Papers for Tuesday, Oct 07 2025

Recent discoveries have shown that a population of hypervelocity stars (HVSs) originate from the Large Magellanic Cloud (LMC). We use three such HVSs as dynamical tracers to constrain the past orbit of the LMC. Since each star was ejected at a finite time in the past, it must intersect the past position of the LMC's central black hole at its ejection time. We model the LMC's orbit under the influence of dynamical friction and extended mass distributions for both the LMC and the Milky Way, generating a large ensemble of orbital realizations. By evaluating which orbits intersect the back-integrated HVS trajectories, we compute posterior distributions over the LMC's orbital history. This approach provides significantly tighter constraints on the past motion of the LMC than previously possible. We find two previously published orbital models that are consistent with these new constraints: a first-passage trajectory from a self-consistent hydrodynamic simulation, and a second-passage trajectory from a collisionless N-body simulation. In parallel, we infer the present-day ejection site of the HVSs -- likely tracing the LMC's dynamical center and supermassive black hole -- independent of conventional methods.

We use constrained idealized simulations of the LMC/Milky Way interaction to determine if the size of the LMC's gaseous halo (Corona) can be used to distinguish between first and second passage models $-$ an orbital trajectory for the LMC in which it has just recently approached the Milky Way for the first time (first passage), or one in which it has had a previous pericenter (second passage). Using live circumgalactic gas particles combined with analytic dark matter potentials evolved to follow previously published orbital trajectories, we find that the first passage model is able to reproduce the observed velocity profile and column density profile of the present day LMC Corona. On the other hand, in a second passage scenario the longer interaction time leads to the velocities and column densities around the LMC at the present day being too low. Based on this observed velocity profile, recent works have found that the LMC's Corona has been truncated to 17$-$20 kpc, and we find truncation radii of $15.3\pm 0.9$ kpc and $7.6\pm 2.0$ kpc for the first and second passage models, respectively. Thus, based on the gas properties of the LMC's CGM at the present day, a second passage trajectory is disfavored.

We present three-dimensional hydrodynamical simulations of mergers between low-mass hybrid HeCO white dwarfs (WDs), offering new insights into the diversity of thermonuclear transients. Unlike previously studied mergers involving higher-mass HeCO WDs and CO WDs, where helium detonation often triggers core ignition, our simulations reveal incomplete helium shell detonations in comparable-mass, lower-mass WD pairs. The result is a faint, rapidly evolving transient driven by the ejection of intermediate-mass elements and radioactive isotopes such as $^{48}$Cr and $^{52}$Fe, without significant $^{56}$Ni production. These transients may be detectable in upcoming wide-field surveys and could account for a subset of faint thermonuclear supernovae. Long-term evolution of the merger remnant shows that high-velocity PG-1159-type stars might be formed through this scenario, similar to normal CO-CO white dwarf mergers. This work expands our understanding of white dwarf mergers and their implications for nucleosynthesis and stellar evolution.

We report statistically significant detection of H I 21-cm emission from intermediate-redshift ($z\approx0.2$-0.6) galaxies. By leveraging multi-sightline galaxy survey data from the Cosmic Ultraviolet Baryon Survey (CUBS) and deep radio observations from the MeerKAT Absorption Line Survey (MALS), we have established a sample of $\approx6000$ spectroscopically identified galaxies in 11 distinct fields to constrain the neutral gas content at intermediate redshifts. The galaxies sample a broad range in stellar mass -- $8\lesssim\log{M_\rm{star}/\rm{M}_\odot}\lesssim11$ with a median of $\langle\log{M_\rm{star}/\rm{M}_\odot}\rangle_\rm{med}\approx10$ -- and a wide range in redshift -- $0.24\lesssim z\lesssim0.63$ with a median of $\langle z\rangle_\rm{med}=0.44$. Our detected emission-line signal exceeds $4\,\sigma$ significance in the stacked spectra of all subsamples, and the observed total H I 21-cm line flux translates to a H I mass $M_\rm{H\;I}\approx10^{10}\rm{M}_\odot$. We find a high H I-to-stellar mass ratio of $M_\mathrm{H\;I}/M_\rm{star}\approx6$ for low-mass galaxies with $\langle\log{M_\rm{star}/\rm{M}_\odot}\rangle \approx9.3$ ($>3.7\,\sigma$). For galaxies with $\langle\log{M_\rm{star}/\rm{M}_\odot}\rangle\approx10.6$, we find $M_\mathrm{H\;I}/M_\rm{star}\approx0.3$ ($>4.7\,\sigma$). Additionally, the redshift evolution of H I mass in both low- and high-mass field galaxies, inferred from the stacked emission-line signal, aligns well with the expectation from the cosmic star formation history. This suggests that the overall decline in the cosmic star formation activity across the general galaxy population may be connected to a decreasing supply of neutral hydrogen. Finally, our analysis has revealed significant 21-cm signals at distances greater than 75 kpc from these intermediate-redshift galaxies, indicating a substantial reservoir of H I gas in their extended surroundings.

