)-safe resummation, ensuring exact IR cancellation, a consistent Gaussian description of baryon acoustic oscillation (BAO) damping, and the correct residual structure in cross spectra between fields with distinct IR behavior. The perturbative expansion of ULPT naturally generates Galileon-type operators, thereby providing a compact and physically motivated operator basis for nonlinear and nonlocal Lagrangian bias, and allowing for a renormalization-free treatment of biased tracers. Within this framework, we derive a unified expression for the power spectrum that applies equally to dark matter, biased tracers, redshift-space distortions, and reconstructed fields. ULPT thus offers a robust and extensible foundation for precision modeling of large-scale structure, with potential extensions to higher-order statistics, such as the bispectrum, and to other two-point observables, such as galaxy--galaxy lensing.

The first detection of a gravitational-wave (GW) signal in 2015 has opened a new observational window to probe the universe. This probe can not only reveal previously inaccessible binaries, black holes, and other compact objects, but also can detect exoplanets through their imprint on GW signals, thereby significantly extend current exoplanet surveys. To date, nearly 6000 exoplanets have been confirmed, yet most of them reside either in the solar neighbourhood or along the sightline toward the Galactic bulge, reflecting the range limits of traditional electromagnetic techniques. In this work, we follow the method proposed in this http URL&this http URL(2019) to investigate frequency modulations in GW signals from early-stage binary neutron stars (BNSs) induced by circumbinary planets (CBPs) and obtain that CBPs can be detected by the future space-borne detector DECi-hertz Interferometer Gravitational wave Observatory (DECIGO). For BNS system with the masses of two components both being 1.4 $M_{\odot}$, DECIGO could detect CBPs with mass being dozens of times that of Jupiter out to distances of $\sim 1$ Gpc, well beyond the Local Supercluster, offering an unprecedented opportunity to study planetary formation and evolution for the post main-sequence stage.

Time series data and their time-frequency representation from gravitational-wave interferometers present multiple opportunities for the use of artificial intelligence methods associated with signal and image processing. Closely connected with this is the real-time aspect associated with gravitational-wave interferometers and the astrophysical observations they perform; the discovery potential of these instruments can be significantly enhanced when data processing can be achieved in O(1s) timescales. In this work, we introduce a novel signal and noise identification tool based on the YOLO (You Only Look Once) object detection framework. For its application into gravitational waves, we will refer to it as GW-YOLO. This tool can provide scene identification capabilities and essential information regarding whether an observed transient is any combination of noise and signal. Additionally, it supplies detailed time-frequency coordinates of the detected objects in the form of pixel masks, an essential property that can be used to understand and characterize astrophysical sources, as well as instrumental noise. The simultaneous identification of noise and signal, combined with precise pixel-level localization, represents a significant advancement in gravitational-wave data analysis. Our approach yields a 50\% detection efficiency for binary black hole signals at a signal-to-noise ratio (SNR) of 15 when such signals overlap with transient noise artifacts. When noise artifacts overlap with binary neutron star signals, our algorithm attains 50\% detection efficiency at an SNR of 30. This presents the first quantitative assessment of the ability to detect astrophysical events overlapping with realistic, instrument noise present in gravitational-wave interferometers.

This study examines the rotational characteristics of asteroids through statistical modeling of the diameter-period relationship. A statistical evaluation of the diameter-period relationship was conducted using a dataset of 34,326 asteroids. Clustering identified three main groups, including a dense cluster below the spin barrier, a population of small, fast-rotating asteroids, and a more diffuse group. Geometric and density-based analyses showed that the densest region consists of objects with diameters from 3 to 10 km and rotation periods between 3 and 9 hours, some of which extend beyond the spin barrier. Polynomial modeling demonstrated that a third-degree fit provides the most stable representation of the overall trend without overfitting. Additionally, an empirical lower boundary was identified and proposed, below which no asteroid was found in either the main sample or the selected targets.

The C-MetaLL project has provided homogeneous spectroscopic abundances of 290 Classical Cepheids (DCEPs) for which we have the intensity-averaged magnitudes in multiple optical and near-infrared (NIR) bands, periods, pulsation modes, and Gaia parallaxes. Our goal is to derive updated period--Wesenheit--metallicity (PWZ) relations using the largest and most homogeneous metallicity sample ever used for such analyses, covering a range of $-1.3<$[Fe/H]$<+0.3$ dex. We computed several optical and NIR Wesenheit magnitudes using 275 DCEPs with reliable parallaxes, by applying a robust photometric parallax technique, which simultaneously fits all parameters -- including the global Gaia parallax counter-correction -- and handles outliers without data rejection. We find a stronger metallicity dependence ($\gamma \approx -0.5$ mag/dex in optical, $-0.4$ mag/dex in NIR) than recent literature reports. Gaia parallax zero-point conter-corrections ($\epsilon$) vary smoothly across bands, with an average value of $\sim$10 $\mu$as, aligning with previous determinations. Applying our PWZ relations to LMC Cepheids yields distances generally consistent within $1\sigma$ with geometric estimates. The choice of reddening law has a negligible impact, while using only fundamental-mode pulsators significantly increases the uncertainties. Including $\alpha$-element corrections increases $|\gamma|$ and reduces $\epsilon$. However, we find statistically consistent $\gamma$ values with the literature, particularly for the key Wesenheit magnitude in the HST bands, by restricting the sample to the brighter (i.e. closer) objects, or by including only pulsators with $-0.7<$[Fe/H]$<$0.2 dex. Our results hint at a large $\gamma$ or a non-linear dependence on metallicity of DCEP luminosities at the metal-poor end, which is difficult to quantify with the precision of parallaxes of the present dataset.

Next-generation air-shower detectors, such as the Global Cosmic Ray Observatory (GCOS) and the Probing Extreme PeVatron Sources (PEPS) experiment, are considering water-Cherenkov detectors as a base design. A key factor in improving the sensitivity to ultra-high-energy gamma rays and to the mass composition of ultra-high-energy cosmic rays is the ability to measure the muonic content of air showers. To address this, a layered water Cherenkov tank design has been previously proposed. The water volume of the tank is divided into two optically separated layers. The electromagnetic component of the shower is mostly absorbed in the top layer, while the bottom layer records the light produced by through-going muons. Two prototype tanks were deployed at the Pierre Auger Observatory site in 2014 and have been recording data for more than 10 years. We present the performance of the prototype tanks and compare it with simulations, focusing mostly on the calibration. We investigate different dimensions for the water volumes. For the GCOS Observatory, one important challenge is to cover extremely large surfaces of 40000 km$^2$ to 60000 km$^2$ and achieve 100% efficiency at 10 EeV. Based on the size of the footprint of air-showers, we compute the number and spacing of detectors needed to fulfill the GCOS requirements.

Recent progress has shown that the geomagnetic field exerts a more significant impact than expected on the behavior of charged secondary particles in inclined air showers. In this study, we for the first time combine it with atmospheric effects to construct a bi-effect model, aiming to investigate the lateral distribution of particles on the ground plane. Despite the complex physical interactions during the development of air showers, a simple formula can describe the overall deflection of $\mu^{\pm}$ and accurately fit the deflection in simulated air showers, thereby validating the hypotheses about these effects in this study. Furthermore, we have obtained the relationship between model parameters and primary particle information for different experimental sites. This new model is highly successful and is promising to provide new insights for improving detector layout design and air shower reconstruction.

Latitudinal variations in turbulent heat flux play a key role in the thermal and magnetic evolution of rapidly rotating planets and stars. Although global spherical-shell simulations have documented such variations, explicit latitude-dependent scaling relations for heat transport have remained elusive. Here we employ the rotating Rayleigh-Bénard convection (RRBC) framework with tilted rotation and gravity axes to model convection at different latitudes $\varphi$ in the geostrophic regime. We derive scaling relations for the latitude dependence of convective length scales $\ell(\varphi)$ and the Nusselt number $Nu(\varphi)$. At high latitudes, the scalings $Nu \sim \sin^{-4/3}\varphi$ (near onset) and $Nu \sim \sin^{-4}\varphi$ (above onset) emerge, while at low latitudes $Nu \sim \cos^{4}\varphi$. These predictions are validated against direct numerical simulations of convection in a spherical shell. The results provide a quantitative framework for regional thermal transport in planetary and stellar interiors and establish a unified interpretation of spherical convection that connects naturally with planar RRBC turbulence.

The interplay between radiative cooling of the circumgalactic medium (CGM) and feedback heating governs the evolution of the universe's most massive galaxies. This paper presents simulations of feedback processes in massive galaxies showing how kinetic, thermal, and magnetic active galactic nuclei (AGN) feedback interacts with the CGM under different environmental conditions. We find that in massive galaxies with shallower central gravitational potential and higher CGM pressure (multiphase galaxy; MPG) pure kinetic AGN feedback is most efficient in preventing CGM cooling from becoming catastrophic while maintaining the CGM entropy within the observed range. For the same galaxy, partitioning AGN energy injection into kinetic ($75\%$) and thermal ($25\%$) energy results in an entropy bump within $r\lesssim15$ kpc while also having a larger amount of cold gas extending out to $r\sim80$ kpc. A magnetohydrodynamic MPG run with seed magnetic field in the CGM (1~$\mu$G) and partial magnetised AGN feedback ($1\%$ of total AGN power) also shows a higher entropy (within $r<15$ kpc) and cold gas mass, albeit the cold gas remains constrained within $r\lesssim30$ kpc. For a similarly massive galaxy with deeper potential well and low CGM pressure (single phase galaxy; SPG) our simulations show that for both hydro and MHD runs with partial thermal AGN energy, the feedback mechanism remains tightly self-regulating with centrally concentrated cooling (within $r<1$ kpc). Our simulations of a similar mass galaxy with a deeper potential well and higher CGM pressure (SPG-Cool) show that our AGN feedback mechanism cannot get rid of the high CGM density and pressure and its long term evolution is similar to the multiphase galaxy.

