Papers for Friday, Feb 13 2026

Magneto-Rossby waves in the solar tachocline are currently considered to be one of the main determinants of solar activity. In particular, they can give rise to the quasi-biennial oscillation (QBO). The latter was recently shown to be dominated by a phase-stable period of around 1.7 years. By analyzing 72 ground-level enhancement (GLE) events and 37 S-flares, we determine that this period is close to 1.723 years. This, in turn, is the dominant beat between the periods of the spring tides of the tidally dominant planets Venus, Earth, and Jupiter, which are suspected to synchronize not only the QBO, but also the 11.07-year Schwabe cycle. We demonstrate that recent events, such as the solar storm of 2024 May 10 and the strong X-flare of 2026 February 1, align well with maxima of the tidal forcing. By contrast, the Carrington event (1959 September 1) does not fit this pattern.

We analyse different properties of central low-surface-brightness galaxies (LSBGs) and their satellite systems using the simulation Illustris TNG-100, in order to deepen our understanding of the formation mechanism of LSBGs in a $\Lambda$CDM cosmology. We find differences in the spin and the concentrations of the LSBGs haloes and the host haloes of high-surface-brightness galaxies (HSBGs), consistent with previous studies. By analysing their spatial and kinematical distribution of satellites, we find that LSBGs tend to have a larger number of satellites than HSBGs and with a larger velocity dispersion. Moreover, we obtain a continuous relation between the number of satellites and surface brightness, particularly for massive central galaxies. We also find a relation between surface brightness and the relative tangential velocity of the satellites. For a given stellar mass, the existence of LSBGs is strongly correlated with their satellite system dominated by rotation. Furthermore, the satellite system is systematically in counter-rotation with respect to the primary disc in LSBGs. We propose that this fact reflects that these galaxies have not experienced a significantly high rate of mergers, which are more likely associated with radial orbits expected in systems of galaxies with a high surface brightness.

We obtain three-dimensional distributions of CO and SiO molecules from high spatial resolution (0.03--0.06") ALMA observations of SN 1987A at two different epochs. The evolution between these two epochs is consistent with homologous expansion. From these 3D maps, we reconstruct the 3D mass distributions of the ejecta in CO and SiO molecules, which we compare with those obtained by state-of-the-art, long-time hydrodynamical supernova explosion models computed with the Prometheus-HotB code for 10 different progenitors, including both red and blue supergiants. The models which best match the mass distributions correspond to explosions of binary-merger blue supergiant progenitors; at least two such models approximately reproduce the observed CO morphology. In contrast, the SiO velocity distribution and morphology are not as well reproduced in these models, indicating insufficient mixing of Si into the outer layers already at the progenitor stage. The theoretical models suggest a strong correlation between the centre of mass of the densest carbon- and oxygen-rich ejecta and the direction of the neutron-star kick. If such a correlation also applies to the CO emission in the ejecta of SN 1987A, the kick of the compact remnant is expected to point towards the observer, at an angle of approximately $45^\circ$ to the north.

While compact, star-forming galaxies are believed to play a key role in cosmic reionization, the physical mechanisms enabling the escape of ionizing photons through the galactic interstellar medium remain unclear. Supernova (SN) feedback is one possible mechanism for clearing neutral gas channels to allow the escape of Lyman continuum photons. Here, we use SN discoveries in low-redshift analogs of high-redshift star-forming galaxies -- Green Pea galaxies and their even lower-redshift counterparts, Blueberry (BB) galaxies -- to understand how SNe shape the properties of their host galaxies at high redshifts. We cross-match 1242 BB galaxies with transient discovery reports and identify 11 SNe, ten of which are likely core-collapse SNe, and compare their hosts to the larger BB population. We find that SN-hosting BBs exhibit elevated star formation rates, burstier star formation histories within the last $\sim$50 Myr, and higher stellar masses. We estimate the occurrence rates of SNe in BB galaxies, finding that the SN rate may be slightly suppressed in BBs compared to field galaxies of similar mass, but we are unable to fully control for observational uncertainties. Finally, SN hosts show bluer UV slopes than non-host BB galaxies at 2.1$\sigma$ significance and lower ionizing photon production efficiency at 7.9$\sigma$ significance; the former result offers modest support for the hypothesis that SN-driven feedback plays a role in facilitating the escape of ionizing photons, while the latter may imply that SN-driven quenching decreases the rate of ionizing photon production in compact star-forming galaxies during the epoch of reionization.

We present a fully Bayesian framework for time delay inference and stationarity tests in quasar light curves using marginalised Gaussian processes. The model separates a deterministic, non-stationary drift (piecewise linear mean) from stationary stochastic variability (Matérn and Spectral Mixture kernels), and jointly models multiple images with per-image microlensing. Bayesian evidence and parameter posteriors are obtained via nested sampling and marginalised over model choices. Applied to the quasars WFI J2033 - 4723, B 1608 + 656, and HE 0435 - 1223, we find strong evidence for non-stationarity in B 1608 + 656 and HE 0435 - 1223, while WFI J2033 - 4723 is consistent with stationarity. The stochastic component favours an Markovian exponential kernel for B 1608 + 656 and a non-Markovian Matérn-$\frac32$ kernel for WFI J2033 - 4723 and HE 0435 - 1223. Multi-length-scale Spectral Mixture kernels are disfavoured. Time delays are shown to be robust to model assumptions and consistent with prior work within the error. We further identify and mitigate a likelihood pathology which biases toward large delays, providing a practical nested sampling convergence protocol.

Centaurus A (CenA) and M83 form one of the most massive galaxy pairs in the nearby Universe. Although their observed heliocentric velocities suggest motion that is not obviously indicative of mutual attraction, this work presents evidence that CenA and M83 are in fact infalling toward each other, exhibiting a dynamical interaction analogous to the binary-like motion of the Milky Way and Andromeda in the Local Group (LG). Using the Timing Argument (TA), calibrated with analog galaxy pairs from the AbacusSummit simulation, we estimate the total mass of the CenA/M83 system under the assumption that the line-of-sight (LoS) velocity is dominated by motion toward the system's barycenter. This yields a total mass of $(6.36 \pm 1.30) \cdot 10^{12}\, M_\odot$. The inferred mass agrees well with independent estimates based on virial mass measurements and $K$-band luminosity--to-mass ratios. Together, the consistent bound signature and robust mass determination highlight the CenA/M83 system as a compelling nearby analog to the LG. Further discussion of NGC 4945 as a main perturber (as the Large Magellanic Could) for the CenA is also discussed.

Recently discovered quasar pairs at high redshifts ($z\gtrsim$5) are likely precursors to supermassive black hole mergers, providing a promising window to high redshift quasar growth mechanisms. However, the large uncertainties on their relative distances along the line-of-sight ($d_{\rm l.o.s.}$) limits our ability to characterize quasar pairs. In this study, we explore synthetic quasar proximity zone spectra as an alternative method to constrain the line-of-sight distance of quasar pairs. We find that for small sky-plane separations ($d_{\rm sky}\approx 10-100$ pkpc), a simple peak finding algorithm can easily distinguish between scenarios of $d_{\rm l.o.s.} \lesssim1$ pMpc and $\gtrsim1$ pMpc. For cases where the true $d_{\rm l.o.s.} \geq 3$ pMpc, the accuracy of $d_{\rm l.o.s.}$ estimation is $\approx 0.2$ pMpc. Large sky-plane separations of $d_{\rm sky}=1$ pMpc have larger absolute uncertainties in $d_{\rm l.o.s.}$ estimates, but the method can still easily distinguish between scenarios where $d_{\rm l.o.s.}\lesssim4$ pMpc and $\gtrsim4$ pMpc. $d_{\rm l.o.s.}$ estimates have an uncertainty of $\approx$0.5 pMpc when true $d_{\rm l.o.s.} \gtrsim4$ pMpc. Our proof-of-concept study illustrates the potential use of quasar proximity zones to constrain the 3-dimensional quasar pair configuration, providing an avenue to characterize quasar pairs.

The satellite system of Centaurus A presents a curious cosmological puzzle: while the global population is consistent with theoretical expectations, its inner regions (d<150 kpc) exhibit a deficit of luminous satellite galaxies. Using the Galacticus semi-analytic model applied to high-resolution N-body merger trees, we investigate potential quenching mechanisms to explain this trend. Our fiducial models, calibrated to the Milky Way, reproduce the overall Cen A population but overpredict the number of bright inner-halo satellites by a factor of 4 +- 1 at Mv < -15.8. We find that this is not due to statistical variance. Instead, the spatial coincidence of this deficiency with Cen A's massive, kiloparsec-scale radio lobes suggests a powerful environmental driver. We explore a range of physical scenarios, including enhanced tidal disruption, reionization quenching, and suppressed accretion into halos from the surrounding intergalactic medium. Our results indicate that AGN-driven thermal feedback at z < 5 can significantly suppress star formation in satellites, effectively truncating the bright end of the inner luminosity function. Our work suggests that the "Curious Case of Centaurus A" may provide evidence of AGN feedback within the host galaxy that regulates the survival and evolution of its dwarf galaxy satellites.

Small exoplanet radii show two populations, referred to as super-Earths and sub-Neptunes, separated by a gap known as the radius valley. This may be produced by the removal of atmospheres due to stellar or internal heating, or lack of an initial envelope. We us transit photometry and radial velocity measurements to detect and characterize four planets orbiting LHS 1903, a red dwarf (M-dwarf) star in the Milky Way's thick disk. The planets have orbital periods between 2.2 and 29.3 days, and span the radius valley within a single planetary system. The derived densities indicate that LHS 1903 b is rocky, while LHS 1903 c and LHS 1903 d have extended atmospheres. Although the most distant planet from the host star, LHS 1903 e, has no gaseous envelope, indicating it formed from gas-depleted material.

Assuming spherical symmetry and dynamical equilibrium within a given gravitational potential, a dwarf spheroidal (dSph) galaxy's globally averaged stellar velocity dispersion depends entirely on the shape of its stellar density profile. Thus, the dynamical inference of a dSph's gravitational potential is necessarily sensitive to assumptions about that shape. Relaxing standard assumptions, we fit flexible stellar density models to observations of the Milky Way's known dSph satellites. Considering various choices for the density profile shape and spatial extent of a host dark matter halo, we use the virial theorem to propagate observational uncertainties about the shapes of the inferred dSph stellar density profiles to uncertainties in the inferred dynamical masses. We find that the observed structural diversity of the Milky Way dSph population implies a large range of potential systematic errors (up to factors of 10) associated with standard dynamical mass estimators. We show that accounting for these observational and systematic uncertainties can significantly alter the appearance and behavior of dSph dynamical scaling relations, including enclosed dynamical mass vs. stellar mass and the Radial Acceleration Relation.