Young planetary systems are subjected to different dynamical effects that can influence their orbital structure over time. In systems with more than one planet, other planets can internally influence each other, e.g. via planet-planet scattering. External perturbing effects also need to be taken into account, as stars do not form by themselves but together with other stars in young star-forming regions. This birth environment can externally affect young multi-planet systems, e.g. via fly-bys. Previous work has shown that the absence/presence and location of an outer giant planet around a close-in planet system do not change how these inner planets react to a single fly-by with another star. We further explore this by comparing the effects of these external perturbations on four close-in sub-Neptune planets to those caused by a situation where only the distant giant is perturbed by the same kind of encounter. Our results indicate that the close-in planet systems have a "preferred" end state after 500 Myr, which is reached regardless of how it was perturbed. In addition, the mass of the giant appears not to impact the reaction of the inner planet system in the scenario of an external perturbation in our tested set-ups, i.e. either a single 1 or 5 M_Jup giant placed at 2.5, 5, 10 or 20 au. However, the mass affects the subsequent evolution of the inner planets if only internal perturbations by the giant are considered. The reduction in mass leads to an absence of collisions during the 500 Myr.

Luminous Fast Blue Optical Transients (LFBOTs) are rare extragalactic events of unknown origin. Tidal disruptions of white dwarfs by intermediate mass black holes, mergers of black holes and Wolf-Rayet stars, and failed supernovae are among the suggestions. In this paper, we explore the viability of very massive star core-collapse events as the origin of LFBOTs. The appeal of such a model is that the formation of massive black holes via core collapse may yield observational signatures that can match the disparate lines of evidence that point towards both core-collapse and tidal disruption origins for LFBOTs. We explore the formation rate of massive black holes in population synthesis models, and compare the metallicities of their progenitors with the observed metallicities of LFBOT host galaxies. We further examine the composition, mass loss rates and fallback masses of these stars, placing them in the context of LFBOT observations. The formation rate of black holes with mass greater than ~30-40Msol is similar to the observed LFBOT rate. The stars producing these black holes are biased to low metallicity (Z<0.3Zsol), are H and He-poor and have dense circumstellar media. However, some LFBOTs have host galaxies with higher metallicities than predicted, and others have denser environments (plausibly due to late mass loss not captured in the models). We find that long-lived emission from an accretion disc (as implicated in the prototypical LFBOT AT2018cow) can plausibly be produced in these events. We conclude that (very) massive star core-collapse is a plausible explanation for LFBOTs. The preferred progenitors for LFBOTs in this scenario overlap with those predicted to produce super-kilonovae. We therefore suggest that LFBOTs are promising targets to search for super-kilonovae, and that they may contribute non-negligibly to the r-process enrichment of galaxies.