We report the results of a simultaneous X-ray and optical spectroscopy campaign on the Galactic black hole X-ray binary V4641 Sgr, carried out with XRISM and the Seimei telescope during a low-luminosity phase towards the end of its 2024 outburst. Despite a very low X-ray luminosity of $10^{34}$ erg s$^{-1}$, the continuum spectrum is well reproduced by a disk blackbody model with a high inner disk temperature ($1.8$ keV). XRISM/Resolve provides the highest-resolution X-ray spectrum ever obtained from the source, and several strong, narrow emission lines were detected, resolved and characterized at a high significance level. The continuum shape and narrow emission lines both indicate that the inner disk region is obscured by the surrounding high-density gas, and the intrinsic luminosity is several orders of magnitude higher. In the simultaneous optical observation from the Seimei telescope, the line features are largely dominated by the optical companion. Although we detect a clear emission component in H$\alpha$ that could originate from a cold outflow or the disk atmosphere, there are no signs of the strong outflow signatures historically detected in this source. In X-rays, the combination of significantly redshifted ($\sim 700$ km s$^{-1}$) and weakly blueshifted ($\sim-250$ km s$^{-1}$) components, all varying strongly on ks timescales, along with a marginally significant (99.2%) highly blueshifted ($\sim-1200$ km s$^{-1}$) component, indicates a complex, inhomogeneous outflow geometry. This is corroborated by the erratic long-term evolution of the source seen in the complementary X-ray monitoring, and radio detections spanning 3 orders of magnitude.

The orientation of a polarization vector on the Poincare sphere is defined by its position and ellipticity angles. The radio emission from pulsars, magnetars, and fast radio bursts can be elliptically polarized, and measurements of the ellipticity angle (EA) have become increasingly important in interpretations and models of their polarization. An in-depth understanding of the statistical properties of the measured polarization angles is a prerequisite to their detailed interpretation. While the statistics of the position angle (PA) have been understood for some time, the statistics of the EA do not appear to be as well developed as those of the PA. The statistical properties of the EA are derived when the amplitude of the polarization vector is constant, to include its probability density, mean, standard deviation, and confidence limits. Similarly to the PA, the standard deviation and confidence limits of the EA vary inversely with the polarization signal-to-noise ratio. However, unlike the PA, the probability density of the EA is generally asymmetric, its standard deviation and confidence limits are dependent upon the intrinsic value of the EA, and the measured EA is biased by the instrumental noise, particularly at low signal-to-noise ratios and large values of the intrinsic EA. General expressions for the joint probability density of the polarization angles and the probability density of the EA are also derived when the amplitude of the polarization vector fluctuates due to the superposition of incoherent modes of orthogonal polarization.

We present near-infrared (NIR) and optical observations and analysis of the Type Ibn/Icn supernova (SN) 2023xgo, spanning the period from two days to 100 days past explosion. A comparison of the NIR light curves and color evolution with those of other Type Ibn SNe reveals prominent NIR excess persisting from 15 to 100 days. The spectral energy distribution (SED) is well explained by a combination of a hot blackbody component and a carbon dust model. The dust temperature remained relatively constant at $T=1600\pm100$ K up to $t=60$ d. The estimated dust mass is $\sim1.2 \times10^{-4}~M_{\odot}$. Based on the SN emission of $10^{42}$ erg s$^{-1}$ at peak luminosity, the evaporation radius is estimated to be $1.2\times10^{16}$ cm, consistent with the expectation from light travel time. The dust shell is located outside the shocked cool dense shell (CDS) at the position of $7.6\times10^{14}$ cm. It suggests that the observed NIR excess originates from pre-existing circumstellar (CS) dust. Considering a typical dust-to-gas mass ratio, the CS gas mass is estimated to be $\simeq10^{-2}~M_{\odot}$, implying a high mass-loss rate of $\sim0.1~M_{\odot}$ yr$^{-1}$ from either a low-mass helium star progenitor with a binary interaction, or may be a massive Wolf-Rayet star that experienced a significant eruption.

Coronal mass ejections (CMEs) are major drivers of space weather disturbances, and their deflection from the radial direction critically affects their potential impact on Earth. While the influence of the surrounding magnetic field in guiding CME trajectories is well established, accurately predicting non-radial propagation remains a challenge. In this work, we introduce and compare recently developed techniques for analyzing the early deflection of eruptive events. We revisit a largely deflected prominence-CME event of 2010 December 16 using an improved tracking framework and a new application of the topological path method. Our results suggest the deflection of the eruption is dominated by the channeling of the magnetic field lines. This study offers new physical insight into CME guidance mechanisms and validates the predictive capability of the topological path, highlighting its potential as a diagnostic tool for estimating the propagation direction of strongly deflected events.

All stars rotate. While magnetic braking slows massive stars, the effect a stellar companion has on stellar rotation is still being explored. To prepare for future observations from rotating core-collapse supernovae (CCSNe), we analyze a set of 30 2D neutrino radiation-hydrodynamic CCSN simulations for a variety of compactness values, rotation rates, and equations of state. We systematically explore how rotation lowers expected neutrino counts and energies for a realistic detector, while accounting for adiabatic Mikheyev-Smirnov-Wolfenstein matter effects. We quantify the effect of viewing angle for neutrino emission for multiple rotation rates. Using 'multimessenger synthesis', we develop a technique that correlates multimessengers to constrain the neutrino mass ordering for a future supernova event. Likewise, we develop a method to constrain the distance to a rotating or nonrotating CCSN, regardless of explosion outcome.

The stochastic-$\delta \mathcal{N}$ formalism is widely used to study inflation models in which the quantum diffusion of inflatons dominates the background dynamics, leading to interesting phenomena such as the production of primordial black holes. Among numerical approaches to calculate the curvature perturbation spectrum $\mathcal{P}_\zeta(k)$ in this formalism, the Monte Carlo simulation-based approach has been proposed as a promising choice, especially in multifield cases. In this approach, we generate many paths of inflatons from the initial points to the end of inflation, obtain statistics of $\delta N$ from the paths, and then estimate $\mathcal{P}_\zeta(k)$. However, this method involves a nested Monte Carlo simulation, which requires generating many branch paths from each trunk path at the point corresponding to the scale $k$ of interest, resulting in a high computational cost. In this paper, we propose a new Monte Carlo-based approach that utilizes least squares fitting, introducing two novel features for reducing computational cost. First, we devise a simple estimator of a key statistic $\langle \delta\mathcal{N}_{\mathbf{X}}^2\rangle$, the variance of $\delta \mathcal{N}$ conditioned on the branching point, to avoid nesting path generation. Second, via least squares fitting of a parametric function to the sampled values of the estimator, we obtain not just an estimate of $\mathcal{P}_\zeta(k)$ for a single value of $k$ but an approximating function of $\mathcal{P}_\zeta(k)$ over a range of $k$ of interest. We also conduct numerical demonstrations for concrete inflation models, which show the usefulness of our method.

Fast blue optical transients (FBOTs) are luminous, rapidly evolving events with blue spectra, possibly powered by newborn magnetars and linked to fast radio bursts (FRBs). Given this potential connection, we conducted deep radio observations of two nearby FBOTs (AT2018cow and CSS161010) using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), but detected no FRB-like signals. Our observations establish the most stringent upper limits on millisecond radio transients from FBOTs, reaching $\sim$10 mJy flux density. Assuming a log-normal luminosity function analogous to the repeating FRB 121102, we constrain the burst rate from potential magnetars in FBOTs to $<0.01$ hr$^{-1}$. The short ejecta escape timescale ($\sim$2.6 yr) compared to our observation epochs (4$-$6 years post-explosion) suggests that nondetection may not be attributed to FBOT's ejecta absorption. These findings impose useful constraints on the FRB activity emanating from newborn magnetars within FBOTs. They indicate that if there is a burst phase, it is either characterized by weaker bursts, occurs less frequently compared to those in known repeating FRB sources, or takes place beyond the time frame of our current observations. To gain deeper insights into the birth-related activity of magnetars, it is of importance to conduct timely and sustained FRB searches in FBOTs that emerge in the future.

We present 1.25 GHz observations of the rotating radio transient (RRAT) J2325-0530, conducted with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Approximately 60% of detected single pulses occur in clusters of 2 to 5 consecutive bursts. Consequently, the waiting-time distribution between successive single pulses exhibits a pronounced excess at one rotation period, deviating from the exponential distribution expected for a Poisson process. After grouping consecutive bursts into single emission events, the recalculated waiting-time distribution is well described by a Weibull distribution with a shape parameter $k \gtrsim 1$. Monte Carlo simulations incorporating both intrinsic burst on-windows and rotational modulation successfully reproduce the observed one-rotation excess. These results suggest that RRAT J2325-0530 emits through a quasi-random process with on-windows slightly longer than its spin period, modulated by the the rotation of emission beam. Additionally, the polarization position angle shows complex behavior that cannot be fully described by the standard rotating vector model, and several pulses exhibit quasi-periodic micro-structures. Taken together, these features indicate complex magnetospheric dynamics underlying the sporadic emission behavior of RRAT J2325-0530.

The very high-energy (VHE; $>$100 GeV) radiation carries the signatures of the matter-energy interaction in some of the most extreme astrophysical environments. Considering broad emission line blazars, i.e., flat spectrum radio quasars (FSRQs), the dense photon fields surrounding the relativistic jet can prohibit the particle population from accelerating to very high energies and producing VHE radiation. They can also possibly make the environment opaque for the VHE $\gamma$ rays due to $\gamma\gamma$ pair production, thus explaining the paucity of VHE-detected FSRQs and non-detection of TeV radiation ($>$1 TeV) from them. Here we report, for the first time, a $>$7$\sigma$ detection of an FSRQ, S5 1027+74 ($z=0.123$), in the VHE band, including the first ever detection of TeV emission from an object of this class, using the Fermi Large Area Telescope observations. Its $\gamma$-ray spectrum covering the 100 MeV to 2 TeV band revealed a prominent spectral break with a flat, rising shape above $\sim$10 GeV, a feature never detected from other VHE-detected FSRQs. The radio-to-$\gamma$-ray spectral energy distribution of S5 1027+74 provides strong evidence of a third bump peaking at multi-TeV energies. These enigmatic findings imply that FSRQ jets can accelerate particles to extremely high energies and provide tantalizing clues about the complex radiative environment of relativistic jets.