Transitional millisecond pulsars (tMSPs) are old neutron stars spun up by accretion from a low-mass companion. These objects can switch between two emission regimes: rotation-powered radio pulsar and accreting X-ray pulsar. The origin of their optical and X-ray pulsations is still debated, although one model attributes them to synchrotron emission produced in a shock between the pulsar wind and the accretion flow. The small phase lag observed between optical and X-ray pulses in PSR J1023+0038 supports a common origin. We present a new measurement of the phase lag between optical and X-ray pulse profiles of PSR J1023+0038 and investigate the evolution of the time of passage at the ascending node ($T_{\rm{asc}}$) up to 2023. We performed a timing analysis of optical observations obtained with Aqueye+ between 2021 and 2023 and of X-ray data from NICER in 2023. We derive updated values of $T_{\rm{asc}}$ and measure the optical - X-ray phase lag from simultaneous observations. We find that $T_{\rm{asc}}$ increases by about 20 s per year. In January 2023, we measure a phase lag of $0.067 \pm 0.018$, corresponding to $112.3 \pm 30.7\,\mu$s. Since 2017, the evolution of $T_{\rm{asc}}$ follows a parabolic trend, indicating an increase in the orbital period and orbital separation of the system. This behaviour is consistent with non-conservative Roche-lobe overflow, with the donor losing mass at a rate much higher than the accretion rate. The phase lag measurement further supports a common origin of the optical and X-ray pulsations.

Galaxies evolve within vast gaseous halos that fuel star formation and carry signatures of feedback-driven outflows. Deep integral field data have enabled the study of MgII halos, which trace galaxy-scale outflows in emission, but their faintness has limited studies to single-object analyses. Here, we present the first statistical study of MgII-emitting halos using deep MUSE observations of 47 star-forming galaxies at $0.7<z<2.0$. Building on our previous work, where we developed and applied an outflow modeling framework for a single MgII halo, we now extend this approach to a larger sample, enabling robust population-level insights on the properties of circumgalactic outflows traced by their extended MgII emission. We detect extended emission out to tens of kiloparsecs and model the outflows as an ensemble of radially accelerating shells. Galaxies with MgII outflows tend to have higher SFRs, sSFRs, and younger stellar populations, consistent with star-formation-driven winds. The observations are consistent with winds that accelerate linearly with radius, from launching velocities of ~60 km/s up to maximum velocities that correlate with stellar mass and reach ~490 km/s. Their inner regions are highly opaque, and we find a tentative trend between stellar mass and central optical depth. The opening angle of the outflow shows some dependency on the host-galaxy stellar mass, with less massive galaxies showing primarily wide opening angles, and more massive galaxies showing a broader range of values, with both wide and narrow opening angles. The distribution of the spatial extent of MgII halos exhibits a clear peak at half-light radius (HLR) of ~5 kpc, with an extended tail of larger HLR values, up to ~20 kpc. Compact halo sizes (HLR $< 8$ kpc) correlate with stellar mass, but extended halos do not, which could suggest a difference in the powering mechanism between compact and extended halos.

Estimating redshift is a central task in astrophysics, but its measurement is costly and time-consuming. In addition, current image-based methods are often validated on homogeneous datasets. The development and comparison of networks able generalize across different morphologies, ranging from galaxies to gravitationally-lensed transients, and observational conditions, remain an open challenge. This work proposes DeepRed, a deep learning pipeline that demonstrates how modern computer vision architectures, including ResNet, EfficientNet, Swin Transformer, and MLP-Mixer, can estimate redshifts from images of galaxies, gravitational lenses, and gravitationally-lensed supernovae. We compare these architectures and their ensemble to both neural networks (A1, A3, NetZ, and PhotoZ) and a feature-based method (HOG+SVR) on simulated (DeepGraviLens) and real (KiDS, SDSS) datasets. Our approach achieves state-of-the-art results on all datasets. On DeepGraviLens, DeepRed achieves a significant improvement in the Normalized Mean Absolute Deviation compared to the best baseline (PhotoZ): 55% on DES-deep (using EfficientNet), 51% on DES-wide (Ensemble), 52% on DESI-DOT (Ensemble), and 46% on LSST-wide (Ensemble). On real observations from the KiDS survey, the pipeline outperforms the best baseline (NetZ), improving NMAD by 16% on a general test set without high-probability lenses (Ensemble) and 27% on high-probability lenses (Ensemble). For non-lensed galaxies in the SDSS dataset, the MLP-Mixer architecture achieves a 5% improvement over the best baselines (A3 and NetZ). SHAP shows that the models correctly focus on the objects of interest with over 95% localization accuracy on high-quality images, validating the reliability of the predictions. These findings suggest that deep learning is a scalable, robust, and interpretable solution for redshift estimation in large-scale surveys.

Pair-instability supernovae leave behind no compact remnants, resulting in a predicted gap in the distribution of stellar black-hole masses. Gravitational waves from binary black-hole mergers probe the relevant mass range and analyses of the LIGO-Virgo-KAGRA catalog (GWTC-4) indicate a possible mass cutoff at $40$-$50M_\odot$. However, the robustness of this result is yet to be tested. To this end, we simulate a comprehensive suite of gravitational-wave catalogs with full Bayesian parameter estimation and analyze them with parametric population models. For catalogs similar to GWTC-4, confident identification of a cutoff is not guaranteed, but GWTC-4 results are compatible with the best constraints among our simulations. Conversely, spurious false identification of a cutoff is unlikely. For catalogs expected by the end of the O4 observing run, uncertainty in the cutoff mass is reduced by $\gtrsim20\%$, but a cutoff at $40$-$50M_\odot$ yields only a lower bound on the $^{12}\mathrm{C}(\alpha,\gamma)^{16}\mathrm{O}$ reaction rate, which in terms of the S-factor at $300\,\mathrm{keV}$ may be $S_{300}\gtrsim125\,\mathrm{keV}\,\mathrm{b}$ at $90\%$ credibility by the end of O4. Relative uncertainties on the Hubble parameter $H_0$ from gravitational-wave data alone can still be up to $100\%$. We also analyze GWTC-4 with the nonparametric PixelPop population model, finding that some mass features are more prominent than in parametric models but a sharp cutoff is not required. However, the parametric model passes a likelihood-based predictive test in GWTC-4 and the PixelPop results are consistent with those from our simulated catalogs where a cutoff is present. We use the simple focus of this study to emphasize that such tests are necessary to make astrophysical claims from gravitational-wave catalogs going forward.

In the context of a spatially flat $\Lambda(t)$CDM cosmology, we investigate interacting dark energy (IDE) scenarios characterized by phenomenological interaction terms proportional to the Hubble expansion rate and the dark energy density. Our analysis is performed at both the background and linear perturbation levels, with particular emphasis on the evolution of dark matter density fluctuations. Cosmological constraints are derived from a joint analysis of CMB distance priors, Baryon Acoustic Oscillations (BAO), Type Ia supernovae (SNe Ia) from Pantheon+, Redshift-Space Distortions (RSD), and $H(z)$ data from Cosmic Chronometers (CC). Using the linear growth of matter perturbations, we estimate the clustering parameter $S_8$ within IDE extensions of the flat $\Lambda(t)$CDM framework. At the perturbative level, we consider interaction terms of the form $Q_{\text{I}}=\varepsilon a H\bar{\rho}_{\Lambda(t)}$ (Model I) and $Q_{\text{II}}=\varepsilon H\bar{\rho}_{\Lambda(t)}$ (Model II). From the combined dataset, we obtain the constraints $S_8 = 0.870 \pm 0.026$ for Model I and $S_8 = 0.872 \pm 0.026$ for Model II. Finally, we discuss the implications for the coupling parameter $\varepsilon$, taking into account the semi-analytical approximations and observational data employed in this study.

Nanophase iron (npFe) plays a crucial role in controlling the optical, chemical, and physical evolution of lunar regolith grains. While in-situ formation of npFe via reduction of native Fe-bearing minerals has long been considered a dominant pathway, recent mineralogical evidence from this http URL et al. (2025) reveals that the source of a significant fraction of npFe may be delivered directly by exotic micrometeoroid impacts (exotic npFe). Yet the atomic-scale processes governing how exotic np-Fe forms and survives during hypervelocity impacts remain largely unknown. To quantitatively compare in-situ and exotic delivery and formation of npFe, we perform a series of innovative atomistic modeling of micrometeoroid impacts with distinct projectile target compositions: (1) SiO$_2$ projectiles on Fe$_2$SiO$_4$ targets (in-situ formation), (2) Fe$_2$SiO$_4$ projectiles on SiO$_2$ targets (exotic delivery). Our results reveal distinct mechanistic fingerprints: in-situ np-Fe forms diffusely and radially around the impact site, whereas exotic np-Fe is efficiently retained and concentrated in asymmetric, momentum-aligned clusters. These contrasting spatial signatures provide a potential diagnostic criterion for distinguishing exotic versus in-situ np-Fe in returned lunar soils. In agreement with Chang'e-5 observations, our simulations demonstrate that exotic np-Fe production can be substantial, particularly in Fe-poor terrains such as highland regions. These findings highlight the need to account for exotic np-Fe when interpreting space weathering processes and remote-sensing data for the Moon and other airless bodies.

We investigate thermonuclear explosions within the delayed detonation framework. While spherical delayed detonation models generally reproduce key observational features, a fundamental inconsistency emerges in three dimensions: 3D hydrodynamic simulations exhibit insufficient white dwarf expansion during the deflagration phase. We identify the early deflagration stage, when the burning is dominated by the laminar speed, as a critical phase and explore potential solutions using three dimensional magnetohydrodynamic simulations performed with the FLASH code. In hydrodynamical simulations, the early deflagration phase produces large pockets of unburned C/O, leading to inefficient burning. Much of the released energy is deposited into buoyantly rising plumes rather than into the global pre-expansion of the white dwarf, which is required to produce the partially burned layers characteristic of SNe Ia. In contrast, when preexisting turbulent velocity fields and strong magnetic fields, on scales expected from the smoldering phase, are included, the effective burning approaches that in spherical models. Both turbulence and magnetic fields promote the entrainment of burned material into unburned pockets, addressing a long-standing problem in multi-dimensional deflagration models. The resulting streaks of burned material enable the conductive ignition of the surrounding unburned fuel. The dominant effect is not a change in the small-scale flame physics (~10^{-3} cm), but rather enhanced mixing between burned and unburned material. As expected, this mechanism is most efficient when the turbulent length scales are smaller than those of the unburned plumes.

