Papers for Wednesday, Nov 19 2025

The origin of the Universe and its material content remains one of the most fundamental questions in science. Gamma-ray bursts (GRBs), with their extreme luminosities and high-redshift detectability, provide a unique window into the history of cosmic formation and chemical evolution. Consequently, the GRB formation rate (FR) has been employed to trace the star formation rate (SFR) across cosmic time. GRBs are conventionally classified into long and short categories (lGRBs and sGRBs) based on their $ T_{90} $ duration. sGRBs are widely employed as tracers of the delayed SFR, owing to their origin linked to the inspiral timescales of compact binary systems. However, some studies suggest that the detection of supernova-associated sGRBs may indicate potential contamination by core-collapse events. In this work, we move beyond the $ T_{90} $ classification and focus exclusively on GRBs with confirmed kilonova signatures, which provide unambiguous evidence of binary compact star mergers, to reassess their connection with the delayed SFR. Through analysis of a kilonova-associated GRB (KN/GRBs) sample, we find that even within this robust subset, the KN/GRB FR displays a trend contrary to that of the delayed SFR at low redshifts ($ z < 1 $). This result challenges the conventional theory by indicating that low-redshift KN/GRBs may not accurately trace the delayed SFR, independent of core-collapse contamination, while further validation with larger KN/GRB samples is essential to determine the reliability of compact binary mergers as probes of delayed SFR.

Cosmic ray (CR) electrons are key tracers of non-thermal processes in galaxies, yet their spectra are often modelled under the untested assumption of steady state between injection and cooling. In this work, we present a time-dependent modelling of CR electron spectra in a galactic context using the CREST code, applied to magnetohydrodynamical simulations of an isolated Milky Way-mass galaxy performed with AREPO. CR electrons are injected at supernova sites and evolved with adiabatic changes and cooling processes on Lagrangian tracer particles, including losses from synchrotron, inverse Compton, bremsstrahlung, and Coulomb interactions. We compare these fully time-dependent spectra to local and global steady-state models computed with CRAYON+, as well as to one-zone analytic steady-state solutions. We find that the global CR electron spectrum in the simulated galactic disk closely resembles a steady-state solution up to energies of 500 GeV, with deviations only at higher energies where cooling times become shorter than injection timescales. High-energy electrons are dominated by recently injected populations that have not yet reached equilibrium, however, producing a steeper spectrum and lower normalisation than a steady-state model predicts. Spatially, the electrons modelled on-the-fly with CREST are more confined to the star-forming disk, in contrast to the more extended distributions from steady-state post-processing models. Our results demonstrate that while steady-state assumptions capture the bulk CR electron population in star-forming disks, a time-dependent treatment is essential to describe the high-energy and outflowing components.

To examine how AGN feedback shapes the intracluster medium (ICM) and fuels black hole accretion in the cool-core galaxy cluster Abell 2597, we present deep ($\sim$600 ks) Chandra X-ray observations complemented by archival GMRT radio and SINFONI near-infrared data. Radio-mode AGN activity has inflated seven X-ray cavities and driven one to three potential weak shocks ($M \sim 1.05-1.14$) extending to $\sim 150$ kpc, suggesting recurrent outbursts occurring on $\sim 10^7$ year timescales. We also detect a narrow, $\sim$57 kpc X-ray surface brightness deficit-a potential plasma depletion layer-likely shaped by residual sloshing motions that amplified magnetic fields and/or displaced gas within the cluster core. Although the AGN injects $\sim 10^{44}$ erg s$^{-1}$ of energy, comparable to the cluster's cooling luminosity, radiative cooling persists at $\sim$15 M$_{\odot} $yr$^{-1}$, replenishing the billion solar mass cold gas reservoir at the heart of the brightest cluster galaxy. Sustaining this level of activity requires a continuous fuel supply, yet the estimated Bondi accretion power ($\sim 2 \times 10^{43}$ erg s$^{-1}$) falls an order of magnitude short of the observed cavity power, suggesting that "hot" gas fueling is insufficient. Instead, archival ALMA observations continue to support a chaotic cold accretion scenario, where turbulence-driven condensation fuels the AGN at rates exceeding Bondi accretion, sustaining a self-regulated feedback cycle that repeatedly shapes the core of Abell 2597.

The recent binary black hole (BH) merger GW231123, with both components likely in the high-mass gap and with high spins, challenges standard BH binary formation models. It is usually thought that the BHs are of second (or higher) generation (2G), resulting from the mergers of smaller BHs. But the physical processes that produce the merging 2G BH binaries are unclear and highly unconstrained. We show that such 2G mergers can be naturally produced in the nuclear star cluster of Milky Way-like galaxy. The dominant channel combines a sequence of binary-single interactions with secular evolution driven by the central supermassive BH. Our model produces a merger rate consistent with GW231123 and further predicts an abundant population of 2G BH-star (or low-mass BH) binaries; these binaries may observationally manifest as micro tidal disruption events or low-frequency gravitational-wave (GW) sources. Detecting these binaries would provide crucial insights into the dynamical pathways of hierarchical BH assembly.

Deconstructing galaxies through two-dimensional decompositions has been shown to be a powerful technique to derive the physical properties of stellar structures in galaxies. However, most studies employ fitting algorithms that are prone to be trapped in local minima, or involve subjective choices. Furthermore, when applied on samples beyond the nearby Universe, results on the fraction of classical bulges in disc galaxies do not agree with studies on nearby galaxies. The latter studies point to a small fraction of classical bulges, possibly challenging our merger-driven picture of galaxy formation. Therefore, understanding the discrepancy between observations in and beyond the nearby Universe is of paramount importance. In this paper, I use a sample of 16 nearby galaxies drawn from the TIMER project, which previously have been shown to not host classical bulges, and perform decompositions applying different methodologies and employing the original images as well as artificially redshifted images. I show that the Differential Evolution algorithm is able to provide accurate measurements of structural properties with little subjective intervention, correctly indicating the presence of nuclear discs (not classical bulges). However, I also show that when the physical spatial resolution is not adequate, a systematic overestimation of the photometric bulge Sérsic index leads to the false conclusion of the presence of classical bulges. I discuss how this may be the root cause of the discrepancy mentioned above, and point out how this issue may be a problem even with data from facilities such as Euclid, HST and JWST.

We present Aletheia, a new emulator of the non-linear matter power spectrum, $P(k)$, built upon the evolution mapping framework. This framework addresses the limitations of traditional emulation by focusing on $h$-independent cosmological parameters, which can be separated into those defining the linear power spectrum shape ($\mathbf{\Theta}_{\mathrm{s}}$) and those affecting only its amplitude evolution ($\mathbf{\Theta}_{\mathrm{e}}$). The combined impact of evolution parameters and redshift is compressed into a single amplitude parameter, $\sigma_{12}$. Aletheia uses a two-stage Gaussian Process emulation: a primary emulator predicts the non-linear boost factor as a function of ($\mathbf{\Theta}_{\mathrm{s}}$) and $\sigma_{12}$ for fixed evolution parameters, while a second one applies a small linear correction based on the integrated growth history. The emulator is trained on shape parameters spanning $\pm$5$\sigma$ of Planck constraints and a wide clustering range $0.2 < \sigma_{12} < 1.0$, providing predictions for $0.006\,{\rm Mpc}^{-1} < k < 2\,{\rm Mpc}^{-1}$. We validate Aletheia against N-body simulations, demonstrating sub-percent accuracy. When tested on a suite of dynamic dark energy models, the full emulator's predictions show a variance of approximately 0.2%, a factor of five smaller than that of the state-of-the-art EuclidEmulator2 (around 1% variance). Furthermore, Aletheia maintains sub-percent accuracy for the best-fit dynamic dark energy cosmology from recent DESI data, a model whose parameters lie outside the training ranges of most conventional emulators. This demonstrates the power of the evolution mapping approach, providing a robust and extensible tool for precision cosmology.

We investigate how the obscured IR-derived and the dust-corrected UV star formation rate functions (SFRFs) compare with each other, and with predictions from state-of-the-art theoretical models of galaxy formation and evolution. We derive the IR-SFRF from the ALMA A$^3$COSMOS survey, by converting the IR luminosity functions (IR-LFs) into SFRF after correcting for AGN contribution. Similarly, we obtain the UV SFRFs from literature UV LFs, corrected for dust-extinction. First, we fit the two SFRFs independently via a MCMC approach, then we combine them to obtain the first estimate of the total SFRF out to $z \sim 6$. Finally, we compare this SFRF with the predictions of a set of theoretical models. We derived the UV (dust-extinction corrected, from literature UV-LFs) and IR SFRFs (from Herschel and ALMA IR-LFs) at $0.5 < z < 6$ , finding that they are mostly complementary, covering different ranges in star formation rate (SFR$ < 10-100$ M$_{\odot}$yr$^{-1}$ for the UV-corrected and SFR$ > 100$ M$_{\odot}$yr$^{-1}$ for the IR). From the comparison of the total SFRF with model predictions we find an overall good agreement at $z < 2.5$, with increasing difference at higher redshifts, with all models missing the galaxies that are forming stars with the highest SFRs. We finally obtained the UV (dust-corrected), IR and total star formation rate densities (SFRDs), finding that there are no redshift ranges where UV and IR alone are able to reproduce the whole total SFRD.

The first explorations of temperate sub-Neptune exoplanets have been the hallmark of early JWST observations. The bulk properties of such planets are consistent with a range of possible internal structures, which can be distinguished through their interactions with the observable atmospheres. JWST observations of TOI-270 d, a temperate sub-Neptune, have previously led to contrasting conclusions: either a Hycean world, possessing a liquid water ocean, or a mixed-envelope sub-Neptune, where high temperatures prevent a liquid ocean and lead to a high mean molecular weight atmosphere. In order to resolve this uncertainty, we present a comprehensive retrieval analysis of TOI-270 d using recent NIRISS and NIRSpec transit spectroscopy across $\sim$1-5 $\mu$m. We find that prior inferences of a mixed envelope were affected by specific modelling choices leading to a high terminator temperature and high mean-molecular weight in the atmosphere. We confirm an H$_2$-rich atmosphere in TOI-270 d and present revised constraints on the molecular log-mixing ratios and maximal detection significances of CH$_4$ at $-1.86^{+0.30}_{-0.29}$ (6.4 $\sigma$), CO$_2$ at $-1.71^{+0.38}_{-0.66}$ (3.9 $\sigma$), H$_2$O at $-1.88^{+0.78}_{-4.13}$ (2.1 $\sigma$) and CS$_2$ at $-4.74^{+0.65}_{-1.10}$ (2.0 $\sigma$), with a terminator temperature of $323^{+58}_{-52}$ K at 10 mbar. We also find tentative evidence for more complex methyl-bearing species such as C$_2$H$_6$ and/or DMS at a 2.1-2.5 $\sigma$ level. The present constraints are consistent with TOI-270 d being a Hycean or dark Hycean world, with planet-wide or nightside liquid water oceans. However, more observations are required to verify the present findings and robustly constrain the atmospheric conditions and internal structure of TOI-270 d.

Observations have shown that planets similar to Neptune are rarely found orbiting Sun-like stars with periods up to ~4 days, defining the so-called Neptune desert region. Therefore, the detection of each individual planet in this region holds a high value, providing detailed insights into how such a population came to form and evolve. Here we report the detection of TOI-333b, a Neptune desert planet with a mass, radius, and bulk density of 20.1 $\pm$ 2.4 M$_{\oplus}$, 4.26 $\pm$ 0.11 R$_{\oplus}$, and 1.42 $\pm$ 0.21 \gccc, respectively. The planet orbits a F7V star every 3.78 d, whose mass, radius and effective temperature are of 1.2 $\pm$ 0.1 \msun, 1.10 $\pm$ 0.03 \rsun, and 6241$^{+73}_{-62}$ K, respectively. TOI-333b is likely younger than 1 Gyr, which is supported by the presence of the doublet Li line around 6707.856 textup{~Å} and its comparison to Li abundances in open clusters with well constrained ages. The planet is expected to host only 8.5$^{+10.9}_{-8.3}\%$ gas-to-core mass ratio for a H/He envelope. On the other hand, irradiated ocean world models predict 20$^{+11}_{-10}\%$ H$_2$O mass fraction with a core fraction of 35$^{+20}_{-23}\%$. Therefore, we expect that TOI-333b internal composition may be dominated by a pure rocky composition with almost no H/He envelope, or a rocky world with almost equal mass fraction of water. Finally, TOI-333b is more massive and larger than 77$\%$ and 82$\%$ of its Neptune desert counterparts, respectively, while its host ranks among the hottest known for Neptune Desert planets, making this system a unique laboratory to study the evolution of such planets around hot stars.

Dust-continuum observations of many protoplanetary disks reveal rings and gaps that are widely interpreted as evidence of ongoing planet formation. Here we present the first framework for inferring planet and disk parameters from such images using variational autoencoder (VAE) based generative machine learning (ML). The new framework is called VADER (Variational Autoencoder for Disks with Embedded Rings). We train VADER on synthetic images of dust continuum emission, generated from \texttt{FARGO3D} hydrodynamic simulations post-processed with Monte Carlo radiative transfer calculations. VADER infers the masses of up to three embedded planets as well as the disk parameters viscous $\alpha$, dust-to-gas ratio, Stokes number, and flaring index. VADER returns a full posterior distribution for each of these quantities. We demonstrate that VADER reconstructs disk morphologies with high structural similarity (index $>$ 0.99), accurately recovers planet parameters with $R^2 > 0.9$ across planet masses, and reliably predicts disk parameters. Applied to ALMA dust continuum images of 23 protoplanetary disks, our model returns mass estimates for embedded planets of 0.3-2~$M_{\mathrm{Jup}}$ that agree to within $1\sigma$ of published values in most cases, and infers disk parameters consistent with current literature. Once trained, the VAE performs full posterior parameter inference in a matter of minutes, offering statistical rigor with enough computational speed for application to large-scale ALMA surveys. These results establish VAE-based models as powerful tools for inferring from disk structure the masses of embedded planets and the global disk parameters, with their associated uncertainties.

