Papers for Monday, Dec 08 2025

The thermal structures of highly irradiated ultra-hot Jupiters can deviate substantially from those of cooler hot Jupiters. For planets orbiting rapidly rotating, and consequently oblate, host stars, photometric light curves provide a unique opportunity to measure the spin-orbit angle. Moreover, in systems with significant spin-orbit misalignment, the stellar oblateness can induce observable orbital precession. We wish to study the atmosphere and orbital architecture of an ultra-hot Jupiter WASP-189 b, orbiting around a hot A-type star. We use the photometric phase curves and gravity-darkened transits of WASP-189 b observed with the Transiting Exoplanet Survey Satellite (TESS), complemented with the archival observations from CHaracterising ExOPlanet Satellite (CHEOPS). We detected a phase curve signal with significant occultation depth of 203.4 (+16.2) (-16.3) ppm, while the nightside flux, -71.8 (+36.4) (-36.0) ppm, is consistent with zero at 2-sigma. We invert the phase curve signal to construct the temperature map of the planet. The map was subsequently used to estimate the Bond albedo and heat redistribution efficiency, the expected median ranges of which are found to be 0.19-0.35 and 0.09-0.41, respectively. Finally, we analysed gravity-darkened transits to find that the planet is in polar orbit with the spin-orbit angle of 89.46 (+1.08) (-1.08) deg. We found no hint of orbital precession while comparing our results with those from the literature. Our observations, together with atmospheric modelling, suggest that the dayside emission of WASP-189 b in TESS and CHEOPS bandpasses is dominated by thermal emission from an atmosphere with extremely inefficient heat transport and negligible contribution from reflected light.

"Little red dots" (LRDs) represent a new population of astronomical objects uncovered by JWST whose nature remains debated. Although many LRDs are suspected as active galactic nuclei (AGN), they show little variability on days-years timescales. We report the discovery of two gravitationally lensed LRDs at redshift $\sim$4.3 behind the cluster RXCJ2211-0350, one of which (RX1) is quadruply imaged with time delays spanning $\sim$130 years. RX1 exhibits intrinsic color and brightness variations of up to 0.7 magnitude among its images. These changes are consistent with blackbody-temperature variations of a photosphere, indicating long-term variability analogous to Cepheid-like pulsations but in a far more extended ($R \sim 2000$ AU) and massive ($M \gtrsim 10^6 \, M_{\odot}$) systems. These results suggest LRDs as a distinct class of AGN with stellar-like envelopes.

The Nancy Grace Roman Space Telescope will expand the reach of gravitational microlensing surveys by increasing the number of events monitored and the precision of their light curves. We investigate Roman's ability to detect triple-lens microlensing systems, cases where a foreground star with two bound exoplanets produces detectable anomalies in a microlensing event, using its planned high-cadence observations toward the Galactic bulge. We simulate a large set of high-magnification microlensing light curves based on Roman's expected survey characteristics. A detection criterion, based on a required $\chi^2$ improvement for a two-planet model, is applied to determine whether the second planet can be reliably distinguished from a single-planet (binary-lens) model. Our simulations show that the majority of two-planet microlensing events would be detectable with Roman. Events in which both planets are relatively massive (planet-star mass ratios of order $10^{-3}$), or in which the more massive planet occupies a favorable resonant configuration, produce strong central perturbations, resulting in detection efficiencies of roughly 90\%. By contrast, systems with only low-mass planets ($q \sim 10^{-4}$) or with less favorable alignments generate much weaker signals, which often fall below the detection threshold. In general, the planetary mass ratios and the resulting caustic geometry (e.g., central caustic size in resonant versus wide/close orbits) are the dominant factors governing detectability. Taking into account the expected frequency of planetary systems and the fraction of high-magnification events, we estimate that Roman will detect a high-magnification triple-lens event in approximately 4.5\% of multi-planet microlensing events, corresponding to about 64 events over the course of the full survey.

We use machine learning to measure the intracluster light (ICL) fractions of 177 galaxy groups and clusters identified from Hyper Suprime-Cam Subaru Strategic Program imaging to explore how the ICL varies with the properties of its host cluster. We study the variation in ICL fraction with host cluster redshift, halo mass, and magnitude gap to investigate how the ICL develops over time, in various cluster environments, and with cluster relaxation. We find that there is a decreasing correlation with redshift (Spearman correlation $r_S=-0.604$, p-value $=9\times10^{-10}$), however this can be plausibly accounted for by including the effects of cosmological surface brightness dimming and the passive aging of stellar populations. There is a weak negative correlation with halo mass ($r_S=-0.330$, p-value $=8\times 10^{-5}$) where ICL fractions are higher in lower halo mass groups than higher halo mass clusters. We also find that there is a marginal positive correlation with magnitude gap ($r_S=0.226$, p-value = 0.01), indicating that relaxed clusters are more likely to host higher ICL fractions. These results are consistent with a scenario where the dominant formation mechanism of the ICL is galaxy-galaxy interactions such as tidal stripping, and demonstrates the capability of the method to easily construct large samples and study large-scale trends in the ICL fraction.

We present the first discoveries from Keck Observations in the INfrared of Taurus and $\rho$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU), an adaptive optics imaging survey of young stars in the Taurus and $\rho$ Oph star-forming regions using the Keck infrared pyramid wavefront sensor (PyWFS). We have found two faint ($\Delta$K~7 mag), wide-separation companions to two ~3-Myr-old Taurus members. Relative astrometry for these systems show that both companions are bound to their host stars. We obtained near-infrared spectra of these companions using IRTF/SpeX (R~100) and Gemini/GNIRS (R~1000-2000), and combine these with photometry from our NIRC2 imaging, the Pan-STARRS survey, and Spitzer/IRAC archival imaging to constrain their properties. One companion, KOINTREAU-1b (at a projected separation of 690 au), has an average near-IR spectral type of M9$\pm$2, a gravity classification of VL-G, and a changing spectral type between the SpeX (M7) and GNIRS (L1) observations. We estimate this object's mass to be $10.6^{+2.5}_{-2.3}$ M$_{\rm Jup}$, making KOINTREAU-1b the fifth planetary-mass companion found in Taurus. The other companion, KOINTREAU-2b (projected separation 560 au), has a spectral type of M4.5$\pm$1 but is ~4 magnitudes underluminous relative to other Taurus stars of the same spectral type. We detect exceptionally strong He I 1.083 micron emission from this object, indicative of outflows driven by ongoing accretion, but with a conspicuous lack of accompanying H emission. We conclude that KOINTREAU-2b is a young star obscured by an edge-on disk and observed in scattered light. Finally, we derive a distortion solution for NIRC2 imaging which shows a 0.118° difference in position angle from the previous distortion solution.

A number of simulations have seen the emergence of strongly-toroidally-magnetized accretion disks from interstellar medium inflows. Recently, Guo et al. 2025 (G25) studied an idealized test problem of toroidally-magnetized disks in isothermal ideal MHD with an Eulerian static-mesh method, and argued the midplane behavior changes qualitatively (with a significant loss of toroidal magnetic flux) when the the thermal scale-length is resolved ($\Delta x < H_{\rm thermal}$). We rerun the G25 test problem with two Lagrangian methods: meshless finite-mass, and meshless finite-volume. We show that Lagrangian methods reproduce the high-resolution ($\Delta x \ll H_{\rm thermal}$) Eulerian G25 results. At low resolution ($\Delta x \gg H_{\rm thermal}$), behaviors differ: Lagrangian methods still lose flux and evolve 'as close as possible' to the converged solution, while Eulerian methods show no evolution. We argue this difference in convergence behavior is related to the ability of Lagrangian codes to follow flows to an arbitrarily thin midplane layer, analogous to the well-studied difference in Jeans fragmentation problems. This and results from other higher-resolution simulations and different codes suggest that the sustained midplane toroidal fields seen in recent Lagrangian multi-scale, multi-physics simulations cannot be a numerical resolution effect, and some physical difference between those simulations and the G25 test problem explains their different behaviors.