The development of molecular complexity during stellar and planetary formation owes much to the interaction of gas and dust. When the first astrochemical models including solid-state chemistry were developed more than forty years ago, data from dedicated laboratory experiments were limited. Since then, many groups have developed specific experimental setups to address this issue, but astrochemical models have rarely been directly confronted with these new results. We want to demonstrate whether it is possible to use rate-equation-type astrochemical models developed in the context of the Interstellar Medium to compare them with laboratory astrophysics experiments. In this work, we use the case of low-temperature hydrogenation of CO, which is known to lead to methanol, among other molecules. We carried out 9 experiments, varying the experimental parameters such as temperature and dose. We give quantitative results and take care of detailing the vocabulary used in the experiments. We use astrochemical codes, NAUTILUS, pyRate and MONACO, to reproduce our experimental conditions, which requires good control of the change of vocabulary and scales, especially for fluxes and time scales. This work demonstrates that it is possible to use different astrochemical codes to compare modelling results directly with the output of experiments. There are discrepancies between models and experiments, as well as between models, but a fair agreement is achieved. We discuss the possible origin of the differences, which could originate from the chemical network or the difference in the description of physical processes.

The rhoOphW photo-dissociation region (PDR) is an example source of bright excess microwave emission (EME), over synchrotron, free-free, and the Rayleigh-Jeans tail of the sub-millimetre (sub-mm) dust continuum. Its filamentary morphology follows roughly that of the IR poly-cyclic aromatic hydrocarbon (PAHs) bands. The EME signal in rhoOphW drops abruptly above ~30GHz and its spectrum can be interpreted in terms of electric-dipole radiation from spinning dust grains, or ``spinning dust''. Deep and high-fidelity imaging and spectroscopy of rhoOphW may reveal the detailed morphology of the EME signal, free from imaging priors, while also enabling a search for fine structure in its spectrum. The same observations may constrain the spectral index of the high-frequency drop. An ALMA Band1 mosaic yields a deep deconvolved image of the filament at 36-44GHz, which we use as template for the extraction of a spectrum via cross-correlation in the uv-plane. Simulations and cross-correlations on near-infrared ancillary data yield estimates of flux-loss and biases. The spectrum is a power law, with no detectable fine structure. It follows a spectral index alpha=-0.78+-0.05, in frequency, with some variations along the filament. Interestingly, the Band1 power at high spatial frequencies increases relative to that of the IR signal, with a factor of two more power in Band1 at ~20'' than at ~100'' (relative to IRAC3.6um). An extreme of such radio-only structures is a compact EME source, without IR counterpart. It is embedded in strong and filamentary Band1 signal, while the IRAC maps are smooth in the same region. We provide multi-frequency intensity estimates for spectral modelling.

Resolved metallicity studies of local disk galaxies have revealed that their interstellar media (ISMs) are far from chemically homogeneous, displaying significant ($\sim 0.05$ dex) variations in the metallicity on characteristic scales of a few hundred parsecs. Such data is at odds with most analytical models, where the ISM is predicted to be more well-mixed. Here, we suggest that the observed small-scale features seen in galaxies may be superbubbles of metal-enriched gas created by a collection of core collapse supernovae with tight spatial (and temporal) correlation. In this scenario, the size of the metallicity fluctuations (superbubble radius, $\phi$) is set by the disk scale height of the galaxy in question (after which point shock breakout favours preferential expansion along directions perpendicular to the dense disc), and the amount of additional metals contained within a fluctuation is proportional to the star formation efficiency in superbubble regions ($\epsilon$). To test this theory, we analysed metallicity maps from the PHANGS-MUSE sample of galaxies using a geostatistical forward-modelling approach. We find $\phi \simeq 300$ pc and $\epsilon = 0.1-0.2$, in good agreement with our theoretical model. Further, these small-scale parameters are found to be related to the global galaxy properties, suggesting that the local structure of the interstellar medium of galaxies is not universal. Such a model of star formation paints a new picture of galaxy evolution in the modern universe: in large local galaxies, star formation appears steady and regular when averaged over large scales. However, on small scales, these large galaxies remain intrinsically bursty like their smaller, high-redshift counterparts.

To investigate the origin of the dependence of the covering factor on the Eddington ratio suggested by X-ray observations, we examined the angular distribution of HI and HII based on two-dimensional radiative hydrodynamic simulations. To calculate the Compton-thin covering factor $C_{22}$ and Compton-thick covering factor $C_{24}$ of HI alone, we performed one-dimensional photoionization equilibrium calculations with the XSTAR code based on radiative hydrodynamic simulations. The results obtained are as follows. (1) The Compton-thin covering factor $C_{22}$ of HI and HII is independent of the Eddington ratio and is approximately $70\%$, while $C_{22}$ of HI alone is also independent of the Eddington ratio and is approximately $30\%$. (2) The Compton-thick covering factor $C_{24}$ of HI has the same value as $C_{22}$ of HI. (3) Our $C_{24}$ is consistent with that obtained from X-ray observations. (4) Our $C_{22}$ agrees with that obtained from X-ray observations in a high Eddington ratio, while our $C_{22}$ is smaller than that from X-ray observations in a low Eddington ratio. (5) To explain the difference between $C_{22}$ obtained from theoretical calculations and that inferred from X-ray observations, a Compton-thin gas is required in regions extending at least $10~\mathrm{pc}$ beyond the current computational regions.

The orbit of a black hole moving within an ultralight dark matter (ULDM) soliton is naively expected to decay due to dynamical friction. However, single black holes can undergo ``stone skipping'', with their orbital radius varying quasi-periodically. We show that stone skipping is induced by the dipole excitation of the soliton. We model it as resonance in a forced, damped harmonic oscillator, demonstrating that the coherent response of the soliton can significantly modify the dynamics of objects orbiting within it. This suggests that a dipole perturbation of a soliton can modify inspiral timescales if the black holes masses are significantly less than the soliton mass, with implications for supermassive black hole dynamics, the final parsec problem and gravitational wave observations in a ULDM cosmology.

Warm Jupiters-giant exoplanets with orbital periods between 10 and 200 days-exhibit a broad range of eccentricities and are often accompanied by nearby low-mass planets. Understanding the origins of their orbital architectures requires examining both their migration histories and subsequent dynamical interactions. In this study, we perform extensive N-body simulations to explore how distant giant planet perturbers affect the eccentricity evolution of warm Jupiters and the role of nearby super-Earth companions in mediating these interactions. We find that while distant perturbers can induce large-amplitude eccentricity oscillations in warm Jupiters via the von Zeipel-Lidov-Kozai mechanism, the presence of nearby super-Earth companions often suppresses these variations via strong dynamical coupling. This mechanism naturally leads to a bimodal eccentricity distribution: warm Jupiters with nearby companions tend to maintain low eccentricities, whereas those without exhibit significantly broader eccentricity distributions. We show that reproducing the observed eccentricity distribution of warm Jupiters lacking nearby companions is most naturally explained if a substantial fraction of distant perturbers occupy dynamically extreme orbits, either with large mutual inclinations or high orbital eccentricities. These results support a scenario in which warm Jupiters experience substantial post-disk dynamical evolution, shaped jointly by distant perturbers and nearby companions.

We use our home catalog of the asteroid proper elements to study the Karin family. The hierarchical clustering method provides formal identification with 3,863 members, but this set also includes objects from the neighboring Koronis2 and Kuitaisi families, as well as interlopers originating from the much older Koronis family. By tracking the trajectories of cluster objects backward in time, we identified 2,161 asteroids whose orbits converged with that of their parent body (832) Karin at $5.72\pm 0.09$ My ago ($95$\% C.L.). This method of calculating the family's age is based on a novel convergence metric that is directly related to the velocities at which fragments were ejected from (832) Karin. We analyze the extent to which members $\leq 1.5$ km in diameter had drifted in semimajor axis due to Yarkovsky thermal forces and find it reflects the tilt of their rotation poles away from the ecliptic, recording the influence of the YORP torque. Karin's size frequency distribution in the $\simeq(0.8-3)$ km range follows a power-law with a cumulative slope index $-3.20\pm 0.01$. Removing members of the Karin family from the original group, we examine the Koronis2 family, whose members are associated with (158) Koronis. We find it difficult for large members of the Koronis2 family to converge with the orbit of (158) Koronis within its previously estimated age of $7.6$ My. Achieving such convergence would require the Koronis2 family to be older than $10$ My, but our result must be verified with a direct numerical approach in the future.

Recent time-domain surveys have revealed rapid transients that evolve on timescales of $\lesssim 10$ days, expanding the transient population into the short-duration regime. The transient search on even shorter timescales, particularly those lasting only seconds or less, remains a largely unexplored frontier. Very short-duration optical transients could serve as potential counterparts to millisecond-duration fast radio bursts (FRBs), providing clues to their origins. However, the optical search for transients on such short timescales has been limited primarily by instrumental constraints. Here we report the discovery of an optical transient candidate (TMG20200322) with a duration of $\lesssim 2$~s by wide-field video observations in the direction of the Earth's shadow. TMG20200322 was detected in just two consecutive images of 1-second exposure time, with its shape becoming elongated in the second frame. PSF shape variability analysis of field stars reveals that such an elongated PSF cannot be explained by atmospheric fluctuations. We investigate the potential origins of TMG20200322 in two scenarios: meteoroid impact flashes on near-Earth asteroids (NEAs) and head-on meteors in the Earth's atmosphere. None of the scenarios provides a satisfactory explanation for this transient. We derive a sky-projected rate of the TMG20200322 event of $R_{\mathrm{trans}} = (3.4 \times 10^{-2})^{+0.13}_{-0.028}$~deg$^{-2}$~day$^{-1}$ and an upper limit on second-timescale transients with durations of $1~\mathrm{s} \leq \tau \lesssim 15~\mathrm{s}$ of $R_{\mathrm{trans}} \lesssim 0.10$~deg$^{-2}$~day$^{-1}$ for the non-detection case. We highlight that continuous monitoring observations in the direction of the Earth's shadow could be a key strategy to unveil a new population of optical transients on timescales of seconds or less.