We report on the timing and spectral properties of PSR J1838-0655 using joint observations from the Neutron Star Interior Composition Explorer (NICER) and the Nuclear Spectroscopic Telescope Array (NuSTAR). By disentangling the pulsar's emission from its surrounding wind nebula across joint Chandra, NuSTAR, and NICER observations, we find the pulsar's broad-band X-ray spectrum (1.3--79\,keV) is best-described by a broken power-law model. The model features photon indices of $\Gamma_1 = 1.19 \pm 0.07$ and $\Gamma_2 = 1.47 \pm 0.02$ below and above a break energy of $E_{\rm b} = 7.7 \pm 0.8$\,keV. The resulting unabsorbed 2--10\,keV flux from the pulsar is $(9.5^{+0.4}_{-0.3}) \times 10^{-12}~\mathrm{erg\,cm^{-2}\,s^{-1}}$. Furthermore, timing analysis of NICER data spanning MJD 58250 to 60630 reveals a very large glitch occurring around MJD 59300, characterized by a frequency jump of $\Delta \nu = 29.367(7) \times 10^{-6}$ Hz, which can be well explained by the vortex creep model. Phase-resolved spectral analysis indicates a clear anti-correlation between the photon index and the pulse intensity, suggesting spectral hardening at the pulse peak.

Hot accretion disks around massive protostars provide a unique opportunity to study ice-free silicate grains that cannot be investigated in protoplanetary disks. We conduct a self-consistent investigation into grain-size evolution and its impact on (sub)millimeter-wave emission from massive protostellar disks. Our radiative transfer modeling accounts for dust self-scattering and includes vertical temperature gradients in the disk structure. The results show that once silicate grains grow to sizes exceeding the observing wavelength, enhanced scattering dims the disk emission by 20\%--30\% relative to the blackbody emission expected at the disk surface temperature. By comparing our model with Atacama Large Millimeter/submillimeter Array 1.14 mm observations of the disk around the massive protostar GGD27-MM1, we constrain the threshold velocity for collisional fragmentation of silicate grains to approximately 15 m s-1. This fragmentation velocity is lower than the typical maximum collisional velocities in protoplanetary disks around low-mass stars, suggesting that collisional coagulation alone is insufficient for silicate dust to form rocky planetesimals in such environments. Furthermore, our analysis identifies two potential scenarios to better reproduce the bright inner-disk emission of GGD27-MM1. One possibility is that the grain growth is limited to 160 mum by another growth barrier (e.g., collisional bouncing), reducing scattering dimming. Alternatively, the stellar luminosity may be as much as five times higher than current estimates, compensating for the reduced brightness. Future multiwavelength observations, particularly at shorter submillimeter wavelengths, will be crucial to distinguish between these scenarios and further constrain silicate grain coagulation processes in massive protostellar disks.

We present a Chandra/ACIS-I study of X-ray sources in BOSS 1441, a protocluster at $z=2.32\pm0.02$ that exhibits a prominent overdensity of Ly$\alpha$ emitters (LAEs). Using a 45 ks observation, we identify seven X-ray sources spatially coincident with LAE density peaks. The average X-ray photon index for the seven sources, derived from an absorbed power-law model with Galactic absorption fixed, is 1.49 (ranging from -0.68 to 2.51), corresponding to an average luminosity of $\rm 6.85\times 10^{44}~erg~s^{-1}$ in the rest-frame 2-33 keV band, with individual luminosities spanning $(3.57 - 13.96)\rm\times 10^{44}~erg~s^{-1}$. Three sources exhibit relatively flat spectral slopes. Two are associated with the MAMMOTH-1 nebula, while the third, located at the edge of BOSS 1441 with a $> 5'$ offset from the LAE density peak, resides in a region with a high submillimeter-band density. We estimate the fraction of X-ray detected AGNs among the LAEs to be $11.5^{+3.8}_{-4.6}\%$, approximately double that of previously studied LAEs. This elevated fraction suggests BOSS 1441 is in a mature evolutionary stage, with even higher AGN fractions expected in massive LAEs such as PKS 1138-262. In contrast, the submillimeter galaxy population shows a lower AGN fraction ($6.9^{+6.9}_{-4.5}\%$), consistent with their typically obscured nature. These results indicate that the protocluster's massive galaxies are evolving into the bright red sequence galaxies observed in local clusters, where AGNs likely play a critical role in quenching their star formation.

We determined the metal/silicate partition coefficients of hydrogen and carbon, DH and DC, simultaneously under typical conditions of Earth's core formation. Experiments demonstrate that both DH and DC diminish in the presence of carbon and hydrogen, respectively, indicating their strong interactions in liquid metal. With these partitioning data, we investigated the core and bulk Earth abundances of hydrogen and carbon based on core formation scenarios that are compatible with the bulk silicate Earth composition and the mass fraction and density deficit of the core. The results of the single-stage core formation modelling are markedly different from those using DH and DC individually determined in earlier experiments, indicating that the Earth building blocks do not match enstatite chondrites in water abundance and require contributions by carbonaceous chondrites. The multi-stage core formation models combined with an Earth accretion scenario accounting for isotopic composition show 0.18-0.49 wt% H and 0.19-1.37 wt% C in the core, leading to 0.53-1.40 wt% H2O (present as H in the core) and 0.07-0.44 wt% C in the bulk Earth. Our modelling also demonstrates that up to 53% and 72% of Earth's water (hydrogen) and carbon, respectively, could have been derived from non-carbonaceous chondritic materials.

Astrochemical models can be greatly simplified, with obvious computational advantages, if the reaction networks for key species can be reduced to a bare minimum. In addition, if chemical equilibrium holds, then simple analytical solutions can be formulated. These have particular advantages in the application to complex models evolving over multi-point spatial grids. In this study, the equilibrium solutions to highly simplified chemical networks for CO and H2O have been re-assessed with particular attention to the formulation of the ice desorption rates in the context of 'three-phase' gas-grain astrochemical models. The analytical solutions have also been updated to account for the chemically inert reservoir of molecules below the surface ice layers, and to include the effects of reactive desorption. We find that a very close match is obtained to the results from detailed three-phase models of the time-dependent astrochemistry, and the abundances are typically accurate to within a factor of two over the entire range of densities and extinction that are applicable to dense clouds and young star-forming regions. In addition, these solutions give accurate results over most of the range of conditions even for systems undergoing rapid dynamical evolution. Although there are some caveats of applicability, we therefore recommend that these solutions be used in models of cold molecular environments where the rapid calculation of the abundances of CO, H2O and atomic coolants is helpful.

Sun-as-a-star analyses serve as a bridge for comparative studies on solar and stellar activities. To investigate the typical Sun-as-a-star Ha temporal spectral characteristics in solar eruption source regions, we analyzed five different types of solar eruptions, using spectroscopic data from the Chinese Ha Solar Explorer (CHASE). Because the spatially-integral Ha spectrum of source region is mainly contributed by emission from heated plasma in flare ribbons and absorption from cold plasma in evolving filaments, we separately analyze the sub-regions of the source region dominated by different dynamical processes. It is revealed that filament eruptions show emission near Ha line center, accompanied by blueshifted/redshifted absorption, while flare ribbons show Ha line center emission with red asymmetry and line broadening. Moreover, a special spectral signature likely associated with coronal mass ejections (CMEs) is identified: prominent blueshifted absorption without a clear deceleration phase, along with redshifted absorption, which can be used as a probe when searching stellar CMEs. Furthermore, in the X9.0 flare (SOL2024-10-03T12:18) accompanied by a violent CME, the expected blueshifted signal is not visible in the spatially-integral Ha spectra. This suggests that filament-lifting signals associated with CMEs in the source region can be obscured by the simultaneous dominant flare-ribbon emission within the integration region, which may explain the relatively small number of confirmed stellar CMEs observed in Ha. We also find that comparison between the Ha and UV spectral observations can effectively reveal the velocity evolution of erupting filaments and potential existence of associated CMEs.

Context. Stars with masses ranging from 3 to 11 M_\odot exhibit multiple evolutionary paths. Less massive stars in this range conclude their evolution as carbon-oxygen (CO) white dwarfs. However, those that achieve carbon ignition before the pressure by degenerate electron halts the core contraction may either form massive CONe/ONe white dwarfs, or undergo an electron-capture supernova, or photo-disintegrate neon and proceed with further thermonuclear burning, ultimately leading to the formation of a gravitationally unstable iron core. Aims. An evaluation of the impact of the energy loss caused by the production of axion-like-particles (ALPs) on evolution and final destiny of these stars is the main objective of this paper. Methods. We compute various sets of stellar models, all with solar initial composition, varying the strengths of the ALP coupling with photons and electrons. Results. As a consequence of an ALP thermal production, the critical masses for off-center C and Ne ignitions are both shifted upward. When the current bounds for the ALP coupling strengths are assumed, the maximum mass for CO WD progenitors is about 1.1 M_\odot heavier than that obtained without the ALP energy loss, while the minimum mass for a core collapse supernova (CCSN) progenitor is 0.7 M_\odot higher. Conclusions. Current constraints from observed Type II-P supernova light curves and pre-explosive luminosity do not exclude an ALP production within the current bounds. However, the maximum age of CCSN progenitors, as deduced from the star formation rate of the parent stellar population, would require a smaller minimum mass. This discrepancy can be explained by assuming a moderate extra mixing (as due to core overshooting or rotational induced mixing) above the fully convective core that develops during the main sequence.

Only 8% of the protoplanetary discs orbiting a T Tauri star show emission features of polycyclic aromatic hydrocarbons (PAHs). As PAHs are strong absorbers of UV radiation, they contribute to the heating of the discs photosphere, shielding of UV radiation that drives photo-chemistry in the disc, and their abundance is a key parameter to determine the strength of photo-evaporative disc winds. We want to understand the photochemical evolution of PAHs in protoplanetary discs around T Tauri stars and thus explain the absence of PAH features. We want to determine whether PAHs are destroyed because of the X-ray emission from their host stars or whether PAHs can withstand these conditions. We developed a model for the absorption of X-rays by PAHs. X-rays with more energy than the K edge of carbon will double ionise PAHs and will vibrationally excite them by ~ 15-35 eV. With a Monte Carlo model, we modelled the dissociation of H, H2, and C2H2 from PAH monomers. Furthermore, we modelled the dissociation of PAH clusters and the desorption of PAH clusters from dust grains caused by X-ray excitation. We find that small PAH clusters will quickly desorb and dissociate into individual molecules. PAH molecules experience rapid loss of H and acetylene C2H2 by the high excitation and will lose C2H2 on average after three X-ray excitations. However, large PAH clusters can stay intact and frozen out on dust grains. Based on our results, we expect a gas-phase PAH abundance that is lower than 0.01 times the ISM abundance and will rapidly decrease over time due to the dissociation of small clusters that are subsequently destroyed. To maintain a higher abundance, replenishment processes must exist such as vertical mixing. Large PAH clusters remain in the disc, frozen out on dust grains, but barely emit PAH features because of their strong thermal coupling to dust grains.