Rotating galaxies with relaxed gaseous disks have been discovered across cosmic time, from the local Universe to high redshift (z>4). But few such sources have been confirmed at z>4, making them a precious sample to examine what conditions result in such ordered kinematics in an early, more chaotic Universe. One of the best examples of this sample is the galaxy DLA0817g1 (z=4.2603), which shows remarkably clear rotation in ALMA [CII] data. We present recent JWST/NIRSpec IFU data (R~2700) of DLA0817g1, which we combine with archival ALMA [CII] observations to place constraints on its ISM conditions and morpho-kinematics. From a combination of line ratios, we find a high gas-phase metallicity (~0.7 solar), high fraction of obscured star formation, low ionisation (compared to other high-redshift galaxies observed with JWST), and no significant evidence for AGN (based on the WHAN diagnostic). Dynamical modelling with 3DBarolo reveal nearly identical rotation in Halpha and [CII], but with a higher velocity dispersion in the former. Using our metallicity estimate and previous CO and [CII] detections, we derive a new estimate of the molecular gas mass, relieving a previous strain in the mass budget. Altogether, we suggest that this is a 'smouldering' galaxy, where past star formation resulted in significant chemical enrichment (i.e., Zgas and Mdust), but the current activity is low (i.e., lower ionisation parameter and electron temperature). These new observations have opened a window into questions regarding the interplay of gas, metallicity, star formation, and kinematics in a prototypical early disk galaxy.

Rapid detection and follow-up of electromagnetic (EM) counterparts to gravitational wave (GW) signals from binary neutron star (BNS) mergers are essential for constraining source properties and probing the physics of relativistic transients. Observational strategies for these early EM searches are therefore critical, yet current practice remains suboptimal, motivating improved, coordination-aware approaches. We propose and evaluate the Two-Step Localization strategy, a coordinated observational protocol in which one wide-field auxiliary telescope and one narrow-field main telescope monitor the evolving GW sky localization in real time. The auxiliary telescope, by virtue of its large field of view, has a higher probability of detecting early EM emission. Upon registering a candidate signal, it triggers the main telescope to slew to the inferred location for prompt, high-resolution follow-up. We assess the performance of Two-Step Localization using large-scale simulations that incorporate dynamic sky-map updates, realistic telescope parameters, and signal-to-noise ratio (SNR)-weighted localization contours. For context, we compare Two-Step Localization to two benchmark strategies lacking coordination. Our results demonstrate that Two-Step Localization significantly reduces the median detection latency, highlighting the effectiveness of targeted cooperation in the early-time discovery of EM counterparts. Our results point to the most impactful next step: next-generation faster telescopes that deliver drastically higher slew rates and shorter scan times, reducing the number of required tiles; a deeper, truly wide-field auxiliary improves coverage more than simply adding more telescopes.

Novae are thermonuclear eruptions on accreting white dwarfs in interacting binaries. Although most of the accreted envelope is expelled, the mechanism -- impulsive ejection, multiple outflows or prolonged winds, or a common-envelope interaction -- remains uncertain. GeV $\gamma$-ray detections from $>20$ Galactic novae establish these eruptions as nearby laboratories for shock physics and particle acceleration, underscoring the need to determine how novae eject their envelopes. Here we report on near-infrared interferometry, supported with multiwavelength observations, of two $\gamma$-ray detected novae. The images of the very fast 2021 nova V1674~Her, taken just 2--3 days after discovery, reveal the presence of two perpendicular outflows. The interaction between these outflows likely drives the observed $\gamma$-ray emission. Conversely, the images of the very slow 2021 nova V1405~Cas suggest a delay in the ejection of the bulk of the accreted envelope of more than 50 days after the start of eruption, as the nova slowly rises to visible peak and during which the envelope engulfed the system in a common envelope phase. These unprecedented images offer direct observational evidence that the mechanisms driving mass ejection from the surfaces of accreting white dwarfs are not as simple as previously thought, revealing multiple outflows and delayed ejections.

As the architecture for the Habitable Worlds Observatory (HWO) is being developed, it is crucial to optimize the observing strategies for a survey to detect and characterize Earth-like planets around Sun-like stars. Efficient target identification and characterization will help drive mission requirements that can be matched to the planned observations. Current HWO concepts allow simultaneous multi-bandpass observations with the coronagraph instrument, critical for performing a qualitative planetary reconnaissance to optimize observing time for deriving orbital constraints and prioritize characterization of promising targets. We describe a new algorithm designed to determine the best combination of broadband photometric observations for extracting maximum information from the first visit. It identifies degeneracies in the orbital configurations, fluxes, and noise, and determines optimal secondary photometry bands to reduce these. We demonstrate its application by comparing an Earth seen at quadrature with a cold and a warm Neptune at inclined orbits and varying phases, with comparable flux in the discovery bandpass centered at 500 nm (20\% bandwidth). Using the noise and exposure time calculator that we developed for the HWO coronagraph instrument, we find that the baseline $S/N=7$ (corresponding to 3.2 hours observing time for a planet at 10pc) is only sufficient to marginally differentiate the Earth from a cold Neptune-like planet assuming two parallel bandpasses (550 nm + 850 nm). However, increasing to $S/N=15$ (7 hours observing time) and using three parallel bandpasses (360 nm + 500 nm + 1.11 micron) would differentiate the Earth from either a warm or cold Neptune.

We discuss synchrotron absorption of a short electromagnetic pulse that propagates in a cold magnetized pair plasma. We show that the pulse can be absorbed when $\omega_{\rm B}/a_0< \omega< a_0\omega_{\rm B}$, where $a_0>1$ is the strength parameter of the pulse, and $\omega$ and $\omega_{\rm B}$ respectively are the frequency of the wave and the cyclotron frequency in the background magnetic field (all quantities are defined in the reference frame where the particles are at rest before being illuminated by the pulse). The condition $\omega_{\rm B}/a_0< \omega< a_0\omega_{\rm B}$ is essentially a generalization of the cyclotron resonance to strong electromagnetic pulses with $a_0>1$. When $\omega_{\rm B}/a_0< \omega< a_0\omega_{\rm B}$, the propagation of electromagnetic waves in a plasma can be very different with respect to the propagation in vacuum because the wave equation is strongly non-linear. Then it is unclear whether the particles are heated stochastically due to synchrotron absorption, as found by studying the motion of a test particle in the field of a vacuum electromagnetic wave. We discuss implications of our results for constraining emission models of fast radio bursts.

Radio pulsar timing, X-ray pulse profile modeling or gravitational-wave detections of binary mergers involving at least one neutron star offer the opportunity to elucidate the properties of dense and neutron rich matter in thermodynamic regimes inaccessible to nuclear laboratories. Such inference relies on building appropriate equation-of-state priors, such as the recently introduced semi-agnostic constructions that incorporate nuclear theory and experimental information available in low to intermediate density regimes, while offering the necessary flexibility at high density. In this paper, we assess how detections of mass, radius, and tidal deformability for low-mass ($\sim 1$M$_{\odot}$) or high-mass ($\sim 1.9$M$_{\odot}$) neutron stars would contribute to constraining nuclear empirical parameters in an inference based on semi-agnostic equation-of-state priors. We first assessed the correlation factors between nuclear empirical parameters and the zero-temperature and $\beta$-equilibrated pressure in different regimes of density. We then simulate observations for three nucleonic equations of state to test the recovery of the corresponding nuclear empirical parameters. We show that not all nuclear empirical parameters significantly correlate with the pressure and find a competition between them in the high-density regime that challenges their inference. We also find that using semi-agnostic constructions instead of assuming a nucleonic content up to the highest densities in the neutron-star core can help recover more accurately the true nuclear empirical parameters. Parameterizing the high-density regime of the equation of state with the nucleonic meta-model can pollute the inference of nuclear empirical parameters; semi-agnostic constructions are a solution to that. However, many nuclear matter empirical parameters contribute in a similar way to the building of baryonic pressure.

