Papers for Wednesday, Jan 14 2026

The stellar dynamical evolution of massive star clusters formed during starburst periods leads to the segregation of $\gtrsim10^4 M_\odot$ stellar-mass black hole sub-clusters in their centres. In gas-rich environments, such as galactic central molecular zones, these black hole clusters are likely to accrete large amounts of the gas from their surroundings, which in turn affects their internal dynamics. In this Letter we estimated the corresponding accretion rate onto the black hole cluster and its radiative feedback. We assessed whether such an accretion flow can lead to the collapse of the black hole cluster into an intermediate-mass black hole. The estimates were obtained analytically, considering the astrophysical conditions and star formation history reported for the central molecular zone of our Galaxy. We find that a stellar black hole cluster with mass $\gtrsim10^4 M_\odot$ located in the twisted ring of molecular clouds with radius $\approx100$ pc that is observed in the central molecular zone of our Galaxy can accrete about the same mass in gas on a timescale of a few million years. We suggest that this is sufficient for its subsequent collapse into an intermediate-mass black hole. Based on an estimate of the dynamical friction inspiral time, we further argue that the locations of the intermediate-mass black hole candidates recently observed in the central molecular zone are compatible with their formation therein during the last starburst period reported to have occurred $\approx1$ Gyr ago.

The properties of substructure in galaxy clusters, exquisitely probed by gravitational lensing, offer a stringent test of dark matter models. Combining strong and weak lensing data for massive clusters, we map their total mass--dominated by dark matter--over the dynamic range needed to confront small-scale predictions for collisionless cold dark matter (CDM). Using state-of-the-art lens models, we extract four key subhalo properties: the mass function, projected radial distribution, internal density profile, and tidal truncation radius. We find that the subhalo mass function and truncation radii are consistent with CDM expectations. In contrast, the inner density profiles and radial distribution of subhalos are strongly discrepant with CDM. The incidence of galaxy-galaxy strong lensing (GGSL) from subhalo cores exceeds CDM predictions by nearly an order of magnitude, requiring inner density slopes as steep as $\gamma \gtrsim 2.5$ within $r \lesssim 0.01\,R_{200}$ consistent with core-collapsed self-interacting dark matter (SIDM), while the same subhalos behave as collisionless in their outskirts. Additionally, the observed radial distribution of subhalos hosting bright cluster member galaxies, explicitly modeled in the lens reconstructions, remains incompatible with CDM. Together, these small-scale stress tests reveal an intriguing paradox and challenge the dark matter microphysics of purely collisionless CDM and motivate hybrid scenarios, such as a dual-component model with both CDM and SIDM, or entirely new classes of dark matter theories.

We introduce an effective framework to model star-formation burstiness and use it to jointly fit galaxy UV luminosity functions (UVLFs), clustering, and H$\alpha$/UV ratios, providing the first robust empirical evidence that early galaxies hosted in lower-mass halos are burstier. Using $z\sim 4-6$ observations, we find that galaxies show approximately $0.6$ dex of SFR variability if hosted in halos of $M_h = 10^{11}\, M_\odot$ (typical of $M_{\rm UV}\approx -19$ galaxies at $z = 6$). This translates into a scatter of $\sigma_{M_{\rm UV}}\approx 0.75$ in the UVLF, in line with past findings. Strikingly, we find that burstiness grows for galaxies hosted in smaller halos, reaching $\gtrsim 1$ dex for $M_h \leq 10^{9}\, M_\odot$ (corresponding to $\sigma_{M_{\rm UV}} \approx 1.5$ for faint $M_{\rm UV} \gtrsim -15$ galaxies). Extrapolating to higher redshifts, when small halos were more prevalent, the inferred mass-dependent burstiness can reproduce observed UVLFs up to $z\sim 17$ within 1$\sigma$, potentially alleviating the tension between pre- and post-JWST galaxy-formation models. Current observations allow us to constrain burst timescales to approximately $20$ Myr, consistent with expectations from supernova feedback, and suggest broad distributions of ionizing efficiencies at fixed $M_{\rm UV}$. Our results demonstrate that mass-dependent burstiness, as predicted by hydrodynamical simulations, is critical for understanding the mass assembly of early galaxies.

We present a quantitative symmetry-identification pipeline for astrophysical images based on Transformation Information (TI), an information measure of self-similarity under geometric transformations. TI is expressed as a Kullback-Leibler (cross-entropy) divergence between an image and its rotated or reflected counterpart on the overlapping domain. By scanning rotation angles and reflection axes, we obtain TI curves whose local minima identify symmetry operations. We validate the method on a wind-rose pattern and then apply it to planetary nebulae, where the recovered axes trace bipolar and multipolar lobes consistent with morphology-based classifications. Applying TI to supernova remnants yields estimate axes associated with protrusions, rims, and substructure. To emphasize global morphology, we introduce a thresholded two-level variant that compares binary silhouettes and can reveal outline-driven symmetries. Finally, we quantify symmetry using a minima prominence-to-width score and show that this compact descriptor separates Type Ia and core-collapse remnants into distinct populations for an X-ray sample. TI provides a non-parametric, reproducible framework for symmetry identification, classification and population studies.

We present a detailed study of the physical properties of absorbers associated with $z\approx3.3$ \lya\ emitters (LAEs) from the MUSEQuBES survey. Using \HI\ and ionic column densities derived from Voigt profile fitting, we determine the density and metallicity of 75 absorbers associated with 59 LAEs through a custom-built Bayesian framework. The overall sample shows a median density $\log\,(n_{\rm H}/{\rm cm^{-3}})=-2.7\pm0.7$ and metallicity \met$=-1.6^{+1.2}_{-0.9}$ with $\approx15\%$ ($\approx 40\%$ including upper limits) of systems showing metallicities consistent with the IGM at these redshifts (\met$\lesssim -2.8$). Intriguingly, absorbers with $\log\, N(\rm HI)/{\rm cm^{-2}} \gtrsim 16.5$, corresponding to an overdensity of $\sim 100$ at $z=3$, exhibit a bimodal metallicity distribution with peaks at \met$=-3.8\pm 0.2$ and $-1.8\pm 0.6$. The latter are observed at large impact parameters ($\gtrsim150$~pkpc) and often exhibit low-ionization species (e.g., \SiII, \AlII). We interpret the former as pristine inflowing gas from the cosmic web, while the latter likely traces metal-enriched CGM associated with outflows from faint galaxies not detected in Ly$\alpha$ emission. We find no significant correlations between absorber metallicity or density and host galaxy properties, including redshift, impact parameter, SFR, Ly$\alpha$ luminosity, or environment. Absorbers separated by $\lesssim500$~\kms\ show $\sim$1~dex metallicity and $\sim$0.5~dex density variations, indicating physical and chemical inhomogeneity of the medium around these LAEs.

We explore the formation of intermediate mass black holes (IMBHs), potential seeds for supermassive black holes (SMBHs), via runaway stellar collisions for a wide range of star cluster (surface) densities ($4\times10^3 M_\odot$ pc$^{-2} \lesssim \Sigma_\mathrm{h}$ $\lesssim 4\times10^6 M_\odot$ pc$^{-2}$) and metallicities ($0.01 Z_\odot \lesssim Z \lesssim 1.0 Z_\odot)$. Our sample of isolated $(>1400)$ and hierarchical ($30$) simulations of young, massive star clusters with up to $N=1.8\times10^6$ stars includes collisional stellar dynamics, stellar evolution, and post-Newtonian equations of motion for black holes using the BIFROST code. High stellar wind rates suppress IMBH formation at high metallicities $(Z \gtrsim 0.2 Z_\odot)$ and low collision rates prevent their formation at low densities ($\Sigma_\mathrm{h} \lesssim 3\times10^4 M_\odot$ pc$^{-2}$). The assumptions about stellar wind loss rates strongly affect the maximum final IMBH masses $(M_\bullet \sim 6000 M_\odot$ vs. $25000 M_\odot$). The total stellar mass loss from collisions and collisionally boosted winds before $t=3$ Myr can together reach up to 5-10% of the final cluster mass. We present fitting formulae for IMBH masses as a function of host star cluster $\Sigma_\mathrm{h}$ and Z, and formulate a model for the cosmic IMBH formation rate density. Depending on the cluster birth densities, the IMBH formation rates peak at $z\sim2$-$4$ at up to $\sim10^{-7}$ yr$^{-1}$cMpc$^{-3}$. As more than 50% form below $z\lesssim1.5$-$3$, the model challenges a view in which all local IMBHs are failed early Universe SMBH seeds.

Rapidly rotating, strongly magnetized neutron stars (``millisecond proto-magnetars'') formed in stellar core-collapse, neutron star mergers, and white dwarf accretion-induced collapse have long been proposed as central engines of gamma-ray bursts (GRB) and accompanying supernovae/kilonovae. However, during the first few seconds after birth, neutrino heating drives baryon-rich winds from the neutron star surface, potentially limiting the magnetization and achievable Lorentz factors of the outflow and casting doubt on whether proto-magnetars can launch ultra-relativistic jets at early times, as needed to power short-duration GRB. We present 3D general-relativistic magnetohydrodynamic simulations of neutrino-heated proto-magnetar winds that incorporate M0 neutrino transport. While the global wind properties broadly agree with previous analytic estimates calibrated to one-dimensional models, our simulations reveal essential multidimensional effects. For rapidly rotating models with spin periods P = 1 ms, centrifugal forces strongly enhance mass loss near the rotational equator, producing a dense, sub-relativistic outflow ( ~0.1c). This equatorial wind naturally confines and collimates less baryon-loaded outflows emerging from higher latitudes, leading to the formation of a structured bipolar jet with a peak magnetization up to ~ 30-100 along the pole, sufficient to reach bulk Lorentz factors ~ 100 on larger scales. The resulting angular stratification of the outflow energy into ultra-relativistic polar and sub-relativistic equatorial components is broadly consistent with the observed partition between beaming-corrected GRB energies and supernova/kilonova ejecta. Our results demonstrate that millisecond proto-magnetars can launch relativistic jets within seconds of formation and highlight their potential role in powering the diverse electromagnetic counterparts of compact-object explosions.

The 1-100 pc region embedding long-duration gamma-ray bursts (lGRBs) has been hitherto unexplored, as extremely high ionisation by the GRB prevents application of optical absorption spectroscopy on such distances. We show that the GRB ionising flux imprints a unique time- and spatially-dependent ionisation structure on the gas, that can be probed by X-ray absorption. Application of this model to a selected sample of 7 bright GRB X-ray afterglow spectra observed by \textit{XMM-Newton} EPIC-pn enables an independent, quantitative estimation of the density (log(n) $\sim$ 2-4) and distances (5-100 pc) of the ionized absorber directly from the GRB X-ray spectrum, thereby allowing us to locate the absorbing medium of this representative sample of long GRBs in the region of the density-size diagram populated by star-forming regions versus other gravitationally bound objects in the Universe.