(abridged)We explore a phenomenological model that quantifies the deviation of the Hubble expansion rate from the standard scenario. The specific form of this model is expressed as $H^{2}(z) = H^{2}_{\rm \Lambda CDM}(\Omega_m, z)[1+\delta(z)]$. We consider three forms of $\delta(z)$: model I, $\delta(z)=\delta_c$; model II, $\delta(z)=\delta_{c}z/(1+z)$, and model III, $\delta(z)=\delta_{c}{\rm ln}(1+z)$. Here, $\delta_c$ represents a constant value. To constrain the models, we utilize a comprehensive set of observational data, including DESI BAO, CMB, CC, SNIa data, and the $H_0$ measured by the SH0ES. Our results show that for most combined datasets, $\delta_c$ tends to take on negative values for models I and II, while consistently taking positive values in model III. Our analysis further discloses that for model I, in which the deviation parameter is redshift-independent, there is a notable 2$\sigma$ deviation from the $\Lambda$CDM model when considering the combined datasets of DESI BAO+CMB+CC+SH0ES. However, this deviation decreases to less than $2\sigma$ once SNIa datasets are included. In contrast, model II remains consistent with the standard $\Lambda$CDM model across all datasets examined. Model III exhibits a significant deviation from the $\Lambda$CDM model, exceeding $2\sigma$ and reaching $3\sigma$ for the full combined datastes. The Akaike Information Criterion indicates that models I and II are consistent with the $\Lambda$CDM model, whereas model III is preferred over the standard $\Lambda$CDM model, with the $\Lambda$CDM model being substantially disfavored for the combined datasets DESI BAO+CMB+CC+SH0ES+DESY5. These results suggest that the Hubble expansion rate likely deviates from the standard $\Lambda$CDM prediction-a conclusion that aligns with various studies on dark energy, wherein dynamic dark energy is often favored over a cosmological constant.

The standard $\Lambda$CDM model, despite its success, is challenged by persistent observational tensions in the Hubble constant ($H_0$) and the matter clustering amplitude ($S_8$), motivating the exploration of alternative cosmological scenarios. We investigate a dark energy model with a phenomenological interaction in the dark sector, constructed to be exactly degenerate at the background level with the Chevallier-Polarski-Linder (CPL) parameterization. This setup allows us to test whether models with identical expansion histories but distinct physical mechanisms can be distinguished by cosmological data. We perform a Bayesian analysis using a combination of recent datasets: DESI DR2 BAO measurements, DESY5 supernovae, and CMB data from Planck and ACT. We find that both the interacting model and the CPL model provide significantly better fits to the data than $\Lambda$CDM. Although indistinguishable in background observables, the interacting model predicts a distinct matter-sector evolution driven by a late-time sign change in the dark sector interaction at $z \approx 0.8$, corresponding to the $w=-1$ crossing in the CPL description. In this sense, the interacting picture may be considered more physical, since it avoids the problematic crossing by construction. The resulting decay of dark energy into dark matter lowers $S_8$, potentially alleviating the weak-lensing $S_8$ tension. At the same time, it predicts a sharp suppression of the growth rate $f\sigma_8(z)$ at $z \lesssim 0.8$, which is in tension with current measurements of structure formation. This indicates that the model may not simultaneously reconcile the expansion history and the observed growth of cosmic structure, highlighting the need for a more comprehensive analysis to fully assess its viability.

Solar radio emissions offer unique diagnostic insights into the solar corona. However, their dynamic and multiscale nature, along with several orders of magnitude variations in intensity, pose significant observational challenges. To date, at gigahertz frequencies, MeerKAT stands out globally with high potential of producing high-fidelity, spectroscopic snapshot images of the Sun, enabled by its dense core, high sensitivity, and broad frequency coverage. Yet, as a telescope originally designed for observing faint galactic and extragalactic sources, observing the Sun at the boresight of the telescope requires customized observing strategies and calibration methods. This work demonstrates the technical readiness of MeerKAT for solar observations at the boresight of the telescope in the UHF (580-1015 MHz) and L-band (900-1670 MHz) frequency ranges, including optimized modes, a dedicated calibration scheme, and a tailored, entirely automated calibration and imaging pipeline. The quality of solar images is validated through morphological comparisons with the solar images at other wavelengths. Several unique early science results showcase the potential of this new capability of MeerKAT. Once fully commissioned and operational, this will unlock novel solar studies, significantly expand the scientific portfolio of MeerKAT, and lay the groundwork for solar observations with the mid-frequency telescope of the upcoming Square Kilometre Array Observatory, for which MeerKAT serves as a precursor.

We present radial velocity measurements of the star HD 28471, observed by HARPS at the ESO 3.6 m telescope over a baseline of $\sim19$ years. We have searched for planetary companions to HD 28471 using kima, a trans-dimensional diffusive nested sampling algorithm where the number of planetary signals is explored as a free parameter. We detect a compact system of three planets, with signals in the preferred solution corresponding to orbits of $P\sim3.16,~6.12,~\textrm{and }11.68$ d. These planets lie firmly in the super-Earth and sub-Neptune mass regime, with (minimum) masses of $3.7, 5.7, \textrm{and }4.9$ M$_{\oplus}$, respectively. A long-period ($\sim1500$ d) signal is also strongly detected. Assessment of activity indicator periodicities and RV correlations suggests that the three short-period signals are genuine planets, but casts doubt upon the nature of the long-period signal. The origin may be a short stellar magnetic cycle, though additional data are required to fully sample the periodicity without intervening offsets. HD 28471 b exhibits a more eccentric orbit than the other planets, which may be due to dynamical interaction, or a result of RV variation from an as-yet-undetected 4th planet interior to this compact system. The detected planets lie close to a resonant configuration, indicating that the system may retain features of its natal configuration, with convergent migration potentially responsible for evolving the planets onto such short-period orbits.

Shocks are promising sites of particle acceleration in extragalactic jets. In electron-ion shocks, electrons can be heated up to large Lorentz factors, making them an attractive scenario to explain the high minimum electron Lorentz factors regularly needed to describe the emission of BL Lac objects. Still, the thermal electron component is commonly neglected when modelling the observations, although it holds key informations on the shock properties. We model the broadband emission of the HSP blazar Mrk421 employing particle distributions that include a thermal relativistic Maxwellian component at low energies followed by a nonthermal power-law, as motivated by PIC simulations. The observations in the optical/UV and MeV-GeV bands efficiently restrict the nonthermal emission from the Maxwellian electrons, which we use to derive constraints on the basic properties, such as the fraction $\epsilon_e$ of the total shock energy stored in the nonthermal electrons. The best-fit model yields a nonthermal electron power-law with an index of ~2.4, close to predictions from shock acceleration. Successful fits are obtained when the ratio between the Lorentz factor at which the nonthermal distribution begins ($\gamma_{\rm nth}$) and the dimensionless electron temperature ($\theta$) satisfies $\gamma_{\rm nth}/\theta \lesssim 8$. Since $\gamma_{\rm nth}/\theta$ controls $\epsilon_e$, the latter limit implies that at least $\epsilon_e \approx 10\%$ of the shock energy is transferred to the nonthermal electrons. These results are almost insensitive to the shock velocity $\gamma_{\rm sh}$, but radio observations indicate $\gamma_{\rm sh} \gtrsim 5$ since for lower shock velocities the radio fluxes are overproduced by the Maxwellian electrons. If shocks drive the particle energisation, our findings indicate that they operate in the mildly to fully relativistic regime with efficient electron acceleration.

Context. The Kepler Legacy sample is, to this day, the sample of solar-like oscillators with the most exquisite asteroseismic data. In this work, we carry out a detailed modelling of a subsample of these stars for which the surface lithium abundance has also been observed by the GALAH survey and a photometric surface rotation as been measured. Aims. We aim at studying the impact of additional mixing processes on the asteroseismic modelling of Kepler Legacy G and F-type stars. We also investigate whether a single process can be invoked to reproduce the lithium depletion and asteroseismic constraints at the same time. Methods. We use detailed asteroseismic modelling techniques combining global and local minimization techniques. We start by using standard models and then aim at improving this solution by the addition of extra-mixing at the border of convective regions using either convective penetration or turbulence in radiative layers. Results. We find that lower mass models (~ 1M_Sun ) have no problem in reproducing the observed lithium depletion using only turbu- lence in the radiative zone, similarly to solar models. F-type stars, having a shallower convective envelope, are unaffected by additional turbulence at the BCZ, but require significant convective penetration values to actually reproduce the observed lithium depletion. The extent of this penetration is however incompatible with the frequency separation ratios. Conclusions. We conclude that the impact of extra-mixing is moderate for solar-type stars of the Kepler Legacy sample and well within the requirements of the PLATO mission. For more massive stars (~ 1.5M_Sun ), we conclude that the behaviour of the frequency separation ratios must be further investigated, as even models with large convective penetration at the base of their convective envelope are unable to reproduce them.

We present the design and initial testing of a low-frequency radio telescope prototype developed for the CANTAR (Colombian Antarctic Telescope for 21-cm Absorption during Reionization) experiment. Operating from 100 to 200 MHz, the system integrates a blade dipole antenna inspired by the EDGES high-band design with a software-defined radio (SDR) receiver. We report simulations of antenna impedance and beam chromaticity, along with SDR performance tests (Limenet Mini, Ettus E310, USRP2920). A dual-stage low-noise amplifier reduces system temperature, enabling foreground-sensitive observations. Radiometric estimates suggest sub-mK sensitivity is achievable with 1000 h of integration. This prototype forms part of Colombia's emerging infrastructure for 21-cm cosmology, with deployments planned in low-RFI sites in the Colombian Andes and Antarctica.