The wide-angle Polarimetric Camera (PolCam) onboard South Korea's first lunar orbiter, Danuri, is a pioneering instrument designed to conduct the first global polarimetric and high-phase-angle survey of the Moon. Precise geometric calibration is critical for this mission, particularly due to PolCam's highly oblique viewing geometry, which introduces significant topographic distortion. We present a comprehensive on-orbit geometric calibration that relies on 160,256 tie points derived from matching features between PolCam images and the well-orthorectified global map of the Kaguya Multiband Imager (MI). This dataset allows us to address two fundamental challenges: (1) the accurate reconstruction of the observation time for each line of an observation strip via a simple linear model, and (2) the refinement of the precise camera model, geometric model for PolCam optics. Our optimization method for these two challenges transforms the 2D image coordinates of identified features into 3D lunar coordinates and minimizes the reprojection error against the reference coordinates provided by the Kaguya MI map. From the refined observation time and camera model, we compute the precise longitude, latitude, and elevation of each pixel of an observed image. These estimated 3D coordinates are then used to generate orthorectified images, the final product of the geometric calibration. The resulting calibration achieves a geometric precision comparable to that of previous lunar orbiters and establishes the foundational framework necessary to produce geometrically-corrected data products of PolCam.

Axion quark nuggets (AQNs) are macroscopic dark-matter candidates, with masses of the order of a few grams to a kilogram and sub-micron radius, thought to form at the Quantum Chromo Dynamic era through axion-induced charge separation. This framework naturally links the dark and visible matter abundances ($\Omega_{\rm DM} \sim \Omega_{\rm visible}$) and provides a mechanism for generating the baryon-antibaryon asymmetry where dark matter is composed of matter AQNs and antimatter AQNs. Although behaving as cold dark matter on cosmological scales, baryons annihilate with antimatter AQNs, producing ionizing high-energy photons. The resulting energy injection may imprint spectral distortions on the cosmic microwave background (CMB) and modify the reionization history. Using a modified version of the \texttt{CLASS} Boltzmann code we compute the impact of this energy injection on the $\mu$ and $y$ spectral distortion parameters as well as on the optical depth. We find that (1) the CMB anisotropies remain essentially unaffected by baryon annihilation, and (2) the associated spectral distortion signatures lie within the sensitivity reach of proposed CMB spectral distortion missions. Finally, we discuss the similarities and differences between the AQN scenario and annihilating or decaying dark matter models.

With the goal of extracting as much information as possible from Chandra and XMM-Newton observations of faint, diffuse sources such as galaxy clusters, as well as those of future X-ray telescopes, we present a strategy for forward modeling all the foreground and background signals present in these data. This work leverages widespread efforts to understand the soft X-ray emission from the Galaxy, as well as the cosmic X-ray background and instrument-specific, particle-induced backgrounds. Statistically, a forward model of the foregrounds and backgrounds is preferable to alternatives because it requires no binning of the data, and allows straightforward marginalization over systematic uncertainties. We apply these methods to several galaxy clusters at intermediate-to-high redshifts, spanning a range of masses and morphologies, using Chandra and/or XMM-Newton data. Our results suggest a modest improvement even for relatively bright clusters at these redshifts, and more substantial advantages in the high-redshift, low-surface-brightness regime. We also discuss and provide a simple correction for a time-dependent miscalibration of the Chandra ACIS detectors identified in archival galaxy cluster data.

We investigate the formation of primordial black holes (PBHs), their spin and abundance, in a single-field inflationary model based on a mutated hilltop potential inserted with a small step-like feature. This step induces a brief phase of ultra-slow-roll inflation, producing the large enhancement of the scalar power spectrum required for an appreciable amount of PBH abundance. Instead of the commonly used analytical power spectra, we compute the primordial power spectrum accurately by numerically solving the Mukhanov-Sasaki equation. Using the obtained power spectrum, we apply peak theory with $\nabla^2 \zeta$ treated as a Gaussian random field and parametrize the curvature profile by its amplitude $\mu$ and characteristic width $K$. Confining the study to Type-I PBH, the threshold value is calculated using two robust methods: the average of the compaction function and the q-function method. Using the result, the dimensionless spin parameter of the resulting PBHs is calculated at linear order and found to be $\sqrt{\langle a_\star^2 \rangle} \sim 10^{-3}$; however, it can be higher for smaller masses. We present detailed predictions for two representative parameter sets, calculate the present-day PBH mass function $f_{\rm PBH}(M)$ and the associated scalar-induced gravitational waves (SIGW). The first produces PBHs of mass $M \simeq 10^{-13}\,M_\odot$ that can account for $100\%$ of dark matter, while the second yields $M \simeq 10^{-2}\,M_\odot$ PBHs contributing approximately $2.4\%$ of the dark matter density. The predicted signals of SIGWs lie within the sensitivity bands of future experiments such as LISA, DECIGO, BBO, and SKA. In particular, the second parameter set produces a SIGWs compatible with the recent NANOGrav evidence for a low-frequency gravitational-wave signal.

Extended main-sequence turnoffs are observed in the color-magnitude diagrams of some young and intermediate-age star clusters. Here we report the case study of NGC 3532. Among the cluster member candidates identified using the ML-MOC algorithm on Gaia DR3 sources, we found that fast rotators are significantly redder. Stars near the main-sequence turnoff exhibit a multi-modal distribution in the Gaia broadening velocity ($v_{\rm broad}$). A comparison with relevant literature suggests binaries being typically interspersed with fast rotators, often manifesting as slow to moderate rotators. Additionally, chemically peculiar stars are predominantly located in the bluer regions of the turnoff, with those in the fast-rotator region having large values of Gaia re-normalised unit weight error, indicating plausible companions. Our analysis suggests multiple channels responsible for angular momentum loss to account for the extended turnoff.

A major challenge in ground-based ultra-high-energy gamma-ray observations remains in discriminating sporadic gamma-ray signals from a huge background of cosmic-ray events. To achieve good discrimination power of gamma rays against protons, an unconventional approach is presented that exploits the geomagnetic influence on air shower muons in Monte Carlo shower events. A recognizable polar asymmetry in the positive and negative muon distributions is noticed after transforming the impact coordinates of each muon from the observer plane onto the shower front plane, plus a judicious ignoring of the minimal attenuation of muons in the space between the two planes. A couple of observables, $d_{\text{max}}$ and $N_{\mu; \text{IQS}}^{\text{tr.}}$, can be extracted from the formation of two densely populated positive and negative muon zones in each shower. Both observables demonstrate excellent gamma/proton discrimination power, with efficiencies of $93.2\%$ and $98.6\%$. This analysis permitted the usage of muon detectors just covering a small area of $\simeq{1.4}\%$ of a square-km array for ultra-high-energy gamma-ray observations. It is expected that the present and future gamma-ray observatories will implement the current approach.

The cosmic microwave background absorption intensity in the 21 cm line of neutral hydrogen in the presence of additional power in the form of a "bump" in the spectrum of cosmological density perturbations is calculated. The main absorption-amplifying effect is the earlier birth of the first stars forming an ultraviolet radiation background. This radiation reduces the spin temperature of neutral hydrogen and, thus, amplifies the absorption in the 21 cm line. A comparison of various cosmological models (with and without a bump in the density perturbation spectrum) shows that it is possible to determine the probable position of the bump in the perturbation spectrum and, thus, to reconstruct the spectrum of cosmological perturbations on scales $k>1$~Mpc${}^{-1}$ from the position of the absorption frequency profile.