Stellar bow shocks are formed when an outflow interacts with the interstellar medium. In white dwarfs accreting from a binary companion, outflows are associated with either strong winds from the donor star, the accretion disk, or a thermonuclear runaway explosion on the white dwarf surface. To date, only six accreting white dwarfs are known to harbour disk-wind driven bow shocks that are not associated to thermonuclear explosions. Here, we report the discovery of a bow shock associated with a high-proper-motion disk-less accreting white dwarf, 1RXS J052832.5+283824. We show that the white dwarf has a strong magnetic field in the range B~42-45 MG, making RXJ0528+2838 the a bonafide known polar-type cataclysmic variable harbouring a bow shock. The resolved bow shock is shown to be inconsistent with a past thermonuclear explosion, or being inflated by a donor wind, ruling out all accepted scenarios for inflating a bow shock around this system. Modelling of the energetics reveals that the observed bow shock requires a persistent power source with a luminosity significantly exceeding the system accretion energy output. This implies the presence of a powerful, previously unrecognized energy loss mechanism - potentially tied to magnetic activity - that may operate over sufficiently long timescales to influence the course of binary evolution.

We present Sahyadri, a suite of cosmological $N$-body simulations designed to enable precision studies of the low-redshift Universe with next-generation spectroscopic surveys. Sahyadri includes systematic variations of six cosmological parameters around Planck 2018 constraints, with seed-matched initial conditions enabling cosmological parameter derivatives. Each simulation evolves $2048^3$ particles in a periodic box of side length $200$ $h^{-1}$ Mpc, yielding a particle mass of $m_{\rm{p}} = 8.1 \times 10^{7}\,h^{-1}\,M_{\odot}$ in the fiducial Planck 2018 cosmology. This resolution enables robust identification of dark matter halos down to $M_{\rm min} = 3.2 \times 10^{9}$ $h^{-1}$ $M_\odot$, which represents a factor of $\sim$25 improvement over the AbacusSummit suite, and is over two orders of magnitude better than the Quijote and Aemulus suites. We estimate that approximately 40% of DESI BGS galaxies at redshift $z < 0.15$ - roughly 1.6 million objects - reside in halos accessible to Sahyadri but beyond the reach of existing parameter-varying simulation suites. We demonstrate Sahyadri's capabilities through measurements of the matter power spectrum, halo mass function and power spectrum, and beyond 2-point statistics such as the Voronoi volume function and $k^{\rm th}$ nearest neighbour statistics, showing excellent agreement with theoretical predictions and significant sensitivity to $\Omega_{\rm m}$ variations. We implement a custom compression scheme reducing storage requirements by a factor of $\sim$3 while maintaining sub-percent clustering accuracy. Key data products will be made publicly available.

We report the discovery of ATLAS J101342.5-451646.8 (hereafter ATLAS J1013-4516), an eclipsing, mass-transferring AM Canum Venaticorum binary with an 8.56-minute orbital period, identified via periodic variability in light curves from the Asteroid Terrestrial-impact Last Alert System survey of Gaia white dwarf candidates. Follow-up spectroscopy with the Large Lenslet Array Magellan Spectrograph reveals a helium-dominated accretion disk, while high-speed photometry with ULTRACAM shows pronounced primary and secondary eclipses. We construct a decade-long timing baseline using data from ATLAS, Gaia, ULTRACAM on the Gran Telescopio Canarias, and the proto-Lightspeed instrument on the Magellan Clay telescope. From this baseline, we measure an orbital period derivative of dP/dt = -1.60 +/- 0.07 x 10^-12 seconds per second. Interpreted in the context of stable mass transfer, the magnitude and sign of the period derivative indicate that the orbital evolution is governed by the interplay between gravitational-wave-driven angular momentum losses and mass transfer, directly probing the donor star's structural response to mass loss. Assuming angular momentum loss dominated by gravitational wave emission, we constrain the component masses and infer the characteristic gravitational wave strain of the system for future space-based observatories such as the Laser Interferometer Space Antenna. We predict a characteristic strain corresponding to a four-year signal-to-noise ratio greater than approximately 20, establishing ATLAS J1013-4516 as a strong prospective source for probing long-term orbital evolution in the mass-transferring regime.

We present the distribution of the intrinsic duration of gamma-ray bursts' prompt emission. This expands upon the analysis of Bromberg et al., 2012 and Bromberg et al. 2013 who showed evidence for collapsar progenitors based on the presence of a plateau in the distribution of $T_{90}$, the duration over which 90 % of the prompt emission is observed for any given detector. We confirm the presence of this plateau in the distribution of duration corrected for cosmological time dilation (what we call intrinsic duration, $T_{int}$), but shifted to smaller timescales by a factor of $1/(1+z_{\rm av}) \sim 1/3$, where $z_{\rm av}$ is the average GRB redshift. More significantly, we show this plateau is only present in the sample of GRBs with redshifts greater than $(1+z) \sim 2$, and does not appear in the duration distribution of lower redshift GRBs. This result aligns with suggestions that the low redshift population of GRBs has a significant contribution from non-collapsar progenitors (while the high redshift sample is dominated by collapsars). We also show the difference in this distribution between spectrally hard and soft GRBs, confirming that a plateau is only present for the soft subset of GRBs. However, when we separate the soft GRBs into low and high redshift subsets, we find that only the high redshift soft GRBs show evidence of a plateau, while the low-redshift soft GRBs do not. This suggests there exists a significant subset of spectrally soft non-collapsar progenitors at low redshift. Finally, we use the end time of the plateau to constrain the GRB progenitor density profile and radius, and show the maximum size of a collapsar is a few tenths of a solar radius.

We study the local gravitational instability of non-rotating astrophysical fluids allowing for the presence of an external gravitational potential in addition to the fluid self-gravity. We present a self-consistent linear-perturbation analysis taking into account pressure and density gradients in the background medium. We explore two different steady-state configurations for the unperturbed gas: hydrostatic equilibrium and infall into a gravitational potential well. We show that in both cases the instability criterion is the classical Jeans criterion, which, contrary to previous claims, is not modified by the presence of the external gravitational field. While in the case of hydrostatic equilibrium linear local perturbations are always gravitationally stable, the conditions for gravitational instability can be met in the case of infalling gas, also in the presence of additional non-gravitational forces such as that due to a wind. We conclude that the Jeans criterion can have a role in regulating the formation of clumps and star clusters in streams or shells of gas infalling into galactic gravitational potential wells, as well as, on smaller scales, the fragmentation of gas in collapsing molecular clouds.

Context. Cosmic voids are underdense regions of the Universe that provide a unique environment to study galaxy evolution in relative isolation. Galaxy triplets in voids are rare systems where local interactions may strongly influence galaxy properties. Aims. We study the stellar populations, morphologies, mass assembly histories, and dynamical properties of six galaxies belonging to two void triplets from the Calar Alto Void Integral-field Treasury surveY (CAVITY): CAVITY5273X and VGS31. Methods. We used integral-field unit spectroscopy and performed full spectral fitting with the FADO code, which models stellar and nebular emission simultaneously. Spatially resolved maps of stellar age, metallicity, and star formation rate were reconstructed using the integrated nested Laplace approximation. Morphological properties were derived using morfometryka, emission-line diagnostics were applied, and mass assembly functions were computed. Stellar masses and metallicities were compared to the mass-metallicity relation for void galaxies. Results. The two triplets show different evolutionary behaviours. CAVITY52731 is a massive quenched galaxy hosting an active galactic nucleus, while its companions and all galaxies in VGS31 are dominated by young stellar populations and recent star formation. Five galaxies experienced rapid stellar mass growth in the last 2 Gyr. Disturbed morphologies, including asymmetries and tidal features, indicate ongoing interactions. Galaxies in CAVITY5273X follow the expected void mass-metallicity relation, while VGS31 members show significant deviations. Conclusions. Our results show that local interactions can drive significant galaxy evolution even in the most underdense cosmic environments.

Geologic records of cosmogenic 10Be are sensitive to changes in the radiation environment with time. Recent works suggest there are periods when the Sun encountered massive cold clouds which compressed the heliosphere to within Earth's orbit. This would expose Earth to increased galactic cosmic rays and MeV-energy particles of heliospheric origin. We model 10Be production in Earth's atmosphere during possible cold cloud encounters, and estimate their detectability in marine records of variable temporal resolution. We find that an AU-scale cold cloud encounter can be detected using ocean sediment measurements of 10Be if Earth spends time inside the compressed heliosphere. For typical relative speeds between the Sun and local interstellar clouds, this translates to a crossing time of ~100 years. A cloud must have an extension on the scale of parsecs to tens-of-parsecs (crossing time 0.1-1 Myr) to be detectable through 10Be measurements in iron-manganese crusts.

This letter presents an analysis of the infrared ($\sim 3-28\,\mu m$) spectra extracted from the nuclear ($r < 150$ pc) regions of four low-luminosity active galactic nuclei (AGN), observed by JWST NIRSpec/IFU and MIRI/MRS as an extension of the Galaxy Activity, Torus, and Outflow Survey (GATOS). We find that, compared to higher-luminosity AGN, these low-luminosity AGN exhibit distinct properties in their emission of ionized gas, polycyclic aromatic hydrocarbons (PAHs), and molecular hydrogen (H$_2$). Specifically, the low-luminosity AGN exhibit relatively weak high-ionization potential lines (e.g., [Ne V] and [O IV]), and the line ratios suggest that fast radiative shocks (with $v_{\rm s}$ of $\sim \rm 100s\,km\,s^{-1}$) are the primary excitation source of ionized gas therein. Under the low-excitation conditions of their nuclear regions, these low-luminosity AGN generally exhibit a higher fraction of PAHs with large size ($N_{\rm C} \gtrsim 200$), reflecting the preferential destruction of smaller PAH molecules by AGN feedback. Furthermore, the H$_2$ transitions in these low-luminosity AGN are not fully thermalized, with slow, plausibly jet-driven molecular shocks (with $v_{\rm s} \leq \rm 10\,km\,s^{-1}$) likely being the extra excitation source. Taken together with results from the literature, these findings indicate that feedback operates in both low- and high-luminosity AGN, albeit its impact varies with AGN luminosity. In particular, systematic variations in PAH band ratios are found across AGN, demonstrating the differing influence of feedback in AGN of varying luminosities and highlighting the potential of PAH band ratios as diagnostics for distinguishing kinetic- and radiative-mode AGN feedback.

Mapping the boundary of an extended source is a key step in the study of its morphology. The background contamination and statistical fluctuations of typical astronomical images make this a challenging statistical task, particularly for X-ray images with low surface brightness. We develop a three-step Bayesian procedure to identify the boundaries of irregularly shaped sources. We first apply a Bayesian multiscale reconstruction algorithm known as LIRA to obtain posterior pixelwise probability distributions of the source intensity that properly account for known structures, astrophysical background, and the effect of the telescope point spread function. Next, we adopt an Ising model to group pixels with similar intensities into cohesive regions corresponding to background and source. Finally, the boundary is derived on the basis of the most likely aggregation of pixels into the source region. Because the overall model combines LIRA and the Ising model, we call it LIRA-Ising. We verify the proposed method using a set of simulation studies. We then apply it to the Chandra X-ray Observatory images of two high redshift quasars, PKS J1421-0643 and 0730+257, to determine the extent and morphology of X-ray jets. Our method shows a uniform X-ray surface brightness of PKS J1421-0643 jet, and identifies knotty structure in the X-ray jet of 0730+257.