Many transients believed to originate from magnetars are thought to be triggered by crustal activity, which feeds back on the surrounding magnetosphere. These perturbations, through a variety of proposed mechanisms, can convert a fraction of the magnetic energy stored in the magnetosphere, as well as the energy injected by crustal activity itself into electromagnetic emission, including X-ray bursts and fast radio bursts. Here we provide a first glimpse of this process by coupling magneto-elastic dynamics simulations of the crust to fully three-dimensional relativistic resistive force-free electrodynamic simulations of the magnetosphere. Our simulations demonstrate that the elastodynamical motions of the surface launch a series of fast magnetosonic and Alfvén waves into the magnetosphere. These waves rapidly enter a nonlinear regime, ultimately giving rise to a wide range of phenomena, including monster shock formation, relativistic blast waves, trapped Alfvén waves, nonlinear Alfvén wave ejecta, and transient equatorial current sheets interacting with these waves. After the initial nonlinear phase, the magnetosphere is partially combed out, resembling a strongly perturbed split monopole configuration. Our results can offer hints and potential constraints on fast radio burst emission mechanisms, in particular for hyperactive repeating sources, by placing tight bounds on energy conversion efficiency, and possible quasi-periodic imprints on magnetospheric waves by elastic oscillations of the crust.

Radio astronomy observations at frequencies below 10~MHz could provide valuable science, such as measuring the cosmic dark age signal in the redshifted 21~cm hydrogen absorption line, detecting exoplanetary auroral emissions which lead to inferences about magnetic fields and atmospheres, and characterizing the effects of solar wind and coronal mass ejections on the magnetospheres of solar system planets. Despite their value, few resolved measurements in the sub-10~MHz band have been made. At frequencies below 10~MHz, the Earth's ionosphere reflects, attenuates, and distorts radio waves, making radio astronomy in this band possible only from space. However, a space-borne array would need thousands of electrically-small antennas to reach the sensitivity required for detecting faint astronomical signals, and it would need to be positioned far from the Earth to reduce the impact of Earth-based radio interference. Using more efficient antennas would minimize the number needed, and using antennas that are more resilient to interference would reduce the required distance from Earth. To this end, we consider constructing a low frequency array out of vector sensor antennas. These advanced antennas consist of three orthogonal dipole and three orthogonal loop antennas with a common phase centre. Their benefits include direction-finding and polarimetric capabilities, but they have not been considered for this application previously. We show that vector sensors can provide four times more Fisher information during interferometry than tripoles, simpler antennas that are commonly considered for space applications. We also present an all-sky imaging simulation to demonstrate a spherical harmonic imaging technique.

We present a comprehensive study of the optical and dynamical properties of a rotating black hole immersed in a Dehnen-type $(1,4,0)$ galactic dark matter halo, modeled by a double power-law density profile commonly used to describe realistic galactic cores. By extending our previous Schwarzschild-Dehnen solution using a modified Newman-Janis algorithm, we construct a Kerr-like axisymmetric spacetime that smoothly incorporates both black hole rotation and the influence of the surrounding dark matter halo. We systematically investigate the effects of the halo parameters-the central density and halo radius-on horizon structure, the shape and extent of the ergoregion, and the null geodesics associated with black hole shadows. Our results show that the presence of a dense or extended halo expands the event horizon and ergoregion, and significantly alters the size and distortion of the black hole shadow. Furthermore, by applying the WKB approximation to scalar field perturbations, we compute the quasinormal mode (QNM) spectra and demonstrate that the frequencies and damping times of ringdown signals are highly sensitive to the halo profile. These results open promising avenues for probing the dark matter environment of astrophysical black holes through black hole imaging and gravitational wave observations.

The classic model of the Local Group (LG) is that of two dominant constituents, the Milky Way and M31, first separating and then detaching from the Hubble flow, leading to a nearly radial approaching orbit. This simple model has been confronted by new measurements of the 3D M31 kinematics, by cosmological simulations, and by theoretical understanding of the impact of massive substructures such as the Large Magellanic Cloud. This article explores the consequences of new observations and theory on the determination of the mass and dynamics of the LG. The M31 tangential velocity measurement and contribution from the cosmological constant both increase the implied timing mass of the LG to be $\sim 5 \times 10^{12}$ M$_\odot$. Timing mass estimates for the LG tend to be larger than the sum of the Milky Way and M31 halo masses, and larger than independent LG mass estimators. Precision future kinematics have the potential to explore the origin of this difference, shed light on dark matter in the LG, the origin of its angular momentum, and possibly even local values of cosmological parameters.

We detail the population properties of merging compact objects using 158 mergers from the cumulative Gravitational-Wave Transient Catalog 4.0, which includes three types of binary mergers: binary neutron star, neutron star--black hole binary, and binary black hole mergers. We resolve multiple over- and under-densities in the black hole mass distribution: features persist at primary masses of $10\,M_\odot$ and $35\,M_\odot$ with a possible third feature at $\sim 20\,M_\odot$. These are departures from an otherwise power-law-like continuum that steepens above $35\,M_\odot$. Binary black holes with primary masses near $10\,M_\odot$ are more likely to have less massive secondaries, with a mass ratio distribution peaking at $q = 0.74^{+0.13}_{-0.13}$, potentially a signature of stable mass transfer during binary evolution. Black hole spins are inferred to be non-extremal, with 90\% of black holes having $\chi < 0.57$, and preferentially aligned with binary orbits, implying many merging binaries form in isolation. However, we find a significant fraction, 0.24--0.42, of binaries have negative effective inspiral spins, suggesting many could be formed dynamically in gas-free environments. We find evidence for correlation between effective inspiral spin and mass ratio, though it is unclear if this is driven by variation in the mode of the distribution or the width. (Abridged)

Context. Active regions on the stellar surface can induce quasi-periodic radial velocity (RV) variations that can mimic planets and mask true planetary signals. These spurious signals can be problematic for RV surveys such as those carried out by the ESPRESSO consortium. Aims. Using ESPRESSO and HARPS RVs and activity indicators, we aim to confirm and characterize two candidate transiting planets from TESS orbiting a K4 star with strong activity signals. Methods. From the ESPRESSO FWHM, TESS photometry, and ASAS-SN photometry, we measure a stellar rotation period of 21.28 $\pm$ 0.08 d. We jointly model the TESS photometry, ESPRESSO and HARPS RVs, and activity indicators, applying a multivariate Gaussian Process (GP) framework to the spectroscopic data. Results. We are able to disentangle the planetary and activity components, finding that TOI-2322 b has a $11.307170^{+0.000085}_{-0.000079}$ d period, close to the first harmonic of the rotation period, a $\leq 2.03 M_\oplus$ mass upper limit and a $0.994^{+0.057}_{-0.059}$ $\mathrm{R_\oplus}$ radius. TOI-2322 c orbits close to the stellar rotation period, with a $20.225528^{+0.000039}_{-0.000044}$ d period; it has a $18.10^{+4.34}_{-5.36}$ $\mathrm{M_\oplus}$ mass and a $1.874^{+0.066}_{-0.057}$ $\mathrm{R_\oplus}$ radius. Conclusions. The multivariate GP framework is crucial to separating the stellar and planetary signals, significantly outperforming a one-dimensional GP. Likewise, the transit data is fundamental to constraining the periods and epochs, enabling the retrieval of the planetary signals in the RVs. The internal structure of TOI-2322 c is very similar to that of Earth, making it one of the most massive planets with an Earth-like composition known.

We study the dust content of massive ($\log(M_*/M_{\odot})\geq10.8$) quiescent galaxies (QGs) at redshift $z=0.5-3$ to place constraints on the evolution of their cold interstellar medium (ISM), and thereby obtain insights on the processes of galaxy quenching throughout cosmic time. We use a robust sample of 458 colour-selected QGs covered by the A$^3$COSMOS+A$^3$GOODSS database to perform a stacking analysis in the $uv$-domain and measure their mean dust masses from their stacked submillimetre luminosities. We use the CIGALE SED-fitting code to obtain star formation histories and infer the time since quenching for all QGs in our sample. We use this information to gain insight on the time evolution of the dust content after quenching. Most QGs in our sample quenched around a redshift of $z\sim1.3$, following the peak of cosmic star formation. The majority of QGs observed at $z>1$ are recently quenched (i.e., quenched for no longer than $500\,$Myr), whereas the majority of QGs observed at $z<1$ have already been quenched for a significant amount of time ($\gtrsim1\,$Gyr). This implies that high-redshift galaxies ($z\gtrsim2$) are ideal for studying the mechanisms of quenching and its effects on the ISM, while lower-redshift galaxies are more suitable for studying the long-term effects of the QG environment on their ISM. We obtain upper limits on the dust mass fraction of the QG population, pointing towards lower dust content in high-redshift massive QGs than found by earlier stacking studies, and significantly lower (by a factor $\sim2-6$) than that of normal star forming galaxies. We also place constraints on the initial gas fraction right after quenching. We find that within the first $\sim600\,$Myr after quenching, QGs already lose on average $\gtrsim70\%$ of their cold ISM. Our findings support a gas consumption or removal scenario acting on short timescales.

We present a new harmonic development of the long-periodic band of the Earth tide-generating potential (TGP). It updates the corresponding part of the previous TGP expansion, KSM03 (Kudryavtsev, J. Geodesy, 77:829, 2004), and includes 38 terms of period longer than $\simeq$18 years (yr) and amplitude not less than $10^{-8}~{\rm m}^2\,{\rm s}^{-2}$. The development is made through a modified spectral analysis of the TGP numerical values tabulated over more than 30,000 yr (13,200~BC--17,191~AD). The latest JPL NASA's long-term numerical ephemeris DE441 (Park et al., Astron. J., 161:105, 2021) is used as the source of the Moon, the Sun and major planets coordinates. For comparison, the KSM03 series were done on the basis of an older DE406 ephemeris (Standish, JPL IOM 312.F, 1998) and over a shorter time interval of 2000 yr (1000--3000). As a result of using an extended time span several new long-periodic waves in the Earth TGP are found and most of other terms are updated. In particular, a relatively large term of amplitude of $3\times 10^{-5}~{\rm m}^2\,{\rm s}^{-2}$ and period of $\simeq$7.4~kyr is revealed. Several new waves of period close to 18.61 yr (the period of the lunar nodal cycle, LNC) are separated from the main LNC term. The effect of the general precession in longitude (of $\simeq$25.7~kyr period) on the Earth TGP for the first time is evaluated. As a result, a number of updated TGP terms include the precession rate in their arguments. A new catalogue of the long-periodic terms in the Earth TGP spectrum in both standard HW95 and KSM03 format is released.