Understanding disc-corona geometry through X-ray reverberation variability studies in Seyfert galaxies is crucial, yet our knowledge mostly relies on flux-averaged mean spectral analysis. In this study, we investigate the origin of the large X-ray variability of the Seyfert 1 galaxy NGC 4593 using two \xmm{} observations, which are at least 65 ksec long and have a 0.3-10 keV X-ray flux difference by a factor of $\sim$2.5. We extracted mean spectra, Fourier-frequency resolved covariance, and time-lag spectra and performed modelling of all spectra in a self-consistent manner. From the best-fit covariance spectra, we have shown that energy-dependent covariance during low flux shows dominances of direct powerlaw continuum over reflection continuum at all Fourier frequencies (2.1 $-$ 390 $\times$ 10$^{-5}$ Hz). However, during high flux, the variabilities are dominated by the reflection components most of the time. Our results are further supported by the Fourier frequency-dependent time-lag (between soft: 0.3-1 keV and hard: 1-5 keV bands) spectral modeling during high and low fluxes. A significant change is observed in the X-ray reverberation delay timescale from 483 $\pm$ 135 sec (during high flux) to $<$96 sec (during low flux), indicating a change in coronal size at least by a factor of $\sim$2 (from $<$3.3 R$_g$ to $>$7.2 R$_g$) during low to high flux transitions.

The quenching of star formation is a crucial phase in galaxy evolution. Although active galactic nuclei (AGN) feedback has been proposed as a key driver of this transition, the lack of strong AGN in nearby quenching galaxies raises questions about its effectiveness. In this study, we investigate AGN activity in post-starburst galaxies (PSBs), star-forming galaxies (SFGs), and quiescent galaxies (QGs) at $z<$ 0.2, using multiwavelength data from eROSITA/eFEDS (X-ray), WISE (mid-infrared), and FIRST (radio). We assess AGN incidence and strength across different stages and apply stacking techniques to undetected galaxies to recover average AGN properties. Comparisons between observed luminosity and that expected from star formation (L$_{\rm obs}$/L$_{\rm SF}$) show that PSBs are consistent with star formation dominating their radio and X-ray emission. Although PSBs exhibit a MIR AGN incidence rate twice that of SFGs, their estimated AGN luminosities are small compared to those of MIR AGN in the literature. PSBs overall do not display significantly enhanced AGN emission relative to mass- and redshift-matched SFGs and QGs. While the presence of obscured, low-luminosity AGN in PSBs cannot be excluded, such AGN, if present, could be fueled by residual gas from the preceding starburst and may not play a dominant role in quenching. Our findings suggest that AGN's role in quenching at low redshift is more subtle than violently removing the gas -- the feedback is likely more "preventive" than "ejective".

Solar atmospheric elemental abundances are now known to vary both in space and time. Dynamic modeling of these changes is therefore necessary to improve the accuracy of radiative hydrodynamic simulations. Recent studies have shown that including spatio-temporal variations in coronal abundances during solar flares leads to the formation of coronal condensations (rain), which are otherwise difficult to create in impulsively heated field aligned hydrodynamic flare models. These simulations start with a solar corona dominated by the first ionization potential (FIP) effect, and evaporate photospheric material into the post-flare loops. We here explore perhaps the most extreme non-solar starting condition for the coronal composition in these simulations: an initial corona dominated by the inverse FIP (iFIP) effect, such as is observed on active M-dwarf stars. We show that a flaring event in a corona enriched with high FIP elements leads to a solution similar to the solar case. Coronal rain is harder to form by this method during flares on M-dwarfs, however, if the corona is depleted of low FIP elements.

We numerically investigate stochastic dynamics in cosmology by solving Langevin equations for Infrared (IR) modes with stochastic noises generated by Ultraviolet (UV) modes at the coarse-graining scale. By construction, the stochastic formalism relies on the separation of scales, which requires solving the equations for UV modes on top of the evolving IR modes for all modes at every time step, leading to a non-Markovian system in general. In this paper, working on a de Sitter background, we analyze several representative models by simultaneously solving the Langevin equations for IR modes and the equations for UV modes at each time step. We demonstrate that once the effects of effective masses are treated consistently by our simulation, the flat direction in the minimal supersymmtric model (MSSM) does not saturate but instead evolves as an exactly flat direction. Furthermore, we investigate memory effects in simple two models; $V=\lambda\phi^4$ and $V=\mu\phi\chi + \lambda\phi^4$, and non-Markovian contributions can lead to quantitative differences, even in stationary configurations, when compared with Markovian approximations, particularly in the strong-coupling regime.

By extending the Hubble Frontier Fields (HFF) observations to the F225W band using HST WFC3/UVIS, we measure the rest-frame UV luminosity function (LF) of galaxies at $0.4 < z < 0.7$, pushing into the low-luminosity galaxy regime. In this first paper of a series, we describe the HST Cycle-27 GO-15940 F225W observations and data reduction, and present a corresponding catalog for the Abell 2744 field, which is the most data-rich HFF cluster field. Combining deep Near-UV imaging and the high magnification from strong gravitational lensing of the foreground cluster, we identify 152 faint galaxies with $-19.5 < M_{UV} < -12.1$ at $0.4 < z < 0.7$ through hybrid photometric-spectroscopic redshift selection from the Abell 2744 F225W catalog. Using a sample defined by a $50\%$ completeness cut and applying the maximum likelihood estimation, we derive the best-fit Schechter parameters for the UV LF at $z \sim 0.55$ down to $M_\text{UV} < -13.5$ mag, including a faint-end slope of $\alpha = -1.324^{+0.072}_{-0.074}$. We incorporate a curvature parameter $\delta$ in parameter estimation to account for a possible turn-over at the faint end of the UV LF, leveraging the exceedingly low luminosities probed by our sample. Our results rule out a turn-over brighter than $M_{UV} = -15.5$ at the $3\sigma$ confidence level.

The superconducting Transition-Edge Sensor (TES) is a critical technology for next-generation X-ray spectrometers, known for its exceptional energy resolution. In the last decade, TESs based on AlMn alloy films have been extensively used in several cosmic microwave background (CMB) experiments. The advantages of simple fabrication process and easily tunable critical temperature make them an alternative to bilayer TESs. However, they have rarely been applied to X-ray detection until now. We developed an annular AlMn TES for X-ray detection and tested it in a dilution refrigerator with a Superconducting Quantum Interference Device (SQUID) amplifier, achieving an Full Width at Half Maximum (FWHM) of 12.1 +- 0.3 eV at 17.48 keV. To the best of our knowledge, this is the first demonstration of an AlMn TES achieving an energy resolution below 0.1%, highlighting its potential for high-resolution X-ray detection.

Submillimeter galaxies (SMGs) provide valuable insights into galaxy formation and evolution and are likely influenced by their cosmic environment. However, their rarity makes environmental trends difficult to establish. We use the FLAMINGO simulation, which simultaneously reproduces the redshift distribution and number counts of SMGs. We use the DisPerSE to identify filamentary structures at $z=4$, 3, 2, 1.5, and 1. We define inner cluster-halo, outer cluster-halo, inner filament, outer filament, and void/wall environments at each redshift considering mass evolution of cluster-halos and density evolution of filaments. For a fixed stellar-mass cut of $M_* \geq 10^{9}$ M$_{\odot}$, the fraction of SMGs in the inner cluster-halo environment declines from $\sim30\%$ at $z=4$ to $\sim3\%$ by $z=1$, and similar trends are observed in other environments. The abundance of SMGs within a cluster-halo increases with halo mass, mirroring the increase in the total galaxy population. Consequently, the ratio of SMG halo occupation to that of all galaxies is largely insensitive to halo mass, but varies with redshift. In contrast, the ratio of the halo occupation of non-SMGs to that of all galaxies declines with halo mass and shows little redshift evolution. We show that the central and satellite SMGs form two distinct populations in inner cluster-halos. SMGs occupy the metal-rich side of the metallicity distribution, but rarely attain the highest metallicities because ongoing enrichment is limited by gas depletion. The brightest SMGs (S$_{850} > 10$ mJy) are found exclusively in inner cluster-halos, highlighting a strong connection between SMG luminosity and environmental density. Our results show that SMGs dominate star formation in dense environments, contributing up to $80\%$ of the SFR in inner cluster-halos at $z=4$, but less than $50\%$ in low-density regions.

We use population synthesis modelling to predict the gravitational wave (GW) signal that the Laser Interferometer Space Antenna (LISA) will detect from the Galactic population of compact binary systems. We implement a realistic star formation history with time and position-dependent metallicity, and account for the effect of supernova kicks on present-day positions. We consider all binaries that have a white dwarf (WD), neutron star (NS), or black hole primary in the present-day. We predict that the summed GW signal from all Galactic binaries will already be detectable 3 months into the LISA mission, by measuring the power spectrum of the total GW strain. We provide a simple publicly available code to calculate such a power spectrum from a user-defined binary population. In the full 4 year baseline mission lifetime, we conservatively predict that $>2000$ binaries could be individually detectable as GW sources. We vary the assumed common envelope (CE) efficiency $\alpha$, and find that it influences both the shape of the power spectrum and the relative number of detectable systems with WD and NS progenitors. In particular, the ratio of individually detectable binaries with chirp mass $\mathcal{M} < M_\odot$ to those with $\mathcal{M} \geqslant M_\odot$ increases with $\alpha$. We therefore conclude that LISA may be able to diagnose the CE efficiency, which is currently poorly constrained.

One of the major conundrums in contemporary extragalactic astrophysics is the apparent overabundance of a remarkable population of UV-bright galaxies at redshifts $z\gtrsim 9$. We analyse galaxies spectroscopically observed by JWST/NIRSpec Prism and confirmed to lie at $z>9$, with sufficient signal-to-noise to carefully model their rest-frame UV to optical continua and line emission. In particular, we model the damped Lyman-$\alpha$ (Ly$\alpha$) absorption (DLA) features of each galaxy to place observational constraints on the gas assembly of neutral atomic hydrogen (HI) onto the galaxy halos at the onset of cosmic reionisation. Based on the derived HI column densities and star-formation rate (SFR) surface densities, we show that all galaxies are highly efficient at forming stars on rapid $\sim 10-100\,$Myr depletion timescales, greatly in excess compared to the canonical local universe Kennicutt-Schmidt relation and predictions from state-of-the-art galaxy formation simulations. The dense HI gas appears to also drive the offset from the fundamental-metallicity relation of these galaxies though its dust-to-gas ratio is seemingly consistent with values derived for local galaxies except for the lowest metallicity sight-lines. Our results provide the first robust observational constraints on the impact of pristine HI gas on early galaxy assembly, and imply that a combination of highly efficient star formation and low dust obscuration can likely explain the UV-brightness of galaxies at cosmic dawn.