Wisdom-Holman (WH) integrators are symplectic operator-splitting methods widely used for long-term N-body simulations of planetary systems. Most implementations use either Jacobi coordinates or democratic heliocentric coordinates (DHC) for the Hamiltonian splitting, resulting in slightly different algorithms. In this paper we report results from numerical experiments, which show that integrations of the Solar System using DHC coordinates with typical timesteps of a few days suppress instabilities of the planet Mercury. We further show that this is due to an eccentricity dependent artificial numerical precession introduced by the DHC splitting. While the DHC splitting converges to the correct results at shorter timesteps of ~0.6 days, we argue that Jacobi coordinates remain reliable to significantly longer timesteps when orbits become moderately eccentric, and are thus a better choice when the innermost planet can reach high eccentricities.

Recently Quenched Elliptical galaxies (RQEs) represent a critical phase in the transition from star-forming to quiescent galaxies. However, the mechanisms driving their quenching remain elusive. We conduct a multi-wavelength analysis of 155 RQEs, along with their precursors (preRQEs) and descendants (postRQEs), focusing on their neutral hydrogen (HI) content and star formation properties. Contrary to conventional quenching models emphasizing gas depletion, RQEs retain substantial HI reservoirs ($f_{\text{gas}} \geq 17\%$), suggesting that quenching is not primarily driven by gas exhaustion. We identify a critical halo mass threshold at $\log M_{\text{halo}} = 12.1 M_{\odot}$, delineating different evolutionary pathways for RQEs. This threshold aligns with the transition from cold-mode to hot-mode gas accretion in theoretical models. RQEs in lower-mass halos ($\log M_{\text{halo}} < 12.1 M_{\odot}$) likely experience rapid quenching, possibly initiated by major mergers, followed by brief AGN activity and sustained LINER emission. We propose two evolutionary pathways: (a) rapid quenching via major mergers followed by AGN/LINER activity and passive evolution, and (b) rapid quenching followed by rejuvenation through minor mergers before evolving into more massive, long-term quenched ellipticals. These results challenge the conventional understanding of galaxy quenching, especially in low-density environments where RQEs typically reside. Our findings suggest that while RQEs may follow a rapid quenching pathway, their evolution is influenced by interactions between gas accretion modes, feedback mechanisms, and environmental factors. Future observations with advanced radio interferometers like SKA will be crucial for elucidating the quenching mechanisms in RQEs and their role in galaxy evolution.

The Active Galactic Nuclei (AGN) glossary is vast and complex. Depending on selection method, observing wavelength, and brightness, AGNs are assigned distinct labels, yet the relationship between different selection methods and the diversity of time-domain behavior within and across classes remains difficult to characterize in a unified framework. Changing-look AGNs (CLAGNs), which transition between classifications over time, further complicate this picture. In this work, we learn a data-driven, low-dimensional representation of multi-wavelength photometric light curves of AGNs, in which the structure of the projected manifold correlates with AGN class and independent spectroscopic properties. Using the NASA Fornax Science Platform, we assemble light curves from ZTF, Pan-STARRS, Gaia, and WISE/NEOWISE for two samples: (1) a heterogeneous set of $\sim$2000 AGNs spanning $z \lesssim 1$, including SDSS quasars, variability-selected sources, and CLAGNs; and (2) a homogeneous sample of $\sim$65000 narrow-line AGNs at $z \approx 0.1$ with well-characterized optical emission-line measurements. Without using class labels during training, the learned manifolds organize variability-selected AGNs into coherent regions of the low-dimensional space, distinguish between turn-on and turn-off CLAGNs, and place tidal disruption events in distinct regions. Manifold coordinates correlate with key spectroscopic and host-galaxy properties, including stellar mass, [OIII] luminosity, and D$_n$(4000), demonstrating that heterogeneous multi-band variability can be combined in a purely data-driven manner to recover correlations with independent physical diagnostics, without requiring explicit physical modeling. These results show that manifold learning offers a practical, assumption-light approach for integrating time-domain surveys and prioritizing spectroscopic follow-up.

Recent observations of galaxies continue to reveal new ultraluminous X-ray sources (ULXs), increasing their known population and improving the statistics needed to understand their nature. We study the ULX populations of NGC 4631 and NGC 1097 using archival Chandra, XMM-Newton, and Swift/XRT observations to identify new ULXs and investigate their X-ray and optical properties. We analyzed X-ray data spanning 2000-2025. Spectral fitting was performed for sources with sufficient counts using absorbed power-law and diskbb models. Variability analyses, including hardness-intensity diagrams and light curves, were used to assess short- and long-term variability. Optical color-magnitude diagrams and near-infrared (NIR) spectral energy distributions (SEDs) were employed to identify possible donor stars. In NGC 4631, we identified two new transient ULXs, X-6 and X-7, with X-ray count rates varying by more than an order of magnitude. The LX-T^4 relation from diskbb fits provides strong evidence that NGC 4631 X-6 is powered by a stellar-mass black hole accreting via a standard disk. The optical sources within the X-ray error circles of X-6 and X-7 are candidate counterparts, suggesting these systems are candidate HMXBs. In NGC 1097, we discovered a new transient ULX, ULX-3, showing X-ray luminosity variations by a factor of about 30 and evidence for spectral state transitions, consistent with either a stellar-mass black hole or a neutron star. We identified a unique optical and NIR counterpart. While the optical emission is variable, the NIR emission is stable. The NIR SED is consistent with a blackbody temperature of about 3300 K, compatible with a red supergiant donor with a radius of about 200 solar radii.

We have acquired high-resolution optical spectroscopy for a sample of T Tauri stars (TTSs) in open clusters using Hydra on the WIYN 3.5m telescope, and present projected rotational velocities (v sin i values) for 54 stars in IC 5070 and 99 stars in IC 348. We combine these with published values for stellar temperature, luminosity, rotation period, circumstellar disk status, and binarity; we are predominantly interested in how the last two factors may affect the rotation speeds of the stars. We find evidence to support theories that interaction with circumstellar disks may slow the rotation of TTSs compared to Class III stars in both clusters. We also identify a higher fraction of slow-rotating Class III stars in IC 348 compared to other clusters; we suggest that some fraction of these may be stars that recently lost their disks. We find that a higher fraction of binary stars are rapid rotators compared to single stars, though not to a statistically significant degree. We also combine our v sin i measurements with rotation periods to estimate projected stellar radii, which we compare to predictions from stellar evolution models using a maximum likelihood method. We continue to show that models with increasing starspot coverage reduce radius inflation and align better with published age estimates than models without starspots.

Type Ia supernovae, type II supernovae, and asymptotic giant branch (AGB) stars are important sites of stellar nucleosynthesis, but they differ greatly in their rates, their location within a galaxy, and the mean thermal energy and abundance distribution of their ejecta. In earlier papers in this series we have shown that a significant fraction of metals newly synthesized by type II supernovae are promptly lost to galactic winds -- i.e., galactic winds are metal loaded. Here we investigate whether the elements returned by type Ia supernovae and AGB stars are similarly metal loaded, or whether metal loading varies significantly with nucleosynthetic site. We use a series of high-resolution ``tall box'' simulations of the interstellar medium with the \quokka~GPU-accelerated code, within which we systematically vary the galaxy gas surface density, metallicity, and the scale heights and relative rates of the different nucleosynthetic sources. We show that the metal loadings of galactic winds differ substantially between metals produced by different sources, with typical variations at the level of $\approx 0.3$ dex, a phenomenon we term differential metal loading. Which set of metals suffers preferential loss from this phenomenon varies depending on the galactic environment, and is not easily predictable \textit{a priori}. Our findings call into question the the interpretation of diagnostics of galaxy formation, for example star formation timescales and initial mass functions, based on abundance diagnostics, since the abundance variations upon which these techniques rely are often at levels comparable to those we show can be induced by differential metal loading.

With upcoming facilities capable of detecting photometric and gravitational wave signals from supermassive black hole (SMBH) binaries, studying their long-term accretion-driven variability is timely. OJ287 is a bright, nearby ($z=0.3$), and well-studied candidate for a SMBH binary. As such, it is an excellent case study for how binary dynamics could influence observed active galactic nucleus (AGN) photometric variability. We present 3D hydrodynamic simulations of OJ287, using the code PHANTOM. We simulate two mass ratios: (i) M$_1$ $=$ 1.835$\times$10$^{10}$ M$_\odot$ with M$_2$ $=$ 1.4$\times$10$^{8}$ M$_\odot$, (ii) M$_1\approx$ M$_2$ ($\sim10^{8}$ M$_\odot$) along and (iii) control of a single SMBH and accretion disc. We find that the simulation with masses 1.835$\times$10$^{10}$ M$_\odot$ and 1.4$\times$10$^{8}$ M$_\odot$ evolves consistently with the most currently accepted model of OJ287 as a precessing SMBH binary. The secondary's impacts with the disc result in the formation of spiral density waves and a corresponding $\sim$10-20% increases in the mass accretion rate of the primary SMBH. The impact timings and the mass accretion rate spikes show quasi-periodic variability as a result of the precession of the secondary's orbit with intervals between impacts ranging from $\sim$ 1 year to $\sim$ 10 years. In the near-equal mass case, the disc of the primary becomes tidally disrupted after $\sim$ 2 years. Consequently, the near-equal mass system with a period of 12 years is not a viable candidate for OJ287. This modeling provides insights into the potential signatures of SMBH binaries by both gravitational wave observatories and the Rubin Legacy Survey of Space and Time.

Star clusters are well known for their dynamical interactions, an outcome of their high stellar densities; in this paper we use multiwavelength observations to search for the unique outcomes of these interactions in three nearby Galactic open clusters: IC 2602 (30 Myr), NGC 2632 (750 Myr) and M67 (4 Gyr). We compared X-ray observations from all-sky surveys like eROSITA, plus archival observations from Chandra X-ray Observatory, survey radio observations from ASKAP's Evolutionary Map of the Universe survey plus archival VLA observations, in conjunction with new cluster catalogs with Gaia. From X-ray, we found 77 X-ray sources likely associated with IC 2602, 31 X-ray sources in NGC 2632, and 31 near M67's central regions. We were further able to classify these X-ray sources based on their optical variability and any radio emission. Three IC 2602 X-ray sources had radio counterparts, which are likely all chromospherically active binary stars. We also identified luminous radio and X-ray variability from a spectroscopic triple system in M67, WOCS 3012/S1077, which is either consistent with a quiescent black hole binary, or due to an active binary stellar system. A recent population study of optical variables by Anderson & Hunt 2025 shows that the population of optical variables in open clusters clearly changes over cluster age; this pilot study gives evidence that the X-ray population also changes with time, and demonstrates the need for a broader multiwavelength study of Galactic open clusters.