We performed a detailed analysis of the magnetic structure and asymmetric eruption of a large (about 500 Mm) inverse S-shaped filament partially located in AR 13229 on February 24, 2023. We linked the filament's pre-eruptive magnetic configuration to its highly asymmetric eruption dynamics and the formation of a large-scale coronal dimming in a weak-field region (mean unsigned flux of about 5 G). To reconstruct the coronal magnetic field, we applied a physics-informed neural network (PINN)-based nonlinear force-free field (NLFFF) extrapolation method to a pre-eruption HMI vector magnetogram. The NLFFF extrapolation reveals a large-scale magnetic flux rope (MFR) of about 500 Mm in length, consistent with the filament. We identified an extended MFR footprint to the east that connects to the J-shaped flare ribbon, outlining where the coronal dimming began. Overlying strapping fields connect to the area into which the dimming and flare ribbon later expand. This configuration explains the formation of the dimming as a stationary flux rope and strapping flux dimming, with subsequent expansion driven by the growth of the MFR footprint through strapping-strapping reconnection. Conversely, the western filament leg shows multiple anchor points and strong overlying magnetic fields, which suppressed the dimming and partially confined the eruption on that side. The reconstructed pre-eruptive NLFFF configuration offers a clear physical explanation for the asymmetries seen in the eruption, flare geometry, and coronal dimming. This demonstrates that PINN-based NLFFF extrapolation can effectively model large-scale filaments extending into weak-field regions, enhancing our understanding of complex solar eruptions.

We test the impact of an evolving supermassive black hole (SMBH) mass scaling relation (Mbh-Mbulge) on the predictions for the gravitational wave background (GWB). The observed GWB amplitude is 2-3 times higher than predicted by astrophysically informed models which suggests the need to revise the assumptions in those models. We compare a semi-analytic model's ability to reproduce the observed GWB spectrum with a static versus evolving-amplitude Mbh-Mbulge relation. We additionally consider the influence of the choice of galaxy stellar mass function on the modeled GWB spectra. Our models are able to reproduce the GWB amplitude with either a large number density of massive galaxies or a positively evolving Mbh-Mbulge amplitude (i.e., the Mbh / Mbulge ratio was higher in the past). If we assume that the Mbh-Mbulge amplitude does not evolve, our models require a galaxy stellar mass function that implies an undetected population of massive galaxies (Mstellar > 10^11 Msun at z > 1). When the Mbh-Mbulge amplitude is allowed to evolve, we can model the GWB spectrum with all fiducial values and an Mbh-Mbulge amplitude that evolves as alpha(z) = alpha_0 (1 + z)^(1.04 +/- 0.5).

(Abridged) Giant planets are observed orbiting the primary stars of close binary systems. Such planets may have formed in compact circumprimary disks, under conditions much different than those around single stars. To quantify the effects of the strong gravitational perturbations exerted on circumprimary disk material, the 3D dynamics of gas and dust in orbit around the primary star of a compact and eccentric binary was modeled by using gamma Cephei as a representative of a class of close binary systems. Circumprimary gas was approximated as an Eulerian viscous and compressible fluid. Dust grains were modeled as Lagrangean particles, subjected to gravity and drag forces. Some models also include a giant planet. Models show that spiral density waves excited around pericenter passage propagate toward the inner disk boundary, through a few pressure scaleheights from the midplane, inducing radial and vertical mixing in the gas. However, perturbations imparted to gas, both in terms of eccentricity and precession, are far weaker than previously estimated by 2D simulations. Models predict small eccentricities, <~ 0.03, and slow retrograde precession. The addition of a giant planet does not change the low eccentricity state of the disk. The parameters applied to the disk would lead to the formation of a planet many times the mass of Jupiter, in agreement with some observations. Micron to mm-size dust grains are well coupled to the gas, resulting in similar dynamics and statistically similar distributions of orbital elements. The planet only affects the dust distributions locally. In agreement with results of recent 2D models, the lifetime of an isolated circumprimary disk would be brief, ~1e5 years, due to its compact nature, requiring a long-term external supply of mass to allow for the in situ formation of a giant planet.

We use Magellan/MIKE echelle spectroscopy to conduct an in-depth chemodynamical analysis of the most luminous star-forming region within the metal-poor starburst dwarf galaxy CGCG 007-025. Leveraging the exceptional high resolution (R$\sim$50,000) and broad wavelength coverage, we apply Bayesian inference to simultaneously model the fluxes of 30 emission lines spanning the wavelength range 3400-9200Å. Employing a two-region ionisation model, we characterise various gas properties including electron temperature, electron density, and chemical abundances across different elements. Our direct-method inferred metallicity yields $\rm 12+\log(O/H)=7.77\pm0.03$, placing the galaxy in the metal-poor regime. Furthermore, Metal-to-Oxygen ratios such as log(S/O), log(Ne/O) or log(Ar/O) are in full agreement with the values derived for the Milky Way, consistent with expectations from stellar evolutionary models. The brightest emission lines are kinematically complex, with modelling requiring up to four distinct components. The exceptional resolution and signal-to-noise ratio of the data unveil asymmetric and wide ($\sigma_{HeII} \approx$ 35km/s) HeII$\lambda$4686 emission. The flux ratio of this nebular line, together with the absence of other high ionisation species such as [NeV]$\lambda$3426, indicates the presence of fast radiative shocks. This dataset underscores the capability of echelle spectroscopy in delivering comprehensive chemodynamical analyses of starbursts in the Local Volume.

We present the confirmation of HD 190360 d, a warm ($P=88.690^{+0.051}_{-0.049}~\mathrm{d}$), low-mass ($m\sin i=10.23^{+0.81}_{-0.80}~\mathrm{M_\oplus}$) planet orbiting the nearby ($d=16.0$ pc), Sun-like (G7) star HD 190360. We detect HD 190360 d at high statistical significance even though its radial velocity (RV) semi-amplitude is only $K=1.48\pm0.11~\mathrm{m~s^{-1}}$. Such low-amplitude signals are often challenging to confirm due to potential confusion with low-amplitude stellar signals. The HD 190360 system previously had two known planets: the $1.7~\mathrm{M_J}$ (true mass) HD 190360 b on a $7.9$ yr orbit and the $21~\mathrm{M_\oplus}$ (minimum mass) HD 190360 c on a $17.1$ d orbit. Here, we present an in-depth analysis of the HD 190360 planetary system that comprises more than 30 years of RV measurements and absolute astrometry from the Hipparcos and Gaia spacecrafts. Our analysis uses more than 1400 RVs, including nearly 100 from NEID. The proper motion anomaly as measured by these two astrometric missions solves for the dynamical mass of HD 190360 b and contributes to our understanding of the overall system architecture, while the long baseline of RVs enables the robust characterization of HD 190360 c and confirms the discovery of HD 190360 d.

We present a method for the detection and characterization of random changes in the flux from $\gamma$-ray pulsars on sub-hour timescales, much shorter than variations that can be accessed using direct flux measurements. Flux variations are a proxy for the variations in spindown power ($\dot{E}$) or particle acceleration, which can be produced by random switches between quasi-stable configurations of the pulsar magnetosphere. This technique therefore probes the stability of pulsar magnetospheres and discrete spindown states on timescales much shorter than can be achieved with pulsar timing. We apply the method to a sample of 115 bright $\gamma$-ray pulsars, finding no new instances of state changes. We derive the sensitivity of the method and find that, for a wide range of possible state changing models, over a wide range of timescales, we can limit the amplitude of flux ($\dot{E}$) variations to $<$10%. Substantial nulling is excluded in nearly all cases. The best cases limit variations of any sort to $\leq$1%. These results indicate that $\gamma$-ray pulsar magnetospheres maintain a single configuration or narrow range of configurations with nearly constant power output.

3I/ATLAS is the third confirmed interstellar object to visit our Solar System, and only the second to display a clear coma. Infrared spectroscopy with the James Webb Space Telescope (JWST) provides the opportunity to measure its coma composition and determine the primary activity drivers. We report the first results from our JWST NIRSpec campaign for 3I/ATLAS, at an inbound heliocentric distance of $r_H=3.32$ au. The spectral images (spanning 0.6-5.3 $\mu$m) reveal a CO2 dominated coma, with enhanced outgassing in the sunward direction, and the presence of H2O, CO, OCS, water ice and dust. The coma CO2/H2O mixing ratio of $8.0\pm1.0$ is among the highest ever observed in a comet, and is 6.1-sigma above the trend as a function of heliocentric distance for long-period and Jupiter-family comets (excluding the outlier C/2016 R2). Our observations are compatible with an intrinsically CO2-rich nucleus, which may indicate that 3I/ATLAS contains ices exposed to higher levels of radiation than Solar System comets, or that it formed close to the CO2 ice line in its parent protoplanetary disk. A low coma H2O gas abundance may also be implied, for example, due to inhibited heat penetration into the nucleus, which could suppress the H2O sublimation rate relative to CO2 and CO.

The interstellar dust grains are swept up during the expansion of the supernova (SN) remnant, they penetrate behind the shock front, where they are heated and destroyed in the hot gas. This leads to a change in emissivity of such grains. In this work, we consider the evolution of the infrared (IR) luminosity of the SN remnant expanding into an inhomogeneous interstellar medium with lognormal distribution of the density fluctuations. The IR luminosity of the swept-up interstellar dust rapidly increases during the first several thousand years after the SN explosion, and reaches the maximum value. Afterwards, it decreases due to the destruction of the dust grains in hot gas and their declining emissivity in the cooling down gas of the shell. We show how the IR luminosity of dust in the SN remnant depends on the dispersion of the gas density in front of the SN shock front. We find that for the significant period of time (40 - 50 kyr) the maximum of the dust IR luminosity peaks at the range centered at 70$\mu$m. Therefore, this band can be considered as the most optimal range for studying the late SN remnants. We illustrate that during evolution, the dust temperature changes from 70 to 20 K, and only slightly depends on the inhomogeneity of the medium. In the radiative phase, the strong emission lines of metal ions emerge above the dust continuum. Their luminosity rapidly increases and exceeds the dust continuum luminosity by $\sim 10-10^3$ times. The point in time when the high luminosity in the lines is reached strongly depends on the inhomogeneity of the medium. We discuss possibilities for detection of the IR emission both in dust continuum and in lines. We expect that their ratios will allow to estimate the inhomogeneity of the medium, where the remnant is expanding.