We study the impact of crust-core connection procedures on various neutron-star properties, especially on the tidal deformability. We consider three types of connection procedures to treat the discontinuity in a nonunified equation of state around the crust-core transition: (1) the direct connection procedure, (2) the crossover connection procedure, and (3) the segmented method. Our results indicate that the mass-radius relations of neutron stars are almost unaffected by the details of the connection procedure. However, the tidal deformabilities of neutron stars are sensitive to the crust-core connection procedures. The tidal deformability is closely related to gravitational-wave measurements. For a canonical 1.4$M_\odot$ neutron star, uncertainties in the tidal deformability $\Lambda_{1.4}$ from different connection procedures can exceed 20\%. We find that the direct connection procedure yields significantly larger uncertainties in the tidal deformability, while the segmented method and crossover connection procedure provide relatively stable results.

The inner regions of protoplanetary discs, which encompass the putative habitable zone, are dynamically complex, featuring a relatively well-ionised, turbulent active zone located interior to a poorly ionised 'dead' zone. In this second paper, we investigate a model of the magnetohydrodynamic processes around the interface between these two regions, using five three-dimensional global magnetohydrodynamic simulations of discs threaded by a large-scale poloidal-net-flux magnetic field. We employ physically motivated profiles for Ohmic resistivity and ambipolar diffusion, alongside a simplified thermodynamic model comprising a cool disc and hot corona. Our results show that, first, the interface acts as a one-way barrier to inward transport of large-scale magnetic flux from the dead zone. This leads to magnetic flux depletion throughout most of the active zone, whereby it either advects inwards to the inner numerical boundary or accumulates just inside the interface. Second, two sources of strong variability emerge from the interface due to the difficulty of maintaining a constant, vertically integrated electrical current across distinct and evolving magnetic-field states. Third, despite the weak magnetothermal wind in the dead zone, a pressure maximum forms at the interface, leading to Rossby-wave-induced vortices. Fourth, unlike the model of Iwasaki et. al (2024), there is no 'transition zone' devoid of magnetic flux and magnetic winds. Instead, multiple outflow zones span all disc radii reflecting the radially varying launch conditions, with an inner turbulent wind impinging upon an outer, more laminar one. Fifth, a heated corona prevents the 'puffing up' of poloidal-net-flux, active disc regions.

Free electrons in the Galactic interstellar medium (ISM) disperse and scatter coherent radio waves, by amounts that depend on the distance to the radio source. Models of the Galactic electron density are thus widely used to predict distances and scattering of compact radio sources (including pulsars, fast radio bursts (FRBs), and long-period transients), in addition to mitigating ISM foregrounds in Galactic and extragalactic studies. We use a sample of 171 precise pulsar distances, based entirely on parallaxes and globular cluster associations, as well as scattering measurements of 568 pulsars, active galactic nuclei, and masers, to update the NE2001 Galactic electron density model. We refit the thick and thin disks and three of the spiral arms. The new parameters for these large-scale components significantly repartition free electrons between the thick disk and spiral arms, thereby correcting NE2001's systematic underestimation of pulsar distance and scattering. Sightlines with excessive dispersion and scattering are used to identify new clumps that are added to the model, in addition to refining clumps that were already included (e.g., Cygnus, Vela, and Gum). The Galactic Center component is revised, yielding scattering time predictions that are $10^3$ times smaller than the Galactic Center in NE2001. The updated model, NE2025, provides a factor of $20\times$ improvement in median distance prediction accuracy and $100\%$ median improvement in scattering predictions based on DM, relative to NE2001. There is a $15\times$ improvement in median distance prediction accuracy relative to YMW16. NE2025 is available on Github and the Python Package Interface.

Galactic Cosmic Rays (GCRs) have to travel through the heliosphere before they interact with the Earth's atmosphere. During this, they are deflected by the Sun's magnetic field, causing variations in this field to imprint on the flux, spectrum and angular distribution of GCRs detected at or near Earth. Studies of these variations over the past several decades have revealed the impact of both transient phenomena such as solar flares, coronal holes, sunspot activity and coronal mass ejections (CMEs) as well as their effects such as Forbush Decreases (FDs), precursors and Ground-Level Enhancements (GLEs). Periodic variations, such as due to the solar diurnal modulation, the 27-day solar rotation, the 11-year solar cycle, and the 22-year solar magnetic cycle have also been characterized. These Sun-induced phenomena are most prominent in GCR intensity variations up to $\sim$30 GeV/nuc, beyond which the influence of solar modulation decreases rapidly as the gyro-radii of GCRs exceed the characteristic size of the heliosphere ($\sim$100 AU).

Diagnosing solar flare conditions is essential for understanding coronal energy release. Using combined microwave and X-ray data, we reconstruct three-dimensional maps of the magnetic field and plasma parameters in the SOL2021-05-07 flare. We use imaging spectroscopy from the Expanded Owens Valley Solar Array (EOVSA) to derive spatial maps of the magnetic field strength, thermal and nonthermal electron densities, and the power-law index of nonthermal electrons through gyrosynchrotron modeling. Simultaneous X-ray observations from Hinode/XRT and Solar Orbiter/STIX, obtained from different vantage points, enable a stereoscopic reconstruction of the flaring loop. By correlating the positions of microwave and thermal X-ray sources, we associate the three-dimensional coordinates with the microwave-derived plasma parameters. We derive observational three-dimensional maps of magnetic field strength, Alfvén speed, and plasma beta in the flaring volume, revealing a magnetically dominated environment. These spatially resolved diagnostics provide valuable constraints for models of magnetic reconnection and flare dynamics and represent a step toward a realistic three-dimensional characterization of energy release in solar eruptive events.

The Chinese Space Station Survey Telescope (CSST) will perform a decade-long high-precision wide-field imaging survey that relies on rigorous on-orbit calibration. This necessitates stable celestial benchmark fields to maintain photometric and astrometric consistency throughout the mission lifetime. We establish comprehensive selection criteria including observational visibility, stellar number density, bright-star contamination, and interstellar dust extinction. Using the CSST Observation Strategy Analysis Tool (COSAT) and all-sky dust maps from Planck and SFD, we constrain eligible regions to the ranges of ecliptic latitude $ |\beta| > 50^\circ$ and galactic latitude $|b| > 15^\circ$. From an initial sample of 29 candidate clusters meeting these spatial constraints, six globular clusters (M13, M92, NGC 104, NGC 362, NGC 1261, and NGC 1851) are identified as optimal calibration fields, fulfilling all the critical criteria. These selected clusters are recommended as optimal calibration field candidates for CSST's on-orbit calibration program, and are fundamental to achieving unprecedented photometric precision in CSST's space-based survey.

The origin of the large-amplitude, quasi-periodic X-ray flux variations in several classes of the Galactic microquasar GRS~1915+105 remains unresolved. We address this issue through flux-resolved, broadband (0.8-20 keV) spectral modelling and simultaneous covariance spectral analysis during two $\kappa$ and two $\omega$ class observations using \textit{AstroSat}/SXT and LAXPC. The lightcurves show strong, quasi-periodic oscillations involving rapid transitions between bright bursts and deep dips on timescales of a few tens of seconds. Flux-resolved spectroscopy indicates that high-flux intervals in both classes are dominated by a hot, optically thick accretion disc with steep Comptonized emission, whereas low-flux intervals correspond to a cooler or partially recessed disc and a harder coronal continuum. These transitions involve a systematic 1-2 keV drop in disc temperature and a pronounced hardening of the Comptonized component, with flux reductions of up to a factor of five. Using covariance spectra across 0.015-5 Hz, we show that the rapid coherent variability arises almost entirely from the disc, which exhibits strong energy-dependent variations, while the Comptonized component contributes minimally. The combined results suggest that radiation-pressure-driven structural changes in the disc, with a slower coronal response, produce the observed oscillations, consistent with cyclic disc evacuation and refilling in the $\kappa$ and $\omega$ classes.

Large-amplitude decaying kink oscillations of coronal loops are strongly influenced by nonlinear processes, such as Kelvin-Helmholtz instability (KHI) and turbulence, though comprehensive theory and observational confirmation remain limited. Building on the recently developed theory on nonlinear damping by KHI-induced turbulence in impulsively driven transverse loop oscillations, we investigate its observational signatures using 3D magnetohydrodynamic simulations and forward-modelled EUV images. The simulated oscillations exhibit time-varying frequency shifts and damping rates, which are broadly consistent with nonlinear turbulence-damping theory. Additionally, they exhibit excitation of higher-order modes, slightly increased periods relative to the linear kink period, and reduced displacement amplitudes. These features are generally preserved in synthetic observations, though resolving higher-order modes requires higher spatial resolution than currently available. For loops embedded in a hotter background, hotter channels (e.g., 193 Angstroms) are more sensitive to boundary dynamics, thus their oscillations decay faster with smaller displacements and larger phase shifts than those in cooler channels (e.g., 171 Angstroms). Comparisons of simulated and synthetic oscillations show close agreement at the early stage. At later times, synthetic oscillations exhibit smaller displacements and larger phase shifts, due to turbulence-induced asymmetry in the loop cross-section. Bayesian fitting shows that the initial oscillation amplitude and kink period are robustly constrained, whereas parameters controlling the damping profile are degenerate, indicating that additional observables would aid reliable seismological inference. These results provide a quantitative basis for identifying nonlinear damping and detecting KHI-driven turbulence in transverse loop oscillations.

The demographics of Kepler planets provide a key testbed for models of planet formation and evolution, particularly for explaining the radius valley separating super-Earths and sub-Neptunes. A primordial interpretation based on differences in bulk densities -- where rocky and water-rich planets form via migration pathways -- offers an alternative to atmospheric loss scenarios. Updated interior structure models of water worlds with adiabatic steam atmospheres reproduce the observed valley near $\sim2~R_\oplus$ more accurately. Furthermore, migration models from our Genesis library suggest that these formation pathways can also account for the distinct period distributions of super-Earths and sub-Neptunes, as well as the emergence of the hot Neptune desert. Motivated by this, we develop a Bayesian hierarchical mixture model for close-in Kepler planets ($P<100$ days), combining rocky planets and water worlds without H/He envelopes. The inferred mass distributions of rocky and water-rich planets peak at $\sim2.6~M_\oplus$ and $\sim7~M_\oplus$, respectively, with the water mass fraction of water worlds peaking at $\sim41\%$. Water worlds provide a good representation of the Kepler sub-Neptune population, with the radius cliff emerging as a ``waterfall" -- a sharp decline in their occurrence. However, our mass-radius analysis shows that water worlds alone cannot explain planets with $R \gtrsim 3~R_\oplus$, implying that at least $\sim20\%$ of sub-Neptunes in the sample are enriched in H/He gas.