Infrared-luminous galaxies are important sites of stellar and black hole mass assembly at most redshifts. Their luminosities are often estimated by fitting spectral energy distribution (SED) models to near- to far-infrared data, but the dependence of these estimates on the data used is not well-understood. Here, using observations simulated from a well-studied local sample, we compare the effects of wavelength coverage, signal-to-noise (S/N), flux calibration, angular resolution, and redshift on the recovery of starburst, AGN, and host luminosities. We show that the most important factors are wavelength coverage that spans the peak in a SED, with dense wavelength sampling. Such observations recover starburst and AGN infrared luminosities with systematic bias below $20\%$. Starburst luminosities are best recovered with far-infrared observations while AGN luminosities are best recovered with near- and mid-infrared observations, though the recovery of both are enhanced with near/mid-infrared, and far-infrared observations, respectively. Host luminosities are best recovered with near/far-infrared observations, but are usually biased low, by $\gtrsim20\%$. The recovery of starburst and AGN luminosity is enhanced by observing at high angular resolution. Starburst-dominated systems show more biased recovery of luminosities than do AGN-dominated systems. As redshift increases, far-infrared observations become more capable, and mid-infrared observations less capable, at recovering luminosities. Our results highlight the transformative power of a far-infrared instrument with dense wavelength coverage from tens to hundreds of microns for studying infrared-luminous galaxies. We tabulate estimates of systematic bias and random error for use with JWST and other observatories.

Detection and analysis of the cosmic 21 cm signal of neutral hydrogen has long been considered the most promising route towards exploration of the Epoch of Reionization (EoR). 21CMMC, a Markov Chain Monte Carlo sampler of the semi-numerical simulation code 21cmFAST, has already been used in conjunction with published upper limits on the 21 cm signal from the Murchison Widefield Array (MWA), the LOw Frequency ARray (LOFAR), and the Hydrogen Epoch of Reionization Array (HERA) to constrain the astrophysics of the EoR. Here we investigate the extent to which analysis of the EoR performed using 21CMMC is dependent on the underlying semi-numerical model. We used 21cmFAST to simulate two datasets of 21 cm light-cones which differ only in the algorithm used to identify ionized regions (the so-called "bubble-finding" algorithm). We then tested 21CMMC's ability to return key astrophysical parameters when using the different bubble-finding algorithms. We find that the performance of 21CMMC depends sensitively on the agreement between the astrophysical model of our mock data and the model used for sampling. This result has important implications for the analysis of the 21 cm signal performed using 21CMMC and further motivates investigation into model-independent analysis techniques for 21 cm EoR data.

Magnetars are the leading candidate sources of fast radio bursts (FRBs). However, the observational probes of the connections between magnetars and FRBs are severely limited by the paucity of detection of highly energetic radio events from magnetars -- to date, only one radio burst as energetic as FRBs has been detected from a Galactic magnetar. Here, we present a detailed analysis of a large sample of low-energy bursts detected from the magnetar XTE J1810$-$197, and probe their implications for FRB emission from magnetars. We report detection of over 97000 bright radio pulses from 242 observations of the magnetar XTE J1810$-$197 over 4.5 years and two decades in frequency (300 MHz to 6.15 GHz), using the Giant Meterwave Radio Telescope and the Green Bank Telescope, after its recent outburst onset in December 2018. We present detailed analysis of the burst fluence distributions and their trends with time as well as frequency, and the waiting time distribution. We show that XTE J1810$-$197 rapidly switches between pulsar-like and giant-pulse-like emission states, and magnetars like XTE J1810$-$197 remain viable and likely emitters of FRBs, in the form of giant-pulses with energies comparable to FRBs. We also demonstrate that the lack of the detection of an underlying periodicity in the bursts from repeating FRBs might be caused by emission across a wide range of spin phases.

A massive "dark companion"-such as an intermediate-mass black hole or other compact dark object-orbiting the supermassive black hole at the Galactic Center can dynamically reshape the surrounding dark-matter spike. Through gravitational heating and angular-momentum exchange, the companion excavates a "scoured" region that lowers the inner density and suppresses the expected annihilation signal. We quantify this effect by computing the suppression of the dark-matter annihilation $J$-factor induced by such a companion, combining an analytic scouring-radius model with full numerical integrations of the modified density profile. We scan the parameter space of companion mass, orbital separation, system age, and spike slope, explicitly including the interplay with the annihilation plateau. For canonical Gondolo-Silk spikes with $\gamma_{\rm sp} \gtrsim 2$, we find that the distribution is remarkably resilient and that the companion produces at most mild reductions of the $J$-factor. In contrast, for pre-heated or otherwise shallow spikes with $\gamma_{\rm sp} \lesssim 1.8$, even a modest $\sim 10^{4}\,M_\odot$ companion on a O(100) AU orbit and O(Gyr) age can suppress the annihilation flux by one to two orders of magnitude. The numerical results are accurately captured (typically at the $\lesssim 10\%$ level) by a simple fitting formula in terms of a dimensionless scouring parameter that measures the ratio between the scoured region and the annihilation core. Our findings demonstrate that neglecting a dark companion can lead to substantial overestimates of the Galactic Center $J$-factor, with direct consequences for interpreting gamma-ray, neutrino, and antimatter searches for annihilating dark matter.

We detect rapid downflows of 150-217 km/s in IRIS Si IV 1402.77 nm measurements of an X9-class solar flare on 2024 October 3rd. The fast redshift values persist for over 15 minutes from flare onset, and can be split into two distinct stages of behavior, suggesting that multiple mechanisms are responsible for the downwards acceleration of flare ribbon plasma. The first stage of rapid downflows are synchronized with peaks in emission from the Advanced Space-based Solar Observatory Hard X-ray Imager (ASO-S/HXI) and Large Yield Radiometer (LYRA) Lyman-alpha measurements, indicative that the chromospheric downflows (with a maximum redshift of 176 km/s) result from chromospheric condensations associated with impulsive energy release in the solar flare. Later in the event, strong Si IV flare ribbon downflows persist (to a maximum value of 217 km/s), despite the magnetic flux rate falling to zero, and high-energy HXR and Lyman-alpha measurements returning to background levels. This is reflective of downflows in the flare ribbon footpoints of flare-induced coronal rain. Hard X-ray spectral analysis supports this scenario, revealing strong non-thermal emission during the initial downflow stage, falling near background levels by the second stage. Despite these distinct and contrasting stages of ribbon behavior, Si IV Doppler velocities exhibit quasi-periodic pulsations with a constant ~50 s period across the 15-minute flare evolution (independently of loop length). We deduce that these pulsations are likely caused by MHD oscillations in the magnetic arcade. Finally, we utilize machine learning K-means clustering methods to quantify line profile variations during the stages of rapid downflows.

The generation of white noise on large scales is a generic property of the dynamics of physical systems described by local non-linear partial differential equations. Non-linearities prevent the small scale dynamics from being erased by smoothing. Unresolved small scale dynamics act as an uncorrelated (white or Poissonian) noise (seemingly stochastic but actually deterministic) contribution to large scale dynamics. This white noise exists even when the dynamics is very nearly linear. In cases where the power spectrum is sub-Poissonian on large scales, this noise will dominate on the largest scale power no matter the amplitude of the inhomogeneities. Such is the case in the standard model of cosmology, where the primordial density power spectrum is expected to have an almost Harrison-Zel'dovich, $P[k]\sim k$, spectrum on a much broader range of scales than can be observed. Even though linear gravitational evolution dominates non-linear corrections by a factor $\sim10^5$, the non-observation of white noise on the Hubble scale precludes the extrapolation of this power law below the comoving $1\,$pc scale. More generally, observation or non-observation of large scale white noise provides a powerful probe of the universe on very small scales in the early early universe. Gravitational radiation, phase transitions, vorticity, and running of the spectral index are all phenomena that can be probed with large scale white noise. Large scale white noise is a non-optional feature of all cosmological models but one which has not heretofore been appreciated.

The KM3NeT collaboration has reported the detection of the highest energy neutrino event observed to date. The energy of the event is of the order of 220 PeV hinting towards a neutrino flux at the highest energies. In this article, the potential blazar origin for this event is explored. The publicly available Astro-Multimessenger Modeling software is used to model the blazar gamma-ray and neutrino fluxes. It is concluded that a population of blazars could produce the diffuse flux compatible with the observation of the ultra-high energy event detected by the KM3NeT/ARCA detector. At the same time, the gamma-ray flux produced by such a population of blazars is consistent with the diffuse gamma-ray flux measured by the Fermi Large Area Telescope.

Chemistry in diffuse molecular clouds relies primarily on rapid ion-molecule reactions. Formation of the initial ions, H$^+$ and H$_2^+$, is dominated by cosmic-ray ionization of H and H$_2$, making the cosmic-ray ionization rate (denoted $\zeta({\rm X})$ for species X) an important parameter for chemical modeling. We have made observations targeting absorption lines of H$_3^+$, one of the most reliable tracers of $\zeta({\rm H_2})$, toward diffuse molecular cloud sight lines where the H$_2$ column density has been directly measured in the ultraviolet, detecting H$_3^+$ in 12 out of 27 sight lines. The 3D-PDR modeling method introduced by Obolentseva et al. (2024) was used to infer cosmic-ray ionization rates in the clouds along these sight lines, and our combined sample has a mean ionization rate of $5.3\times10^{-17}$ s$^{-1}$ with standard deviation $2.5\times10^{-17}$ s$^{-1}$. By associating H$_3^+$ absorption with gas density peaks derived from the differential extinction maps of Edenhofer et al. (2024) we have constructed a sparsely sampled 3D map of the cosmic-ray ionization rate in targeted regions within about 1~kpc of the Sun. Specific regions show reasonably uniform ionization rates over length scales of tens of parsecs, with the average ionization rate in each region being different. Large differences (factor of 5) in $\zeta({\rm H_2})$ are found over length scales of about 100 pc. This supports a picture where the cosmic-ray ionization rate varies smoothly over small size scales, but is not uniform everywhere in the Galactic disk, likely being controlled by proximity to particle acceleration sites.

Ultra Fast Outflows (UFOs) are powerful, highly ionized winds launched from the innermost regions of Active Galactic Nuclei (AGNs), reaching velocities of 0.03 -- 0.3 c and playing a key role in AGN feedback. We present a photoionization analysis of an 18 ks \xmm\ snapshot of the Seyfert 1 AGN Mrk 877, revealing three distinct UFO components with line-of-sight velocities of $0.10^{+0.005}_{-0.005}~c$ , $ 0.04^{+0.005}_{-0.004}~c$ , and $0.05^{+0.005}_{-0.004}~c$. These components span a broad range of ionization parameters and column densities, producing absorption features across both soft and hard X-ray bands. Even under the most conservative assumption for the volume filling factor, the fastest component exceeds $5\%$ of the Eddington luminosity, making it capable of driving strong galaxy-scale feedback. The soft X-ray UFO component, despite its lower ionization, shares a similar velocity as a higher-ionization component, hinting at a two-phase medium likely shaped by clumpiness or interactions with ambient material. The density profile inferred from the Absorption Measurement Distributions (AMD) and the positive trend between outflow momentum rate and radiation momentum flux suggest that wind is powered by a combination of radiative and magnetic driving.

In this work we introduce the concept of self-interacting dark matter with scale-dependent equation of state, in the context of which dark matter is collisional and its equation of state is radius-dependent and has the form $P(r)=K(r)\left(\frac{\rho(r)}{\rho_{\star}}\right)^{\gamma(r)}$. We confronted the effectively 2-parameter model with 174 galaxies from the SPARC data, and we found that the rotation curves of 100 galaxies can be perfectly fitted by the model. These galaxies are dark matter dominated, mostly dwarfs, low-luminosity and low-surface-brightness spiral galaxies. We demonstrate that scale-dependent self-interacting dark matter solves the cusp-core issue for dark matter dominated galaxies. More importantly, the structure of the scale-dependent SIDM model produces in a semi-theoretically and semi-empirically way the canonical Tully-Fisher and the baryonic Tully-Fisher relations when these 100 viable dwarfs, low-surface-brightness and low-luminosity galaxies are taken into account. The behavior of the entropy function $K(r)$ is assumed to be $K(r)=K_0\times\left(1+\frac{r}{r_c}\right)^{-p}$. The perfect fits of the rotation curves come for a nearly isothermal and virialized dark matter halo, which naturally predicts the correlation $K_0\sim V_{\mathrm{max}}^2$. This correlation holds true empirically as confirmed by the data and we also find empirically $L\sim K_0^2$ from the data, thus the canonical Tully-Fisher relation is reproduced semi-theoretically and semi-empirically. We perform the same task and we find theoretically, for dark matter dominated galaxies, that $K_0\sim V_{\mathrm{flat}}^2$ which is also confirmed empirically from the data, along with the correlation $K_0\sim M_b^{0.5}$, hence the baryonic Tully-Fisher law naturally emerges in a semi-theoretical and semi-empirical manner.

The homogeneity scale, $R_{\rm H}$, offers a fundamental test of the Cosmological Principle, yet it has not yet been measured with 21cm intensity mapping surveys. A key limitation for such a measurement is the telescope beam, which artificially smooths the observed signal. We quantify this effect using the two-point correlation function and the correlation dimension, $\mathcal{D}_2(r)$, to model how beam convolution suppresses intrinsic clustering. For any given redshift $z$, we identify a maximum beam width, $\sigma_{\rm max}(z)$, beyond which the homogeneity scale cannot be recovered. This limit defines an inaccessible region in the $\sigma \times z$ parameter space, where $R_{\rm H}$ is erased by beam smoothing. Applying this framework to several current and upcoming radio telescopes, we assess their ability to probe $R_{\rm H}$. Our results provide the first quantitative forecast of the instrumental requirements for measuring the cosmic homogeneity scale with 21cm IM, and establish a theoretical basis for future observational applications.

The Ice Giants Study was commissioned by NASA to take a fresh look (as of 2017) at science priorities and concepts for missions to the Uranus and Neptune systems in preparation for the third Planetary Science Decadal Survey. This study was led by a Science Definition Team (SDT) and the Jet Propulsion Laboratory (JPL) with participation from Langley Research Center, Ames Research Center, The Aerospace Corporation, Purdue University, and the European Space Agency. The SDT was appointed by NASA and co-chaired by Mark Hofstadter (JPL) and Amy Simon (Goddard Space Flight Center). The Study Manager was Kim Reh (JPL) and the Study Lead was John Elliott (JPL). The study team assessed and prioritized science objectives taking into account advances since the last Decadal Survey, current and emerging technologies, mission implementation techniques and celestial mechanics. This study examined a wide range of mission architectures, flight elements, and instruments. Six of the prioritized concepts were studied via JPL's Team X process and resulting cost estimates were subjected to independent assessment by The Aerospace Corporation. Results presented herein show that high-value flagship-class mission concepts to either Uranus or Neptune are achievable within ground rule budgetary constraints.