The XMM-Newton X-ray observatory has played a prominent role in astrophysics, conducting precise and thorough observations of the X-ray sky for the past two decades. The most recent iteration of the 4XMM catalogue and one of its latest data releases DR11 mark significant improvements over previous XMM-Newton catalogues, serving as a cornerstone for comprehending the diverse inhabitants of the X-ray sky. We employ detections and spectra extracted from the 4XMM-DR11 catalogue, subjecting them to fitting procedures using simple models. Our study operates within the framework of the XMM2ATHENA project, which focuses on developing state-of-the-art methods that exploit existing XMM-Newton data. We introduce and publicly release four catalogues containing measurements derived from X-ray spectral modelling of sources. The first catalogue encompasses outcomes obtained by fitting an absorbed power law model to all the extracted spectra for individual detections within the 4XMM-DR11 dataset. The second catalogue presents results obtained by fitting both an absorbed power law and an absorbed blackbody model to all unique physical sources listed in the 4XMM-DR11s catalogue, which documents source detection results from overlapping XMM-Newton observations. For the third catalogue we use the five band count rates derived from the pipe line detection of X-ray sources to mimic low resolution spectra to get a rough estimate of the spectral shape (absorbed power-law) of all 4XMM-DR11 detections. In the fourth catalogue, we conduct spectral analyses for the subset of identified sources with extracted spectra, employing various models based on their classification into categories such as AGN, stars, X-ray binaries, and cataclysmic variables. The scientific potential of these catalogues is highlighted by discussing the capabilities of optical and mid-infrared colours for selecting absorbed AGN. (abridged)

We present a new selected sample of 69 Galactic supernova remnants (SNRs) for calibration of radio $\Sigma-D$ relation at 1 GHz. Calibrators with the most reliable distances were selected through an extensive literature search. The calibration is performed using kernel smoothing of the selected sample of calibrators in $\Sigma-D$ plane and an orthogonal offsets fitting procedure. We use the obtained calibration to derive the distances to 164 Galactic SNRs and 27 new detected SNRs/SNR candidates with none or poor distance estimates. The analysis given in this paper confirms the expected predictions from our previous papers that the kernel smoothing method is more reliable for SNR distance calibration than the orthogonal offset fitting method, except for the distance determinations of the very low brightness SNRs.

Extragalactic stars within galaxy clusters contribute to the intracluster light (ICL), which is thought to be a promising tracer of the underlying dark matter (DM) distribution. In this study, we employ the TNG300 simulation to investigate the prospect of recovering the dark matter distribution of galaxy clusters from deep, wide-field optical images. For this, we generate mock observations of 40 massive clusters ($M_{200}\gtrsim 10^{14.5}\,{\rm M}_\odot$) at $z=0.06$ for the $g'$ band of the Wendelstein Wide-Field Imager (WWFI), and isolate the emission from the brightest cluster galaxy (BCG) and the ICL by masking the satellite galaxies, following observational procedures. By comparing $\Sigma_{\rm BCG+ICL}$ profiles from these images against $\Sigma_{\rm DM}$ profiles for the central subhaloes, we find that $\Sigma_{\rm cen-DM}/\Sigma_{\rm BCG+ICL}$ exhibits a quasi-linear scaling relation in log space with the normalised distance $r/R_{\Delta}$, for both $R_{\Delta}=R_{200}$ and $R_{500}$. The scatter in the scaling is predominantly stochastic, showing a weak dependence on formation time and dynamical state. We recover the DM concentration and mass within $\approx 23$ and $\approx 15$ per cent of their true values (for $R_{200}$), respectively, and with $\approx 3$ per cent larger uncertainties for $R_{500}$. Alternatively, we find that the concentration can be estimated using the BCG+ICL fraction, the central's DM mass using the BCG+ICL flux, and the total DM mass using the bolometric flux. These results demonstrate the feasibility of deriving dark matter characteristics of galaxy clusters to be observed with facilities like the Vera C. Rubin Observatory in the near future.

Cosmic rays interacting with the Earth's atmosphere generate extensive air showers, which produce Cherenkov, fluorescence and radio emissions. These emissions are key signatures for detection by ground-based, sub-orbital, and satellite-based telescopes aiming to study high energy cosmic ray and neutrino events. However, detectors operating at ground and balloon altitudes are also exposed to a background of atmospheric charged particles, primarily pions, kaons, and muons, that can mimic or obscure the signals from astrophysical sources. In this work, we use coupled cascade equations to calculate the atmospheric pion, kaon and muon fluxes reaching detectors at various altitudes. Our analysis focuses on energies above 10 GeV, where the influence of the Earth's magnetic field on particle trajectories is minimal. We provide angular and energy-resolved flux estimates and discuss their relevance as background for extensive air shower detection. Our results are potentially relevant for interpreting data from current and future balloon-borne experiments such as EUSO-SPB2 and for refining trigger and veto strategies in Cherenkov and fluorescence telescopes.