We test the dynamical dark-energy $w_0w_a$CDM (CPL) framework against $\Lambda$CDM using CMB anisotropies and lensing together with late-time distance probes: DESI DR2 BAO, the completed SDSS-IV BAO consensus compilation, a transverse/angular BAO compilation (BAOtr), and the Cepheid-calibrated PantheonPlus SN~Ia likelihood (PP\&SH0ES). We find that CPL inferences are strongly dataset-dependent. With CMB data alone, the broad geometric degeneracy in $(H_0,\Omega_{\rm m},w_0,w_a)$ admits an extrapolation tail that can extend to $q_0<-1$ (super-acceleration), whereas adding DESI DR2 BAO pulls the reconstruction toward a weakly accelerating or nearly coasting present-day Universe ($q_0\simeq 0$). In contrast, combining CMB with PP\&SH0ES and BAOtr yields a conventional moderately accelerating expansion ($-1<q_0\lesssim 0$) and substantially reduces the Hubble tension. Across all combinations, $w(z\to\infty)=w_0+w_a<-1$, while at post-recombination redshifts the expansion remains matter dominated ($q\to1/2$). The origin of this behavior can be traced to low-redshift distance information: BAOtr and DESI prefer different BAO distance ratios at $z\lesssim 0.5$, which propagates into divergent expansion histories in CPL. In all cases, $r_{\rm d}$ stays nearly unchanged, indicating that shifts in $H_0$ arise from late-time expansion freedom rather than early-Universe physics. Bayesian evidence mirrors this contingency: it is strong for CPL mainly when PP\&SH0ES and/or BAOtr are included, while it is inconclusive for CMB-only and CMB+DESI and moderately favors $\Lambda$CDM for CMB+SDSS. Overall, our results show that the apparent support for CPL and its ability to ease the Hubble tension are not universal but depend sensitively on the adopted low-redshift distance data, motivating either more flexible late-time models or closer scrutiny of residual systematics in current BAO determinations.

We present a cosmological analysis of the X-ray-selected galaxy cluster sample from the XXL survey, employing a simulation-based inference (SBI) framework to jointly constrain cosmological parameters and X-ray scaling relations through forward modeling of cluster counts, X-ray observables, and weak-lensing measurements. Our analysis combines X-ray data from the XMM-XXL survey with shear measurements from the three-year shape catalog of the Hyper Suprime-Cam Subaru Strategic Program. The analysis focuses on the XXL C1 sample, comprising 171 clusters for abundance modeling, a subset of 86 clusters located within the XXL-N region for lensing-based mass calibration, and 162 clusters with X-ray temperature and luminosity measurements used to constrain scaling relations. Using the density-estimation likelihood-free inference (DELFI) algorithm, we construct a forward model with 12 parameters that incorporates the XXL selection function and cluster population modeling and accounts for key systematic effects including cluster miscentering, photometric redshift bias, and mass-dependent weak-lensing bias. Our SBI analysis yields a constraint on the cosmological parameter $S_8 \equiv \sigma_8 (\Omega_{m}/0.3)^{0.5} = 0.867 \pm 0.063$, with an additional 3% systematic uncertainty from neural network stochasticity. The result is consistent with Planck and recent cluster-based measurements. The inferred temperature-mass relation is consistent with self-similar expectations within uncertainties, whereas the luminosity-temperature relation exhibits a slope steeper than the self-similar prediction. From the resulting posterior distribution of the forward model, we derive lensing-calibrated mass estimates for all individual XXL clusters with measured X-ray temperatures or luminosities. These results provide a self-consistent mass calibration for future multi-probe cosmological analyses of the XXL sample.

Aims: We derive SBCRs for classical Cepheids in the Milky Way and in the Magellanic Clouds using the photometric data available in the Gaia database, and we quantify the metallicity effect. Methods: We first selected the data on the basis of a number of quality criteria and chose the best photometric data and the best parallaxes available in Gaia for Milky Way classical Cepheids. Secondly, we compiled an extensive list of period-radius (PR) relations available in the literature, and we also provide a new PR relation based on interferometric data in our previous work. Thirdly, combining the radius of classical Cepheids with distance estimates (based on Gaia parallaxes for the Milky Way and on eclipsing binaries for the Magellanic Clouds), we derived the surface brightness and colour of about 1700 classical Cepheids. Results: We first derived a new PR relation based on interferometric data and distances from the literature of seven classical Cepheids: $\mathrm{\log(R/R_{\odot}) = 1.133_{\pm 0.019} + 0.688_{\pm 0.016} log(P)}$. The metallicity does not affect the PR relations. Secondly, we calculated three different SBCRs for the Milky Way and Large and Small Magellanic Cloud classical Cepheids based on this new PR relation that clearly show the dependence of the metallicity on the SBCR based on Gaia magnitudes alone. Finally, we derived relations between the slopes, the zero points (ZP), and the metallicity ([Fe/H]) of these three SBCRs: $\mathrm{Slope_{SBCR}=-0.0663_{\pm 0.0121} [Fe/H] - 0.3010_{\pm 0.0030}}$ and $\mathrm{ZP_{SBCR}=-0.1016_{\pm 0.0091} [Fe/H] + 3.9988_{\pm 0.0029}}$. Conclusions: These new SBCRs, dedicated to classical Cepheids in the Milky Way and Magellanic Clouds, are of particular importance to apply the inverse Baade-Wesselink method to classical Cepheids observed by Gaia in a forthcoming study.

We investigate the velocity evolution of free-floating planets and interstellar objects (``free floaters'') through gravitational scatterings by field stars (with the stellar mass $m$ much larger than the mass of the floater, $m_p$). We show that the equilibrium velocity -- where dynamical friction balances stochastic acceleration -- is given by $\sigma \sqrt{2\ln(m/m_p)}$ (where $\sigma$ is the velocity disperson of the field stars), diverging from the standard energy equipartition scaling. While the timescale to reach this equilibrium is prohibitively long, we find that slow floaters ($v \lesssim \sigma$) undergo mass-independent acceleration, doubling their velocities within a few relaxation times. Consequently, free floaters initially following the Maxwellian distribution of their parent stars develop distinctly non-Maxwellian velocity distributions on a relaxation timescale. Since the relaxation time of the Galactic disk is longer than the age, our results suggest that the kinematics of low-mass free floaters in the disk may preserve signatures of their parent stars and ejection history.

Simulation-based inference (SBI) is a powerful inference technique for cases where the exact functional form of the likelihood is not known. A prime example is the likelihood of cross-correlation power spectra of the cosmic microwave background (CMB) fields at low multipoles, $\ell\lesssim 10$. In this paper, we investigate a parity-violating cross-correlation between $E$- and $B$- mode polarization fields using SBI. The $EB$ correlation at low $\ell$ is essential to distinguish between possible axion dark energy and dark matter interpretations of `cosmic birefringence', a rotation of the plane of linear polarization of the CMB, recently reported from WMAP, Planck, and Atacama Cosmology Telescope data. We use neural likelihood estimation to infer the likelihood of the $EB$ correlation at low $\ell$ and show that it is highly non-Gaussian. We then employ neural posterior estimation to constrain the scalar field mass ($m_\phi$), the cosmic birefringence amplitude ($g\phi_\mathrm{in}/2$), and the instrumental miscalibration angle ($\alpha$), from simulated datasets. We find that the posterior on $m_{\phi}$ shows two regimes, with a transition marked by $10^{-32}$ eV, highlighting a strong sensitivity to the scale dependence of cosmic birefringence. To quantify this behavior, we compute the probability $p(m_{\phi} < 10^{-32}$\,eV) for various fiducial values of $m_{\phi}$. We find that $\alpha$ and the contribution of lensed $B$ modes ultimately limit our ability to exclude the dark energy scenario fully.

The B335 protostar has undergone a major outburst detected in the scattered light of its outflow cavity that has not yet ended. B335 therefore offers the rare opportunity to study its effect on the jet of a protostellar object. Photometry of background stars behind B335 is used to map visual continuum extinction and H$_2$O ice absorption and demonstrates that the outflow has carved out a cavity. Precise proper motions of the shock fronts emerging from the B335 protostar were obtained. The kinematic age of the most prominent shock front (3E) corresponds to the early phases of the ongoing outburst of the B335 protostar. Shock 3E shows strong CO gas emission, as well as H$_2$ and [\ion{Fe}{2}] emission. Older shock fronts show diminished CO emission and are dominated by H$_2$ and [\ion{Fe}{2}]. The emission feature 0E, closest to the protostar, is distinct in proper motion and radial velocity from the other shock fronts in the jet. In the span of 4\arcsec\ closest to the protostar, the continuum extinction in front of the outflow cavity increases by A$_V$~$\approx$~200 mag. The CO-line-removed spectra close to the protostar show the unsaturated absorption features of $^{13}$CO$_2$, OCN$^-$, and OCS have strongly increasing column densities toward the protostar. The ice characteristics are overall similar to those found in lines of sight with less extinction. The central regions of the bipolar nebula show CO gas emission, but at distances of a few arcsec from the protostar, absorption by CO gas is also detected.

The Poisson equation governing a planet's gravitational field is posed on the unbounded domain, $\mathbb{R}^3$, whereas finite-element computations require bounded meshes. We implement and compare three strategies for handling the infinite exterior in the finite-element method: (i) naive domain truncation; (ii) Dirichlet-to-Neumann (DtN) map on a truncated boundary; (iii) multipole expansion on a truncated boundary. While all these methods are known within the geophysical literature, we discuss their parallel implementations within modern open-source finite-element codes, focusing specifically on the widely-used MFEM package. We consider both calculating the gravitational potential for a static density structure and computing the linearised perturbation to the potential caused by a displacement field - a necessary step for coupling self-gravitation into planetary dynamics. In contrast to some earlier studies, we find that the domain truncation method can provide accurate solutions at an acceptable cost, with suitable coarsening of the mesh within the exterior domain. Nevertheless, the DtN and multipole methods provide superior accuracy at a lower cost within large-scale parallel geophysical simulations despite their need for non-local communication associated with spherical harmonic expansions. The DtN method, in particular, admits an efficient parallel implementation based on an MPI-communicator limited to processors that contain part of the mesh's outer boundary. A series of further illustrative calculations are provided to show the potential of the DtN and multipole methods within realistic geophysical modelling.