On the framework of relativistic force-free magnetohydrodynamic (MHD) turbulence, we explore the fundamental properties of strong and weak turbulent cascades using high-resolution numerical simulations in the presence of a uniform background magnetic field. We find that (1) power spectra and scale-dependent anisotropies both for the strong and weak turbulence resemble those observed in the non-relativistic MHD turbulence; (2) intermittency of magnetic fields in strong turbulence is stronger than that in the weak one; (3) generated Alfvén modes show similar energy spectra and scale-dependent anisotropies to those of non-relativistic case; (4) generated fast modes present a power spectrum similar to that of Alfvén modes, with a strong (for strong turbulence) or weak (for weak turbulence) scale-dependent anisotropy, which are significantly different from non-relativistic turbulence; and (5) applications of our numerical results to neutron star magnetospheres show that the strong (or moderately weak) turbulent cascade can explain the X-ray radiation of the Vela pulsar. Our study is of great significance for understanding energy transfer, magnetic field evolution, and particle acceleration mechanisms in extreme astrophysical environments.

We present a measurement of Baryon Acoustic Oscillations (BAO) in the cross-correlation of triply ionized carbon C IV absorption with the positions of quasars (QSO) and Emission Line Galaxies (ELG). We use quasars and ELGs from the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI) survey. Our data sample consists of 2.5 million quasars, 3.1 million ELGs, and the C IV absorption is measured along the line of sight of 1.5 million high redshift quasars with $z > 1.3$. We measure the isotropic BAO signal at 4.2$\sigma$ for the CIV$\times$QSO cross-correlation. This translates into a 3.0% precision measurement of the ratio of the isotropic distance scale, $D_{\rm V}$, and the sound horizon at the drag epoch, $r_{\rm d}$, with $D_{\rm V}/r_{\rm d}(z_{\rm eff} = 1.92) = 30.3 \pm 0.9$. We make the first detection of the BAO feature in the CIV$\times$ELG cross-correlation at a significance of 2.5$\sigma$ and find $D_{\rm V}/r_{\rm d}(z_{\rm eff} = 1.47) = 24.6 \pm 1.0$.

We compute the cosmic stellar, dust and neutral gas mass history at $0<z\lesssim3$ using ProSpect spectral energy distribution modelling of $\approx 800 \, 000$ galaxies in the Galaxy and Mass Assembly (GAMA) survey and the Deep Extragalactic VIsible Legacy Survey (DEVILS). The cosmic dust mass history broadly follows the shape of the cosmic star formation history; though, the decline is slower, suggestive of a slowing rate of dust growth and destruction as the star formation declines past its peak at $z\approx 2$. Neutral gas masses were estimated by scaling the dust masses by the metallicity-dependent dust-to-gas ratio. The neutral gas mass density as traced by the dust is an average of $\approx 0.6$ dex lower than that measured from $21$cm experiments, most likely due to differences in the spatial scales inhabited by dust and HI. Folding in measurements of the supermassive black hole mass density obtained previously with similar data and methods, we present a self-consistent census of the baryons confined to galaxies. Stars, neutral gas, SMBHs and dust contained within the optical radii of galaxies account for $\approx 5$ per cent of the baryons. Most of the remaining $\approx 95$ per cent of baryons must be ionised and dispersed throughout the interstellar, circumgalactic and intergalactic media within, around and between galaxies.

The Andes Large area PArticle detector for Cosmic ray and Astronomy (ALPACA) is a new air-shower array experiment under construction in the Bolivian Andes, and its prototype ALPAQUITA surface array has been operating since 2023 April. In addition to the traditional $\ge$3-hit or $\ge$4-hit coincidences to trigger recording air-shower events, ALPAQUITA records the counting rates of the $\ge$1-hit and $\ge$2-hit events (Any1 and Any2, respectively). We report a successful detection of a Forbush decrease occurred on 2024 May 10 caused by a passage of an interplanetary shock formed ahead of the Interplanetary Coronal Mass Ejection. The amplitude detected in the Any1 rate is 4.26$\pm$0.33% at the median primary rigidity of 76GV which is consistent with the observations with the worldwide neutron monitor and muon detector networks. Under the assumption of a power-law rigidity spectrum, we renormalized the errors of the observed amplitude ($A_{obs}$) and fitted them as a function of the median primary rigidity ($R_{m}$) of each detector and observational method. The result $A_{obs} = (10.9\% \pm 0.9\%) \times (R_{m}/10\,GV)^{-0.55 \pm 0.07}$ exhibits a hard nature of this event. Our non-detection in the Any2 rate decrease constrains the amplitude with a 2$\sigma$ upper limit to be 0.95% at 960GV. This marginally suggests an existence of a spectral softening between 100GV and 1000GV as also suggested by the Misato underground muon detector at 145GV. Although a strong geomagnetic storm was observed during this period, we conclude it does not impact our results. Our novel technique realizes a unique coverage to study the behavior of the Forbush decreases at the highest rigidity.

Slow-rotating evolved stars frequently exhibit radial velocity (RV) variations on annual timescales, complicated by instrumental systematics and aliasing in the one-year regime. Here we investigate the origin of the near-yearly periodicity in 2 Dra, a star located in the red-clump region, assessing possible causes between stellar activity, instrumental profile (IP) effects, sampling alias, and planetary companions. We applied two independent approaches: (1) constraining diagnostic signals and performing a correlation analysis ($r$) between period-confined signals, and (2) evaluating phase stability by partitioning Keplerian fits. These methods enabled us to examine the physical connections and phase coherence among stellar activity indicators, RV measurements, and IP diagnostics. Our analysis suggests a stellar rotation period of $\simeq270\text{--}320$\,d for 2~Dra. The 340-d RV signal does not appear to originate from stellar activity in this chromospherically quiet star ($|r| \lesssim 0.33$), nor from instrumental systematics near the annual period ($|r| \lesssim 0.1$). This conclusion is supported by contrasting phase behavior: the RV and stellar activity phases remain stable, whereas the IP phases do not. We therefore propose that the 340-d variation likely arises from either small-amplitude intrinsic variability or a tentative gas giant companion with potential weak activity-induced modulation. The case of 2~Dra provides a framework for distinguishing the origins of $\sim$1-yr RV variations in other evolved stars.

According to the classical AGN model, broad emission lines originate from the broad-line region (BLR) and are observable only when the attenuation by the dusty torus is small. However, we recently found several heavily-obscured ($A_V > 50$ mag) AGNs with broad H$\alpha$ detections: MCG -3-34-64, UGC 5101, and Mrk 268. To investigate the origin of the observed broad line in these AGNs, we performed multi-epoch optical spectroscopic observations to search for flux variability of the broad H$\alpha$ line. For MCG -3-34-64 and UGC 5101, no significant variability was detected, suggesting that the broad line of these AGNs may arise from sources other than the BLR. Spectral fitting analysis suggests possible large contribution of ionized outflows to the observed broad component of MCG -3-34-64, while both the outflow and scattering by polar material can explain that of UGC 5101. For Mrk 268, we detected a significant ($4.3\sigma$) flux variation of the broad H$\alpha$ line by using the flux ratio of the H$\alpha$ complex and the [SII]$\lambda\lambda6716$, 6731 doublet, indicating that the broad line originates directly from the BLR. The lack of significant flux variation in the optical continuum implies that the line of sight to the nucleus of Mrk 268 is mildly obscured. Our results demonstrate that the observed broad H$\alpha$ lines in obscured AGNs likely have multiple origins. Such complexity may introduce additional uncertainties in black hole mass measurements of distant AGNs revealed by e.g., JWST.

The accretion of icy and rocky solids during the formation of a gas giant planet is poorly constrained and challenging to model. Refractory species, like sulfur, are only present in solids in the protoplanetary disk where planets form. Measuring their abundance in planetary atmospheres is one of the most direct ways of constraining the extent and mechanism of solid accretion. Using the unprecedented sensitivity of NASA's James Webb Space Telescope (JWST), we measure a detailed chemical make-up of three massive gas giants orbiting the star HR~8799 including direct detections of H$_2$O, CO, CH$_4$, CO$_2$, H$_2$S, $^{13}$CO, and C$^{18}$O. We find these planets are uniformly and highly enriched in heavy elements compared to the star irrespective of their volatile (carbon and oxygen) or refractory (sulfur) nature, which strongly suggests efficient accretion of solids during their formation. This composition closely resembles that of Jupiter and Saturn and demonstrates that this enrichment also occurs in systems of multiple gas giant planets orbiting stars beyond the Solar System. This discovery hints at a shared origin for the heavy element enrichment of giant planets across a wider range of planet masses and orbital separations than previously anticipated.

In this {\it Letter}, we present a compelling and robust argument for the roles of neutrino fast flavor conversion (FFC) in the explosion mechanism of core-collapse supernova (CCSN), combining the {\it multi-angle} FFC subgrid model rooted in quantum kinetic theory with the multi-dimensional four-species Boltzmann neutrino radiation hydrodynamics. Employing various progenitor masses and the nuclear equations of states, we find that the effect of FFC on CCSN explosion is bifurcated depending on the progenitors. For the lowest-mass progenitor, FFC facilitates the shock revival and enhances the explosion energy, whereas for higher-mass progenitors its impact is inhibitory. We identify the mass accretion rate as the key determinant governing this bifurcation. When the mass accretion rate is low (high), the contribution of FFC to neutrino heating becomes positive (negative), because the heating efficiency enhancement via FFC-driven spectral hardening of electron-type neutrinos dominates over (is outweighed by) the concurrent reduction in neutrino luminosity. Our results further highlight the limitations of approximate neutrino transport, and demonstrate that a multi-angle treatment is essential for accurately capturing FFC effects; otherwise, FFCs are missed and even generated spuriously.

The formation channels of binary black hole (BBH) mergers detected by the LIGO/Virgo/KAGRA (LVK) network remain uncertain. While BBH mergers occurring inside active galactic nucleus (AGN) disks may interact with surrounding gas and generate observable optical flares. We test this scenario by quantifying the spatial and temporal correlation between BBH events in GWTC-4.0 and AGN flares identified from six years of the Zwicky Transient Facility (ZTF) DR23 data. Using 80 BBH mergers selected for adequate localization, redshift reach, observing-epoch overlap, and ZTF sky coverage, we construct a likelihood for the flare-associated fraction, $f_{\rm flare}$, that combines each event's 3D localization with a locally estimated flare number density derived from a 3D Voronoi tessellation, while explicitly accounting for survey boundaries and incomplete catalog coverage. Adopting a 200-day post-merger time window for potential counterparts, we infer $f_{\rm flare} = 0.07_{-0.05}^{+0.25}$ (90\% confidence level). This non-zero maximum-likelihood value is driven primarily by GW190412, for which a single flare candidate (J143041.67+355703.8) is consistent in both time and spatial position. Excluding GW190412 yields results consistent with no association and an upper limit of $f_{\rm flare} < 0.17$ at 90\% confidence level. The intrinsic properties of GW190412 and the characteristics of the candidate host AGN are broadly consistent with theoretical expectations for the AGN-disk formation channel, motivating continued, targeted electromagnetic follow-up of well-localized and highly asymmetric BBH mergers in current and upcoming time-domain surveys.