Delayed radio emission has been associated with a growing proportion of tidal disruption events (TDEs). For many events, the radio synchrotron emission is inferred to originate from the interaction of mildly-relativistic outflows, launched with delay times of $\sim 100$--$1000$ d after the TDE optical peak. The mechanism behind these outflows remains uncertain, but may relate to instabilities or state transitions in the accretion disk formed from the TDE. We model the radio emission powered by the collision of mass outflows ("flares") from TDE accretion disks, considering scenarios in which two successive disk flares collide with each other, as well as collisions between the outflow and the circumnuclear medium (CNM). For flare masses of $\sim 0.01$-$0.1 M_{\odot}$, varied CNM densities, and different time intervals between ejected flares, we demonstrate that the shocks formed by the collisions have velocities $0.05c$-$0.3c$ at $\sim 10^{17}$ cm and power bright radio emission of $L_{\nu} \sim 10^{27}$-$10^{30}$ erg s$^{-1}$ Hz$^{-1}$, consistent with the properties inferred for observed events. We quantify how the typical peak timescale and flux varies for different properties of our models, and compare our model predictions to a selection of TDEs with delayed radio emission. Our models successfully reproduce the light curves and SEDs for several events, supporting the idea that delayed outflows from disk instabilities and state transitions can power late-time radio emission in TDEs.

White dwarfs which explode by the double-detonation mechanism may have a binary white dwarf donor which is subsequently ignited by its collision with the ejecta. This results in the destruction of the donor via either the triple- or quadruple-detonation mechanism, adding significant mass to the resulting ejecta as well as modifying its structure and composition. We simulate the evolution of supernova remnants resulting from such detonations in a variety of binary progenitors and compare them against a double detonation with a surviving donor. Because of the time delay between the detonations of the two white dwarfs, high-velocity ejecta from the first explosion governs the first few centuries of remnant evolution, whereas at later times the dense core resulting from the donor detonation drives both the forward and reverse shocks to larger radii. The collision between the highest-velocity ejecta of the primary explosion and the donor carves a conical wake into the ejecta, which persists into the remnant phase regardless of whether or not the donor detonates. Our suite of simulated remnants are found to exhibit multiple distinguishing features of the explosion properties: a distinct X-ray morphology in the thermal emission and iron lines for triple detonations and smaller remnants with centrally-concentrated emission for double detonations. The remnants are also varied in their elemental abundances and distributions, particularly for lighter elements, but these have limited observational utility and are sensitive to the properties of the progenitor binary.

The Moon-forming giant impact significantly influenced the initial thermal state of Earth's mantle by generating a global magma ocean, marking the onset of mantle evolution. Recent Smoothed Particle Hydrodynamics (SPH) simulations indicate that such a collision would produce a superheated core, whose cooling would strongly influence subsequent mantle dynamics. Here, we present systematic SPH simulations of diverse giant-impact scenarios and show that the superheated core formed after the impact can trigger secondary mantle melting, thereby governing the final state of the magma ocean. To further quantify this effect, we employ a parameterized mantle-melting model to evaluate the influence of secondary melting on the lower mantle. Our results suggest three possible outcomes: complete mantle melting, the formation of a basal melt layer, or the initiation of an early superplume. Combined with recent two-phase magma-ocean solidification models, we infer that all three scenarios would result in basal melt layers of varying thickness, partially retaining the thermal energy of the superheated core. In the canonical Moon-forming scenario, the superheated core would rapidly transfer heat to Earth's lower mantle, causing secondary mantle melting within approximately 277--5983 years and generating either a basal melt layer or a fully molten mantle. Both outcomes would effectively erase primordial heterogeneities in the lower mantle and impose distinct pathways for its subsequent thermal evolution.

Coronal holes (CHs) are low-activity, low-density solar coronal regions with open magnetic field lines (Cranmer 2009). In the extreme ultraviolet (EUV) spectrum, CHs appear as dark patches. Using daily hand-drawn maps from the Space Weather Prediction Center (SWPC), we developed a semi-automated pipeline to digitize the SWPC maps into binary segmentation masks. The resulting masks constitute the CHASM-SWPC dataset, a high-quality dataset to train and test automated CH detection models, which is released with this paper. We developed CHASM (Coronal Hole Annotation using Semi-automatic Methods), a software tool for semi-automatic annotation that enables users to rapidly and accurately annotate SWPC maps. The CHASM tool enabled us to annotate 1,111 CH masks, comprising the CHASM-SWPC-1111 dataset. We then trained multiple CHRONNOS (Coronal Hole RecOgnition Neural Network Over multi-Spectral-data) architecture (Jarolim et al. 2021) neural networks using the CHASM-SWPC dataset and compared their performance. Training the CHRONNOS neural network on these data achieved an accuracy of 0.9805, a True Skill Statistic (TSS) of 0.6807, and an intersection-over-union (IoU) of 0.5668, which is higher than the original pretrained CHRONNOS model Jarolim et al. (2021) achieved an accuracy of 0.9708, a TSS of 0.6749, and an IoU of 0.4805, when evaluated on the CHASM-SWPC-1111 test set.

Solar active region 11283 produced an X2.1 flare associated with a solar eruption on September 6, 2011. Observations revealed a preflare sigmoidal structure and a circular flare ribbon surrounding the typical two ribbon structure, along with remote brightenings located at a considerable distance from the main flare site. To interpret these observations in terms of the three dimensional (3D) coronal magnetic field dynamics, we conducted data constrained magnetohydrodynamic (MHD) simulations. Using a non linear force free field (NLFFF) as the initial condition, we reconstructed a realistic pre flare magnetic environment, capturing a sheared sigmoid above the polarity inversion line (PIL) surmounted by a fan spine structure. Our simulations revealed that reconnection between the sigmoidal field, the adjacent fan dome field lines, and the neighboring large loops facilitated the transfer of magnetic twist and led to the formation of a large magnetic flux rope (MFR). This transfer and propagation of twist are clearly visible throughout the MFR. As reconnection progresses, the entire fan spine structure expands along with the evolving MFR. A notable outcome of the simulation is that the footpoints of the newly formed MFR align closely with the observed circular flare ribbon and the remote brightening region. Our findings suggest that a large MFR formed during the X2.1 flare, providing a coherent explanation for the observed phenomena.

Solar flares effectively accelerate particles to non-thermal energies. These accelerated electrons are responsible for energy transport and subsequent emissions in HXR, radio, and UV/EUV radiation. Due to the steeply decreasing electron spectrum, the electron population and consequently the overall flare energetics, are predominantly influenced by low-energy non-thermal electrons. However, deducing the electron distribution in this energy-containing range remains a significant challenge. In this study, we apply the warm-target HXR emission model with kappa-form injected electrons to two well-observed GOES M-class flares. Moreover, we utilize EUV observations to constrain the flaring plasma properties, which enables us to determine the characteristics of accelerated electrons across a range from a few keV to tens of keV. We demonstrate that the warm-target model reliably constrains the properties of flare-associated electrons, even accounting for the uncertainties that had previously been unaddressed. The application of a kappa distribution for the accelerated electrons allows for meaningful comparisons with electron distributions inferred from EUV observations, specifically for energy ranges below the detection threshold of RHESSI. Our results indicate that the accelerated electrons constitute only a small fraction of the total electron population within the flaring region. Moreover, the physical parameters, such as electron escape time and acceleration time scale, inferred from both the warm-target model and the EUV observations further support the scenario in which electrons undergo thermalization within the corona. This study highlights the effectiveness of integrating the warm-target model with EUV observations to accurately characterize energy-containing electrons and their associated acceleration and transport processes.

This project presents the development and implementation of a compact spectrometer, named SPECTRUMMATE, tailored for small telescopes. Small telescopes offer several advantages: they are cost-effective, occupy less space, and are simpler to set up than larger instruments. This makes them particularly suitable for amateur astronomers and educational institutions with limited resources. Moreover, small telescopes can effectively observe bright celestial objects, enabling valuable contributions to astronomical projects. Based on the Sol'EX design, SPECTRUMMATE was constructed using optical components available at the Space and Applications Laboratory (SpaceLAB), University of Science and Technology of Hanoi, Vietnam. The instrument is designed to meet the specific needs of astronomers who require detailed analysis within the visible spectrum (SPECTRUMMATE can capture a waveband of 368 angstrom/image, spectral coverage from 4000 to 6600 angstrom, and resolving power R = 2546 at 5500 angstrom). To achieve optimal performance, the design process involved selecting and configuring optical elements, including a collimator, diffraction grating, and objective lens. Experimental setups were tested to minimize spectral dispersion while ensuring the system's compactness and ease of alignment. Spectra obtained by SPECTRUMMATE demonstrated efficient spectral calibration and the capability to capture high-resolution spectra of bright light sources, such as the Sun, making it a valuable tool for specialised spectroscopic observations. The modular design of SPECTRUMMATE also allows users to change its components easily to achieve the desired spectral range and resolution.

Shell burning and internal mixing in massive stars play an important role in setting the initial conditions for core-collapse supernova explosions. In the late stages of stellar evolution, intense shell burning can cause distinct convective regions to merge, fundamentally restructuring the stellar interior. Although such phenomena are difficult to observe directly, the observation of ``Mg-rich'' supernova remnants (SNRs) has recently emerged as a potential signature of these events. In this study, we reanalyze X-ray observations of J0550--6823, a SNR in the Large Magellanic Cloud (LMC) and a new candidate Mg-rich SNR. Our spectral analysis confirms a low Ne/Mg mass ratio of $\approx$1, and its classification as Mg-rich. By comparing the observational results with pre-supernova models, we suggest that the progenitor of J0550-6823 likely had an extended convective shell that reduces the Ne/Mg ratio prior to its explosion. Furthermore, we observe that $\sim$2--3 Mg-rich SNRs exist in the LMC, suggesting that $\lesssim$10--40\% of massive stars in the LMC may have had an extended convective shell, similar to what we observed in J0550-6823. This fraction would be important for understanding the final stages of the evolution of massive stars and galactic chemical evolution.

The assumption that photons are massless is a foundational postulate of modern physics, yet it remains subject to experimental verification. Fast radio bursts (FRBs), with their cosmological distances and precisely measured dispersion, offer an excellent laboratory for testing this hypothesis. In this work, we propose an improved distribution function for the dispersion measure arising from extragalactic gas and demonstrate that it provides an excellent fit to mock data. We then apply this distribution to constrain the photon rest mass under the $\Lambda$CDM, $w$CDM, and $w_{0}w_{a}$CDM cosmological models, the last of which is favored by recent DESI baryon acoustic oscillation observations. The corresponding 1$\sigma$ upper limits on the photon mass are found to be $4.83\times10^{-51}\,\mathrm{kg}$, $4.71\times10^{-51}\,\mathrm{kg}$, and $4.86\times10^{-51}\,\mathrm{kg}$, respectively, which are the most stringent constraints derived from FRBs to date. These results indicate that the choice of cosmological model has only a minor impact on photon-mass bounds, demonstrate that FRBs provide robust and reliable constraints, and offer strong empirical support for the massless nature of the photon.

We introduce the KPF SURFS-UP (Spectroscopy of the Upper-atmospheres and ReFractory Species in Ultra-hot Planets) Survey, a high-resolution survey to investigate the atmospheric composition and dynamics of a sample of ultra-hot Jupiters with the Keck Planet Finder (KPF). Due to the unique design of KPF, we developed a publicly available pipeline for KPF that performs blaze removal, continuum normalization, order stitching, science spectra combination, telluric correction, and atmospheric detection via cross-correlation. As a first demonstration, we applied this pipeline to a transit of WASP-76 b and achieved some of the highest signal-to-noise detections of refractory species in WASP-76 b to date (e.g., Fe I is detected at a SNR of 14.5). We confirm previous observations of an asymmetry in Fe I absorption, but find no measurable ingress-egress asymmetry in Na I and Ca II. Together, these results suggest variations within different layers of the atmosphere of WASP-76 b: neutral metals such as Fe I trace deeper regions with stronger asymmetries, while Na I and Ca II probe regions higher in the atmosphere where the ingress-egress asymmetries are weaker. These findings provide new insights into the complex atmosphere of WASP-76 b and highlight the power of using KPF for atmospheric characterization. More broadly, the KPF SURFS-UP Survey will observe a large sample of UHJs, using transmission, emission, and phase-resolved spectroscopy to characterize their refractory abundances, upper atmospheres, and 3D dynamics.

PSR J1951+2837 is a nearby pulsar with a period of 7.334 s and dispersion measure of DM = 2.9 $\pm$ 0.6 pc cm$^{-3}$, located about 200 or 300 pc from the Sun. It occasionally radiates bright pulses and has been observed by the Large Phased Array (LPA) radio telescope at 110 MHz and by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at 1250 MHz. We detected only 343 pulses in 228 LPA observation sessions and 5 bright pulses in two FAST sessions. Based on the times of arrival (TOAs) of these bright pulses, we determined the coherent timing solution for this pulsar at a frequency of 110 MHz. Based on flux densities (S) of these bright pulses at two frequencies ($\nu$), we found that it is probably one of the known pulsars with the lowest luminosities to date, with a spectral index of about $\alpha$ = (2.5 - 3.2) for S $\sim \nu^{-\alpha}$.

Magnetic monopoles are an inevitable feature of post-inflation symmetry-breaking phase transitions in grand unified theories. Analytic estimates of their density indicate that they are compatible with standard cosmology only if their mass is less than $10^{11}$ GeV. We initiate a programme of numerical studies of monopole dynamics by simulating a gas of 't Hooft-Polyakov monopoles formed by the Kibble mechanism after a phase transition. In this paper we simulate monopoles in a radiation background, but without interactions with the radiation, in order to resolve differences between analytical models. We find that during the radiation era, the monopoles find each other and annihilate efficiently enough to keep their density fraction constant, which supports the modelling of Zel'dovich and Khlopov and Preskill in the epoch when plasma interactions can be neglected. In the matter era the density fraction decreases logarithmically. Further work is needed to quantify the effect of the thermal bath, which is expected to reduce the annihilation rate at later times.