Crater~II (CraII) is a very intriguing, low-surface brightness and extended galaxy in the vicinity of our Milky Way. Motivated by its huge area and the number of RR Lyrae stars (RRLS) detected near to its core, we performed a follow-up campaign to get deep multi-band ($g,i$) and multi-epoch DECam observations in the outskirts of CraII, covering up to 8$r_h$ in the North-East direction and up to 13$r_h$ in the South-West direction (spanning almost 10 degr in the sky across the galaxy). We confirm the existence of tails coming out from CraII. In our survey, we detected a total of 97 periodic variable stars, of which 46 are CraII members [37 RRLS and 7 anomalous Cepheids (AC)]. The RRLS show a strong gradient in distance of 3.7~kpc/deg, which follows the relation: $d (\rm {kpc}) = (-3.70\pm 0.21)\, \xi' + (116.2 \pm 0.32)$ (where $\xi'$ is the planar coordinate rotated to fit the CraII tails). We also found an indication that the gradient in distance in the distant part of the near-side tail (North-East) may be less steep than it is in the inner $5°$. The leading tail also displays a significant over-density of RRLS located $\sim 3.25$ deg from the center of CraII. Despite covering a smaller area than previous works, our deeper photometry has allowed us to unveil more variable stars in the region and better define the tidal tails of CraII.

We present a comprehensive broadband spectral and variability study of the newly detected black hole X-ray binary Swift~J1727.8--1613 in the intermediate states during its 2023 outburst, using multi-mission observations from NICER, NuSTAR, AstroSat, and Insight-HXMT. The spectral data up to $78$ keV in the hard-intermediate state (HIMS) requires models with two Comptonizing regions. In contrast, models with a single Comptonizing region adequately describe the soft-intermediate states (SIMS), implying a significant evolution in the disk-corona geometry between the states. The hard X-ray tail above $100$ keV in the HIMS, detected with both AstroSat/CZTI and Insight-HXMT/HE, indicates that the electron population in the corona is not purely thermal but rather hybrid, with a power-law distribution above the thermal cutoff. While both the reflection modeling and disk continuum fitting favor a truncated disk geometry in the HIMS, the disk substantially moves close to the innermost stable circular orbit in the SIMS, accompanied by a significant rise in the disk temperature. This interpretation is further supported by the increase in the QPO frequency from $\sim1.3$ to $\sim6.6$ Hz. From joint modeling of the disk continuum and reflection component, we estimate a black hole mass of $10.5^{+7.7}_{-3.0}$, spin of $0.79^{+0.03}_{-0.13}$, and disk inclination angle of $42^\circ$-$50^\circ$, which match well with the previously reported spectro-polarimetric measurements. The inferred source distance of $\sim3.5$ kpc is consistent with the recent estimate based on optical spectroscopy. We find a weakly variable or stable disk and a highly variable Comptonized component.

Using late-Universe observations, we demonstrate that freeing dark energy and dark matter equations of state (EoS) dramatically alters the inferred strength and direction of their interactions. When dark sector EoS are fixed to $w_{\mathrm{de}}=-1$ and $w_{\mathrm{dm}}=0$, the data consistently favor an energy transfer from dark energy to dark matter across various interaction forms. This apparent evidence, however, proves highly sensitive to the EoS assumptions: treating $w_{\mathrm{de}}$ as a free parameter substantially weakens the evidence for interaction, with its value converging to the quintessence regime ($w_{\mathrm{de}}>-1$). In contrast, freeing $w_{\mathrm{dm}}$ maintains a preference for interaction, revealing a correlation where positive $w_{\mathrm{dm}}$ is associated with energy transfer from dark energy to dark matter, and negative $w_{\mathrm{dm}}$ with energy transfer from dark matter to dark energy. These findings caution against the simplistic assumption of $\Lambda$CDM EoS values when attempting to detect a possible interaction. Despite these fundamental degeneracies, model comparison using the Akaike and Deviance information criteria shows that all of the tested interacting dark energy scenarios receive substantial support over the $\Lambda$CDM model.

In this work, we test a framework to perform the analysis of redshift-space distortions simultaneously in configuration and Fourier space. We test our methods with the AbacusSummit suite of N-body simulations as well as a more numerous set of approximate EZmocks, reproducing the sample of luminous red galaxies of from the Baryon Oscillation Spectroscopic Survey (BOSS) and its extension (eBOSS). Our clustering models are based on the effective field theory of large-scale structures in a Lagrangian frame, used in the latest results from the Dark Energy Spectroscopic Instrument. We perform a template type of analysis, including dilation parameters and the slope parameter from the ShapeFit framework. We find that the joint space inference yields unbiased and robust constraints on simulated datasets, consistent with results from individual spaces or previous methods to obtain consensus results. Our joint space analysis on the the BOSS+eBOSS LRG sample obtains $ f\sigma_8 = 0.463 \pm 0.052 $, in good agreement with the official 2020 results.

Stellar feedback, as a key process regulating the baryon cycle, is thought to greatly redistribute baryonic material inside and outside the dark matter halos (DMHs), however the observational evidences are lacking. Through stacking analyses of ~400,000 galaxy spectra from Dark Energy Spectroscopic Instrument (DESI), we find star formation driven cool outflows in Mg II absorption line. Assuming only gravity acts on the launched gas, our calculations reveal that outflows from low mass galaxies (log M*<10) are capable of escaping beyond the DMHs, which aligns well with our finding in the circumgalactic medium (CGM) absorption along the minor-axes of galaxies using background quasars. This research offers indirect evidence that stellar feedback drives the low baryon retention rate in low-mass haloes, implicating that baryonic processes within galaxies are connected with the diffuse matter beyond the DMHs.

We present a way to set up an inexpensive out of the shelf spectrograph at a local observatory. Stability and resolution of the spectrograph are high enough for radial velocity determination of binary stars or determination of stellar characteristics. Even some exoplanets might be detectable via the radial velocity method.

Galactic-scale outflows are a crucial component of galaxy evolution, yet their properties in the early universe remain poorly constrained. We present the first statistical investigation of cool gas outflows in galaxies spanning a wide cosmic timeline from $z \approx 1$ to $z \approx 10$. Using thousands of public JWST/NIRSpec spectra, we employ a signal-to-noise weighted spectral stacking technique on the \ion{Mg}{2} $\lambda\lambda2796, 2803$ absorption doublet. We robustly detect blueshifted \ion{Mg}{2} absorption in all stellar mass and redshift bins. The outflow equivalent width exhibits a strong, positive correlation with stellar mass ($M_*$) at all epochs, increasing from $\sim 1$~Å at $M_* \approx 10^9~\mathrm{M}_\odot$ to over $3$~Å at $M_* > 10^{10.5}~\mathrm{M}_\odot$. Our work provides the first statistical constraints on cool outflows in the low-mass ($M_* \lesssim 10^{9.5}~\mathrm{M}_\odot$), high-redshift ($z > 3$) regime, vital for constraining feedback in the numerous progenitors of typical present-day galaxies. Crucially, the scaling relation between outflow properties and stellar mass shows no significant evolution at $z > 3$. This suggests a persistent, unevolving feedback mechanism governing the baryon cycle in the early universe, placing strong constraints on models that invoke a fundamental change in feedback physics at Cosmic Dawn, such as the feedback-free starburst model.