The small number of impact craters found on Titan suggests that its surface is relatively young. Previous work estimated its surface age to be between 200 and 1000 Myr. This estimate, however, is based on crater scaling laws for water and sand, which are not representative of the composition of Titan's icy surface. Titan's surface is likely composed of water ice, methane clathrates, or a combination of both. Here, we perform impact simulations for impactors of various sizes that strike an icy target with a 0-15 km thick methane clathrate cap layer. We derive new crater scaling laws based on our numerical results, and find that Titan's surface age is 300-340 Myr, assuming heliocentric impactors and surface clathrates. This age, which represents the crater retention age, indicates a relatively youthful surface, suggesting that active endogenic and/or exogenic processes have recently reshaped Titan's surface.

Aims. The blazars Mrk 421 and Mrk 501 have shown multiwavelength variability on all observed timescales, and have been well studied at high energies on short timescales. We aim to characterise the long-term temporal behaviour of these blazars at synchrotron energies, namely optical, UV, and X-ray, in order to assess current models of these objects and their processes. Methods. Amongst the longest light curves ever studied for these sources, we investigated 20 years of data (2005-2025) from the Swift-UVOT and Swift-XRT telescopes. We examined spectral models, fractional variabilities, flux distributions, and X-ray photon index vs flux relations, as well as carrying out in-depth time series analysis using structure functions, Lomb-Scargle periodograms, and discrete correlation functions. Results. Mrk 421 and Mrk 501 both showed intriguing variability in all studied wavelengths; this variability has been found to be energy dependent, as has the trend of lognormality in flux distributions. X-ray photon indices fluctuated greatly throughout the entire period, showing an overall harder-when-brighter trend. Hints of a quasi-periodicity have been found in the X-ray of Mrk 501 (host frame time scale $\sim390$ days, >3$\sigma$) but not in the UV or X-ray of Mrk 421, or in the UV of Mrk 501. No correlation at any time lag was found between the optical/UV and X-ray bands in either source.

Rotation curves are a fundamental tool in the study of galaxies across cosmic time, and with the advent of large integral field unit (IFU) kinematic surveys there is an increasing need for efficient and flexible modelling tools. We present RotCurves, a parametric forward-modeling tool designed for rotation curve analysis at high-z, correcting for ``beam smearing" by projecting and convolving the beam PSF in the plane of the galaxy. We benchmark RotCurves against the established parametric code dysmalpy using synthetic observations. The typical runtime with RotCurves is a few ~10ms, a factor 250 faster than dysmalpy for a single realization. For well-resolved systems (PSF FWHM < Reff), the mock observed rotation and dispersion curves agree to within 5% up to 3Reff, where most of the discrepancies are in the inner disk. whereas in marginally resolved systems (PSF FWHM > 1.5 Reff) discrepancies increase to up to 15%. Using a built-in MCMC fitting procedure, RotCurves recovers well the intrinsic model parameters across a wide range of galaxy properties and accounting for realistic noise patterns. Systematic biases emerge for the effective radius and for low disk masses (Mdisk < 3x10^9 Msun). We show excellent parameter recovery at high signal-to-noise ratios (S/N > 25), with increasing deviations in parameter recovery at lower S/N. RotCurves is best suited for inclinations of 10 < i < 80. RotCurves is built as an exploratory tool for rapid testing of mass model assumptions, parameter studies and for efficiently processing large samples of observational data from large IFU surveys. The code is publicly available on github.

Radio Frequency Interference (RFI), the presence of artificial and/or terrestrial signals in astronomical data, poses a great challenge to the search for pulsars and radio transients, such as Rotating Radio Transients (RRATs) and Fast Radio Bursts (FRBs), by obscuring or distorting the signal of interest and resulting in large numbers of erroneous detections. RFI mitigation algorithms aim to remove this interference and improve the chance of detection of transients, but with the growing number of techniques, selecting the most appropriate method for a given survey can be problematic. The choice of method is particularly important in real-time searches planned for next-generation telescopes such as those of the SKAO, where there is no possibility to reprocess the data. In this paper, we explore the algorithm selection problem by injecting pulses into data which simulates several RFI environments. A set of these files is then cleaned using RFI mitigation algorithms and run through a single pulse search pipeline to analyse the recovery of the injected pulses. We examine the recovery of the injected single pulses with an emphasis on a number of cases spanning a range of pulse brightness, width and dispersion measure. The efficacy and side effects of a few popular RFI excision methods, namely IQRM, SKF, and ZDMF are evaluated.

Many stellar systems exhibit a finite spatial extent, yet constructing self-consistent spherical models with a prescribed outer boundary is non-trivial because sharp density cutoffs introduce discontinuities that lead to inconsistencies in the associated distribution function. In this paper we show that these difficulties arise from the abruptness of the truncation rather than from the finite extent itself. We introduce a general and infinitely differentiable radial truncation scheme that can be applied to any density profile, and illustrate its behaviour using the Hernquist model. We find that softly truncated models are dynamically consistent provided that the truncation is sufficiently gradual, and we determine the corresponding critical truncation sharpness. Their distribution functions display a characteristic bump-dip feature near the truncation energy that signals the transition between consistent and inconsistent cases. In contrast to sharply truncated models, softly truncated systems can support an extensive family of Osipkov-Merritt orbital structures, including moderately radial ones. Soft truncations therefore offer a general and physically motivated route to constructing finite-extent dynamical models with well-controlled outer-edge behaviour.

The parameters of an axisymmetric model for the gravitational potential of the Galaxy have been refined. The basic curve of the Galaxy's rotation in a distance interval of $R:0-190$ kpc was constructed using the velocities of masers, classical Cepheids, Red Clump stars, Blue Horizontal Branch stars, halo stars, globular clusters, and dwarf satellite galaxies of the Milky Way. The rotation curve was selected in such a way that there would be no dominant burst of circular velocities in the central ($R<2$ kpc) region of the Galaxy. As a result, we constructed two two-component models of the galactic potential, which include contributions from the disk and the halo of invisible matter, as well as a three-component model with a small-mass bulge added in advance. These models can be useful in studying the long-term orbital evolution of stars and open and globular star clusters in the central ($R<4$ kpc) region of the Galaxy. The constructed models were tested for self-consistency by comparing their rotation curves with a set of model curves generated with the Illustris TNG50 software package.

The next great leap in Martian exploration will be the return of samples to Earth. To ensure the maximum scientific return from studying these samples, the development and utilisation of nondestructive analytical techniques are essential to enable early three-dimensional characterisation of their interiors. Neutron computed tomography is a powerful method in this context: it is highly sensitive to hydrogen and complements the more conventional X-ray computed tomography. Because the distribution and nature of hydrous phases are central to understanding the habitability, the climatic and geological evolution, and potential biosignatures of Mars, identifying hydrogenbearing phases in Martian crustal rocks is of particular importance. Using the only Martian crustal material available on Earth, the NWA 7034 meteorite and its pairs, we show that combined neutron and X-ray computed tomography enables non-destructive sample-wide mapping of hydrogen and reveals the distribution and petrographic contexts of hydrous phases. We identify hydrogen-rich iron oxyhydroxides within ancient igneous clasts, forming a macroscopic mineralogical water reservoir within the meteorite. These alteration assemblages closely resemble those observed in samples collected by the Perseverance rover in Jezero crater, where hydrated iron oxyhydroxides are also present. This similarity suggests that such phases may represent a widespread near-surface water reservoir on early Mars.

Transit spectroscopy is a powerful tool for probing atmospheric structures of exoplanets. Accurately accounting for the effects of aerosols is key to reconstructing atmospheric properties from transit spectra, yet this remains a significant challenge. To advance this effort, it is invaluable to examine the spectral features of well-characterized planetary atmospheres. Here, we synthesize empirical transit spectra of Mars across different seasons based on data from the NOMAD's Solar Occultation channel onboard ExoMars/TGO, which operates at wavelengths of 0.2-0.65 and 2-4 micron. In the generated empirical transit spectra, the atmosphere below 25 km is found to be largely opaque due to the presence of micron-sized dust and water ice clouds, both of which substantially weaken spectral features. The spectra exhibit CO2 absorption features at 2.7-2.8 micron and signatures of sub-micron-sized mesospheric water ice clouds around 3.1 micron, accompanied by a continuum slope. The amplitudes of these spectral features are found to vary with the Martian seasons, where the dust storms weaken the CO2 signatures and strengthen the water ice features, which serve as potential indicators of a dusty planet like Mars. If TRAPPIST-1f possessed a Mars-like atmospheric structure, both CO2 and water ice features would be detectable at a noise level of 3 ppm, a level likely beyond current observational capabilities. Nevertheless, the 3.1 micron feature produced by sub-micron-sized mesospheric water ice clouds offers a novel avenue for characterizing the atmospheres of habitable-zone exoplanets.

The high sensitivity of the pyramid wavefront sensor has made it the preferred sensor in high contrast adaptive optics systems. Future higher contrast systems, like the Extremely Large Telescope's Planetary Camera System, will require higher performance wavefront sensing. A further performance improvement could be achieved with a polychromatic pyramid wavefront sensor by using additional information over a broader wavelength range. The development of such systems is becoming more feasible with the emergence of new detector technologies such as Microwave Kinetic Inductance Detector arrays. These are arrays of superconductor detectors that give a position, arrival time and measure of the energy for each incident photon. This paper introduces the polychromatic pyramid wavefront sensor concept by defining the technologies and techniques employed and their requirements. A method is developed to track the optical gains, taking advantage of the additional wavelength information, and used to compensate for optical gains within an optimised reconstructor to minimise noise propagation. An overview of expected performance improvement, using end-to-end simulations, is provided using the Keck II adaptive optics system as a reference design. The polychromatic pyramid wavefront sensor was shown to increase the limiting magnitude by 1 to 2 magnitudes, and the contrast by factors of 1.5 to 4, versus single band pyramid wavefront sensors, by sensing over a wavelength range approximately five to ten times broader (800-1800 nm) compared to Z band (152 nm wide) and H band (300 nm wide). Practical design and implementation issues have also been considered.

Our Local Group, dominated in mass by the Milky Way (MW) and M31, provides a unique laboratory for testing $\Lambda$CDM cosmology on small scales owing to its proximity. However, its connection to the surrounding large-scale environment, which is essential for interpreting its properties, is inadequately understood. In this work, we explore the connection between Local Group analogues (LGAs) and their surrounding large-scale environments using the ABACUSSUMMIT simulation suite, highlighting the key role of the coupling energy of the MW-M31 orbit, $E_{\rm coupling}$. We find that LGAs with high $E_{\rm coupling}$ preferentially reside in denser regions, whereas those with low $E_{\rm coupling}$ tend to occupy low-density environments. Furthermore, LGAs with low $E_{\rm coupling}$ exhibit strong alignment with cosmic filaments, manifested as a pronounced polar anisotropy in the distribution of tracer haloes. By contrast, LGAs with high $E_{\rm coupling}$ show a weaker polar anisotropy but an enhanced azimuthal anisotropy, with large-scale tracer haloes preferentially lying in the plane spanned by the halo pair and the orbital spin vector. Within this framework, our Local Group is characterised by typical $E_{\rm coupling}$ residing in a relatively under-dense environment, yet it remains consistent with the 95\% range of analogue systems identified in the simulation.