Europa's surface composition and physical characteristics are commonly constrained using spectral deconvolution through linear mixture (LM) modeling and radiative transfer-based (RT) intimate mixture modeling. Here, I compared the results of these two spectral modeling- LM versus RT- against laboratory spectra of water (H$_{2}$O) ice and sulfuric acid octahydrate (SAO; H$_{2}$SO$_{4}$$\cdot$8H$_{2}$O) mixtures measured at near-infrared wavelengths ($\sim$1.2-2.5 $\mu$m) with grain sizes of 90-106 $\mu$m (Hayes and Li, 2025). The modeled abundances indicate that the RT more closely reproduces the laboratory abundances, with deviations within $\pm$5% for both H$_{2}$O ice and H$_{2}$SO$_{4}$$\cdot$8H$_{2}$O with $\sim$100 $\mu$m grains. In contrast, the LM shows slightly larger discrepancies, typically ranging from $\pm$5-15% from the true abundances. Interestingly, both LM and RT tend to consistently overestimate the abundance of H$_{2}$SO$_{4}$$\cdot$8H$_{2}$O and underestimate H$_{2}$O ice across all mixtures. Nonetheless, when H$_{2}$SO$_{4}$$\cdot$8H$_{2}$O either dominates (>80% as observed on Europa's trailing hemisphere; Carlson et al. 2005) or is present only in trace amounts ($\sim$10% on areas in Europa's leading hemisphere; Dalton III et al. 2013; Ligier et al. 2016), both the LM and RT render acceptable results within $\pm$10% uncertainty. Thus, spectral modeling using the RT is preferred for constraining the surface composition across Europa, although the LM remains viable in specific compositional regimes.

(abridged) We aim to characterize kinematic processes in the G012.80 protocluster. We principally focus on the N$_2$H$^+$(1$-$0) emission to trace the dense and cold gas. Additionally, we use lines such as DCN(3$-$2), H41$\alpha$, C$^{18}$O(1$-$0), and SiO(5$-$4), as well as continuum maps. We perform a N$_2$H$^+$ hyperfine spectral line fitting to analyze multiple velocity components and spectral parameters. We estimate velocity gradients, column densities, and line-mass profiles for the two main filaments in G012, named R1 and R2. Line-mass profiles follow $\lambda$($\omega$) = 5660 M$_{\odot}$ pc$^{-1}$($\omega$/pc)$^{0.30}$ (R1) and $\lambda$($\omega$) = 6943 M$_{\odot}$ pc$^{-1}$($\omega$/pc)$^{0.20}$ (R2), which are much larger than those of typical low-mass filaments. R1 and R2 show disparate position-velocity (PV) features. R1 exhibits a transverse velocity gradient of 10.4 kms$^{-1} $pc$^{-1}$ and few dense cores. This gradient is interpreted with a simple rotation toy model, combined with line-mass profile, and corresponds to a rotational timescale of 0.1 Myr. In contrast, R2 exhibits compact velocity structures ($\Delta$V < 2 kms$^{-1}$), likely due to collapse, as evidenced by the presence of a comparatively large number of massive cores and protostellar outflows. R2 is forming prestellar and protostellar cores at a rate of 55.3 M$_{\odot}$ Myr$^{-1}$, with an efficiency similar to the Orion Integral Shaped Filament (ISF). The R1 filament, in contrast, lacks protostellar cores and only contains a few prestellar cores, resulting in an estimated SFR of 4.2 M$_{\odot}$ Myr$^{-1}$, more than an order of magnitude below that of R2. Combining these lines of evidence, we suggest that R1 is younger and still rotating, while R2 has evolved to collapse with a higher SFR. G012 thus hosts filaments at different evolutionary stages.