The Galactic magnetar SGR 1935+2154 has exhibited prolific high-energy (HE) bursting activity in recent years. Investigating its potential tera-electronvolt counterpart could provide insights into the underlying mechanisms of magnetar emission and very high-energy (VHE) processes in extreme astrophysical environments. We aim to search for a possible tera-electronvolt counterpart to both its persistent and sub-second-scale burst emission. We analysed over 25 h of observations from the Large-Sized Telescope prototype (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) during periods of HE activity from SGR 1935+2154 in 2021 and 2022 to search for persistent emission. For bursting emission, we selected and analysed nine 0.1 s time windows centred around known short X-ray bursts, targeting potential sub-second-scale tera-electronvolt counterparts in a low-photon-statistics regime. While no persistent or bursting emission was detected in our search, we establish upper limits for the tera-electronvolt emission of a short magnetar burst simultaneous to its soft gamma-ray flux. Specifically, for the brightest burst in our sample, the ratio between tera-electronvolt and X-ray flux is less than $10^{-3}$. The non-detection of either persistent or bursting tera-electronvolt emission from SGR 1935+2154 suggests that if such components exist, they may occur under specific conditions not covered by our observations. This aligns with theoretical predictions of VHE components in magnetar-powered fast radio bursts and the detection of MeV - GeV emission in giant magnetar flares. These findings underscore the potential of magnetars, fast radio bursts, and other fast transients as promising candidates for future observations in the low-photon-statistics regime with Imaging Atmospheric Cherenkov Telescopes, particularly with the CTAO.

In this paper, we present a description and characterisation of the 2-Channel Focal Reducer Rozhen (FoReRo2), with an emphasis on its polarimetric and spectropolarimetric observation modes. FoReRo2 is a multimode instrument mounted at the Ritchey-Chretien(RC) focus of the 2-meter Ritchey-Chretien-Coude (RCC) telescope at the Bulgarian National Astronomical Observatory (BNAO) - Rozhen. The primary targets of this instrument include novae, Be/X-ray binaries, symbiotic stars, asteroids, and comets. Standard stars with a high degree of polarisation are an essential part of the polarimetric observations. In our sample, HD 204827 shows short-term variability in position angle, making it unsuitable for calibration. HD 183143 displays intrinsic polarisation variability but remains stable in position angle. For the first time, we present a statistical study of K and {\lambda}_max of the Serkowski law, including their mean value, standard deviation, and distribution. In order to show the FoReRo2 polarimetric capabilities, we also present several examples. The recurrent nova RS Oph shows variability of Serkowski's K parameter due to dust formation within the first few days after the 2021 outburst. The examples also include imaging polarimetry of comet C/2019 Y4 (ATLAS) and spectropolarimetric observations of the symbiotic star Z And.

Solar flares and coronal mass ejections, originating from solar active regions (ARs), are the primary drivers of space weather and can disrupt technological systems. Forecasting efforts heavily rely on photospheric magnetic field data from the Space-weather HMI Active Region Patch (SHARPs) data products. However, the crucial energy release occurs higher in the solar corona. Radio observations from instruments like the RATAN-600 telescope directly probe this region, but their scientific use has been hindered by a lack of standardized and accessible data products. To address this gap, we have developed the Ratan Active Region Patches (RARPs) database, a new public resource of multi-frequency radio spectra for solar ARs. Generated using RATANSunPy software, RARPs provides the first standardized radio counterpart to magnetic field archives. The database contains over 160,000 calibrated AR observations from 2009 to 2025, each including 3-18 GHz spectra and rich metadata. We demonstrate the scientific utility of this database by using machine learning to forecast solar flares. The radio spectra are first compressed into low-dimensional embedded features using an autoencoder, which are then used as predictors in baseline logistic regression classifiers. We compare the predictive power of these embedded RARPs features with that of the 18 SHARPs magnetic field parameters provided in the SHARPs data product headers. Our results show that while SHARPs data provides superior flare discrimination, the radio signatures in RARPs possess clear predictive potential and, for M-class and above flares, yield lower Brier Scores and positive Brier Skill Scores relative to SHARPs, indicating more accurate probabilistic forecasts for these events. This establishes radio data as a valuable and complementary information source.

The existence of cuspy or cored centers of dark matter halos is a crucial discriminant between different dark matter models. It has recently been claimed based on dynamical arguments that perfectly cored stellar systems cannot survive inside cuspy dark matter halos, which would make the observation of stellar cores in ultra-faint dwarf galaxies, where dark matter cores cannot form through baryonic processes, a direct falsification of the cold dark matter paradigm. Here, we use idealized simulations to show explicitly that cored stellar systems like those observed in dwarf galaxies can be stable within cuspy dark matter halos over at least several Hubble times. We also demonstrate that observations of ultra-faint dwarf galaxies cannot distinguish mildly positive, flat, or negative inner density slopes, further precluding the dynamical inference of the gravitational potential from the stellar configuration.

This study investigates the signatures of pressure extrema on global oscillations in discs. To this end, we use the framework of wave topology to establish a generalised local dispersion relation that includes pressure gradients. We highlight the influence of a previously unrecognized epicyclic-acoustic frequency and derive an analytical criterion for the existence of a branch of modes transiting between the inertial and the pressure bands. We find that pressure extrema consist of wave guides in which such topological modes propagate. The fundamental mode trapped at a pressure bump can propagate at all frequencies, allowing it to resonate with any temporal forcing, while the mode associated with a pressure gap propagates at a fixed frequency, propagates with arbitrary vertical phase velocity. These specific features make them attractive candidates for future discoseismology.

Recent intensive monitoring campaigns of active galactic nuclei (AGN) have provided simultaneous X-ray, UV, and optical data of unprecedented quality. The observations reveal a strong correlation between the UV and optical variability, but a weaker correlation between the X-ray and UV bands, challenging the standard X-ray reprocessing scenario. We revisit the X-ray/UV connection in NGC 5548 by fitting archival 2014 HST and Swift/XRT light curves assuming X-ray reverberation from a dynamically evolving X-ray corona. Our results show that, as long as the corona height, photon index and power vary over time, X-ray reverberation can explain the observed UV and optical variability within 2% and 5%, respectively (on average). The evolution of the best-fit parameters suggests that fast changes in coronal geometry and energetics on a time scale of days are required to explain the observed variability.

The interpretation of the origin of observed exoplanets is usually done only qualitatively due to uncertainties of key parameters in planet formation models. To allow a quantitative methodology which traces back in time to the planet birth locations, we train recently developed conditional invertible neural networks (cINN) on synthetic data from a global planet formation model which tracks growth from dust grains to evolved final giant planets. In addition to deterministic single planet formation runs, we also include gravitationally interacting planets in multiplanetary systems, which include some measure of chaos. For the latter case, we treat them as individual planets or choose the two or three planets most likely to be discovered by telescopes. We find that training on multiplanetary data, each planet treated as individual point, is promising. The single-planet data only covers a small range of planets and does not extrapolate well to planet properties not included in the training data. Extension to planetary systems will require more training data due to the higher dimensionality of the problem.

Polarization-mode observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are powerful tools for studying the dust grain populations in circumstellar disks. Many sources exhibit polarization signatures consistent with aligned dust grains, yet the physical origin of this alignment remains uncertain. One such source is BHB07-11, a Class I protobinary object in the Pipe Nebula with complex spiral arm structures in its circumbinary disk. While magnetic fields are often invoked to explain grain alignment in the interstellar medium, the contrasting conditions in circumstellar disk environments demand further investigation into grain alignment mechanisms. To determine BHB07-11's dominant polarization mechanism, we leverage ALMA polarization-mode dust continuum observations in Bands 3 ($\lambda$=3.1 mm), 6 ($\lambda$=1.3 mm), and 7 ($\lambda$=0.87 mm), in combination with high-resolution dust continuum and spectral line observations in Band 6. Observed polarization vectors in each band are consistent with emission from aligned grains and follow the structure of the spiral arms as shown in the high-resolution observations. Given the relationship between the observed polarization vector orientation and the spiral arms, we find that the polarization morphology is most consistent with grains aligned through a relative velocity flow between gas and dust in the spiral arms, as envisioned in the recently developed badminton birdie-like alignment mechanism, rather than alignment with a magnetic field or other known alignment mechanisms.