We present a new empirical relation between the standardized magnitude ($m$) of Type Ia supernovae (SNe Ia) and redshift ($z$). Using Pantheon+ and DES-SN5YR, we find a negative linear correlation between $m-5\log(z(1+z))$ and $z$, implying that their magnitude--redshift relation can be parametrized with just two parameters: an intercept $\mathcal{M}$ and a slope $b$. This relation corresponds to the luminosity distance $d_L(z)=c\,H_0^{-1}z(1+z)10^{bz/5}$ and is valid up to at least $z\simeq1.1$. It outperforms the $\Lambda$CDM and flat $w$CDM models and the (2,1) Padé approximant for $d_L(z)$, and performs comparably to the flat $\Lambda$CDM model and the (2,1) Padé($j_0=1$) model of Hu et al. Furthermore, the relation is stable in the absence of low-$z$ SNe, making it suitable for fitting Hubble diagrams of SNe Ia without the need to add a low-$z$ sample. In deep fields in particular, assuming that the large-scale density is independent of the comoving radial coordinate, $b\propto q_0+1$. We fit the empirical relation to SN data in eight deep-field regions and find that their fitted $\mathcal{M}$ and $b$ parameters are consistent within $1.6\,\sigma$, in agreement with isotropy. The inferred $q_0$ values, ranging from $-0.6$ to $-0.4$, are consistent within $1.5\,\sigma$ and significantly lower than zero, indicating statistically consistent cosmic acceleration across all eight regions. We apply the empirical relation to the DES-Dovekie and Amalgame SN samples, finding $b$ values consistent with those from DES-SN5YR and Pantheon+. Finally, using the empirical relation in the hemispheric comparison method applied to Pantheon+ up to $z=1.1$, we find no evidence for anisotropies in $\mathcal{M}$ and $b$.

We report new constraints on the vertical distribution of sulfuric acid vapor in the Venusian atmosphere, derived from a refined analysis of radio occultation (RO) data. The method estimates the power spectral density (PSD) of the received signal to recover both the signal intensity and the Doppler shift. The received signal power is estimated at 1-sec cadence which enhances the sensitivity and detection of the signal at lower altitudes of Venus, even in regions of high atmospheric opacity. After correcting total attenuation for refractive losses, absorption by known microwave absorbers is removed, leaving a residual signal attributable to sulfuric acid vapor. Two different methods of estimating the absorption due to Sulfur Dioxide have been presented, including one which incorporates in-situ data, which should better constrain the sulfuric acid vapor abundance below the clouds. Retrieved profiles for altitudes of 40 - 50 km reveal an increasing vapor abundance to more than 10 ppm below the clouds, and a sharp decline above 50 km in line with the expected saturation profile. These measurements agree with current models of the Venusian cloud structure and composition, and demonstrate that RO data, when coupled with optimized spectral analysis, can yield quantitative constraints on trace absorbers in optically thick atmospheres.

Binary evolution plays a central role in producing rapidly rotating stars. Previous studies have shown that mass gainers in binaries can reach critical rotation after accreting only modest amounts of material, particularly during thermal-timescale Case B mass transfer, where tidal spin-down is ineffective due to wide orbits. However, such rapid accretion often drives the mass gainer out of thermal equilibrium, and its subsequent spin evolution during thermal relaxation has not been analysed in depth. In this study, we construct a suite of accreting detailed single-star models with different accretion prescriptions, which inflate and spin up to critical rotation during the accretion. After the accretion has ended, the models relax thermally and deflate. We find that the ratio of surface to critical angular velocity decreases to subcritical values during thermal contraction, with the magnitude of this decrease correlating with the degree of thermal disequilibrium at the end of accretion. This reduction in fractional critical rotation is even stronger when internal angular momentum transport is inefficient. Detailed binary models show the same trend, indicating that the results from our toy single-star models also apply to real binary evolution. Our results highlight that binary mass transfer does not always produce critically rotating stars, but instead may yield a wide range of spin rates depending on the mass transfer and accretion history. Our findings offer new insights into the rotational properties of mass gainers in binaries, stellar merger products, and newly formed massive stars following accretion.

We revisit the Great Attractor using the Manticore-Local suite of digital twins of the nearby Universe. The Great Attractor concept has been proposed as an answer to three distinct questions: what sources the Local Group velocity in the cosmic microwave background frame, where present-day velocity streamlines converge, and where the Local Group is moving to. Addressing the original motivation of the Great Attractor -- explaining the Local Group cosmic velocity -- we find that mass within $155~h^{-1}\mathrm{Mpc}$ accounts for only ${\sim}72\%$ of that velocity magnitude with ${\sim}38\,°$ directional offset. We show that even in the purely linear regime convergence within this volume is not guaranteed, particularly when also accounting for small-scale contributions to the observer velocity; no single structure, including the proposed Great Attractor, would be expected to dominate the velocity budget. Streamline convergence is smoothing-scale-dependent, transitioning from Virgo at small scales through the Hydra--Centaurus region at intermediate scales to Shapley at large scales; at intermediate smoothing the convergence point lies near Abell 3565 with an asymmetric basin of mass $\log( M / (h^{-1} \mathrm{M}_\odot)) = 16.4 \pm 0.1$ that excludes Norma. To address the third question, we evolve the Manticore-Local realisations to scale factor $a = 10$ in a new Beyond-Present-Time simulation suite and identify the asymptotic future location of the Local Group. We find that the dominant motion is towards Virgo, but even it contributes at most one third of the Local Group velocity. Our results demonstrate that the classical Great Attractor is not a dynamically dominant structure but an artifact of the instantaneous velocity field, and that no single attractor is likely to account for the Local Group motion in the cosmic rest frame.

PSR J1455$-$3330 is a $\sim$7.98 ms pulsar in a $\sim$76.17 day nearly circular orbit with a white dwarf companion. In this work, we combine the available Lovell, Nançay decimetric Radio Telescope, Green Bank, and MeerKAT pulsar timing data spanning $\sim$ 30 years to measure the kinematic and relativistic effects of PSR J1455$-$3330 to constrain its 3D orbital geometry and component masses. We detect a relativistic Shapiro delay signal. We measure a significant orthometric amplitude $h_3 = 0.307^{+0.022}_{-0.026}$ $\mu$s and an orthometric ratio $\varsigma = 0.551^{+0.057}_{-0.054}$. We measure the change in projected semi-major axis $\dot{x} = -202.1^{+2.5}_{-2.7} \times10^{-16} \, \rm s\,s^{-1}$ with high significance, parallax, $\varpi$ = 1.11(6) mas, parallax derived distance 0.90(5) kpc, and a precise total proper motion magnitude of 12.432(2) mas yr$^{-1}$. A self-consistent analysis of all kinematic and relativistic effects, assuming general relativity, yields two solutions: (1) a pulsar mass $M_{\rm p} = 1.39^{+0.38}_{-0.18}\, \rm M_{\odot}$, a companion mass $M_{\rm c} = 0.293^{+0.056}_{-0.026}$ $\rm M_{\odot}$, an orbital inclination, $i = 63(2)^{\circ}$, and longitude of the ascending node, $\Omega = 212(12)^{\circ}$ or (2) a pulsar mass $M_{\rm p} = 1.53^{+1.10}_{-0.22} \, \rm M_{\odot}$, a companion mass $M_{\rm c} = 0.309^{+0.163}_{-0.026}\, \rm M_{\odot}$, an orbital inclination, $i = 123(4)^{\circ}$, and longitude of the ascending node, $\Omega = 334(12)^{\circ}$. All uncertainties represent the 68.27$\%$ credibility region. These results strongly favour a helium-dominated white dwarf companion.

Gamma ray bursts (GRBs) offer a powerful probe of the cosmic expansion history far beyond the redshift range accessible to Type Ia supernovae. However, the calibration of GRB luminosity correlations is hindered by the circularity problem, which arises from assuming a fiducial cosmological model during calibration. In this work, we perform a model independent calibration of GRB luminosity relations using observational Hubble parameter H(z) data from the A220 and J220 compilations, thereby avoiding explicit cosmological assumptions. We employ Artificial Neural Network (ANN) to reconstruct the calibration relation directly from the data. In addition, we implement a Bayesian Neural Network (BNN) framework as an alternative approach, enabling a data driven treatment of both statistical and systematic uncertainties. The calibrated GRB sample is used to constrain the Amati relation, and we systematically compare the outcomes obtained from different calibration techniques and datasets. While the Amati Parameters obtained from GRBs caibrated from the ANN and BNN results are consistent with previous low redshifts calibrations using model-independent methods, the BNN approach provides a more robust framework.

The initial mass function (IMF) is a cornerstone of star formation studies, yet its universality remains debated. We investigate the IMF in the young massive cluster RCW 36, located in the Vela Molecular Ridge and comparable to the Orion Nebula Cluster in stellar density. Our goal is to build the most complete census of RCW 36 and derive its first IMF and star-to-brown-dwarf (BD) ratio. We combine new GLAO observations from HAWK-I/VLT with archival data (2MASS, SOFI/NTT) and Gaia DR3 kinematics. Photometric accuracy and source extraction were improved using \textsc{DeNeb}, a deep-learning algorithm that removes complex nebular emission. Membership probabilities were assigned via color-magnitude diagram comparisons with a control field, and stellar masses were estimated using model isochrones. We find a revised distance of $954\pm40\,$pc and determine the IMF down to $\sim0.03\,M_{\odot}$, described by a broken power law ($dN/dM\propto M^{-\alpha}$) with $\alpha=1.62\pm0.03$ for $0.20$-$20\,M_{\odot}$ and $\alpha=0.46\pm0.14$ for $0.03$-$0.20\,M_{\odot}$. The star-BD ratio is $2$-$5$, consistent with other Galactic clusters. Lastly, through a study of the differences in the IMF within and outside $0.2\,$pc and the cumulative mass distributions for low-mass and intermediate to high-mass sources, we also detected signs of possible mass segregation within RCW 36, which should be primordial. RCW 36 shares many characteristics with other young massive clusters, such as a shallower than Salpeter high-mass slope and the possibility of mass segregation. The flatter lower-mass regime of the IMF is similar to most Galactic clusters. The star-BD ratio is also in line with the observed values in other clusters, independent of their inherent properties.

The 2175 Angstrom extinction bump, the most prominent spectral feature superimposed on the interstellar extinction curve, is widely seen in the interstellar medium (ISM) of the Milky Way and external galaxies, both near and far. While its central wavelength is remarkably stable and independent with environment, its width shows considerable variation and environmental dependence. Here we examine the extinction curve for the line of sight toward HD 93222, a young star located in the Carina nebula. It is found that the 2175 Angstrom bump is extremely sharp, which is among the narrowest ever found in the Milky Way and external galaxies. We model the derived extinction curve and find that, to explain the extinction characteristics of HD 93222, in addition to the conventional silicate and graphite dust mixture, an additional population of nano-sized graphitic grains is required.