We use the first eROSITA all-sky survey (eRASS1) to investigate the contributions of AGN and extended gas to the total X-ray luminosity ($L_X$) of galaxy groups with different halo masses ($M_h$) at different redshifts. The presence of AGN in their central galaxies is identified using multi-wavelength catalogs, including the X-ray counterparts, the ASKAP radio catalog, and the DESI spectroscopic measurements. We apply the stacking method to obtain sufficient statistics for the X-ray surface brightness profile and the $L_X$ for groups with different central AGN properties. We find that the X-ray groups exhibit the highest $L_X$, followed by groups with QSO, radio, BPT-AGN, and non-AGN centrals. Moreover, the $L_X$ of the $M_h \lesssim 10^{13}h^{-1}M_\odot$ groups is dominated by the central AGN, while the X-ray emission from extended gas tends to be more prominent in the $M_h \gtrsim 10^{13}h^{-1}M_\odot$ groups. In groups where the AGN play a major role in X-ray emission, the contribution from extended gas is minor, resulting in significant uncertainties concerning the extended X-ray emission. When the subset containing the X-ray detected counterparts is excluded, the extended gas component becomes easier to obtain. A correlation has been identified between the X-ray luminosity of the central AGN and extended gas. However, once we account for the positional offset, their correlation becomes less prominent. Currently, the results are not conclusive enough to confirm whether there is a connection between the AGN feedback and extended gas. However, they provide a new perspective on the feedback processes in the history of group assembly.

Persistent tensions in the Hubble constant (H0) and the matter clustering parameter (S8) motivate late-time new physics that suppresses structure growth without significantly altering the background expansion history of the LambdaCDM model. We study a class of dark-sector dynamics in which a scalar dark energy field, governed by a Z2-symmetric quartic potential, interacts with dark matter through Yukawa and portal couplings. When the matter density drops below a critical threshold, a cosmological spontaneous symmetry breaking mechanism generates a time-dependent vacuum expectation value v(a) and activates an effective coupling eta(a). This creates a symmetric phase (a <= ac) identical to LambdaCDM at early times, and a broken phase (a > ac) in which eta(a) > 0 transfers energy from dark matter to dark energy, suppressing linear structure growth. Using RSD, BAO, cosmic chronometers, Pantheon+SH0ES supernovae, and compressed Planck distance priors, we compare a fixed LambdaCDM background with a self-consistent coupled-scalar evolution. The RSD-only analysis shows a strong shift: the dynamical background gives Omega_m ~ 0.31 +/- 0.10 and sigma8,0 ~ 0.59 +/- 0.01, while the fixed-background case gives Omega_m ~ 0.20 +/- 0.09 and sigma8,0 ~ 0.75 +/- 0.05. In the full joint fit, we obtain Omega_m = 0.29 +/- 0.01, H0 = 69.7 +/- 0.6 km s^-1 Mpc^-1, and sigma8,0 = 0.78 +/- 0.01. A late-time interaction triggered by spontaneous symmetry breaking can therefore damp structure growth and ease the S8 tension while leaving the expansion history and the inferred H0 essentially unchanged, suggesting distinct physical origins for the two tensions.

R Aquarii (R Aqr) is a well-known symbiotic binary that has attracted renewed interest during its recent periastron passage, an event that occurs only once every about 40 years. This passage marks the first to be observed with modern, state-of-the-art instruments. We investigate the inner, sub-arcsecond active region of R Aqr during this recent periastron passage, with the goal of gaining insight into the jet-launching mechanisms at work in this system. We analyse Ha speckle interferometric images obtained one month apart using Fourier techniques. These are complemented by high-resolution optical spectra in the same emission line. Our speckle imaging reveals a newborn two-sided jet orientated in the north-south direction. Its proper motion, 66 +- 19 mas per year, confirms that it was launched around 2020 Jan 7, at the onset of the periastron passage. Further analysis of the elongated central structure reveals a knot in the southern counterpart of the jet, moving away from the binary with a 27 +- 17 mas per year at a position angle of 187 degrees, and an ejection time around 2019 Oct 28. This interpretation is further supported by our high-resolution spectroscopic data. In addition, we update the expansion parallax distance of R Aqr to 260 pc.

High-resolution AstroSat-UltraViolet Imaging Telescope (UVIT) observations revealed a knot of UV emission, $\sim 1.7$ kpc away from the centre of NGC 315, a nearby elliptical galaxy hosting a giant (Mpc scale) radio source with a jet. We suggest that this patchy and spatially extended UV emission is likely due to ongoing star formation (SF) in the galaxy. The estimated SF rate (SFR) averaged over 100 Myr for the UV knot ($0.23\pm0.10$ M$_{\odot}$ yr$^{-1}$) is significantly higher compared to a typical elliptical galaxy. As the galaxy does not show the signatures of recent major mergers, the possible mechanisms for the triggered SF include AGN feedback or minor mergers. Hubble Space Telescope} (HST) observations reveal dust filaments that extend through a UV knot. The origin of dusty filaments, though not clear, could be associated with gas clouds as a result of a minor merger, cooled gas falling into the central BCG and/or condensing of the gas uplifted by AGN jet. No significant clumpy UV emission is observed in other regions along the dust filament. We speculate that mechanical feedback from the AGN jet could be playing a role in triggering SF in the UV knot.

We present an improved approach for constructing the UV source catalogs using observations from the UltraViolet Imaging Telescope (UVIT) onboard AstroSat, by considering the Poisson distribution of the UV background. The method is tested extensively using fields that are not crowded, the Small Magellanic Cloud (SMC) and M31 (Field 13). The results are compared with previous studies that used UVIT observations. This approach is successful in detecting fainter sources and produces a large number of new sources ($\sim 15$ to $92\%$ more). Most of the newly discovered UV sources fall in the faint end of the source distribution (m $\gtrsim 22$). The counterparts at other wavelengths are identified for most sources. This approach is more efficient for source detection and provides an opportunity to explore new classes of UV sources.

Observational evidence regarding the impact of AGN feedback on star formation (SF) in non-jetted galaxies is limited. With the available high-resolution UV observations from AstroSat-UVIT, complemented by GALEX, we studied the SF properties in the outskirts ($>0.5R_{25}$) of six AGN-host galaxies and compared them with four non-AGN galaxies of similar morphology. We observed a higher SF rate density ($\Sigma_{\text{SFR}}$) for the UV knots in AGN-host galaxies, and it falls off less rapidly compared to non-AGN galaxies, suggesting positive AGN feedback in the outskirts of AGN-host galaxies. Additionally, FUV attenuation (A$_{\text{FUV}}$) is also enhanced in the outer regions and falls less rapidly in AGN-host compared to non-AGN, indicating that the feedback could be coupled with dust. We speculate that the radiation-pressure-driven and/or wind mode AGN feedback could be at play even in low-luminosity nearby AGN-host galaxies.

We examine whether quarkyonic equations of state (EOS) can account for compact objects in the $2.5$-$4.5\,M_\odot$ mass range reported for the GW230529 gravitational-wave event. The pressure-energy density and mass-radius (M-R) relations obtained from quarkyonic EOS models indicate a significant stiffening at high densities, allowing stable configurations beyond $2.5\,M_\odot$. The predicted M-R sequences extend into the GW230529 mass window while maintaining radii in the range of $\approx 13$-$15$~km, suggesting that quarkyonic stars can naturally populate the so-called compact object mass gap. These results imply that the heavier component of GW230529 could plausibly be a massive quarkyonic neutron star rather than a low-mass black hole.

Non-uniformity plays an important role for MHD waves. For a uniform plasma of infinite extent the MHD waves can be subdivided in two classes with distinct properties. The first class contains the Alfvén waves. The Alfvén waves are incompressible and propagate parallel vorticity. They do not have a parallel component of displacement, they do not cause variations in pressure and are driven by magnetic tension only. The second class contains the magneto-sonic waves. They are compressible and have a parallel component of displacement. They do not propagate parallel vorticity and are driven by pressure and magnetic tension. In non-uniform plasmas the situation can be very different. The clear division between Alfvén waves and magneto-sonic waves is no longer present. In a given part of the equilibrium an MHD wave can strongly resemble a magneto-sonic wave with little or no resemblance to Alfvén waves; while in another part of the equilibrium the MHD wave is practically an Alfvén wave, which has the amazing property of being accompanied by variations in pressure.

Context. The spectral lines of the CH molecule are a key carbon (C) abundance diagnostic in FGKM-type stars. These lines are detectable in metal-rich and, in contrast to atomic C lines, also in metal-poor late-type stars. However, only 3D LTE analyses of the CH lines have been performed so far. Aims. We test the formation of CH lines in the solar spectrum, using for the first time, 3D Non-LTE (NLTE) models. We also aim to derive the solar photospheric abundance of C, using the diagnostic transitions in the optical (4218 - 4356 Å) and infrared (33025 - 37944 Å). Methods. We use the updated NLTE model molecule from Popa et al. (2023) and different solar 3D radiation-hydrodynamics model atmospheres. The models are contrasted against new spatially-resolved optical solar spectra, and the center-to-limb variation (CLV) of CH lines is studied. Results. The 1D LTE and 1D NLTE models fail to describe the line CLV, and lead to underestimated solar C abundances. The 3D NLTE modelling of diagnostic lines in the optical and IR yields a carbon abundance of A(C)=$8.52\pm0.07$ dex. The estimate is in agreement with recent results based on neutrino fluxes measured by Borexino. Conclusions. 3D NLTE modelling and tests on spatially-resolved solar data are essential to derive robust solar abundances. The analysis presented here focuses on CH, but we expect that similar effects will be present for other molecules of astrophysical interest.

Growing evidence shows that most stars in the Milky Way, including the Sun, are born in high-mass star-forming regions, but due to both observational and theoretical challenges, our understanding of their chemical evolution is much less clear than that of their low-mass counterparts. Thanks to the capabilities of new generation telescopes and computers, a growing amount of observational and theoretical results have been recently obtained, which have important implications not only for our understanding of the (still mysterious) formation process of high-mass stars, but also for the chemistry that the primordial Solar System might have inherited from its birth environment. In this review, we summarise the main observational and theoretical results achieved in the last decades in the study of chemistry evolution in high-mass star-forming regions, and in the identification of chemical evolutionary indicators. Emphasis is especially given to observational studies, for which most of the work has been carried out so far. A comparison with the chemical evolution occurring in other astrophysical environments, in particular in low-mass star-forming cores and extragalactic cores, is also briefly presented. Current open questions and future perspectives are discussed.

We present high-resolution spectroscopic observations of the quiet-Sun center-to-limb variations (CLV) of the He I triplet at 10 830 Å and the nearby Si I 10 827 Å line, observed with GREGOR Infrared Spectrograph (GRIS) and the improved High-resolution Fast Imager (HiFI+). The observations cover the interval $\mu = [0.1,\, 1.0]$, where $\mu$ is the cosine of the heliocentric angle. At each $\mu$-position, the spectra are spatially averaged over 0.02 $\mu$, and the resulting CLVs are given both as these averaged data points and as smooth polynomial curves fitted across each wavelength point. The He I spectra were inverted using the HAnle and ZEeman Light (HAZEL) code, showing an increase in optical depth towards the limb and a reversed convective blueshift for the red component, while the blue component was entirely absent. In addition, we find a strong increase in the steepness of the He I CLV compared to that of the nearby continuum. The Si I showed a behavior more typical of photospheric lines, namely shallower CLV, a reduction in width and depth, and a more typical convective blueshift.

The persistent 4-6$\sigma$ difference between early- and late-time Hubble constant ($H_{0}$) measurements, known as the "Hubble tension," is a major problem in modern cosmology. We study how differences in colour ($c$), stretch ($x_{1}$), and host galaxy properties-stellar mass ($M$) and specific star formation rate (sSFR)-between calibration and Hubble Flow (HF) Type Ia supernova (SN Ia) samples used by SH0ES affect SN luminosity standardization and $H_{0}$ estimates. We generate subsamples from both, estimating $H_{0}$, $M_{B}$, $\alpha$, $\beta$, $\Delta_{host}$, and $\sigma_{int}$. We use Kolmogorov-Smirnov to assess the consistency between subsamples and reveal how parameter estimates change as sample matching improves. The calibration sample is not fully representative of the HF sample, especially in $M$ and sSFR. Improving sample consistency leads to changes in $H_{0}$, $M_{B}$, $\alpha$, and $\sigma_{int}$, though overall values remain broadly stable. Better-matched subsamples tend to yield a mass step consistent with zero within 1$\sigma$. By disentangling SN subpopulations, we find persistent differences in $H_{0}$ ($\sim$2-3$\sigma$) and $M_{B}$ ($\sim2\sigma$) between low- and high-stretch SNe: $H_{0} = 75.27 \pm 1.18$ km s$^{-1}$ Mpc$^{-1}$ for low-stretch and $H_{0} = 71.25 \pm 1.59$ km s$^{-1}$ Mpc$^{-1}$ for high-stretch, resulting in Hubble tensions of 6.07$\sigma$ and 2.52$\sigma$. These differences suggest SNe Ia subpopulations with varying dust and intrinsic colour not captured by a single $\beta$, impacting cosmology. Estimating a single $H_{0}$ for both subpopulations yields $H_{0} = 73.78 \pm 2.17$ km s$^{-1}$ Mpc$^{-1}$, with a much larger uncertainty that lowers the Hubble tension from $5.87\sigma$ to $\sim2.86\sigma$. Our results suggest that the mass step may arise from an over-correction of more than one SN subpopulation associated to different environments.

The polar V379 Vir is a well-known magnetic cataclysmic variable with a brown dwarf donor. Despite numerous studies of this system across various spectral ranges, a detailed investigation of the orbital variability of its optical spectra has not been carried out. In this work, we present an analysis of spectroscopic observations of V379 Vir obtained with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The orbital variability of the H$\alpha$ emission indicates that the line is most likely formed in the accretion stream near the Lagrangian point L$_1$, rather than on the donor's surface as previously assumed. The analysis of the rotational variability of the Zeeman splitting of hydrogen lines reveals a complex magnetic field topology of the white dwarf, which differs from a simple dipole configuration.