Trajectories of test particles in a time-varying nonspherical gravitational potential model of our Galaxy are considered. The role of the quadrupole component of the potential, which at distances greater than 50 kpc is associated with the distribution of matter in the Galaxy's neighborhood (mainly with the influence of the galaxy M31), is studied. It is shown that perturbations of the potential created by the environment can significantly change the trajectories of particles at distances greater than 100 kpc from the Galactic center, but the magnitude of this effect depends on the still poorly known trajectory of the galaxy M31. For some variants of this trajectory, structures resembling a "thin plane" of satellite galaxies cannot exist for more than 2-3 billion years.

Motivated by the idea of using quasars as standardizable candles for cosmology, we examine the relation between X-ray (at 2 keV, $L_{\rm 2keV}$) and ultraviolet (at 2500 Angstrom, $L_{\rm 2500}$) monochromatic luminosities of quasars using a sample of 2414 X-ray sources from the SRG/eROSITA all-sky survey cross-matched with the Sloan Digital Sky Survey data release 16 quasar catalogue (SDSS DR16Q), at redshifts between 0.5 and 2.5. These objects are bright both in X-rays and in the optical, so that the sample is characterized by nearly 100% statistical completeness. We have developed a new method for determining the $L_{\rm 2keV}-L_{\rm 2500}$ relation, which consistently takes into account (i) X-ray and UV flux limited object selection, (ii) X-ray and UV variability of quasars, and (iii) the decreasing space density of quasars with increasing luminosity. Assuming a linear relation between $l_{\rm X}\equiv\log(L_{\rm 2keV}/[{\rm erg\,s^{-1}\,Hz^{-1}}])$ and $l_{\rm UV}\equiv\log(L_{\rm 2500}/[{\rm erg\,s^{-1}\,Hz^{-1}}])$, we find the slope, $\gamma=0.69\pm0.02$ (hereafter all uncertainties are quoted at the 68% confidence level), and normalization, $l_{\rm X}=26.45\pm0.02$ at $l_{\rm UV}=30.5$, of the $L_{\rm 2keV}$ ($L_{\rm 2500}$) dependence. These values are not substantially different from the results of previous studies. A key novel aspect of our work is allowance for intrinsic scatter (which adds to the dispersion induced by quasar variability and flux measurement uncertainties) of the $L_{\rm 2keV}-L_{\rm 2500}$ relation in both variables, i.e. in X-ray and UV luminosity. The intrinsic X-ray scatter ($\sigma^2_{\rm intX}=0.066\pm0.005$) strongly dominates over the UV one ($\sigma^2_{\rm intUV}=0.001^{+0.003}_{-0.001}$). Further studies should seek to explain this behaviour in terms of accretion onto supermassive black holes and orientation of quasars with respect to the observer.

Sub-Neptunes are the most common type of detected exoplanet, yet their observed masses and radii are degenerate with several interior structures. One possibility is that sub-Neptunes have silicate/iron interiors and H$_2$-dominated atmospheres, i.e., they are `gas dwarfs'. If gas dwarfs have molten interiors, interactions between their magma oceans and atmospheres will produce distinct observational signatures. These signatures may break the degeneracy in interior structure, while providing insight into their interior processes, history, and population trends. We expect all such planets are born molten, but under what conditions do they remain molten today? We use the coupled interior-climate evolution model, PROTEUS, to estimate the `solidification shoreline': the instellation flux boundary (as a function of stellar $T_{\rm eff}$) that separates molten gas dwarfs from solidified ones. Our results show that 98\% of detected sub-Neptunes occupy a region of parameter space consistent with their having permanent magma oceans, if they are gas dwarfs. While mantle $f{\rm O}_2$ and bulk volatile C/H ratio both influence magma ocean lifetimes, planets with oxidising mantles and carbon-rich atmospheres are unlikely to have radii consistent with the sub-Neptune classification. Therefore, most detected sub-Neptunes (if they are gas dwarfs) have permanent magma oceans. This result motivates further research into the interactions between molten interiors and overlying atmospheres, and campaigns to identify unambiguous signatures of these interactions.

Microquasars (MQs) are Galactic binary systems, consisting of a star and a compact object, a neutron star or a stellar mass black hole, which accretes matter from its companion star and gives rise to relativistic jets. Recent detection of very-high-energy (VHE; $E \gtrsim 100,\text{GeV}$) and ultra-high-energy (UHE; $E \gtrsim 100,\text{TeV}$) gamma-rays by LHAASO, HAWC and HESS from the MQ V4641 Sgr and SS 433 suggests them as Galactic PeVatrons. In this work, we studied a hadronic origin of the observed TeV-PeV gamma-ray emission from these MQs. We considered the hadronic scenario where the gamma-rays are produced by the interaction of relativistic protons in the MQ jet with the stellar wind. We fitted our model with observed data and constrained physical parameters like the hadronic jet power fraction, the proton spectral index, the maximum proton energy and the jet bulk Lorentz factor. Our best-fit model shows hard proton spectra ($1.84-2.44$) and maximum proton energies between 1 and 5 PeV. We also estimated the all-flavor neutrino fluxes corresponding to the gamma-ray fluxes from the hadronic model and found that V4641 sgr can be detected by next-generation neutrino telescopes like KM3NeT-ARCA and TRIDENT. Furthermore, we modeled a synthetic population of Galactic MQs and estimated their contribution to the diffuse TeV-PeV gamma-ray flux. For the inner Galaxy PSR contribution dominates in the range 10-100 TeV, and above 100 TeV diffused cosmic ray interactions with the molecular clouds is most dominant. We find that a population $\sim 14$ MQs is required to explain the LHAASO data above 100 TeV. For the outer Galaxy, we show that MQs are the dominant class of sources, and we constrain their population $\sim$14. Our findings strongly suggest that MQs are efficient particle accelerators, contributing to Galactic PeVatrons and potential multimessenger sources in our Galaxy.

We present a new theoretical framework for the halo mass function (HMF) that accurately predicts the abundance of dark matter haloes across an exceptionally wide range in mass and redshift. Building on a generalised Press & Schechter model and triaxial collapse (GPS+), we predict the HMF in terms of the variance of the linear density field, with only a weak explicit dependence on halo mass and no explicit dependence on redshift. The GPS+ model naturally provides the correct normalization and high-mass behaviour without requiring empirical fitting. We calibrate and validate the GPS+ model using the Uchuu N-body simulation suite, which combines large cosmological volume and high mass resolution under Planck cosmology. Using six simulations with up to 300 realizations, we obtain precision HMF measurements spanning halo masses in the range 6.5 < log($M_{\rm 200m}$/[h$^{-1}$ $M_{\odot}$]) <16 over 0 < z < 20, with reduced cosmic variance. Across this full domain, the GPS+ model reproduces the simulated HMF with deviations typically below 10-20%. Comparison with the Sheth-Tormen (ST) model shows similar performance at z < 2, but markedly improved agreement at higher redshifts, where ST can deviate by 70-80% while our model remains within ~20%. Finally, we assess the impact of the halo mass definition: adopting the evolving virial overdensity of Bryan & Norman (1998) worsens agreement at low redshift and high masses, whereas M200m yields a more universal, nearly redshift-independent HMF.