We present independent polarimetric observations of the interstellar object 3I/ATLAS, including the first near-infrared polarimetric measurements. Using imaging polarimeters, we measured the degree of linear polarization from the visible RC band (0.64 {\mu}m) to the near-infrared KS band (2.25 {\mu}m), and investigated its dependence on solar phase angle (polarization phase curve; PPC) and wavelength (polarization color curve; PCC). We confirm that the PPC of 3I/ATLAS differs significantly from those of typical Solar System comets, showing an unusually large polarization amplitude. This PPC shows no significant change in the RC band across perihelion passage, despite the perihelion lying within the water snow line. This indicates that the unusual polarimetric behavior of 3I/ATLAS is unlikely to be driven by transient volatile activity, but instead reflects intrinsic optical properties of refractory dust particles. The PCC increases with wavelength over 0.6-1.2 {\mu}m and peaks at 1.5-2.0 {\mu}m, suggesting that the dominant scattering units are dust aggregates composed of submicron-sized monomers, broadly consistent with interstellar dust and solar-system cometary aggregates. Taken together, our results indicate that 3I/ATLAS preserves polarimetric properties characteristic of a primitive cometary planetesimal formed in another planetary system, with a refractory dust composition that differs from that typically observed among Solar System comets, despite sharing a similar size scale of the aggregate building blocks.

In this work, we perform the first numerical study of strong scalar backreaction in spectator chromo-natural inflation (SCNI) in the case where the spectator sector decays during inflation. The tachyonic instability in scalar fluctuations, activated as the system crosses the $m_Q = \sqrt{2}$ threshold, amplifies perturbations and may significantly alter the background dynamics. The strong scalar backreaction regime introduces an effective quartic term in the potential for the gauge field background that rapidly drives it to zero, accelerating the axion-gauge system decay. We describe the dynamics of such decay and derive the gravitational wave spectrum for a set of benchmark parameters. Interestingly, the signal may peak at interferometer scales and lie within LISA's projected sensitivity.

We point out that on 22 January 2026, the interstellar object 3I/ATLAS will align to within an exceptionally small angle, alpha= 0.69 degrees, with the Earth-Sun axis. This rare alignment provides unique circumstances for measuring the opposition surge and polarimetric properties of interstellar cometary dust. We characterize the alignment geometry, outline key scientific opportunities, and define the observational requirements for data collection. Observations before and after the alignment time offer an unprecedented opportunity which may not repeat for decades, for characterizing the albedo, structure, and composition of interstellar matter.

We present new results from the MUSE-ALMA Haloes survey, covering 79 galaxies associated with strong HI absorption at redshift about 0.5. Our ALMA Cycle 10 observations add 39 systems to the initial 21, bringing the total to 60 galaxies. CO emission is detected in 9 new galaxies, and in 12 of 60 total, doubling the number of CO-emitting HI-selected galaxies and probing 1.2 dex deeper in molecular gas mass than previous studies. These galaxies span a wide range of stellar masses and metallicities. By comparing CO(2-1) and CO(3-2) properties with star formation rates and gas-phase metallicities from VLT/MUSE and HST, we find a dual behaviour in star formation efficiency: low-mass systems follow main-sequence scaling relations, while high-mass systems show suppressed star formation. This diversity indicates that HI absorbers trace both evolved and younger galaxies, providing a key step toward completing the baryon census at redshift about 0.5.

Aims: This study investigates whether a U-Net architecture can perform standalone end-to-end blind deconvolution of astronomical images without any prior knowledge of the Point Spread Function (PSF) or noise characteristics. Our goal is to evaluate its performance against the number of training images, classical Tikhonov deconvolution and to assess its generalization capability under varying seeing conditions and noise levels. Methods: Realistic astronomical observations are simulated using the GalSim toolkit, incorporating random transformations, PSF convolution (accounting for both optical and atmospheric effects), and Gaussian white noise. A U-Net model is trained using a Mean Square Error (MSE) loss function on datasets of varying sizes, up to 40,000 images of size 48x48 from the COSMOS Real Galaxy Dataset. Performance is evaluated using PSNR, SSIM, and cosine similarity metrics, with the latter employed in a two-model framework to assess solution stability. Results: The U-Net model demonstrates effectiveness in blind deconvolution, with performance improving consistently as the training dataset size increases, saturating beyond 5,000 images. Cosine similarity analysis reveals convergence between independently trained models, indicating stable solutions. Remarkably, the U-Net outperforms the oracle-like Tikhonov method in challenging conditions (low PSNR/medium SSIM). The model also generalizes well to unseen seeing and noise conditions, although optimal performance is achieved when training parameters include validation conditions. Experiments on synthetic $C^\alpha$ images further support the hypothesis that the U-Net learns a geometry-adaptive harmonic basis, akin to sparse representations observed in denoising tasks. These results align with recent mathematical insights into its adaptive learning capabilities.

We compute the full one-loop corrections to the primordial tensor power spectrum in an inflationary scenario with a non-minimally coupled spectator field, using the in-in formalism. We derive semi-analytic results for the scalar-sourced one-loop tensor spectrum and the effective tensor-to-scalar ratio, $r_{\mathrm{eff}}$ . We consider two representative coupling functions: a localized Gaussian dip (Model G), which leads to moderate loop corrections, and a rapidly oscillatory coupling (Model O), which can yield much larger loop contributions. For Model G, we find a $\mathcal{O}(1)$ correction to $r_{\mathrm{eff}}$ while Model O can significantly enhance $r_{\mathrm{eff}}$ by several orders of magnitude (relative to the tree-level value). We further calculate the energy density of primordial gravitational waves. Assuming that primordial black holes with mass $10^{-12}M_{\odot}$ generated in this scenario, constitute all of the dark matter, we find that the results are several orders of magnitude lower than the sensitivities of Taiji/TianQin/LISA.

JWST observations have suggested that some high-redshift galaxies may be ultra-massive, thereby challenging standard models of early galaxy formation and cosmology. We analyse the stellar masses using different modelling assumptions and with new data of three galaxies (S1, S2 and S3), whose NIRCam/grism redshifts were consistent with $z>5$. These three optically dark galaxies have previously been reported to host exceptionally high stellar masses and star-formation rates, implying extremely high star-formation efficiencies. Recent NIRSpec/IFU observations for S1 indicate a spectroscopic redshift of $z_{\rm spec}=3.2461^{+0.0001}_{-0.0002}$, which is lower than previously reported. Using the Bayesian spectral energy distribution (SED) modelling tool \texttt{Prospector}, we investigate the impact of key model assumptions on stellar mass estimates, such as the choice of star-formation history (SFH) priors (constant versus rising SFH base for the non-parametric prior), the dust attenuation law, and the treatment of emission line fluxes. Our analysis yields revised stellar masses of $\log(M_{\star}/M_{\odot}) \approx 10.36^{+0.47}_{-0.32}, 10.95^{+0.11}_{-0.10}$ and $10.31^{+0.24}_{-0.19}$ for S1, S2, and S3, respectively. We find that adopting a rising SFH base prior results in lower inferred stellar masses compared to a constant SFH base prior. We identify a significant degeneracy between the dust attenuation curve slope, the amount of dust attenuation, and stellar mass. Our results highlight various systematics in SED modelling due to SFH priors and dust attenuation that can influence stellar mass estimates of heavily dust obscured sources. Nevertheless, even with these revised stellar mass estimates, two of the three galaxies remain among the most massive and actively star-forming systems at their respective redshifts, implying high star-formation efficiencies.

Relativistic jets launched in binary neutron star (BNS) mergers are widely accepted as the engines powering most of the population of short gamma-ray bursts (GRBs). Understanding their structure and dynamics-particularly during and after breakout from the merger ejecta-is crucial for interpreting GRB afterglows, especially for off-axis observers. Traditional models often assume simple angular or radial jet profiles, potentially missing key features emerging for jets piercing through realistic environments. This work aims to investigate the formation and evolution of the jet structure as it propagates through a non-homogeneous, anisotropic BNS merger environment. We focus on how the interaction with the ambient medium shapes the jet's angular and velocity distributions and assess the impact of this realistic structure on the resulting afterglow light curves. We perform a series of 3D relativistic magnetohydrodynamic simulations of jets launched in post-merger environments, exploring different injection conditions. Simulations are evolved to late times, approaching the ballistic regime, where further dynamical evolution becomes negligible. From the resulting outflows, we extract energy and velocity profiles and compute multi-wavelength afterglow light curves using a semi-analytic model that includes radial stratification and the full 3D jet geometry. More energetic or earlier-launched jets drill more efficiently through the ejecta, but all develop asymmetries that leave clear imprints in the off-axis afterglow light curves. All models exhibit a complex multi-shock breakout structure responsible for an early, dimmer peak in the afterglow. Despite structural differences, all simulated jets are consistent with the observational data of the multi-messenger BNS merger event GW170817.

We present new precise measurements of electron temperatures and oxygen abundances in the southeast knot of I Zw 18, one of the most metal-poor blue compact dwarf galaxies known, using spectroscopic data from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). For the first time in I Zw 18, we directly measure electron temperature in the low-ionization zone using the rarely detected [O II] $\lambda\lambda7320,7330$ doublet. We also detect the auroral lines [O III] $\lambda4363$ and [S III] $\lambda6312$, associated with high and intermediate ionization zones, respectively. We derive $T_{\mathrm{e}}([\mathrm{O}\,\mathrm{III}])=21\,200\pm860\ \mathrm{K}$, $T_{\mathrm{e}}([\mathrm{O}\,\mathrm{II}])=16\,170\pm950\ \mathrm{K}$, and $T_{\mathrm{e}}([\mathrm{S}\,\mathrm{III}])=17\,290\pm1750\ \mathrm{K}$, highlighting a significant temperature difference between ionization zones. Using these direct temperature measurements, we determine a total oxygen abundance of $12+\log(\mathrm{O}/\mathrm{H})=7.066\pm0.046$, $\log(\mathrm{N}/\mathrm{O})=-1.509\pm0.097$, and $\log(\mathrm{S}/\mathrm{O})=-1.558\pm0.041$. Our results extend the calibration of $t_2$--$t_3$ relations to the highest temperatures, providing important anchor points for the temperature structure of extremely metal-poor H II regions, including high-redshift galaxies where direct temperature measurements are especially challenging.

Radio mini-halos are perplexing features, typically hosted by X-ray cool-core galaxy clusters. Understanding the connection between thermal X-ray and non-thermal radio emission is key to uncovering their origin. Here, we present a multiwavelength study of the cool-core cluster RXCJ1558.3-1410 using archival Chandra X-ray and wideband uGMRT radio data (Bands 3, 4 and 5). Our improved analysis confirms a previously known X-ray cavity at $\sim$36 kpc south-east of the cluster centre and we report a new cavity at $\sim$42 kpc to the north-west. These cavities suggest that the AGN provides mechanical power of $\sim$$6.0 \times 10^{44}$ erg s$^{-1}$, sufficient to offset radiative cooling in the ICM. We also detect a sharp surface brightness edge at $\sim$72 kpc south-east of the centre, characterised by a temperature jump and pressure continuity, consistent with a cold front, likely caused by gas sloshing from a minor merger. Our uGMRT images reveals an interesting diffuse emission surrounding the brightest cluster galaxy (BCG), with its edge spatially coinciding with the sloshing cold front and roughly with the cooling radius. Furthermore, a low star formation rate and uniform metal abundance up to the sloshing edge are consistent with the earlier findings of suppression of star formation and metallicity homogenisation by mixing core gas through sloshing. Finally, the spatial correlation between the mini-halo and the observed X-ray features indicates that ICM sloshing, rather than AGN feedback, plays a dominant role in powering the proposed radio mini-halo emission.