Sunspot numbers constitute the longest and most widely used record of solar activity, with direct implications for space weather forecasting and heliophysical research. Traditional sunspot counting relies on visual inspection or algorithmic feature detection, both of which are limited by subjectivity, image quality, and methodological inconsistencies. Recent advances in deep learning, particularly convolutional neural networks (CNNs), enable the direct use of solar imagery for automated prediction tasks, reducing reliance on manual feature engineering. In this work, we present a supervised vision-based regression framework to estimate daily sunspot numbers from full-disk continuum images acquired by the Helioseismic and Magnetic Imager (HMI) onboard NASA Solar Dynamics Observatory (SDO). Images from 2011-2024 were paired with daily sunspot numbers from the SILSO Version 2.0 dataset of the Royal Observatory of Belgium. After preprocessing and augmentation, a CNN was trained to predict scalar sunspot counts directly from pixel data. The proposed model achieved strong predictive performance, with R2 = 0.986 and RMSE = 6.25 on the test set, indicating close agreement with SILSO reference values. Comparative evaluation against prior studies shows that our approach performs competitively with, and in several cases outperforms, statistical and hybrid machine learning methods, while offering the novel advantage of bypassing explicit detection and manual feature extraction. Interpretability analyses using Grad-CAM and Integrated Gradients confirmed that the network consistently attends to sunspot regions when forming predictions. These results highlight the potential of deep vision-based approaches for operational solar monitoring, providing a scalable and automated pathway for real-time estimation of classical heliophysical indices

Recent observational evidence of axially symmetric anisotropies in the local cosmic expansion rate motivates an investigation of whether they can be accounted for within the Lemaître-Tolman-Bondi (LTB) framework with an off-center observer. Within this setting, we compute the exact relativistic luminosity distance via the Sachs equation and compare it with the approximate expression obtained from the covariant cosmographic approach (including Hubble, deceleration, jerk and curvature parameters). This comparison allows us to identify the regimes in which the covariant cosmographic method remains reliable. In addition, we compare the LTB relativistic distance for small inhomogeneities with the corresponding result derived from linear perturbation theory (LPT) in the standard cosmological model. This analysis establishes a precise correspondence between the LTB and LPT approaches, offering a consistent dictionary for the interpretation of the observed anisotropies of the large-scale gravitational field. This analysis will be instrumental in interpreting expansion-rate anisotropies, facilitating investigations of the local Universe beyond the FLRW framework with a fully non-perturbative metric approach.

Mergers are believed to play a pivotal role in galaxy evolution, and measuring the galaxy merger fraction is a longstanding goal of both observational and theoretical studies. In this work, we extend the consideration of the merger fraction from the standard measure of binary mergers, namely those comprising two merging galaxies, to multiple mergers, namely mergers involving three or more galaxies. We use the Illustris and IllustrisTNG cosmological hydrodynamical simulations to provide a theoretical prediction for the fraction of galaxy systems that are involved in a multiple merger as a function of various parameters, with a focus on the relationship between the multiple merger fraction $f_m$ and the total merger fraction $f_t$. We generally find that binary mergers dominate the total fraction and that $f_m\approx (0.5-0.7)f_t^{5/3}$, a prediction that can be tested observationally. We further compare the empirical simulation results with toy models where mergers occur, on the evolution timeline of a galaxy, either at constant intervals or as a Poisson process at a constant rate. From these comparisons, where the toy models typically produce lower multiple merger fractions, we conclude that in cosmological simulations, mergers are more strongly clustered in time than in these toy scenarios, likely reflecting the hierarchical nature of cosmological structure formation.