In this paper, we explore the kinematic properties of a sample of 19 young (<1 Gyr) and intermediate-age (1-2.5 Gyr) massive star clusters within the Large Magellanic Cloud (LMC). We analyse the proper motions of the clusters, which have been measured based on multi-epoch Hubble Space Telescope (HST) observations. Additionally, we infer from the HST data homogeneous and robust estimates for the distances, ages and metallicities of the clusters. This collection of information, in combination with literature line-of-sight velocities, allows us to investigate the full 3D dynamics of our sample of clusters within the frame of the LMC in a self-consistent way. While most young clusters orbit the LMC close to the stellar disc plane, NGC 1850 (~100 Myr old) depicts a peculiar case. Depending on the exact distance from the disc, it follows either a highly inclined, retrograde orbit or an eccentric orbit along the bar structure. The orbits of young clusters that formed North of the LMC centre show signs that might be connected to the resettling motion of the LMC bar structure. Based on the dynamic properties in combination with the positions of the clusters in the age-metallicity space, we find no clear-cut evidence for clusters in our sample that could have been stripped from the Small Magellanic Cloud (SMC) onto the LMC. We finally compare the kinematics of the intermediate-age clusters with a suite of simple numerical simulations of the Magellanic system to interpret the cluster motions. A possible interaction history of the LMC with the SMC, where the SMC had two past crossings of the LMC disc plane (about 300 and 900 Myr ago), in combination with the recent SMC pericentre passage, can qualitatively explain the observed kinematic structure of the clusters analysed in this work.

The soft X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG) mission, eROSITA (extended ROentgen Survey with an Imaging Telescope Array), has produced the largest sample to date of galaxy groups and clusters detected via their intracluster/intragroup medium (ICM/IGrM) emission. Scaling relations between the intrinsic properties of these systems provide valuable insight into their formation and evolution. In this work, we investigate the scaling relations between key physical properties, such as soft band X-ray luminosity, temperature, gas mass, and the low-scatter mass proxy $Y_{\rm X}$, for the galaxy groups and clusters detected in the first eROSITA All-Sky Survey (eRASS1). Our analysis fully accounts for selection effects and the redshift evolution of the observable distributions. We construct a high-purity sample of $3061$ galaxy groups and clusters spanning the redshift range $0.05<z<1.07$ and mass range of $1.1\times10^{13}<M_{500}/$M$_{\odot}<1.6\times10^{15}$. This represents the largest sample to date used for scaling relation analysis. The selection function, derived from state-of-the-art simulations of the eROSITA sky, is rigorously incorporated into our modeling. We report best-fit parameters - normalization, slope, redshift evolution, and intrinsic scatter - for a set of scaling relations: $L_{\mathrm{X}}-T$, $L_{\mathrm{X}}-M_{\rm gas}$, $L_{\mathrm{X}}-Y_{\rm X}$, as well as the $M_{\rm gas}-T$ relation. Our best-fit models indicate that the slopes of the scaling relations deviate significantly from self-similar expectations, while the redshift evolution remains consistent with the self-similar model. The fits exhibit small statistical uncertainties, likely owing to the large sample size. Our results are in good agreement with previous observational studies that account for selection effects, as well as with simulations that incorporate non-gravitational physics.

We have carried out unprecedentedly deep, nearly confusion-limited JCMT-SCUBA2 mapping observations on the nearest spiral galaxy, M31 (Andromeda). The 850 $\mu$m image with a $\sim$50 pc resolution yields a comprehensive catalog of 383 giant molecular clouds (GMCs) that are associated with the spiral arms. In addition, it unveiled a population of 189 compact inter-arm GMCs in M31, which are mostly unresolved or marginally resolved. The masses of all these GMCs are in the range of 2$\times$10$^4$ -- 6$\times$10$^6$ $M_{\odot}$; the sizes are in the range of 30--130 pc. They follow a mass-size correlation, $M$ $\propto$ $R_{c}$$^{2.5}$. The inter-arm GMCs are systematically less massive, more diffuse, colder, and have lower star-forming efficiency (SFE) than on-arm GMCs. Moreover, within individual spatially resolved on-arm and off-arm M31 GMCs, the SFE is considerably lower than the SFE in molecular clouds in main sequence and green valley galaxies. Follow-up investigations on M31 GMCs may provide clues for how star formation may be quenched in galactic environments. Finally, we reconstrained the dust opacity spectral index $\beta$ in the M31 galaxy by combining our new JCMT observations with archival Herschel and Planck data and found that the radial variation of $\beta$ may not be as large as was proposed by previous studies.

The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a deep wide-field multi-band imaging survey consisting of three layers (Wide, Deep, and UltraDeep), with the Wide layer covering $\sim 1470$ deg$^2$ to a depth of $i \sim 26$ mag. We present the QHSC catalog, a machine-learning selected sample of quasar candidates with photometric redshifts in the Wide layer of the HSC-SSP survey (Public Data Release 3). The full QHSC catalog contains four distinct samples: a master sample with HSC-only photometry, an HSC+WISE sample, and two samples including near-infrared data from UKIDSS and VISTA, denoted as GoldenU and GoldenV. For each sample, an XGBoost classifier is trained and evaluated using independent spectroscopic test sets from HETDEX, VVDS, and zCOSMOS-bright. The numbers of quasar candidates in the QHSC catalog are 1,184,574 (master), 371,777 (HSC+WISE), 87,460 (GoldenU), and 120,572 (GoldenV), with respective completeness values of 85.3%, 92.7%, 89.8%, and 91.3%. We develop ensemble photometric redshift estimators based on bootstrap aggregating (bagging) of multiple XGBoost regressors, achieving outlier fractions of 21.7%, 13.1%, 9.5%, and 10.7% for these samples. The catalog provides quasar classification probabilities (p_QSO), enabling construction of purer subsamples via thresholding. This work offers a valuable resource for studies of quasars and cosmology, and highlights the effectiveness of machine learning for quasar selection in future wide and deep imaging surveys. The catalog is publicly available at this https URL.

Context. The synergy between close binary stars and asteroseismology enables constraints on mass-transfer episodes and their consequences for internal structure, rotation profiles, and oscillation modes. Aims. We investigate how mass accretion and donation in close binaries affects the internal structure and oscillation modes of main-sequence stars. Methods. Building on the established relation between the BruntVaisala (buoyancy) glitch and the Fourier spectra of g-mode period spacings presented in Wu et al. and Guo, we quantitatively explain the origins of the g-mode period-spacing differences between single-star and mass-accretion/donation models of intermediate-mass stars (M = 2.0, 3.0, and 4.5 Msun). In particular, the hydrogen mass fraction profiles X of the donor model show two chemical gradient regions, which results in a double-peaked BruntVaisala profile. The presence of additional buoyancy glitches gives rise to further periodic modulations in the g-mode period spacings. Results. Mass-accretion induced changes in the chemical profile create sharp features in the buoyancy frequency, which modify both the amplitudes and frequencies of the g-mode period-spacing variations. This behavior resembles that produced by multiple chemical transition zones in compact pulsators such as white dwarfs and sub-dwarf B (sdB) stars. Similarly, for acoustic modes in the M = 1 Msun solar-like models, we attribute the differences in frequency-separation ratios between single-star and mass-donor models to the variations in the internal sound-speed gradient (acoustic glitches). We discuss future prospects for using asteroseismology to discover the mass-transfer products and constrain the mass-transfer processes in binary star evolution.

Solar prominences, or solar filaments, are cool and dense plasma structures in the hot solar corona, whose formation mechanisms have remained a fundamental challenge in solar physics. This review provides a comprehensive overview of the current theoretical, numerical, and observational understanding of prominence formation, with a focus on the origin of the dense plasma component. We begin by summarizing the magnetic field configurations that enable prominence support, followed by a classification of four representative plasma formation mechanisms: injection, levitation, evaporation--condensation, and in-situ condensation. Each mechanism is analyzed in terms of its physical basis, numerical realizations, and observational diagnostics. A central focus is placed on the evaporation--condensation scenario, which has seen significant development over the past decade through numerical simulations. We also discuss recent progress in modeling in-situ condensation triggered by magnetic reconnection and levitation dynamics. Throughout, we emphasize the complementary nature of different mechanisms and their potential coexistence in forming and maintaining prominence mass. Observational constraints and recent high-resolution data are reviewed to assess the physical plausibility of each mechanism. We conclude by highlighting open questions and future directions in connecting multi-scale physical processes to the observed diversity of prominence behaviors.

Faraday Rotation Measure (RM) Grids provide a sensitive means to trace magnetized plasma across a wide range of cosmic environments. We study the RM signal from the Shapley Supercluster Core (SSC), in order to constrain the magnetic field properties of the gas. The SSC region consists of two galaxy clusters A3558 and A3562, and two galaxy groups between them, at $z\simeq 0.048$. We combine RM Grid data with thermal Sunyaev-Zeldovich effect data, obtained from the POSSUM pilot survey, and Planck, respectively. To robustly determine the gas density, its magnetic field properties, and their correlation, we study the RM scatter in the SSC region and its behavior as a function of distance to the nearest cluster/group. We compare observational results with semi-analytic Gaussian random field models and more realistic cosmological MHD simulations. With a sky-density of 36 RMs/deg$^{2}$, we detect an excess RM scatter of $30.5\pm 4.6 \, \mathrm{rad/m^2}$ in the SSC region. Comparing with models, we find an average magnetic field strength of 1-3 $\mu$G (in the groups and clusters). The RM scatter profile, derived from data ranging from 0.3-1.8 $r_{500}$ for all objects, is systematically flatter than expected compared to models, with $\eta<0.5$ being favored. Despite this discrepancy, we find that cosmological MHD simulations matched to the SSC structure most closely align with scenarios where the magnetic field is amplified by the turbulent velocity in the intercluster regions on scales $\lesssim 0.8\,r_{500}$. The dense RM grid and precision provided by POSSUM allows us to probe magnetized gas in the SSC clusters and groups on scales within and beyond their $r_{500}$. Flatter-than-expected RM scatter profiles reveal a significant challenge in reconciling observations with even the most realistic predictions from cosmological MHD simulations in the outskirts of interacting clusters.

The ExoClock project is an open platform aiming to monitor exoplanets by integrating observations from space and ground based telescopes. This study presents an updated catalogue of 620 exoplanet ephemerides, integrating 30000 measurements from ground-based telescopes (the ExoClock network), literature, and space telescopes (Kepler, K2 and TESS). The updated catalogue includes 277 planets from TESS which require special observing strategies due to their shallow transits or bright host stars. This study demonstrates that data from larger telescopes and the employment of new methodologies such as synchronous observations with small telescopes, are capable of monitoring special cases of planets. The new ephemerides show that 45% of the planets required an update while the results show an improvement of one order of magnitude in prediction uncertainty. The collective analysis also enabled the identification of new planets showing TTVs, highlighting the importance of extensive observing coverage. Developed in the context of the ESA's Ariel space mission, with the goal of delivering a catalogue with reliable ephemerides to increase the mission efficiency, ExoClock's scope and service have grown well beyond the remit of Ariel. The ExoClock project has been operating in the framework of open science, and all tools and products are accessible to everyone within academia and beyond, to support efficient scheduling of future exoplanet observations, especially from larger telescopes where the pressure for time allocation efficiency is higher (Ariel, JWST, VLT, ELT, Subaru etc). The inclusion of diverse audiences in the process and the collaborative mode not only foster democratisation of science but also enhance the quality of the results.

Our knowledge of the chemical composition of the gas in the inner disc of intermediate-mass young stars is limited, due to the lack of suitable instrumentation. The launch of JWST has provided a significant improvement in our ability to probe gas in these inner discs. We analyse the gas composition and emitting conditions of the disc around HD 35929, a young intermediate-mass Herbig star, using MIRI/MRS data. Our goal is to constrain the chemistry and kinematics of the gas phase molecules detected in the inner disc. We use iSLAT to examine the observed molecular lines and DuCKLiNG to detect, fit, and analyse the molecular emission. We find gas phase H2O, CO, CO2, and OH in the disc, as well as HI recombination lines. Surprisingly, we also detect gas phase SiO in the fundamental v=1-0 vibrational band. We derive column densities and temperature ranges of the detected species, arising from the inner ~0.2 au, hinting towards a compact and very warm disc. The molecular column densities are much higher than found in lower mass T Tauri discs. In general, the molecular composition is consistent with an O-rich gas from which silicate-rich solids condense and the strong gas phase molecular line emission suggests a low dust opacity. The unexpected detection of gas phase SiO at the source velocity points to an incomplete condensation of rock forming elements in the disc, suggesting chemical disequilibrium and/or an underestimate of the gas kinetic temperature.

After nearly a decade of quiescence, the transient Be/X-ray binary pulsar RX J0520.5-6932 underwent an outburst in 2024. We performed X-ray monitoring of the source with NICER and AstroSat near the peak of the event. Our primary objective is to investigate the energy and luminosity dependence of the pulsed emission, characterize the spin evolution, and study the broadband X-ray spectral properties of RX J0520.5-6932 during the outburst. The AstroSat/LAXPC and NICER light curves reveal pronounced short-duration flaring activity lasting ~400-700 s, with enhancements by a factor of ~2. The pulse profile exhibits a strong dependence on both energy and intensity, evolving from a simple single-peaked structure at low energies to complex multi-peaked shapes at intermediate energies, and reverting to simpler morphologies at higher energies. Pulse profiles during the flares differ significantly from those in the persistent state, indicating changes in the pulsed beam pattern with a change in the intensity on a short timescale. Broadband spectral analysis reveals a soft excess and an emission feature at ~1 keV, likely arising from reprocessed emission in the accretion disc and fluorescence from Ne K and Fe L ions. Continuous NICER monitoring over nearly one orbital cycle enabled us to track spin evolution with accretion-driven spin-up and spectral variability in the soft X-ray band. Additionally, a declining spin-up rate is observed during the outburst, likely due to a gradual reduction in mass accretion rate. Our results provide a comprehensive view of the complex accretion dynamics in RX J0520.5-6932 during its 2024 outburst. The strong variability in pulse shape and spin behaviour highlights rapid changes in the accretion geometry and torque as a function of accretion rate. [Abridged]

We present a comprehensive morphological and spectrophotometric analysis of the lunar impact that occurred on September 11, 2013, based on pre- and post-event observations by the Lunar Reconnaissance Orbiter (LRO). The crater formed exhibits a rim-to-rim diameter of $35 \pm 0.7$ m, a depth of $4.9 \pm 0.4$ m, and an ejecta blanket extending over 2 km with an area of approximately $7 \times 10^{5}\,$m$^{2}$. The ejecta shows a pronounced asymmetry and, assuming uniform distribution, an average thickness limit of $\sim 2$ mm. Spectral analysis using WAC images reveals a consistent reddening of the central ejecta region, with an average 16.54 % increase in spectral slope between 321 nm and 643 nm, marking the first reported detection of color changes resulting from a lunar impact. We evaluated several scaling laws and found that the Gault et al. (1974) formulation most accurately reproduces the observed crater size. Furthermore, luminous efficiency values below $\eta = 2 \times 10^{-3}$ and higher projectile densities are most consistent with the morphology of the ejecta. The impact direction inferred from this pattern is not compatible with the radiant of the September $\varepsilon$-Perseids stream. Moreover, an independent probability analysis yields a greater than 96 % likelihood that the event was caused by a sporadic meteoroid. Our results also demonstrate the potential of WAC imagery for the automated detection of new lunar craters, which can improve statistical estimates of the current impact flux. This methodology offers a powerful complement to high-resolution imaging, with important implications for both lunar safety and planetary defense.