The WFC3\IR channel has an innate non-linear response to incident photons, which is corrected for in the calwf3 pipeline with the NLINFILE reference file. The 2009 solution is based on an average polynomial correction for each IR quadrant and is found to be poorly constrained at high fluence levels (e-) approaching the saturation limit. Using a variety of image types, sources, and sample sequences, we test a new pixel-based linearity correction developed by Shenoy et al. (2025). In nearly all cases, the new correction improves the linearity at fluence levels higher than 50,000 e-, with improvements up to 7% for pixels with fluences approaching the saturation limit (80,000 e-) in the last ima reads. The pixel-based solution also significantly decreases the number of cosmic rays erroneously flagged (due to non-linearity correction errors) during ramp fitting in calwf3, leading to improved photometric accuracy in the calibrated flt data and higher signal-to-noise ratios, particularly in Quad 1 (upper-left detector quadrant). Because the new solution tends to make sources brighter, we recalibrate the five HST flux standards used to compute the IR zeropoints and find a negligible impact (0.1-0.2%) on the published values by Calamida et al. (2024), smaller than the RMS dispersion (0.5%) in the observed to synthetic flux ratios for all five flux standards. The new NLINFILE 9au15283i this http URL was delivered to CRDS in October 2025 and will be used to reprocess all WFC3/IR imaging and grism observations in the MAST archive. An updated reference file a2412448i this http URL was delivered in February 2026, improving the results at the highest fluence levels by a few tenths of a percent. Please consult the Addendum for details.

We report the first results of a sub-solar mass compact binary search using the data from the first part of the fourth observing run (O4a) of the Advanced LIGO detectors. Sub-solar mass neutron stars or primordial black holes are not expected to form via standard stellar evolution, and their observation would signify a new class of astrophysical object or the discovery of dark matter. Our search covers binaries with primary masses 0.1 to 2 $\textrm{M}_\odot$ and secondary masses 0.1 to 1 $\textrm{M}_\odot$. We explicitly incorporate tidal effects up to $7\times10^5$ for extremely low mass neutron stars. No statistically significant candidates are identified. The advanced sensitivity of the O4a run enables an improvement in the sub-solar mass black hole merger rate limits by more than $2 \times$ over the previous three observing runs (O1-O3b). We place a $90\%$ confidence upper limit on the merger rate $\mathcal{R}_{90}$ for sub-solar mass black holes to be $< 1.77\times10^4 \textrm{Gpc}^{-3} \textrm{yr}^{-1}$ for a chirp mass of 0.2 $\textrm{M}_\odot$. We place the first constraints for binary neutron stars with tidal deformabilities up to $\sim 7\times10^5$ and improve the merger rate estimate by a factor $\sim 4$ in comparison to previous O3 tidal searches for tidal deformabilities $< 10^4$. We further constrain the fraction of dark matter composed of primordial black hole $f_{\rm PBH}< 2\%$ for a chirp mass of 0.1 $\textrm{M}_\odot$. Our results significantly expand the observational search space for sub-solar binaries and provide rigorous constraints on the local abundance of compact objects that may arise from non-standard formation mechanisms.

The amplification of magnetic fields in black hole accretion flows governs key high-energy phenomena such as magnetically arrested disks and relativistic jets. We develop a semi-analytical general relativistic framework that extends classical compressional amplification models by incorporating rotational shear, and apply it to large-scale poloidal magnetic field evolution in accretion flows around a Schwarzschild black hole. By parameterizing the azimuthal velocity as a fraction of the Keplerian value ($\xi \in [0,1]$), from purely radial infall ($\xi=0$) to Keplerian rotation ($\xi=1$), we examine the combined effects of radial compression and shear. Purely radial flows maximize amplification of both $B_r$ and $B_\theta$ due to strong compression. In rotating flows, a distinct dichotomy emerges: sub-Keplerian regimes ($\xi<1$) preferentially enhance $B_r$, whereas Keplerian rotation strengthens $B_\theta$ via shear. The transition from subsonic outer regions to supersonic relativistic inner regions further accelerates magnetic growth, revealing effects absent in earlier analytical treatments. These results show that rotational support controls both amplification efficiency and magnetic geometry, with sub-Keplerian phases particularly favorable for advecting the radial flux required for MAD formation. This work provides an analytical bridge between classical accretion theory and modern GRMHD simulations, with implications for X-ray binaries, AGNs, and EHT-scale systems.

Cosmological inference from weak lensing (WL) surveys is increasingly limited by uncertainties in baryonic physics, which suppress the non-linear matter power spectrum on small scales. Multi-probe analyses that incorporate complementary tracers of the gas distribution around haloes offer a pathway to calibrate these effects and recover unbiased cosmological information. In this work, we forecast the constraining power of a joint analysis combining fiducial data from a Stage-IV WL survey with measurements of the dispersion measure from fast radio bursts (FRBs). We evaluate the ability of this approach to simultaneously constrain cosmological parameters and the astrophysical processes governing baryonic feedback, and we quantify the impact of key FRB systematics, including redshift uncertainties and source clustering. We find that, even after accounting for these effects, a 3$\times$2-point analysis of WL and FRBs significantly improves cosmological constraints, reducing the degradation factor on $S_8$ by $\sim 80\%$ compared to WL alone. We further show that FRBs alone are sensitive only to a degenerate combination of the key baryonic parameters, $\log_{10} M_{\rm c}$ and $\eta_{\rm b}$, and that the inclusion of WL measurements breaks this degeneracy. Finally, we extend our framework to incorporate galaxy clustering measurements using Luminous Red Galaxy and Emission Line Galaxy samples, performing a unified 6$\times$2-point analysis of WL, dispersion measures of FRBs, and galaxy clustering. While this combined approach tightens constraints on $\Omega_{\rm m}$ and $\log_{10} M_{\rm c}$, it does not lead to a significant improvement in $S_8$ constraints beyond those obtained from WL and FRBs alone.

The Event Horizon Telescope (EHT) is providing unprecedented high-resolution images of supermassive black holes. These images are fundamentally related to properties of the luminous accretion disks, since black holes themselves produce no light. We develop a simple prescription to relate observational features of black hole images to a toy model for the intensity profile of the associated accretion disk. We apply our model to the original EHT image of M87*, as well as to the reanalyzed image from the PRIMO algorithm, providing generic, simultaneous constraints on the mass of the black hole and properties of the accretion disk emission. While current images lack the resolution to confidently detect the photon ring, the consideration of multiple image parameters are found to contain enough information to provide constraints on the inner edge of the accretion disk along with the black hole mass. Using observed features of the original EHT image, we constrain the mass of M87* to be $6.6^{+1.2}_{-1.0}\times 10^9 M_\odot$ to 68$\%$ confidence, and find that emission may extend all the way to the black hole horizon. When instead using constraints from the PRIMO algorithm's image along with constraints on the brightness asymmetry provided by the original EHT analysis, we find M87*'s mass to be $ 6.4^{+0.7}_{-0.7}\times 10^9 M_\odot$ to 68$\%$ confidence, with the inner edge of the accretion disk between $3M$ and $5.3M$. Both analyses rule out an inner edge of the accretion disk coinciding with the innermost stable circular orbit for a Schwarzschild black hole. Furthermore, the narrow ring width reported in the PRIMO image also confidently rules out emission increasing all the way down to the black hole horizon. Further assumptions on the mass of M87* and connections between the accretion disk cutoff and physical radii allow for rudimentary black hole spin estimates.

The evolution of exoplanetary atmospheres is strongly influenced by atmospheric escape, particularly for close-in planets. Fractionation during atmospheric loss can preferentially remove lighter elements such as hydrogen, while retaining heavier species like oxygen. In this study, we investigate how and under what conditions hydrodynamic escape and chemical fractionation jointly shape the mass and composition of exoplanet atmospheres, especially for mixed H2 + H2O atmospheres. We develop BOREAS, a self-consistent mass loss model coupling a 1D Parker wind formulation with a mass-dependent fractionation scheme, which we apply across a range of planet masses, radii, equilibrium temperatures, and incident XUV fluxes, allowing us to track hydrogen and oxygen escape rates at different snapshots in time. We find that oxygen is efficiently retained over most of the parameter space. Significant oxygen loss occurs under high incident XUV fluxes, while at intermediate fluxes oxygen loss is largely confined to low-gravity planets. Where oxygen is retained, irradiation is too weak to drive significant escape of hydrogen and thus limiting atmospheric enrichment. By contrast, our model predicts that sub-Neptunes undergo substantial atmospheric enrichment over approx. 200 Myr when hydrogen escape is efficient and accompanied by partial oxygen entrainment. Notably, our results imply that sub-Neptunes near the radius valley can evolve into water-rich planets, in agreement with GJ 9827 d. Present-day water-rich atmospheres may have originated from water-poor envelopes under some conditions, highlighting the need to include chemical fractionation in evolution models. BOREAS is publicly available.

Primordial non-Gaussianity generated by additional fields during inflation offers a compelling observational target. Heavy fields imprint characteristic oscillatory signals in non-Gaussian correlation functions of the inflaton, a process sometimes referred to as cosmological-collider physics. These distinct signatures are compelling windows into ultra-high-energy physics, but are often suppressed, making standard equilateral non-Gaussianity the most promising discovery channel in many scenarios. In this paper, we show that direct couplings between the inflaton and additional fields can lead to a wide variety of novel, observationally relevant signals which open new parameter regimes that simultaneously exhibit the characteristics of light and heavy fields. We identify these primordial signatures in the late-time observables of the large-scale structure of the Universe, where they most significantly modify the scale-dependent bias of the galaxy power spectrum to include an oscillatory modulation around a non-trivial power law. We explore the full range of parameters that phenomenologically arise in these models and study the sensitivity of current and future galaxy surveys, finding that this new class of primordial non-Gaussianity is particularly accessible in near-term surveys due to its oscillatory feature. Finally, we perform an analysis of existing data from the final release of the Baryon Oscillation Spectroscopic Survey (BOSS DR12). While we find no evidence for a signal, we demonstrate significant improvements in sensitivity over respective non-oscillatory scenarios and place the first constraints on this extended parameter space of oscillatory non-Gaussianity.