We present a novel spectral solver for general relativistic magnetohydrodynamics on dynamical spacetimes. By combining a high order discontinuous spectral method on mapped Chebyshev Fourier grids, our scheme attains exponential convergence. Implemented within a unified BSSN Valencia framework, the code evolves both Einstein and MHD fields self consistently, enabling fully coupled simulations of black hole accretion jet systems. We demonstrate spectral accuracy and entropy stability through convergence tests, and validate physical fidelity via equatorial embedding diagrams of horizon crossing GRMHD variables in Kerr Schild coordinates. Three dimensional scatter visualizations further highlight the solver's capability to capture complex magnetized plasma structures around rotating black holes. This approach paves the way for high order, low dissipation GRMHD simulations on exascale architectures, opening new avenues for precise modeling of strong field astrophysical phenomena.

The discovery of numerous free-floating planets (FFPs) has intensified interest in their origins and dynamical histories. A leading formation mechanism is planet-planet scatterings in unstable multi-planetary systems, which can naturally lead to planetary ejections. If these planets originally host moons, it remains an open question whether such satellites can remain gravitationally bound to FFPs after ejection. In this work, we investigate both the ejection velocity of FFPs produced by planet-planet scatterings and the survival rate of their potential moons; we estimate the latter by determining the statistics of the minimum planet-planet distance prior to planet ejection, and comparing it to the initial orbital radius of the moon relative to its host planet. Using the circular restricted three-body framework, we derive an analytical boundary for the ejection velocity based on Jacobi energy conservation, which agrees with the results of integrations. We also identify a minimum planetary mass required for successful ejection. For two-planet systems with finite planetary masses, we use simulations and analytical arguments to determine how the ejection velocity scales with the planetary mass and initial semi-major axis. Extending our analysis to three-planet systems yields similar results, reinforcing the robustness of our conclusions. These findings offer insights into the property of FFPs and inform future efforts to search for exomoons around them.

The dipole in the angular distribution of the cosmic microwave background (CMB) is typically attributed to the Doppler effect and our motion relative to the CMB rest frame. It is expected that observations of large-scale structures would also exhibit a related kinematic dipole, helping to confirm the kinematic origin of the CMB dipole. However, numerous studies of the large-scale structure dipole have shown significant discrepancies with predictions based on the CMB. In this work, we investigate how considering the clustering dipole affects the cosmic large-scale structure distribution dipole using the National Radio Astronomy Observatory (NRAO) Very Large Array (VLA) Sky Survey (NVSS) and examine the nonlinear regime to calculate the correlation between the clustering dipole and the kinematic dipole. We also determine whether these outcomes help reconcile previous measurements of the NVSS dipole with predictions based on the CMB. Additionally, we explore a model in which the distribution of matter on large scales might be intrinsically anisotropic. Using the remnant discrepancy between the observed and predicted dipole, we derive an upper limit for the amplitude of intrinsic anisotropy and calculate the clustering for this model. Furthermore, we investigate these results within the framework of modified gravity theories, specifically the $f(R)$ gravity model. By examining this model, it is possible to gain a better understanding of how the cosmic dark energy component affects the dipole. Finally, by comparing these two models, we can see that the $f(R)$ model predicts a higher clustering dipole compared to the standard cosmological model, which explains the discrepancy between the kinetic and clustering dipoles and leads to a higher dipole amplitude.

We review the suggestion that it is possible to eliminate the Big Bang curvature singularity of the Friedmann cosmological solution by considering a particular type of degenerate spacetime metric. Specifically, we take the 4-dimensional spacetime metric to have a spacelike 3-dimensional defect with a vanishing determinant of the metric. This new solution suggests the existence of another "side" of the Big Bang (perhaps a more appropriate description than "pre-Big-Bang" phase used in our original paper). The corresponding new solution for defect wormholes is also briefly discussed.

The minimal left-right symmetric model (mLRSM) provides an elegant and testable framework for addressing the origin of neutrino masses. We examine the constraints on the sub-GeV sterile neutrino in the type-II seesaw scenario of the mLRSM without left-right mixing, taking limits from collider searches, meson decays, supernovae, neutrinoless double beta ($0\nu\beta\beta$) decay and cosmology. Specifically, we derive the $0\nu\beta\beta$ decay constraints using the advanced effective field theory approach and up-to-date nuclear matrix element calculations. Besides, we update the SN1987A cooling bound with the state-of-the-art simulations, provide new constraints from the energy deposition in the supernova ejecta, and incorporate the stringent sterile neutrino lifetime upper limit $\tau\lesssim 0.023$ s from the big bang nucleosynthesis. Our results identify the parameter region compatible with all current experimental and observational constraints, where the sterile neutrino mass lies between 700 MeV and 1 GeV and the right-handed $W$ boson mass is slightly below 20 TeV. This region is exclusively probed by the future tonne-scale $0\nu\beta\beta$ decay experiments, providing a unique window to test the mLRSM and the possible origin of neutrino masses.

Nonlinear scalar-tensor theories of gravity have been considered as candidates for dark matter and dark energy. Often, they possess screening mechanisms which allow the fifth force mediated by the additional scalar degree(s) of freedom to evade detection from local experiments. Their classical behaviour is well studied, but their quantum nature is relatively unexplored. We outline a Green's function method for obtaining the leading-order quantum corrections to the classical symmetron field profile in the vicinity of a spherically symmetric extended source. For parameters that experiments had previously ruled out, our calculations indicate that the symmetron force may be weaker than the classical field suggests.

In this tutorial, I discuss how to model a neutron star from the Quantum Hadrodynamics microscopic approach. After a brief discussion about hydrostatic equilibrium, I discuss the role of each meson of the model and how to calculate the corresponding equation of state and the expected values. Each meson is introduced individually. Its effects are analyzed from both an analytical and a numerical point of view. To explicitly show the effects of a given meson, the coupling constant is varied in an arbitrary range before being fixed to reproduce well-known constraints. This work is intended for late undergraduate students as well as early graduate students. The equation of states is obtained from the statistical mechanics formalism, which is more familiar to students at this stage of their research career, instead of the traditional quantum field theory formalism.

We introduce a transformer-based neural network for the accurate classification of real and bogus transient detections in astronomical images. This network advances beyond the conventional convolutional neural network (CNN) methods, widely used in image processing tasks, by adopting an architecture better suited for detailed pixel-by-pixel comparison. The architecture enables efficient analysis of search and template images only, thus removing the necessity for computationally-expensive difference imaging, while maintaining high performance. Our primary evaluation was conducted using the autoScan dataset from the Dark Energy Survey (DES), where the network achieved a classification accuracy of 97.4% and diminishing performance utility for difference image as the size of the training set grew. Further experiments with DES data confirmed that the network can operate at a similar level even when the input images are not centered on the supernova candidate. These findings highlight the network's effectiveness in enhancing both accuracy and efficiency of supernova detection in large-scale astronomical surveys.

We review the cosmic generalisation of the virial theorem known as the Layzer-Irvine equation, also independently derived by Dmitriev and Zeldovich. This equation has been studied in the literature for dark matter-dark energy interaction models, as well as in the context of alternative theories of gravity. We discuss results from the previous scenarios and point out future directions.

A fully automated and continuous calibration framework for All-Sky Imagers (ASIs) that significantly enhances the spatial accuracy and reliability of geo-referenced ASI data is presented. The technique addresses a critical bottleneck in ASI image data reliability and usability for real time space weather via automated geo-referencing under real-world field conditions. The system corrects the lens distortion in ASIs using a well-established fisheye lens model and automatically estimates camera orientation in terms of roll, pitch, and yaw angles relative to True North and the horizontal plane perpendicular to the zenith using star tracking. Unlike traditional methods that require manual intervention and periodic recalibration, Auto-Cal performs nightly unattended recalibrations using observed stellar motion, adapting to mechanical shifts or environmental changes. Each calibration step includes formal error estimates, allowing end users to assess the confidence of geo-located data in real-time. This capability enables dependable ASI operations in remote or unmanned settings and supports higher-fidelity integration with other geophysical instruments. Auto-Cal provides a scalable foundation for maintaining a large array of ASIs, thus enabling long-term atmospheric monitoring and real-time space weather alerts.

The purpose of this paper is to investigate vertical self-resonant (VSR) bifurcations from distant retrograde orbit (DRO) family in the framework of the Earth-Moon CR3BP. To this end, by using a classical corrector-predictor algorithm we compute the vertical stability of DROs and identify twelve vertical-critical DROs. We split them into three groups according to orbiting around libration points $L_i$, $i=1,2,4,5$. (i) We first analyze six VSR bifurcations of multiplicity from five to ten associated to DROs near the Moon. (ii) For DROs that move in addition around $L_1$ and $L_2$, we study four VSR bifurcations of multiplicity from five to eight. (iii) Within DROs additionally orbiting also around $L_4$ and $L_5$, two vertical 1:1 resonant branch points occur. In total, we generate 21 bifurcated families of spatial symmetric periodic solutions and present their orbital characteristics, including bridge families to Butterfly, prograde orbits, quasi DRO and DRO. We also obtain branches whose members approach collision with the Moon and are of Bumble Bee, Hoverfly or Dragonfly shape. In order to provide a structured and systematic overview of such bifurcation results, we determine Conley-Zehnder indices and construct bifurcation diagrams in view of symplectic invariants.

We propose a novel method to constrain the electric charge of the supermassive black hole M87* by analyzing the orbital angular momentum content of the light it emits. By leveraging the established analogy between rotating spacetimes and inhomogeneous optical media, we derive a simple analytical formula that relates the average orbital angular momentum in the observed radiation to the black hole's charge-to-mass ratio. Applying this relation to existing observational data, we place an upper bound of $\mathcal{Q}/M \lesssim 0.39$ on the charge of M87*. While the analysis focuses on electric charge, which is used here purely as a theoretical example since astrophysical black holes are expected to be approximately neutral, the method is general and can be extended to constrain other types of charges $\unicode{x2013}$ degrees of freedom that define distinct black hole solutions. These results demonstrate the potential of orbital angular momentum as a new fundamental degree of freedom to be exploited in astrophysics, providing a complementary and independent alternative to shadow-based techniques for probing the properties of rotating compact objects and testing gravity in the strong-field regime.