OB associations are primordial tracers of star formation and Galactic structure. Originally defined about 80 years ago, their historical membership lists have been superseded thanks to the precise astrometry from ESA's \textit{Gaia}'s satellite. Recent studies have however been mostly focused on individual OB associations or limited by the coverage of spectroscopic surveys. In this paper, we exploit a complete census of $\sim$25,000 O- and B-type stars within 1 kpc of the Sun to produce a highly-reliable catalogue of 57 OB associations using the HDBSCAN clustering algorithm, increasing the number of known OB associations by a factor of two within this volume. We assess the validity of this catalogue by crossmatching our OB association members with other catalogues of OB associations, star clusters and young stellar groups, confirming the high-confidence of our census of OB associations. We characterize these OB associations physically (total initial stellar mass, number of OB stars, ...) and kinematically (velocity dispersion, linear expansion ages, ...). Nearly three quarters of the OB associations (41 out of 57) exhibit a significant expansion pattern in at least one direction, including 13 in both plane-of-the-sky directions, though differences in expansion velocity suggest anisotropical expansion patterns. We compare the locations of these OB associations with superclouds and features in the local Milky Way such as the Radcliffe Wave and discuss the implications for star formation in the solar neighbourhood.

The slowly pulsating B (SPB) stars are a class of variable star with masses between about 3 and 8 M$_{\odot}$. Their gravity-mode pulsation frequencies are sensitive to the near-core structure, which makes them useful probes of rotation and mixing in the deep stellar interior. Time series photometry, such as from the Kepler and TESS space telescopes, allows the extraction of their pulsation frequencies and construction of period spacing patterns. Previously, samples of slowly pulsating B stars were observed by the Kepler mission and underwent forward asteroseismic modelling to retrieve stellar parameters such as mass, age and core mass. However, all of these stars have since been re-observed by the ongoing TESS mission with light curves that are usually shorter and non-continuous, resulting in more difficult frequency extraction and interpretation in terms of constructing period spacing patterns. In this paper we compare the results of forward asteroseismic modelling of a sample of SPB stars using intermittent TESS light curve data to those based on long-duration Kepler light curves. We show how in some cases that the masses and core masses derived from only a few sectors of TESS data agree well with the 4-yr Kepler mission results, despite the stars having far fewer significant pulsation frequencies in their TESS light curves. However, some stars yield incompatible results, emphasising the complexities in forward asteroseismic modelling of gravity-mode pulsators with sparsely sampled or short duration TESS light curves.

Dark matter is expected to accumulate inside neutron stars, modifying the structure of isolated stars and influencing both the dynamics of binary mergers and the evolution of the resulting hypermassive remnants. Since differential rotation is the primary mechanism delaying the collapse of these remnants, understanding its behavior is crucial when assessing the impact of an embedded dark component. In this work, we extend the numerical code RNS to describe two gravitationally coupled fluids in differential rotation, with baryonic matter modeled by a realistic nuclear equation of state and dark matter represented as a self-interacting bosonic condensate. Within this framework, we construct equilibrium sequences for a representative differential rotation law, providing a basis to explore how dark matter may influence the global properties and rotational dynamics of binary neutron star remnants.

We present a novel graph-based machine learning classifier for identifying the dark matter cosmic web environments of galaxies. Large galaxy surveys offer comprehensive statistical views of how galaxy properties are shaped by large-scale structure, but this requires robust classifications of galaxies' cosmic web environments. Using stellar mass-selected IllustrisTNG-300 galaxies, we apply a three-stage, simulation-based framework to link galaxies to the total (mainly dark) underlying matter distribution. Here, we apply the following three steps: First, we assign the positions of simulated galaxies to a void, wall, filament, or cluster environment using the T-Web classification of the underlying matter distribution. Second, we construct a Delaunay triangulation of the galaxy distribution to summarise the local geometric structure with ten graph metrics for each galaxy. Third, we train a graph attention network (GAT) on each galaxy's graph metrics to predict its cosmic web environment. For galaxies with stellar mass $\mathrm{>10^9 M_{\odot}}$, our GAT+ model achieves an accuracy of $85\,\%$, outperforming graph-agnostic multilayer perceptrons and graph convolutional networks. Our results demonstrate that graph-based representations of galaxy positions provide a powerful and physically meaningful way to infer dark matter environments. We plan to apply this simulation-based graph modelling to investigate how the properties of observed galaxies from the Dark Energy Spectroscopic Instrument (DESI) survey are influenced by their dark matter environments.

High-mass stars and star clusters form from the fragmentation of massive dense clumps driven by gravity, turbulence, and magnetic fields. The ALMAGAL project observed $\sim1000$ clumps at $\sim$1000\,au resolution, enabling a statistically significant characterization of this process across a large range of clump physical parameters and evolutionary stages. In this work, we investigated the spatial distribution of dense cores in the 514 massive, potentially cluster-forming, clumps hosting at least 4 cores, to trace fragmentation's initial conditions and early evolution. We used quantitative descriptors, evaluated against the clump bolometric luminosity-to-mass ratio as an indicator of evolution. Core separations were measured with the minimum spanning tree method (MST) and compared with the Jeans gravitational fragmentation theory. We used the $Q$ parameter and the mass segregation ratio, $\Lambda_{MSR}$, to evaluate whether cores have specific arrangements or differences depending on their masses. ALMAGAL cores are usually arranged in elliptical groups with an axis ratio $e\sim2.2$, but $e\geq$5 is also observed. A single characteristic core separation per clump is found in $\sim76$% of cases, but signatures of multiple fragmentation lengths not rare. Typical core separations are compatible with the clump-averaged thermal Jeans length, $\lambda^{th}_{J}$, though a population, typical of low-fragmented/young clumps, has wider separations with $l\approx3\times\lambda^{th}_{J}$. The core separation decreases on average from $l\sim22000$ au in younger systems to $l\sim7000$ au in more evolved ones. Cores are typically distributed in fractal-type subclusters, with centrally concentrated patterns appearing only at later stages, but without a progressive evolutionary transition. Finally, mass segregation is found in 110 systems, with its occurrence increasing with evolution.

The orientation and rotation of a synchronous satellite can be referred to both its Laplace plane and the ICRF equatorial plane, in terms of Euler angles or spin axis Cartesian coordinates and Earth equatorial coordinates, respectively. We computed second-order analytical expressions to make the transformation between the two systems and applied them to the Galilean satellites (Io, Europa, Ganymede, and Callisto). If one term of the spin axis Cartesian coordinates series is dominant, trigonometric series can be generated for the inertial and orbital obliquities, node longitude and offset with respect to the Cassini plane. Since the transformation does not require any fit of amplitudes and frequencies on numerical series, the physical meaning of the frequencies is preserved from the input series and the amplitudes can be directly related to the geophysical parameters of interest. We provide tables for the coordinates and angles' series assuming that the satellites are entirely solid, and considering two different orbital theories. The possible amplitude ranges for the main terms are also examined in the case where a liquid layer is assumed in the interior model. We use our transformation method to propose an updated IAU WG solution which would result in an improvement with respect to zero obliquity models used so far. This method will also be useful for the interpretation of future Earth-based radar observations or JUICE data.

Weak gravitational lensing has emerged as a powerful tool for investigating the matter distribution in the Universe and how it has evolved over cosmic time. The Wide Field Instrument (WFI) on the Nancy Grace Roman Space Telescope (Roman) will deliver some of the highest precision measurements of weak lensing ever made. Since weak lensing is based on statistics of faint sources, it can be biased by even tiny instrument systematics, including correlated read noise. Previous works have shown the infrared detectors used in the Roman WFI show correlations in their noise fields at a level significant for weak lensing measurements, even after application of standard reference pixel corrections; of particular concern is 1/f noise, which appears as horizontal banding in the detector frame. In this paper, we present imDestripe: a new Python module utilizing the multiple roll angles in Roman's observing strategy and linear algebra techniques to remove correlated noise stripes from observed images. We test imDestripe in a hybrid simulation by combining real noise realizations (from darks taken during ground testing) with simulated images of the astronomical scene, and find that the power spectrum of the banding can be suppressed by factors of 10--30 on large scales. We briefly discuss plans for further development of imDestripe in the context of the WFI pipeline.