The parameter $S_8 \equiv \sigma_8 (\Omega_m/0.3)^{0.5}$ quantifies the amplitude of matter density fluctuations. A persistent discrepancy exists between early-universe CMB observations and late-universe probes. This review assesses the ``$S_8$ tension'' against a new 2026 baseline: a unified ``Combined CMB'' framework incorporating Planck, ACT DR6, and SPT-3G. This combined analysis yields $S_8 = 0.836^{+0.012}_{-0.013}$, providing a higher central value and reduced uncertainties compared to Planck alone. Compiling measurements from 2019--2026, we reveal a striking bifurcation: DES Year 6 results exhibit a statistically significant tension of $2.4\sigma$--$2.7\sigma$ \citep{DESY6}, whereas KiDS Legacy results demonstrate statistical consistency at $<1\sigma$ \citep{Wright2025}. We examine systematic origins of this dichotomy, including photometric redshift calibration, intrinsic alignment modeling, and shear measurement pipelines. We further contextualize these findings with cluster counts (where eROSITA favors high values while SPT favors low), galaxy-galaxy lensing, and redshift-space distortions. The heterogeneous landscape suggests survey-specific systematic effects contribute substantially to observed discrepancies, though new physics beyond $\Lambda$CDM cannot be excluded.

The collapse of large-amplitude primordial curvature perturbations into planetary-mass primordial black holes generates a scalar-induced gravitational wave background in the $\mu $Hz frequency range that may be detectable by future Lunar Laser Ranging and Satellite Laser Ranging data. We derive projected constraints on the primordial black hole population from a null detection of stochastic gravitational wave background by these experiments, including the impact of the electroweak phase transition on the abundance of planetary-mass primordial black holes. We also discuss the connection between the obtained projected constraints and the recent microlensing observations by the HSC collaboration of the Andromeda Galaxy.

We present an analysis of the spectral energy distribution (SED) of the off-nuclear tidal disruption event (TDE) AT2024tvd during its late-time plateau phase, combining X-ray spectra and UV/optical photometry. Using a fully relativistic, compact accretion disk model with self-consistent inner-disk Comptonization, we reproduce the observed SED without significant residuals. The inferred black hole mass ${\rm log}{10}(M{\bullet}/M_\odot) \approx 6.0 \pm 0.2$, and the inferred disk parameters place AT2024tvd within known TDE-disk scaling relations ($L_{\rm bol}^{\rm disk}/L_{\rm Edd} \propto T_{\rm p}^4 \propto M_{\bullet}^{-1}$, $L_{\rm plat} \propto M_{\bullet}^{2/3}$, $R_{\rm out}/r_{\rm g} \propto M_{\bullet}^{-2/3}$). Our results show that: (i) there is no \textit{detected} star cluster or dwarf galaxy associated with the source, down to a mass limit of $\log_{10}(M_{\rm gal}/M_{\odot}) \leq 7.6$; (ii) the black hole is a wandering supermassive, rather than intermediate-mass, black hole; and (iii) the source represents an extreme case of black hole-to-host mass ratio, with $M_{\bullet}/M_{\rm gal} > 3\%$, consistent with a heavily tidally stripped nucleus. The latter aligns with cosmological simulations predicting that surviving host remnants of most wandering black holes should not retain a detectable stellar overdensity when located at small halo-centric distances. We discuss differences with previous analyses of this source and highlight why our modeling approach provides a more physically consistent solution with more reliable parameter inference.

We propose a new way to reconstruct the ionized-bubble size distribution during the Epoch of Reionization (EoR) through the real-space cross-correlation of 21-cm and star-forming line-intensity maps. Understanding the evolution and timing of the EoR is crucial for both astrophysics and cosmology, and a wealth of information on the first sources can be extracted from the study of ionized bubbles. Nevertheless, directly mapping bubbles is challenging due to the high redshifts involved, possible selection biases, and foregrounds in 21-cm maps. Here, we exploit the real-space cross-correlation $\xi_{21,\nu}$ between 21-cm and line-intensity mapping (LIM) signals to reconstruct the evolution of bubble sizes during reionization. For the first time, we show that $\xi_{21,\nu}(r)$ departs from a saturation level for each separation $r$ when bubbles of size $r$ begin to form, providing a handle for the onset of bubbles of each radius. Moreover, we demonstrate that $\xi_{21,\nu}$ evolves from positive to negative as the EoR progresses, reaching a minimum (i.e. maximum anti-correlation) when bubbles of radius $r$ reach peak abundance. We show that these results are robust to changes in the astrophysical model as well as the timing/topology of reionization. This real-space observable complements usual Fourier-space estimators by capturing the localized nature of bubbles, offering new insights into the sources driving cosmic reionization.

Optical outburst spectra of low-mass X-ray binaries enable studies of extreme accretion and ejection phenomena. While some of their spectroscopic features have been analysed in detail, the appearance of broad absorptions in the optical regime has been traditionally neglected. In this work, we introduce the first population study dedicated to these features with the aim to understand their fundamental properties and discuss them in the context of their origin. We complement the study with a spectroscopic database of six low-mass X-ray binaries during outburst, in order to assess their evolution. We find that broad absorptions are ubiquitous, with the majority of black hole low-mass X-ray binaries exhibiting them in spite of a typically scarce outburst coverage. Their detection does not depend on the orbital inclination or the compact object nature, but they seem favoured in systems with orbital periods shorter than < 11 h. They predominantly occur in the hydrogen Balmer series, being stronger at shorter wavelengths, and they are detected across all X-ray states. We find that the normalised depth of these broad absorptions is anti-correlated with the system luminosity, and that they show constant line ratios over the whole sample. Based on these properties, we favour a scenario where BAs arise from a stable, optically thick layer of the accretion disc, below the hotter chromosphere-like region producing the emission line components. Our study is consistent with the continuous presence of broad absorptions during the whole outburst, with their visibility being conditioned by the emission lines filling the broad absorption profile and veiling by the X-ray reprocessed continuum.

We study sterile neutrino dark matter (DM) in a classically conformal U(1)' extension of the Standard Model with three right-handed neutrinos and a Majoron-like singlet scalar that generate the observed pattern of active neutrino masses and mixing via the type-I seesaw mechanism. Working in the regime of strongly suppressed active-sterile mixing, we show that the observed DM abundance can be produced through freeze-in from feeble interactions mediated by the heavy Z' and the conformal scalar. We solve the Boltzmann equation for the nonthermal phase-space distribution and confront the scenario with Lyman-$\alpha$ data by computing the matter power spectrum. For keV-scale sterile neutrinos we identify the viable parameter space consistent with structure-formation and X-ray bounds, including regions compatible with a tentative 3.5 keV line. If a second sterile state is long-lived, late decays can realize a two-component setup that alleviates the $S_8$ tension. In a highly fine-tuned variant of the model, the 220 PeV KM3NeT event can also be explained by invoking the decay of a superheavy sterile neutrino.

We demonstrate that a background rotation significantly catalyzes the chiral magnetovortical instability in chiral magnetohydrodynamics. The rotation splits the linearly polarized Alfven wave into two circularly polarized magneto-Coriolis waves, one of which exhibits a lower frequency than the original Alfven wave. We find that this low-frequency magneto-Coriolis wave is always unstable in the presence of even a weak chiral vortical effect. This instability may enable new dynamo mechanism applicable to various rotating chiral plasmas.

In this essay and utilizing the holographic Renormalization Group (RG) flow, we demonstrate how the effective action of a non-gravitating quantum field theory in the ultraviolet (UV) develops an Einstein-Hilbert term in the infrared (IR). That is, gravity is induced by the RG flow. An inherent outcome of holography that plays a crucial role in our analysis is the \textit{RG flow of boundary conditions}: the rigid Dirichlet conditions on the background metric in the UV become an admixture of Dirichlet and Neumann as we flow to the IR, thereby ``unfreezing'' the metric and transforming it from a non-dynamical background into a dynamical field. This mechanism, which is a conceptually new addition to the standard Wilsonian RG flow, also provides the mechanism to evade the Weinberg-Witten no-go theorem. Within the GR from RG picture outlined here, the search for a quantum theory of gravity by treating the metric as a fundamental field may be a hunt for a phantom -- akin to seeking the atomic structure of water by quantizing the equations of hydrodynamics.

Space-borne gravitational wave detectors will expand the scope of gravitational wave astronomy to the milli-Hertz band in the near future. The development of data analysis software infrastructure at the current stage is crucial. In this paper, we introduce \texttt{pespace} which can be used for the full Bayesian parameter estimation of massive black hole binaries with detectors including LISA, Taiji, and Tianqin. The core computations are implemented using the high-performance parallel programming framework \texttt{taichi-lang} which enables automatic differentiation and hardware acceleration across different architectures. We also reimplement the waveform models \texttt{PhenomXAS} and \texttt{PhenomXHM} in the separate package \texttt{tiwave} to integrate waveform generation within the \texttt{taichi-lang} scope, making the entire computation accelerated and differentiable. To demonstrate the functionality of the tool, we use a typical signal from a massive black hole binary to perform the full Bayesian parameter estimation with the complete likelihood function for three scenarios: including a single detector using the waveform with only the dominant mode; a single detector using the waveform including higher modes; and a detector network with higher modes included. The results demonstrate that higher modes are essential in breaking degeneracies, and coincident observations by the detector network can significantly improve the measurement of source properties. Additionally, automatic differentiation provides an accurate way to obtain the Fisher matrix without manual fine-tuning of the finite difference step size. Using a subset of extrinsic parameters, we show that the approximated posteriors obtained by the Fisher matrix agree well with those derived from Bayesian parameter estimation.

One of the fundamental challenges of quantum gravity is to understand how the microscopic degrees of freedom of the cosmological horizon shape the evolution of the Universe. One possible approach to this problem is based on the Barrow--Tsallis entropy. This entropy accounts for both quantum gravitational effects and the nonextensive effects inherent in any long-range interaction. Using a general method we developed for finding the parameters of cosmological models, we discovered a relationship between the parameter describing the microscopic structure of quantum foam and the parameter associated with macroscopic nonextensive effects. We also used our method for finding the parameters of cosmological models to evaluate the feasibility of using fractional derivatives to describe the late evolution of the Universe. The resulting relationships are exact. Therefore, the uncertainty in the relationship between the model parameters depends only on the current uncertainty in the values of the cosmographic parameters.

Recently, astronomers discovered unusual Einstein cross images of the galaxy HerS-3, which feature a bright central spot. Motivated by studies of images produced by regular stars, it has been proposed that optical appearances caused by compact stars acting as gravitational lenses may account for this central bright spot. We further suggest that images produced by regular stars exhibit additional characteristics distinct from those of ordinary black holes, such as the possible partial or complete absence of secondary images. These phenomena may serve as favorable observational criteria for identifying regular stars in future searches.