To reproduce observed galaxy properties, cosmological simulations require that massive galaxies experience feedback from active galactic nuclei, which regulates star formation within those galaxies. However, the energetics and timescales of these feedback processes are poorly constrained. We combine optical, infrared, sub-millimeter and radio observations of the active galaxy VV 340a, hosting a low-power jet launched from a supermassive black hole at its center. We find that the jet undergoes precession, with a period of (8.2 $\pm~$5.5) $\times~$10$^5$ years, and drives an outflow of gas at a rate of 19.4 $\pm~$7.9 solar masses per year. The jet shocks the gas, producing highly ionized plasma extending several kiloparsecs from the nucleus. The outflow ejects sufficient gas from the galaxy to influence its star formation rate.

Massive stars are the key engines of the Universe. However, their evolution and thus their ionizing feedback are still not fully understood. One of the largest gaps in current stellar evolution calculations is the lack of a model for the mass ejections that occur when the stars reach the Eddington limit, such as during an Luminous Blue Variable (LBV) phase. We aim to remedy this situation by providing a physically motivated and empirically calibrated method applicable in any 1D stellar evolution code to approximate the effect of such mass loss on stellar evolution. We employ the 1D stellar evolution code MESA, in which we implement a new mass-loss prescription that is acting when stellar models inflate too much when reaching the Eddington limit. Synthetic massive-star stellar populations using calculated grids of single-star models with this mass loss prescription are compared with the observed populations in the Large and Small Magellanic Clouds. In combination with already computed grids of binary evolution models, we investigate the impact of binarity on our predictions. Our single-star models reproduce key features of the observed stellar populations, namely (i) the absence of stars located beyond the Humphreys-Davidson limit, (ii) an upper limit of RSG luminosities, (iii) the faintest observed single WR stars, (iv) the absolute number of O-stars, WRs, and RSGs, (v) WO stars in low metallicity environments, and (vi) the positions of LBV stars in the HRD. Our binary population explains at the same time the 70% binary fraction of O-stars and the 40% binary fraction of WR stars. However, our synthetic population also has caveats, such as an overproduction of bright H-free WN stars. Our results show that the effect of Eddington-limit induced mass ejections on the structure and evolution of massive stars can remove tension between predicted and observed massive star populations.

We determine the future sensitivity of the TRIDENT neutrino telescope to dark matter annihilation in the Galactic Centre. By applying the full detector design we show that TRIDENT will probe annihilation rates down to $\langle\sigma v\rangle\approx5\times10^{-27}\,{\rm cm}^3\,{\rm s}^{-1}$ for a $10\,{\rm TeV}$ dark matter, which is below the thermal freeze-out benchmark. The analysis is carried out with all-flavour neutrino interactions, where we demonstrate that cascade events, primarily due to $\nu_{e,\tau}$, show greater sensitivity to a dark matter signal compared to the more commonly studied track events. Furthermore, we highlight the impact of a previously overlooked background, Galactic neutrinos produced from interactions between hadronic cosmic rays and interstellar gas. We find dark matter sensitivities are more strongly degraded in the high energy region above $\sim 10\, {\rm TeV}$, with a maximal weakening of approximately a factor of $\sim 2$. This effect remains smaller than the uncertainty associated with the dark matter density profile but can nonetheless mimic a positive annihilation signal. We contextualize these results with a concrete particle model and show that TRIDENT will be able to probe the most interesting untested parts of parameter space.

We confront the ghost-free non-local $F(R)$ gravity theories with the latest Atacama Cosmology Telescope (ACT) constraints on the spectral index of the scalar perturbations and the updated constraints of Planck/BICEP on the tensor-to-scalar ratio. After reviewing how the ghost-free non-local version of $F(R)$ gravity can be obtained, we show that the de Sitter solution can be obtained in this framework. Also, we show that the resulting theory can be cast in terms of an $F(R,\phi)$ theory of gravity. We analyze two models of non-local $F(R)$ gravity, one power-law and the $R^2$ model, and we show that both models can be compatible with the ACT and updated Planck/BICEP constraints.

We formulate a scalar realization of Sciama's Machian programme within the general Bergmann-Wagoner class of scalar--tensor gravity. Starting from a universally conformally coupled matter sector, we rewrite the field equations in terms of the invariant set $\{{\cal I}_1,{\cal I}_2,{\cal I}_3,\hat g_{\mu\nu}\}$, so that Machian requirements can be stated independently of conformal frame. Sciama's causal postulate is implemented not by modifying the local dynamics, but as a selection rule on the solution space of the invariant scalar equation: the admissible configuration is the retarded response to the matter distribution in the causal past, with any source-free contribution removed. In a spatially flat FLRW universe, and in the light, slowly varying regime, the prescription reduces to an explicit temporal kernel that links the background scalar evolution to the matter content within the Hubble region, reproducing the expected Machian scaling in an expanding background. Universal coupling to a single physical metric implies that structureless test bodies share the same acceleration in a given external configuration, so that the Eötvs parameter vanishes at leading order. Nonuniversal effects can arise only when gravitational binding energy contributes appreciably to the total mass, as in strongly self-gravitating objects. Thus, the theory implements a causal Machian determination of the cosmological inertial scale while remaining consistent with standard weak-field tests.

Repeated black-hole mergers in dense stellar clusters are a plausible mechanism to populate the predicted gap in black hole masses due to the pair-instability process. These hierarchical mergers carry distinct spin and tilt features relative to first-generation black holes, for which previous studies have found evidence at a population level by interpreting features in the effective inspiral spin domain. We introduce an astrophysically-motivated model in the joint space of effective inspiral and precessing spins, which captures the dominant spin dynamics expected for hierarchical mergers. We find decisive evidence both for a population transition above $\sim 45M_\odot$, consistent with the anticipated onset of the pair-instability gap, as well as a peak at $\sim 15 M_\odot$, which we interpret as the global peak in the hierarchical merger rate. The existence of low- and high-mass subpopulations of higher-generation black holes suggests the contribution of both near-solar-metallicity and metal-poor star clusters to the hierarchical merger population. Our results reinforce the growing evidence for detailed, mass-dependent substructure in the spin distribution of the binary black hole population.

What flavour structure of $t$-channel thermal dark matter remains compatible with current flavour physics and direct detection bounds? We broadly chart the space of hypotheses using the framework of flavour symmetries and their breaking patterns. We then focus on scenarios in which the fermionic dark matter and its scalar mediator are flavour singlets, falling into the class of rank-1 flavour violation. For two representative benchmarks, quarkphilic ($q_L$) and leptophilic ($e_R$), we perform a comprehensive phenomenological analysis, fitting the relic abundance and examining the interplay among flavour observables, direct detection, and collider searches. Our results quantify the allowed deviations from flavour-symmetric limits and assess the discovery prospects in future flavour and direct detection experiments.

We investigate the behavior of curvature invariants for a large ensemble of neutron stars built with equations of state (EOSs) that satisfy constraints from nuclear theory and perturbative QCD, as well as measurements of neutron-star masses, radii, and gravitational waves from binary neutron-star mergers. Surprisingly, our analysis reveals that stars with negative Ricci scalar $\mathcal{R}$ are rather common and about $\sim 50\%$ of our EOSs produce one or more stars with Ricci curvature that is negative somewhere inside the star. The negative curvature is found mostly but not exclusively at the highest densities and pressures, and predominantly for stiff EOSs and for the most compact and most massive stars. Furthermore, we improve the quasi-universal relation between the stellar gravitational mass $M$ and the baryonic mass $M_\mathrm{b}$, which allows us to express analytically one in terms of the other with a maximum variance of only $\sim 3\%$. Finally, using the relation between the Ricci scalar and the trace anomaly $\Delta$, we determine the conditions under which $\Delta$ vanishes or becomes negative in neutron stars.

The physical origin of 'anomalous' resistivity in magnetic reconnection remains one of the longest-standing problems in space plasma physics. While the empirical Bohm diffusion scaling ($\eta~\propto~T/B$) is widely invoked to explain fast reconnection rates, it lacks a rigorous derivation from first principles. Here, we derive this scaling by modeling the magnetized electron fluid as an overdamped spintronic condensate governed by the Landau-Lifshitz-Gilbert equation. We demonstrate that the breakdown of the "frozen-in" condition is rigorously identified as an Adler-Ohmic bifurcation: a topological phase transition where electron gyro-axes lose synchronization with the magnetic field. By rigorously mapping the breakdown of adiabatic invariance to electron gyro axis slippage on the unit sphere, we show that the resulting resistivity naturally saturates at the Bohm limit. Numerical simulations of the $XY$ universality class confirm that the onset of this resistive state is explosive, following a logistic trigger consistent with the impulsive phase of solar flares. Furthermore, the topological defects in the condensate decay via a $t^{-0.75}$ power law, identifying magnetic island coalescence as the mechanism of anomalous transport. These results suggest that Bohm resistivity is a universal topological property of magnetized matter at the critical point of reconnection.

Three-nucleon force (3NF) plays an important role in understanding the structure of finite nuclei and the saturation properties of infinite nuclear matter. The chiral 3NF derived from the chiral effective field theory has been successful in $\textit{ab initio}$ studies of atomic nuclei. However, challenges remain, such as parameterizing low-energy constants and applying regulators. Most of established chiral nuclear forces have a nonlocal form in the momentum space. In this work, we construct local and hybrid local-nonlocal chiral 3NFs for the newly established Idaho local position-space two-nucleon potential, and calculate binding energies and radii of nuclei up to $^{132}$Sn. The two low-energy constants of 3NF are constrained by the ground-state energies of $^3$H and $^{16}$O, as suggested in a recent work. The chiral Hamiltonian obtained with the local-nonlocal regulator can simultaneously reproduce the experimental ground-state energies and charge radii of nuclei over a large range from $^4$He to $^{132}$Sn.

Context. Observations by Parker Solar Probe (PSP) of electrostatic waves suggest that electrostatic instabilities, including the ion-ion-acoustic instability (IIAI) frequently observed in the inner heliosphere, play an important role in plasma heating and particle acceleration. Aims. Our aim is to explore the application of single spacecraft diagnostics to the IIAI, in anticipation of application to the current missions operating in the inner heliosphere, e.g. PSP and Solar Orbiter. Methods. We apply the field-particle correlation (FPC) technique to fully kinetic simulations of IIAI. We characterize the conversion of energy between the electric field and particle species, allowing the differentiation between oscillatory and secular energy transfer to and from the particles and highlighting the role of resonant energy exchange. We then identify the characteristic IIAI signatures for the proton and electron distributions, and relate them to our previous knowledge of IIAI onset and energy exchange mechanisms. Results. Applying the FPC technique to our simulations run in parameters regime compatible with solar wind conditions, we have identified IIAI signatures that would enable efficient recognition of IIAI in observations. This task is left for future missions, since the time scale over which IIAI signatures develop is too fast for the sampling rates of current missions.