In order to test the robustness and reliability of the new generation spectral-line identifier PyEMILI, as initially introduced in Paper I, in line identification and establish a reference/benchmark dataset for future spectroscopic studies, we run the code on the line lists of a selected sample of emission-line nebulae, including planetary nebulae (PNe), HII regions, and Herbig-Haro (HH) objects with deep high-dispersion spectroscopic observations published over the past two decades. The automated line identifications by PyEMILI demonstrate significant improvements in both completeness and accuracy compared to the previous manual identifications in the literature. Since our last report of PyEMILI, the atomic transition database used by the code has been further expanded by cross-matching the Kurucz Line Lists. Moreover, to aid the PyEMILI identification of numerous faint optical recombination lines (ORLs) of CII, NII, OII and NeII, we compiled a new dataset of effective recombination coefficients for these nebular lines, and created a new subroutine in the code to generate theoretical spectra of heavy-element ORLs at various electron temperature and density cases; these theoretical spectra can be used to fit the observed recombination spectrum of a PN to obtain the electron temperature, density and ionic abundances using the Markov-Chain Monte Carlo (MCMC) method. We present MCMC-derived parameters for a sample of PNe. This work establishes PyEMILI as a robust and versatile tool for both line identification and plasma diagnostics in deep spectroscopy of gaseous nebulae.

We present the discovery of a strongly lensed galaxy at $z\sim11-12$, dubbed the ``Misty Moons'', identified in the JWST Treasury Survey, Vast Exploration for Nascent, Unexplored Sources (VENUS). The Misty Moons is gravitationally lensed by the galaxy cluster MACS J0257.1-2325 at $z=0.505$, and has five multiple images suggested by two independent lensing models. Two of the five images, ID1 and ID2 ($\mu\sim 20-30$), are very bright (F200W$\sim26$ AB mag) and exhibit blue SEDs with prominent Ly$\alpha$ breaks. In the source plane, the Misty Moons is a sub-$L^*$ galaxy ($M_{\rm UV}\sim-18.0$ mag) resolved into multiple stellar clumps, each of which has effective radius of $r_\mathrm{eff}\sim 10-70$ pc and stellar mass of $\sim10^7\ M_\odot$. These clumps dominate the stellar mass budget of the Misty Moons ($\gtrsim80\%$), similar to other high-$z$ clumps, which suggests a highly clustered mode of star formation in the early Universe, unlike seen in local dwarf galaxies. We convolve the source-plane image with the JWST/NIRCam point-spread function to produce a mock NIRCam image of the Misty Moons without lensing magnification, and find that the intrinsic galaxy has a radial surface-brightness profile comparable to those of $z\gtrsim10$ faint galaxies, such as JADES-GS-z13-0 and JADES-GS-z14-1, indicating that the Misty Moons represents a typical $z\gtrsim10$ faint galaxy. The Misty Moons, a lensed galaxy with resolved internal structures, provides an ideal laboratory for exploring the early stages of galaxy formation at $z\gtrsim10$.

We study the cosmological impact of ultralight dark matter (ULDM) with a quadratic coupling to Standard Model particles. In addition to the suppression of small-scale power from ULDM itself, the coupling induces a variation of fundamental constants that is modulated by the ULDM oscillatory field value. In this work, we consider the ULDM-induced, time-dependent variation of the fine structure constant and the mass of the electron. These variations modify the predicted abundance of light elements during Big Bang nucleosynthesis (BBN) and the process of recombination, thereby affecting the anisotropies of the cosmic microwave background (CMB). We use CMB anisotropy data and baryon acoustic oscillation measurements to obtain constraints on the variation of couplings over a wide range of ULDM masses. We self-consistently account for the modification of the primordial helium abundance during BBN in computing the CMB power spectra. We find that the allowed ULDM fraction of total dark matter abundance is more constrained for ULDM masses $\lesssim 10^{-26}~\mathrm{eV}$ in the presence of the variations. Moreover, our constraints on the variational couplings for ULDM masses $\lesssim 10^{-27}~\mathrm{eV}$ are stronger than the ones derived from the primordial helium abundance at BBN. Under our ULDM model, the variation of fundamental constants has no appreciable impact on the Hubble constant inferred from CMB data and thus does not present a viable solution to the Hubble tension.

We have generated strongly photoionized Ar plasmas in experiments designed to use primarily X-ray L-shell line emission generated from Ag foils irradiated by the VULCAN high-power laser at the UK Central Laser Facility. The principle of the experiment is that use of line emission rather than the usual sub-keV quasi-blackbody source allows keV radiation to play a more dominant role compared to softer X-rays and thus mimic the effect of a blackbody with a higher effective spectral temperature. Our aim is to reproduce in the laboratory the extreme photoionization conditions found in accretion-powered astrophysical sources. In this paper, we compare the experimental results on K-$\beta$ X-ray Ar spectra with modelling using the time-dependent version of the Cloudy astrophysical code. The results indicate that photoionized laboratory plasmas can be successfully modelled with codes such as Cloudy that have been developed for application to astrophysical sources. Our comparison of simulation and experiment shows that the flux of sub-keV photons that photoionize the outer-shell electrons can have a significant effect, and that detailed measurements of the X-ray drive spectrum across all photon energy ranges are crucial for accurate modelling of experiments.

To advance our understanding of massive star formation, it is essential to perform a comprehensive suite of simulations that explore the relevant parameter space and include enough physics to enable a comparison with observational data. We simulate the gravitational collapse of isolated, parsec-scale turbulent cores using the FLASH code, modelling stars as sink particles. Our simulations incorporate ionizing radiation and the associated radiation pressure from stellar sources, and non-ionizing radiation and its dust heating, along with self-consistent chemistry, to capture the properties of emerging ultra-compact HII regions. Dust, gas, and radiation temperature are computed independently. The initial conditions are informed by ALMAGAL observations. We assess stellar feedback, comparing ionizing radiation and radiation pressure. Ionizing radiation ultimately halts mass accretion on to sink particles, while direct radiation pressure enhances the expansion of HII regions. Heating from non-ionizing radiation suppresses fragmentation. We examine the effect of spatial resolution, finding that higher resolution leads to more sink particles which are situated in environments with higher densities. As a result, ionizing radiation remains trapped longer, allowing continued accretion and yielding a higher overall star formation efficiency (SFE). We explore the impact of varying initial conditions, including the core density profile, virial parameter, and metallicity. Our parameter study reveals that a flatter density profile, higher virial parameter, and increased metallicity promote fragmentation, potentially enhancing the SFE by slowing the growth of the most massive stars and delaying the onset of stellar feedback. Overall, we find SFEs between 35% and 57%. Stellar feedback dictates the final SFE.

We present a parametric component separation forecast for the QUIJOTE-MFI2 instrument (10-20 GHz), assessing its impact on constraining polarised synchrotron emission at $1^\circ$ FWHM and $N_{\rm side}=64$. Using simulated sky maps based on power-law and curved synchrotron spectra, we show that adding QUIJOTE-MFI2 to existing WMAP+$Planck$+MFI data yields statistically unbiased parameter estimates with substantial uncertainty reductions: improvement factors reach $\sim$10 for the synchrotron spectral index ($\beta_s$), $\sim$5 for the curvature parameter ($C_s$), and $\sim$43 for polarisation amplitudes in bright regions. Deep QUIJOTE cosmological fields enable $\beta_s$ constraints even in intrinsically low SNR regions where WMAP+$Planck$ alone remain prior-dominated. Current combined sensitivities are insufficient to detect a synchrotron curvature of $C_s=-0.052$ on a pixel-by-pixel basis, but a $2\sigma$ detection is achievable for $|C_s|\gtrsim 0.14$ in the brightest regions of the Galactic plane. In those deep cosmological fields, combining QUIJOTE-MFI2 with WMAP and $Planck$ reduces the median synchrotron residual at 100 GHz by a factor 2.2 (to 0.022 $\mu$K$_{\rm CMB}$) and the total residual by a factor 1.8 (to 0.030 $\mu$K$_{\rm CMB}$). These results demonstrate that QUIJOTE-MFI2 will provide critical low-frequency information for modelling Galactic synchrotron emission, offering valuable complementary constraints for future CMB surveys such as LiteBIRD and the Simons Observatory.

We measure the Eddington ratio distribution of local optical narrow line active galactic nuclei (AGN) as a function of host galaxy properties, as a potential test of supermassive black hole growth and feedback models in galaxy formation theory. We base our sample on integral field spectroscopy from the MaNGA data in SDSS-IV's DR17. Starting with MaNGA's calibrated row-stacked spectra, we produce new spectroscopic data cubes with minimal covariance between spaxels and higher resolution point spread functions (PSF), and then extract line fluxes for the central PSF. Using the line ratio diagnostic techniques of Ji & Yan (2020), we identify AGN galaxies and determine their H$\beta$ and [O III] line luminosities. For all galaxies not identified as AGN, we determine the threshold line luminosity they would have needed to be identified as AGN. These luminosity thresholds are essential to determine, because many star forming galaxies likely host AGN of significant luminosity that are unidentified because they are outshone by star formation related emission. We show that ignoring these selection effects when measuring the Eddington ratio distribution would lead to biased results. From the H$\beta$ luminosities and luminosity detection thresholds, accounting for selection effects, we measure the luminosity and Eddington ratio distributions of Seyferts as a function of specific star formation rate (sSFR) and stellar mass. Defining $F_{\rm AGN}$ as the occurrence rate of AGN above a fixed Eddington ratio of $10^{-3}$, we find that $F_{\rm AGN}$ is constant or increasing with stellar mass for star forming galaxies and declines strongly with stellar mass for quiescent galaxies. At stellar masses $\log_{10} M_\ast > 10.25$, the occurrence rate increases monotonically with sSFR. These patterns reveal a complicated dependence of AGN activity on galaxy properties for theoretical models to explain.

As the Extremely Large Telescope (ELT) approaches operational status, optimising its imaging performance is critical. A differential piston, arising from either the adaptive optics (AO) control loop, thermomechanical effects, or other sources, significantly degrades the image quality and is detrimental to the telescope's overall performance. In a numerical simulation set-up, we propose a method for estimating the differential piston between the petals of the ELT's M4 mirror using images from a 2x2 Shack-Hartmann wavefront sensor (SH-WFS), commonly used in the ELT's tomographic AO mode. We aim to identify the limitations of this approach by evaluating its sensitivity to various observing conditions and sources of noise. Using a deep learning model based on a ResNet architecture, we trained a neural network (NN) on simulated datasets to estimate the differential piston. We assessed the robustness of the method under various conditions, including variations in Strehl ratio, polychromaticity, and detector noise. The performance was quantified using the root mean square error (RMSE) of the estimated differential piston aberration. This method demonstrates the ability to extract differential piston information from 2x2 SH-WFS images. Temporal averaging of frames makes the differential piston signal emerge from the turbulence-induced speckle field and leads to a significant improvement in the RMSE calculation. As expected, better seeing conditions result in improved accuracy. Polychromaticity only degrades the performance by less than 5% compared to the monochromatic case. In a realistic scenario, detector noise is not a limiting factor, as the primary limitation rather arises from the need for sufficient speckle averaging. The network was also shown to be applicable to input images other than the 2x2 SH-WFS data.

I identify a point-symmetric morphology in the core-collapse supernova (CCSN) remnant SNR G11.2-0.3 composed of three pairs of opposite morphological features, and attribute their shaping to three energetic pairs of jets during the explosion process in the frame of the jittering jets explosion mechanism (JJEM). The pairs of morphological features are two opposite rings, a strip of dense ejecta extending on both sides of the central pulsar PSR J1811-1925, and an ear-nozzle opposite structure. According to the JJEM, additional weaker pairs of jets may also have participated in the explosion. The jets' axis from the ear to the nozzle coincides with the axis of the presently active pulsar jets, which is the pulsar spin axis. The jets of this pair were the last that the newly born neutron star launched during the explosion, and the accretion disk that launched these jets spun up the neutron star in the same direction as the jets. The identification of a point-symmetric morphology in SNR G11.2-0.3 strengthens the claim that the JJEM is the primary explosion mechanism of CCSNe.

We investigate the impact of the Bondi--Hoyle--Lyttleton (BHL) accretion mechanism on the evolution of nova eruptions in symbiotic systems by systematically varying three key input parameters: the initial donor (asymptotic giant branch; AGB) mass, the initial white dwarf (WD) mass, and the initial binary separation ($a$). We explore models with AGB masses in the range $1.5$--$3.5\,{\rm M_{\odot}}$, WD masses in the range $0.7$--$1.25\,{\rm M_{\odot}}$, and separations in the range $1$--$8\,{\rm kR_{\odot}}$. We find that all models exhibit a significant long-term orbital increase. This trend is primarily driven by the fact that approximately $99\%$ of the AGB mass is lost from the system, either directly via a wind that is not accreted by the WD, or accreted onto the WD and subsequently ejected during nova eruptions. As a result, the secular orbital response to mass loss or mass transfer dominates over angular-momentum-loss sinks that could otherwise shrink the orbit, producing a consistent orbital widening. Consequently, all WD masses gradually decrease with time. More massive WDs achieve higher mass-transfer efficiencies and accretion rates, leading to slightly higher mass-retention efficiencies per nova. However, because higher accretion rates also produce more frequent eruptions, the total WD mass lost over the AGB lifetime is larger in these systems. We conclude that symbiotic systems transferring mass via the BHL mechanism are unlikely to be viable progenitors of Type Ia supernovae.