Many astrophysical processes can produce gravitational wave (GW) sources with significant orbital eccentricity. These binaries emit bursts of gravitational radiation during each pericenter passage. In isolated systems, the intrinsic timing of these bursts is solely determined by the properties of the binary. The presence of a nearby third body perturbs the system and alters the burst timing. Accurately modeling such perturbations therefore offers a novel approach to detecting the presence of a nearby companion. Existing timing models account for Newtonian dynamics and leading-order radiation reaction effects but neglect the higher order post-Newtonian (PN) contributions to the inner binary. In this paper, we present an improved timing model that incorporates conservative PN corrections that lead to the precession of the binary's pericenter. We find that these PN corrections significantly impact the binary's orbital evolution and the timing of the GW burst. In particular, 1PN precession gives rise to distinctive modulation features in the binary's semilatus rectum and eccentricity. These modulations encode valuable information about the presence and properties of the third body, including its mass and distance. Furthermore, unmodeled 1PN effects significantly bias the tertiary's mass and distance. Finally we assess the detectability of GW bursts from such perturbed systems and demonstrate that the inclusion of PN corrections is crucial for accurately capturing the orbital dynamics of hierarchical triples.

In this work we examine a theoretical scenario which combines two fundamental theoretical proposals for the early Universe and a possible evolution for the early post-inflationary epoch. Specifically, we assume that the early Universe contains gravity's rainbow effects on the spacetime and the inflationary Lagrangian contains $R^2$ corrections or $f(R)$ gravity corrections in general. In addition we assume that the era beyond the end of inflation until the reheating temperature is reached, is a kination era. Both theories, $R^2$ and gravity's rainbow emerge from a quantum context so their effects should be first checked at the theory which connects the quantum with the classical, hence inflation. Spacetime is four dimensional and the effects of the quantum theory could possibly be imprinted in the inflationary Lagrangian and of course on the spacetime itself. For the gravity's rainbow deformed Starobinsky model, both Lagrangian quantum effects and spacetime quantum effects are combined. As we show the resulting theory is compatible with the ACT data. We also consider power-law $f(R)$ gravity deformations and we show that in this case, the model is viable without the need of extending the slow-roll era of inflation.

In this work we introduce the rescaled $\mathcal{R}^2$-corrected minimally coupled scalar field theory, a theory that contains minimal quantum corrections of the single scalar field Lagrangian. We develop the theoretical framework in the string frame where the baryons geodesics are free fall geodesics and we do not treat the theory as a two scalar field theory in the Einstein frame. The theoretical framework can be reduced to a single scalar field theory framework by using a perturbative expansion at the level of the field equations, making the resulting theory easy to tackle analytically. The first two quantum corrections contain two terms, a linear $\sim \mathcal{R}$ and a quadratic term $\sim \mathcal{R}^2$. The effect of the linear term alters the Einstein-Hilbert term, making the resulting theory a rescaled version of Einstein-Hilbert gravity. Due to the presence of the rescaled Einstein-Hilbert term $\sim \lambda \frac{\mathcal{R}}{16\pi G}$, the gravitational constant will no longer be that of Newton's, but a rescaled one $\frac{G}{\lambda}$ and hence gravity can be stronger primordially, or even weaker. The perspective of having stronger gravity primordially, is compatible with intuition, since one expects a stronger gravity primordially, but having a weaker gravity for some reason is not prohibited theoretically. The attribute of our theoretical framework is that it allows a stronger gravity primordially, which returns to ordinary gravity as the curvature of the Universe decreases. We examine the effects of the quantum terms on several mainstream scalar field inflationary potentials, such as hybrid inflation, monomial inflation and power-law inflation.

We study a minimally extended version of the Standard Model where baryon number is gauged with a $U(1)_B$ symmetry. This model can be made anomaly-free by adding a set of additional fermions. The lightest component of these fermions behaves as a viable dark matter candidate. We show that the spontaneous breaking of $U(1)_B$ symmetry can produce gravitational waves via bubble dynamics resulting from a first-order phase transition, which can be detected in future gravitational wave experiments like LISA and ET. Such gravitational wave signatures can be used as a probe to constrain the model in future observations and complement dark matter and collider searches. We perform a random numerical scan of the parameter space and derive the viable region consistent with current bounds from dark matter experiments such as LUX-ZEPLIN and XENONnT and sensitive to future gravitational wave experiments. We find that dark matter with mass of order $\mathcal{O}(1 - 10)$ TeV is the most interesting to test in future gravitational wave as well as laboratory experiments. In the viable parameter space, the mass of the $Z'$ gauge boson associated with the $U(1)_B$ lies in the few-tens of TeV region, and the mass of the scalar associated with the symmetry breaking lies around a few hundred GeV to TeV scale. Hence, the dark matter and mediator mass scales typically fall beyond the reach of present direct detection experiments and are marginally accessible at current collider energies.

Gravitational lensing of electromagnetic (EM) waves has yielded many profound discoveries across fundamental physics, astronomy, astrophysics, and cosmology. Similar to EM waves, gravitational waves (GWs) can also be lensed. When their wavelength is comparable to the characteristic scale of the lens, wave-optics (WO) effects manifest as frequency-dependent modulations in the GW waveform. These WO features encode valuable information about the lensing system but are challenging to model, especially in the weak lensing regime, which has a larger optical depth than strong lensing. We present a novel and efficient framework to accurately approximate WO effects induced by general symmetric lens profiles. Our method is validated against numerical calculations and recovers the expected asymptotic behavior in both high- and low-frequency limits. Accurate and efficient modeling of WO effects in the weak lensing regime will enable improved lens reconstruction, delensing of standard sirens, and provide a unique probe to the properties of low-mass halos with minimal baryonic content, offering new insights into the nature of dark matter.

We report the development of a reactive sputtering process for high $T_\mathrm{c}$ NbN films with high normal-state resistivity, tailored for kinetic inductance parametric amplifiers. The process includes precise control to ensure full nitridation of the target prior to deposition. Under optimized conditions, the resulting NbN thin films exhibit a critical temperature of $10.5\,\mathrm{K}$ and a resistivity of $\sim1000\,\mathrm{\mu\Omega\,cm}$. The high $T_\mathrm{c}$ of the NbN thin-films suggests strong potential for application over the entire millimetre-wave frequency range from $24\,\mathrm{GHz}$ to $300\,\mathrm{GHz}$, whereas the high resistivity suggests a reduced power requirement for the pump tone to achieve high gain. Resonator parametric amplifiers have been fabricated from these films using coplanar waveguide geometry. The devices were able to produce high gain exceeding $20\,\mathrm{dB}$ at $25\,\mathrm{GHz}$, with artefact-free, reproducible amplification profiles in good agreement with theoretical models.

We derive analytically the amplitude of the quadratic quasi-normal mode generated in the ringdown stage of the gravitational waveform produced by the ultra-relativistic head-on collision of two non-spinning Schwarzschild black holes. Although being a highly nonlinear event, second-order perturbation theory suffices and that nonlinearities may be derived by a simple bootstrapping procedure.

LIGO, Virgo, and KAGRA form a network of gravitational-wave observatories. Data and analysis results from this network are made publicly available through the Gravitational Wave Open Science Center. This paper describes open data from this network, including the addition of data from the first part of the fourth observing run (O4a) and selected periods from the preceding engineering run, collected from May 2023 to January 2024. The public data set includes calibrated strain time series for each instrument, data from additional channels used for noise subtraction and detector characterization, and analysis data products from version 4.0 of the Gravitational-Wave Transient Catalog.

The Gravitational-Wave Transient Catalog (GWTC) is a collection of short-duration (transient) gravitational wave signals identified by the LIGO-Virgo-KAGRA Collaboration in gravitational-wave data produced by the eponymous detectors. The catalog provides information about the identified candidates, such as the arrival time and amplitude of the signal and properties of the signal's source as inferred from the observational data. GWTC is the data release of this dataset and version 4.0 extends the catalog to include observations made during the first part of the fourth LIGO-Virgo-KAGRA observing run up until 2024 January 31. This paper marks an introduction to a collection of articles related to this version of the catalog, GWTC-4.0. The collection of articles accompanying the catalog provides documentation of the methods used to analyze the data, summaries of the catalog of events, observational measurements drawn from the population, and detailed discussions of selected candidates

The Gravitational-Wave Transient Catalog (GWTC) is a collection of candidate gravitational-wave transient signals identified and characterized by the LIGO-Virgo-KAGRA Collaboration. Producing the contents of the GWTC from detector data requires complex analysis methods. These comprise techniques to model the signal; identify the transients in the data; evaluate the quality of the data and mitigate possible instrumental issues; infer the parameters of each transient; compare the data with the waveform models for compact binary coalescences; and handle the large amount of results associated with all these different analyses. In this paper, we describe the methods employed to produce the catalog's fourth release, GWTC-4.0, focusing on the analysis of the first part of the fourth observing run of Advanced LIGO, Advanced Virgo and KAGRA.

Version 4.0 of the Gravitational-Wave Transient Catalog (GWTC-4.0) adds new candidates detected by the LIGO, Virgo, and KAGRA observatories through the first part of the fourth observing run (O4a: 2023 May 24 15:00:00 to 2024 January 16 16:00:00 UTC) and a preceding engineering run. In this new data, we find 128 new compact binary coalescence candidates that are identified by at least one of our search algorithms with a probability of astrophysical origin $p_{\rm astro} \geq 0.5$ and that are not vetoed during event validation. We also provide detailed source property measurements for 86 of these that have a false alarm rate $< 1 \rm{yr}^{-1}$. Based on the inferred component masses, these new candidates are consistent with signals from binary black holes and neutron star-black hole binaries (GW230518_125908 and GW230529_181500). Median inferred component masses of binary black holes in the catalog now range from $5.79\,M_\odot$ (GW230627_015337) to $137\,M_\odot$ (GW231123_135430), while GW231123_135430 was probably produced by the most massive binary observed in the catalog. For the first time we have discovered binary black hole signals with network signal-to-noise ratio exceeding 30, GW230814_230901 and GW231226_01520, enabling high-fidelity studies of the waveforms and astrophysical properties of these systems. Combined with the 90 candidates included in GWTC-3.0, the catalog now contains 218 candidates with $p_{\rm astro} \geq 0.5$ and not otherwise vetoed, doubling the size of the catalog and further opening our view of the gravitational-wave Universe.

Broad all-sky searches for continuous gravitational waves have high computational costs and require hierarchical pipelines. The sensitivity of these approaches is set by the initial search and by the number of candidates from that stage that can be followed-up. The current follow-up schemes for the deepest surveys require careful tuning and set-up, have a significant human-labor cost and this impacts the number of follow-ups that can be afforded. Here we present and demonstrate a new follow-up framework based on Bayesian parameter estimation for the rapid, highly automated follow-up of candidates produced by the early stages of deep, wide-parameter space searches for continuous waves.