Superconducting transition-edge sensor (TES) detectors have been the standard in Cosmic Microwave Background experiments for almost two decades and are now being adapted for use in nuclear physics, such as neutrinoless double beta decay searches. In this paper we focus on a new high-bandwidth frequency multiplexed TES readout system developed for CUPID, a neutrinoless double beta decay experiment that will replace CUORE. In order to achieve the high energy resolution requirements for CUPID, the readout noise of the system must be kept to a minimum. Low TES operating resistance and long wiring between the readout SQUID and the warm electronics are needed for CUPID, prompting a careful consideration of the design parameters of this application of frequency multiplexing. In this work, we characterize the readout noise of the newly designed frequency multiplexed TES readout system for CUPID and construct a noise model to understand it. We find that current sharing between the SQUID coil impedance and other branches of the circuit, as well as the long output wiring, worsen the readout noise of the system. To meet noise requirements, a SQUID with a low input inductance, high transimpedance and/or low dynamic impedance is needed, and the wiring capacitance should be kept as small as possible. Alternatively, the option of adding a cryogenic low-noise amplifier at the output of the SQUID should be explored.

The cosmological evolution of a scalar field is shaped by Hubble damping. Any non-gravitational couplings of the scalar with the primordial thermal bath generically contribute additional damping. Although rarely considered, such thermal damping could be the dominant dissipative effect. We derive approximate but highly general thermal-damping rates of scalar fields that modulate the masses of thermally populated particles. We extend previous results to cover cases of particular phenomenological interest where the scalar background oscillates sinusoidally but not necessarily slowly compared to the thermalization rates of the primordial bath. Based on these results, we estimate the thermal damping of scalars coupled to neutrinos linearly, to gluons quadratically, and to WIMPs linearly, and demonstrate its importance in certain parameter space of these models. We also estimate the thermal damping rates in models of QCD axion.

The ringdown phase of a binary black-hole merger provides a clean probe of strong-field gravity, as it can be modeled with minimal assumptions. The quasi-normal-mode frequencies encode the mass and spin of the Kerr black-hole remnant, while the mode excitation depends on the progenitor binary. In this paper, we implement a recently developed amplitude model that captures spin precession in a simulation-based inference pipeline that specifically targets ringdown signals. We present a critical re-analysis of GW190521 -- a short-duration, merger-dominated event with conflicting interpretations. Spin-aligned and precessing analyses at two ringdown start times show that precession induces modest but systematic shifts in inferred parameters and subdominant mode amplitudes, although such ringdown-only analyses provide no strong evidence for precession. Our results demonstrate the feasibility of physics-informed precessing ringdown modelling, paving the way for the identification of spin precession in gravitational-wave events using solely their ringdown stages, where waveform systematics are expected to be substantially less prominent.

Single-field freeze-in dark matter barely leaves observable footprints in dark matter direct detection, collider or fixed-target experiments, which can be altered in the two-field context. In this work, we consider sequential freeze-in dark matter through signals of dark photon mediator with a mass range of $m_{A'}\sim 10^{-2}-10$ GeV covered by the proposed SHiP experiment. We show that the dark charge is fixed to be $e'\sim 1.3\times 10^{-12}$ and the mixing parameter is restricted to $10^{-11}\leq \epsilon< 10^{-8}-10^{-7.5}$, as a result of the out-of-equilibrium condition of dark photon and the observed relic abundance of dark matter. Within this $\epsilon$ region, the 5(15)-year data of proton bremsstrahlung process for the dark photon, assuming vector meson (dipole) dominance, excludes $\epsilon\geq 10^{-8.5} (10^{-7.9})$ at 90\% confidence level, implying only a narrow region of $\epsilon$ close to $\sim 10^{-11}$ left for alternative tests.

We provide the first certificate of the gauge-independent bubble nucleation at the electroweak phase transition with the standard model effective field theory. Taking advantage of the thermal effective field theory framework, with the power counting $\lambda \sim g^3$, we rigorously demonstrate the gauge independence of the bubble nucleation rate up to two-loop order. Furthermore, we analyze the influence of relevant phase transition parameters on the gauge parameter and investigate its implications for gravitational waves generated by the electroweak phase transitions.

A central open problem in nuclear physics is the determination of a physically robust equation of state (EoS) for dense nuclear matter, which directly informs our understanding of the internal composition and macroscopic properties of compact objects such as neutron stars and quark stars. Traditional efforts have relied primarily on theoretical modeling grounded in nuclear and particle physics, with subsequent validation against empirical constraints from heavy ion collisions and, increasingly, multimessenger astrophysical observations. Recent developments, however, have introduced complementary analytical strategies that merge theoretical modeling with advanced data driven methodologies. In particular, Bayesian inference, machine learning, and deep learning have emerged as powerful tools for constraining the EoS and extracting physical insight from complex observational datasets. In this work, we employ state of the art machine learning and deep learning techniques to analyze mass radius relations of compact objects with the aim of reconstructing or inferring their underlying equations of state. The analysis is based on an extensive library of physically consistent, multimodal EoSs for neutron stars and a corresponding set for quark stars, each constructed to satisfy established theoretical and observational constraints. By leveraging the predictive capacity of these computational frameworks, we demonstrate the potential of data-driven approaches to provide refined insights into the behavior of matter at supranuclear densities and to contribute to a more unified understanding of the dense matter EoS.

We develop an inelastic Majorana dark matter model gauged by $U(1)_{L_\mu-L_\tau}$ symmetry, featuring a complex scalar and fermions with a small Dirac mass. The model exhibits strong interactions between the dark fermion-antifermion pair and the scalar, with a large coupling generating a Majorana mass after symmetry breaking. The dark fermion splits into two nearly degenerate Majorana eigenstates, with the $U(1)_{L_\mu-L_\tau}$ gauge boson $Z^\prime$ interacting via inelastic axial vector currents. The lighter Majorana serves as dark matter (DM), while the heavier may also contribute. The model predicts DM masses ranging from about 10 GeV to hundreds of GeV, with the scalar favored below 100 MeV. Strong coupling causes DM particles to mainly annihilate into two scalars, which determines the relic abundance, while thermal equilibrium with the bath occurs through $Z^\prime$ interactions. Self-interacting DM particles scatter via ladder exchange of strongly coupled light scalars, helping resolve small-scale issues. The $Z^\prime$ interacts with the muon, affecting its magnetic moment and explaining the $(g-2)_\mu$ discrepancy. Effects on experiments, $N_{\text{eff}}$, and the Hubble tension from kinetic mixing between $Z^\prime$ and the photon, originating from high-energy scales, are discussed. The model details and parameter constraints used in experiments are also covered.

The isotopic abundances of r-process elements in the solar system are traditionally derived as residuals from the subtraction of s-process contributions from total solar abundances. However, the uncertainties in s-process nucleosynthesis -- particularly those arising from Maxwellian Averaged Cross Sections (MACS) -- propagate directly into the r-process residuals, affecting their reliability. Building upon the seminal work of Goriely (1999), who introduced a multi-event s-process model to quantify these uncertainties, we revisit the problem using a simplified yet effective approach. By assuming that the relative uncertainty in s-process isotopic abundances scales linearly with the MACS uncertainties from data libraries (KADoNiS), we identify a subset of isotopes for which the r-process residuals remain significantly uncertain. Using updated solar abundances (Lodders 2025) and s-process contributions from Bisterzo et al. (2014), we present a short list of isotopes that are prime candidates for improved (n,g) measurements at CERN n_TOF in the near future. Our analysis provides a practical framework for prioritizing future experimental efforts that will profit from upgrades and enhancements of the n_TOF facility. It also highlights the need to revisit key neutron-capture cross sections to refine our understanding of the r-process isotopic abundance pattern, commonly used as a benchmark in stellar models of explosive nucleosynthesis.