Hot Jupiters are Jupiter-mass planets with orbital periods of less than ten days. Their short orbital separations make tidal dissipation within the stellar host especially efficient, potentially leading to a measurable evolution of the orbit. One possible manifestation of this is orbital decay, which presents itself observationally through variations in the orbital period and thus times of transit. Here we select four promising exoplanetary systems for detecting this effect: HIP 65, NGTS-6, NGTS-10 and WASP-173. We present 33 new transit light curves taken with the 1.54 m Danish Telescope, and analyse these alongside photometric data from the Transiting Exoplanet Survey Satellite and transit timing data from the literature. We construct two ephemeris models for each target: a linear ephemeris and a shrinking orbital period due to tidal decay. The linear ephemeris is preferred for all four models - the highest significance for the quadratic ephemeris is 2 sigma for WASP-173. We compare these results to theoretical predictions for tidal dissipation of gravity waves in radiation zones, and find that wave breaking is predicted only in WASP-173, making rapid decay plausible in this system but unclear in the other three. The sensitivity of transit timings to orbital decay depends on the square of the time interval covered by available observations, so our results establish a useful baseline against which future measurements can be compared. NGTS-6 and NGTS-10 are important objects for future study as they are in the first field to be observed by the upcoming PLATO mission.

Recognizing and addressing under-representation, exclusion, and problematic behavior within astronomy and astrophysics is crucial. In 2019, a survey was conducted at the Spirit of Lyot conference to evaluate the socio-demographics and well-being of the exoplanet and disk imaging community. This paper presents the results of a second survey, conducted at the 2022 Spirit of Lyot conference in Leiden, aiming to improve the evaluation of the community, expand diversity-related questions, and monitor the evolution of metrics since 2019. Sent to all participants, the survey received 96 responses. It measures respondents' visibility at conferences, recognition through publications and projects, experiences of disrespect or inappropriate behaviors as victims or witnesses, and identification as allies of minorities. These aspects were analyzed with respect to job position, expatriation, gender, belonging to another under-represented group (ethnicity, disability, sexual orientation), and parenthood.

We present an analysis on the kinematics and physical properties of the ionized gas in the lensed galaxy RXCJ2248-ID at z=6.1 based on high-resolution JWST NIRSpec/IFU data in combination with ALMA observations. Our analysis reveals a high electron temperature ($T_e$$\sim$30000K) in the ionized gas, independent of the ionization level. We measure a wide range in the electron densities derived from [OIII]$\lambda$5008/[OIII]88$\mu$m and [ArIV]$\lambda$4713/[ArIV]$\lambda$4742 ratios (log($n_e$[cm$^{-3}$])$\sim$2.7-3.8), and previous values (log($n_e$[cm$^{-3}$])>4.8) based on high-ionization rest-UV emission lines. The ionized gas appears to be clumpy with a low filling factor ranging from about 10% to 0.2% for the low- and high-density clouds. In addition, we observe a very complex ISM kinematic structure, with the presence of two distinct broad and a very-broad components (FWHM$\sim$210 and $\sim$1000 kms$^{-1}$) in addition to the systemic one (FWHM$\sim$60 kms$^{-1}$) in [OIII]$\lambda$5008 and H$\alpha$. These broad components are heavily extinct (A$_V$$\sim$1.5 and 2.5, respectively), based on their Balmer decrements, while the gas associated to the narrow component is consistent with no extinction. The maximal velocities of these outflows ($\sim$115-500kms$^{-1}$) are such that a fraction of the total outflowing gas (0.16-2.1$\times$10$^7$M$_\odot$) could escape into the IGM. The rest of the gas will fall back to the central regions, being available for additional star formation episodes. The presence of dusty outflows and clumpy (i.e., low filling factor) ISM give support to the Attenuation-Free scenario proposed to explain the high-z UV-bright compact galaxies such as RXCJ2248-ID. On the other hand, the high densities in the ISM, together with the high SFR surface brightness, and the amount of returning outflowing mass give support to the Feedback-Free Starburst scenario.

High-resolution mapping of cosmic mass distribution is essential for a variety of astrophysical applications including understanding cosmic structure formation, and galaxy formation and evolution. However dark matter is not directly observed and therefore we need advanced methods for solving inverse problems to reconstruct the underlying cosmic matter distribution. Here, we train a generative diffusion model and use it in the Diffusion Posterior Sampling (DPS) framework to reconstruct mass maps from Dark Energy Survey-Year 3 (DES-Y3) weak gravitational lensing data at high (1 arcminute) resolution. We show that the standard DPS results are biased, but they can be easily corrected by scaling the log-likelihood score during the diffusion process, yielding unbiased results with proper uncertainty quantification. The resulting mass maps reveal cosmic structures with enhanced detail, opening the door for improved astrophysical studies using the obtained mass maps.

Recent observations of cosmic microwave background (CMB) anisotropies combined with large-scale structure may point towards higher values of the scalar spectral index, $n_s$. This puts previously preferred inflationary models, such as $\alpha$-attractors, in tension with the new measurements. Pending a resolution of the tension between BAO parameters as determined by CMB datasets and those determined by DESI, we explore in this work the large-$n_s$ regime of $\alpha$-attractor T-models. We show that some T-models can self-consistently produce an extended reheating stage with a stiff equation of state $(\bar w>1/3)$, which allows values for $n_s$ closer to unity. We employ constraints from P-ACT-LB-BK18 data to illustrate what large-$n_s$ observations might imply for T-models. We show that the $n_s$ measurement yields an upper limit on $\alpha$ that is stronger than the one from the tensor-to-scalar ratio only. We find that $n_s$ is maximised for $\alpha\sim1$, therefore the seven Poincaré models are well placed to deliver large $n_s$. However, the ability of a stiff reheating stage to increase the compatibility of T-models with large-$n_s$ measurements saturates as $\bar{w}\to1$. Thanks to this effect, we establish that the largest $n_s$ that T-models can produce is $n_s=0.9682$. T-models are therefore highly predictive in the large-$n_s$ regime and our result provides, under the assumption of perturbative reheating, a benchmark which could be used in the future to rule out T-models.

Primordial non-Gaussianity (PNG) is a common prediction of a wide class of inflationary models. Equilateral-type PNG, generically predicted by single-field inflationary models with higher-derivative interactions, imprints subtle but measurable signatures on the large-scale distribution of matter. An important parameter of these imprints is the PNG-induced bias coefficient $b_\psi$, which quantifies how the abundance and clustering of dark matter halos and galaxies respond to mode coupling in the initial conditions. Measuring $b_\psi$ is important for constraining equilateral PNG, yet it is notoriously challenging due to its degeneracy with Gaussian scale-dependent bias contributions. In this work, we present the first precision measurements of equilateral $b_\psi$ for dark matter halos using effective field theory at the field level. We show that this approach disentangles PNG effects from those of the Gaussian bias by virtue of noise variance cancellation. We compare our results with the phenomenological predictions based on the Peak-Background Split model, finding some agreement at the qualitative level on the redshift and mass dependence, but poor agreement at the quantitative level. We present a fitting formula for $b_\psi$ as a function of the linear bias, which can be used to set priors in PNG searches with ongoing and future galaxy surveys.

The secondaries of the massive binary systems can be found as runaway stars after being ejected due to the supernova (SN) of the more massive component. We search for such stars inside the supernova remnants (SNRs), where a recent SN is guaranteed to have happened. In this paper, we present the massive runaway star HD~254577 as the pre-supernova binary companion to the progenitor of the supernova remnant IC~443 and the neutron star (NS) CXOU~J61705.3$+$222127. We performed spectroscopic observations of the runaway star and specified its atmospheric parameters. Together with the precise \textit{Gaia} DR3 astrometry and photometry, we identified the possible birth origin of the runaway star, and by isochrone fitting, we determined the progenitor mass. From the \textit{Gaia} DR3 proper motions, we specified the possible explosion sites and calculated the neutron star (NS) velocity. HD~254577 is a hot and evolved star with an effective temperature of $24000\pm1000$ K (B0.5II) and a surface gravity of $\log({g~\rm[cm/s^2]})=2.75\pm0.25$. It is probably a single star with a peculiar 3-D velocity of $31.3^{+1.2}_{-0.9}$ km~s$^{-1}$, lying at a heliocentric distance of $1701^{+55}_{-54}$ pc. The cometary tail of the NS implies that it is moving away from the same site as the runaway star. From the flight trajectories, we calculated that the NS has typical pulsar velocities such as $254-539$ km~s$^{-1}$ at a distance of $1.7$ kpc for $10-20$ kyr ages. Together with the blue-only shifted interstellar medium lines on its spectrum, HD~254577 must be the pre-supernova binary companion to the progenitor of IC~443. By identifying the pre-supernova companion and the possible parent cluster, we showed that the progenitor zero-age main sequence mass is high: $31-64$ M$_\odot$. We also discuss the expansion dynamics of the SNR due to the highly off-centered explosion site.

Unstructured Voronoi mesh simulations offer many advantages for simulating self-gravitating gas dynamics on galactic scales. Adaptive mesh refinement (AMR) can be a powerful tool for simulating the details of star cluster formation and gas dispersal by stellar feedback. Zooming in from galactic to local scales using the star cluster formation simulation package Torch requires transferring simulation data from one scale to the other. Therefore, we introduce VorAMR, a novel computational tool that interpolates data from an unstructured Voronoi mesh to an AMR Cartesian grid. VorAMR is integrated into the Torch package, which integrates the FLASH AMR magnetohydrodynamics code into the Astrophysical Multipurpose Software Environment. VorAMR interpolates data from an AREPO simulation to a FLASH AMR grid using a nearest-neighbor particle scheme, which can then be evolved within the Torch package, representing the first ever transfer of data from a Voronoi mesh to an AMR Cartesian grid. Interpolation from one numerical representation to another results in an error of a few percent in global mass and energy conservation, which could be reduced with higher-order interpolation of the Voronoi cells. We show that the postinterpolation Torch simulation evolves without numerical abnormalities. A preliminary Torch simulation is evolved for 3.22 Myr and compared to the original AREPO simulation over the same time period. We observe similarly distributed star cluster formation between the two simulations. More compact clusters are produced in the Torch simulation as well as 2.3 times as much stellar material as in AREPO, likely due to the differences in resolution.

In this paper we aim to simulate realistic exoplanet populations across different regions of the MW by combining state-of-the-art cosmological simulations of our Galaxy with exoplanet formation models and observations. We model the exoplanet populations around single stars, using planet occurrence rates and multiplicity depending on stellar mass, metallicity, and planet type, and assign them physical parameters such as mass and orbital period. Focussing first on the solar vicinity, we find mostly metallicity-driven differences in the distributions of non-hosting and planet-hosting single stars. In our simulated solar neighbourhood, 52.5% of all planets are Earth-like (23% of them located in the Habitable Zone), 44% are super-Earths/Neptunes, and 3.5% are giant planets. A comparison with the census of Kepler exoplanets and candidates shows that, when taking into account the most relevant selection effects, we obtain a similar distribution of exoplanets compared to the observed population. However, we also detect significant differences in the exoplanet and host star distributions (e.g. more planets around F-type and red-giant stars compared to observations) that we attribute mostly to a too strong recent star formation and a too large disc scale height in the simulation, as well as to some caveats in our exoplanet population synthesis that will be addressed in future work. Extending our analysis to other regions of the simulated MW and to other simulated galaxies, we find that the relative percentages of planet types remain largely consistent as long as the simulated galaxy matches the morphology and mass of the MW. We have created a fast and flexible framework to produce exoplanet populations based on MW-like simulations that can easily be adapted to produce predictions for the yields of future exoplanet detection missions. (abridged)

Gravitational lensing by galaxy clusters provides a powerful probe of the spatial distribution of dark matter and its microphysical properties. Strong and weak lensing constraints on the density profiles of subhalos and their truncation radii offer key diagnostics for distinguishing between collisionless cold dark matter (CDM) and self-interacting dark matter (SIDM). Notably, in the strongly collisional SIDM regime, subhalo core collapse and enhanced mass loss from ram-pressure stripping predict steeper central density slopes and more compact truncation radii--features that are directly testable with current lensing data. We analyze subhalo truncation in eight lensing clusters (Abell 2218, 383, 963, 209, 2390, and MACS J0416.1, J1206.2, J1149.6) that span the redshift range <$z_\text{spec}$>$ \simeq 0.17$-$0.54$ with virial masses $M_{200} \simeq0.41$-$2.2\times 10^{15}$ M$_\odot$ to constrain SIDM versus CDM. Our results indicate that the outer spatial extents of subhalos are statistically consistent with CDM, corroborated by redshift- and mass-matched analogs from the Illustris-TNG simulations. We conclude that the tidal radii of cluster galaxy subhalos serve as an important and complementary diagnostic of the nature of dark matter in these violent, dense environments.

The (large-scale) structures we observe in the Universe are classical, but within the inflationary scenario they do originate from quantum fluctuations. This leads to the question: ''How did this quantum-to-classical transition occur?''. A potential explanation is quantum decoherence due to interactions between different fields present during inflation. The tensor modes (i.e. primordial gravitational waves) can interact with a scalar sector, causing their quantum decoherence to occur and inducing a change in the gravitational wave (GW) background. The power spectrum of these GWs can be constrained using the upper bounds found by Planck, BICEP/Keck Array, LIGO-Virgo-KAGRA, Big Bang Nucleosynthesis, and the Pulsar Timing Array detections. These impose constraints on the interaction between the fields. We find that the observational upper bounds mainly constrain scenarios with a strong interaction, especially if the interaction is also strongly time dependent. Furthermore, we find which observationally allowed scenarios have not completed decoherence by the end of inflation, thus possibly leaving quantum signatures in the GW background. Lastly, we show that, interestingly enough, there are decoherence scenarios corresponding to the signal observed by PTA experiments. This highlights the importance of the quantum decoherence effect on GWs.

Protoplanetary disks observed in millimeter continuum and scattered light show a variety of substructures. Various physical processes in the disk could trigger such features -- one of which that has been previously theorized for passive disks is the thermal wave instability -- the flared disk may become unstable as directly illuminated regions puff up and cast shadows behind them. This would manifest as bright and dark rings, and a staircase-like structure in the disk optical surface. We provide a realistic radiation hydrodynamic model to test the limits of the thermal wave instability in irradiated disks. We carry out global axisymmetric 2D hydrostatic and dynamic simulations including radiation transport with frequency-dependent ray-traced irradiation and flux-limited diffusion (FLD). We found that starlight-driven shadows are most prominent in optically thick, slow cooling disks, shown by our models with high surface densities and dust-to-gas ratios of sub-micron grains of 0.01. We recover that thermal waves form and propagate inwards in the hydrostatic limit. In contrast, our hydrodynamic models show bumps and shadows within 30 au that converge to a quasi-steady state on several radiative diffusion timescales -- indicating a long-lived staircase structure. We find that existing thermal pressure bumps could produce and enhance this effect, forming secondary shadowing downstream. Hydrostatic models with self-consistent dust settling instead show a superheated dust irradiation absorption surface with a radially smooth temperature profile without staircases. We conclude that one can recover thermally induced flared-staircase structures in radiation hydrodynamic simulations of irradiated protoplanetary disks using flux-limited diffusion. We highlight the importance of modeling dust dynamics consistently to explain starlight-driven shadows.

Gravitational waves (GWs) from massive black hole (MBH) mergers will provide a novel way to probe the high-redshift universe and are key to understanding galactic dynamics and evolution. In this work, we analyze MBH mergers, their GW signals and detectability, as well as their population properties, using the cosmological hydrodynamical simulation - NINJA Simulation Suite. We discuss the effect of resolution and finite volume on the black hole mass function (BHMF), which in turn limits the mergers associated with low mass black holes, $M_{BH} \lesssim 10^{6.5} M_\odot$. We find the upper limit on the total mass of the MBH binaries detectable by LISA to be $\sim 10^{8.4} M_\odot$. We also find that adding time delays pertaining to dissipative processes like dynamical friction and stellar hardening during the final stages of the inspiral for which the simulation lacks sufficient resolution to model, considerably shifts the peak of redshift distribution of detectable binaries from $z\sim0.5$ to $z\sim0.1$. Time delays reduce the number of detectable GW events but on the other hand their signal-to-noise is increased. From the observational point of view, we find a strong correlation between the SFR and $L_{\rm bol}$ at high redshifts for the detectable LISA binaries. This may prove to be a future application in the coincident observation of MBH binaries by GW and electromagnetic observations.

We develop a fully relativistic approach for determining the frequency-dependent tidal response of a compact star. The strategy involves matching the solution for the linearised fluid dynamics in the star's interior to the spacetime perturbations in the near-zone surrounding the body, along with an identification of the tidal driving and the star's response. Notably, this identification is exact in Newtonian gravity and we provide strong evidence that it remains robust also in the relativistic case. The argument does not involve a sum over the star's quasinormal modes and hence circumvents one of the obstacles that have held up the development of models for relativistic tides. Numerical results are provided, at the proof-of-principle level, for a realistic matter equation of state from the BSk family, including composition stratification leading to the presence of low-frequency gravity modes. We also sketch the connection with the field-theory inspired approach to the problem, in which the tidal response is expressed in terms of asymptotic scattering amplitudes.

Finite density corrections to the lighter-than-QCD axion can invert the effective axion potential, sourcing a non-trivial axion field inside dense objects. We perform the first numerical study of the complete dynamics of the lighter-than-QCD axion in a neutron star in 1+1 general relativity, extending the region of analysis to low-mass axions with kilometer-scale Compton wavelengths. We calculate gravitational effects of the axion field on the neutron star and show that for a broad range of axion masses and decay constants, neutron star properties, such as the mass, radius, and compactness, are affected at the order-1 level. This result indicates that approximate universal tidal deformability-compactness relation for neutron stars is non-trivially broken and can serve as a probe of lighter-than-QCD axions, independent of the unknown nuclear equation of state. We comment on the potential for axion studies with future gravitational-wave observations of neutron stars and applications of this work to other new physics signatures.

QCD axions would be copiously produced in the proto-neutron star formed in a core-collapse supernova (SN). After escaping, they would convert into gamma rays in the Galactic magnetic field and, as recently shown, in that of the progenitor star itself. Here, we show that Type Ibc SNe -- whose progenitors have lost their hydrogen or even helium envelopes -- are the optimal targets for this search. The stripped progenitors are much more compact, and show larger magnetic fields than both red and blue supergiants, the progenitors of Type IIP/L SNe. If the next galactic SN is of Type Ibc, Fermi-LAT or a similar gamma-ray satellite might be able to discover the QCD axion down to masses as small as $m_a\simeq 10^{-4}\,\rm eV$ (Peccei-Quinn scale $f_a\simeq 10^{11} \,\rm GeV$).

The characteristic decomposition for GRMHD is not known in a form useful for current numerical simulations. This prevents us from using the most accurate known computational methods, such as full-wave Riemann solvers. In this paper, we present a new method of finding decompositions. The method is based on transformations from the comoving frame, where the fluid flow is simplest and the decomposition has been known for a long time. The key innovation we introduce is that of quasi-invertible transformations. In this first paper, we introduce these transformations using the simpler example of relativistic hydrodynamics. We recover the known decomposition for relativistic hydrodynamics in somewhat simpler form than previously derived, and without the need for computer algebra. A new result in this paper is the characteristic decomposition when the the evolution tracks the composition of a fluid in nuclear statistical equilibrium. In Paper II of this series, we apply a quasi-invertible transformation to derive the complete characteristic decomposition for GRMHD in the conserved variables used in simulations.

The characteristic decomposition for GRMHD in the comoving frame of the fluid has been known for a long time. However, it has not been known in the coordinate frame of the simulation and in terms of the conserved variables evolved in typical numerical simulations. This paper applies the method of quasi-invertible transformations developed in Paper I to derive this decomposition. Among other benefits, this will allow us to use the most accurate known computational methods, such as full-wave Riemann solvers. The results turn out to be simpler than expected based on earlier attempts.

Infrared quantum electrodynamics (IR-QED) acquires a natural geometric interpretation once soft photons are described as adiabatically transported electron-photon clouds. Within this framework, the relevant infrared structure is encoded in a functional Berry phase associated with the space of gauge connections, and the corresponding Berry corrections modify the Rayleigh-Jeans spectrum. The infrared scaling symmetry of the Rayleigh-Jeans law leads to a simple renormalization-group equation whose solution determines the frequency dependence of an effective factor $F_{\rm eff}(\omega)$ controlling the strength of the electron-photon cloud dressing. As a result, the energy density of the cosmic microwave background (CMB) receives a Berry-induced correction that scales as a power law and produces a frequency-dependent temperature excess in the radio domain. Although the exponent $\gamma$ governing this scaling behaviour is not fixed internally by the present formulation of IR-QED and must instead be determined phenomenologically, the existence and structure of the excess are genuine predictions of the theory. Remarkably, the resulting expression is extremely simple and naturally aligns with the deviations suggested by the ARCADE 2 data. Taken together, these results indicate that Berry phases in IR-QED may lead to observable consequences in the low-frequency tail of the CMB spectrum.

The accelerated expansion of the universe poses a significant challenge to General Relativity. Non-local modifications to gravity have emerged as a compelling class of theories to address this dark energy puzzle. Building upon earlier proposals, we investigate a specific non-local modified gravity action incorporating terms like $R\Box^{-2}R$, $R^{\mu\nu}\Box^{-2}R_{\mu\nu}$, $R^{\mu\nu\sigma\delta}\Box^{-2}R_{\mu\nu\sigma\delta}$ and demonstrate that it provides a dynamical origin for a massive graviton by reducing to the standard and extended Fierz-Pauli action at the linearized level. A fixed-point analysis of the background cosmology reveals a stable de Sitter attractor, ensuring the model naturally drives accelerated expansion. Crucially, we investigate the cosmological perturbations and show that the theory's six propagating degrees of freedom are free from ghost instabilities. We further demonstrate that all large-scale tensor modes are dynamically stable and decay on the accelerating background. This ghost-free massive gravity extension provides distinct predictions for gravitational wave polarizations and is theoretically consistent with $\mathbf{\Lambda CDM}$ at late times, positioning it as a unique alternative to scalar-tensor models like $f(R)$ and Galileons. This robust stability at both the background and perturbative levels establishes our model as a consistent and compelling alternative to the standard $\Lambda$CDM paradigm.

In this work, we investigate late-time interacting cosmologies within the framework of generalized Rastall gravity, where the interaction arises naturally from the non-conservation of the energy-momentum tensor. We formulate the background evolution of the dark sector as an autonomous dynamical system, defining interaction terms $Q_1=\alpha\,\dot{f}$ and $Q_2=-\dot{f}\,(1+\alpha)$, with $\alpha$ a constant parameter and $f$ a time-dependent function. Three interaction cases are studied: $f \propto \rho_m$, $f \propto \rho_{de}$, and $f \propto \rho_m + \rho_{de}$, assuming a constant dark-energy equation of state $w_{de}$. For each scenario, we derive the closed dynamical system in terms of the density parameters $(\Omega_{de}, \Omega_m)$, identify its fixed points, and analyze their stability across the parameter space. In this context, the phase-space exhibits a standard cosmological dynamics: an unstable radiation point, a transient matter saddle, and a stable late-time attractor with accelerated expansion. In addition, we utilize a joint likelihood analysis with Cosmic Chronometers, PantheonPlus, and DESI data to obtain marginalized parameter estimates at the $68\%$ and $95\%$ confidence levels, constraining the parameter space in each interaction model.

In k-essence theories within general relativity, where the matter Lagrangian depends on a real scalar field $\phi$ and its kinetic term $X$, static and spherically symmetric compact objects with a positive-definite energy density cannot exist without introducing ghosts. We show that this no-go theorem can be evaded when the k-essence Lagrangian is extended to include a dependence on the field strength $F$ of a $U(1)$ gauge field, taking the general form ${\cal L}(\phi, X, F)$. In Einstein-scalar-Maxwell theories with a scalar-vector coupling $\mu(\phi) F$, we demonstrate the existence of asymptotically flat, charged compact stars whose energy density and pressure vanish at the center. With an appropriate choice of the coupling function $\mu(\phi)$, we construct both electric and magnetic compact objects and derive their metric functions and scalar- and vector-field profiles analytically. We compute their masses and radii, showing that the compactness lies in the range ${\cal O}(0.01)<{\cal C}<{\cal O}(0.1)$. A linear perturbation analysis reveals that electric compact objects are free of strong coupling, ghost, and Laplacian instabilities at all radii for $\mu(\phi)>0$, while magnetic compact objects suffer from strong coupling near the center.

It is well known that, at zero wavenumber, the non-hydrodynamic frequencies of uncharged kinetic theory are purely imaginary. On the other hand, it was recently shown that, in resistive magnetohydrodynamics, the interplay between the Israel-Stewart relaxation equation and the Ampère-Maxwell law can give rise to a pair of oscillating non-hydrodynamic modes. In this work, we analyze this phenomenon in detail. We first demonstrate that these oscillatory modes are exact solutions of the Drude model, corresponding to ordinary plasma oscillations. We then invoke the Onsager-Casimir principle to explain that their oscillatory nature reflects the distinct PT-transformation properties of the degrees of freedom: the distribution function is even, while the electric field is odd. Finally, we establish that, in a kinetic theory of charged particles, there can be at most one such pair of oscillatory modes per spatial dimension, while all other modes still must sit on the imaginary axis.

The interplay between supermassive black holes (SMBHs) and their surrounding environment is fundamental to understanding galactic evolution. This work investigates the influence of a cold dark matter (DM) halo on the dynamics of relativistic, low angular momentum, inviscid, and advective hot accretion flow onto a galactic SMBH. Modeling the spacetime geometry as a black hole embedded within various DM distributions, including those with a central density spike, we demonstrate that the presence of a DM halo, particularly one that is massive and compact, enhances the luminosity of the accretion disk. The dominant contribution to this luminosity originates from the inner regions of the flow, suggesting that luminosity measurements could serve as a valuable observational probe for the dense DM environments expected near galactic centers.

The singlet-doublet dark matter model offers a rich framework for exploring the nature of dark matter (DM) through its unique fermion structure. In this model, the important parameters are singlet-doublet mass splitting $\Delta{M}$, singlet-doublet mixing angle $\sin\theta$, and DM mass $M_{\rm DM}$. If the DM is assumed to be of Dirac nature, then the annihilation, co-annihilation, and conversion driven processes combinedly allows a range of parameter space: $1~{\rm GeV} \lesssim M_{\rm DM}\lesssim750$ GeV and $10^{-6}\lesssim\sin\theta\lesssim0.04$ for all $\Delta{M}>1$ GeV. While the nature of DM either Dirac or Majorana is not known, in this work we assume the nature of singlet-doublet DM to be of Majorana type and find that the relic density and direct detection can be satisfied in a larger parameter space. In particular, the allowed ranges of DM mass and $\sin\theta$ are: $1~{\rm GeV}\lesssim M_{\rm DM}\lesssim1750$ GeV and $2\times10^{-7}\lesssim\sin\theta\lesssim0.16$ for all $\Delta{M}>1$ GeV.

The use of machine learning to represent subgrid-scale (SGS) dynamics is now well established in weather forecasting and climate modelling. Recent advances have demonstrated that SGS models trained via ``online'' end-to-end learning -- where the dynamical solver operating on the filtered equations participates in the training -- can outperform traditional physics-based approaches. Most studies, however, have focused on idealised periodic domains, neglecting the mechanical boundaries present e.g. in planetary interiors. To address this issue, we consider two-dimensional quasi-geostrophic turbulent flow in an axisymmetric bounded domain that we model using a pseudo-spectral differentiable solver, thereby enabling online learning. We examine three configurations, varying the geometry (between an exponential container and a spherical shell) and the rotation rate. Flow is driven by a prescribed analytical forcing, allowing for precise control over the energy injection scale and an exact estimate of the power input. We evaluate the accuracy of the online-trained SGS model against the reference direct numerical simulation using integral quantities and spectral diagnostics. In all configurations, we show that an SGS model trained on data spanning only one turnover time remains stable and accurate over integrations at least a hundred times longer than the training period. Moreover, we demonstrate the model's remarkable ability to reproduce slow processes occurring on time scales far exceeding the training duration, such as the inward drift of jets in the spherical shell. These results suggest a promising path towards developing SGS models for planetary and stellar interior dynamics, including dynamo processes.

Large Language Models have demonstrated the ability to generalize well at many levels across domains, modalities, and even shown in-context learning capabilities. This enables research questions regarding how they can be used to encode physical information that is usually only available from scientific measurements, and loosely encoded in textual descriptions. Using astrophysics as a test bed, we investigate if LLM embeddings can codify physical summary statistics that are obtained from scientific measurements through two main questions: 1) Does prompting play a role on how those quantities are codified by the LLM? and 2) What aspects of language are most important in encoding the physics represented by the measurement? We investigate this using sparse autoencoders that extract interpretable features from the text.