Galactic and intergalactic flows often exhibit relative motion between the cold dense gas and the hot diffuse medium. Such multiphase flows -- involving gas at different temperatures, densities, and ionization states -- for instance, galactic winds, are frequently turbulent. However, idealized simulations typically model the winds and driven turbulence separately, despite their intertwined roles in galaxy evolution. To address this, we investigate the survival of a dense cloud in a hot wind subject to continuous external turbulent forcing. We perform 3D hydrodynamic simulations across a range of turbulent Mach numbers in the hot phase $\mathcal{M}_{\rm turb}=v_{\rm turb}/c_{\rm s, wind}$ from 0.1 to 0.7 ($c_{\rm s, wind}$ and $v_{\rm turb}$ being the sound speed and the turbulent velocity in the hot phase, respectively). We find that in spite of the additional subsonic turbulence, cold clouds can survive if the cooling time of the mixed gas $t_{\rm cool, mix}$ is shorter than a modified destruction time $\tilde{t}_{\rm cc}$, i.e., $t_{\rm cool,mix}/\tilde{t}_{\rm cc}<1$ where $\tilde{t}_{\rm cc}=t_{\rm cc}/(1+\left(\mathcal{M}_{\rm turb}/\left(f_{\rm mix}\mathcal{M}_{\rm wind}\right)\right)^2)^{1/2}$, where $f_{\rm mix}\sim0.6$ is a fudge factor. Moreover, in the `survival regime', turbulence can enhance the growth of cold clouds by up to an order of magnitude because of more efficient stretching and an associated increase in the surface area. This increase in mass transfer between the phases leads to significantly faster entrainment of cold material in turbulent winds. In contrast to the narrow filamentary tails formed in laminar winds, turbulence stretches the cold gas orthogonally, dispersing it over a larger area and changing absorption line signatures.

We study low angular momentum, advective accretion flows around a Kerr black hole within the framework of general relativistic magnetohydrodynamics (GRMHD) in the steady state. By solving the full set of GRMHD equations, we aim to provide a comprehensive understanding of the behavior of magnetized plasma in the strong gravity regime near a rotating black hole. The accretion solutions are obtained for a set of input parameters, namely energy (${\cal E}$), angular momentum (${\cal L}$), magnetic flux ($\Phi$), and isorotation parameter ($I$). By systematically varying these parameters, we generate a family of global GRMHD accretion solutions that characterize the physical environment around the black hole. Using this approach, we investigate whether the inferred magnetic field strengths reported by the Event Horizon Telescope (EHT) for Sagittarius A$^*$ at various radii can be reproduced. We find that, for a broad range of parameter values, our model successfully recovers the EHT inferred magnetic field strengths with an accuracy of approximately $10\%$, offering a self-consistent framework for interpreting near-horizon accretion physics.

The CCAT Observatory is a ground-based submillimeter to millimeter experiment located on Cerro Chajnantor in the Atacama Desert, at an altitude of 5,600 meters. CCAT features the 6-meter Fred Young Submillimeter Telescope (FYST), which will cover frequency bands from 210 GHz to 850 GHz using its first-generation science instrument, Prime-Cam. The detectors used in Prime-Cam are feedhorn-coupled, lumped-element superconducting microwave kinetic inductance detectors (KIDs). The telescope will perform wide-area surveys at speeds on the order of degrees per second. During telescope operation, the KIDs are exposed to changes in the magnetic field caused by the telescope's movement through Earth's magnetic field and internal sources within the telescope. We present and compare measurements of the magnetic sensitivity of three different CCAT KID designs at 100 mK. The measurements are conducted in a dilution refrigerator (DR) with a set of room temperature Helmholtz coils positioned around the DR. We discuss the implications of these results for CCAT field operations.

We investigate the influence of a fine-scale (FS) layered structure in the atmosphere on the propagation of infrasound signals generated by fragmenting meteoroids. Using a pseudo-differential parabolic equation (PPE) approach, we model broadband acoustic signals from point sources at altitudes of 35-100 km. The presence of FS fluctuations in the stratosphere (37-45 km) and the lower thermosphere (100-120 km) modifies ray trajectories, causing multiple arrivals and prolonged signal durations at ground stations. In particular, meteoroids fragmenting at 80-100 km can produce two distinct thermospheric arrivals beyond 150km range, while meteoroids descending to 50 km or below yield weak, long-lived arrivals within the acoustic shadow zone via antiguiding propagation and diffraction. Comparison with observed infrasound data confirms that FS-layered inhomogeneities can account for multi-arrival "N-waves," broadening potential interpretations of meteoroid signals. The results also apply to other atmospheric-entry objects, such as sample return capsules, emphasizing how FS structure impacts shock wave propagation. Our findings advance understanding of wavefield evolution in a layered atmosphere and have broad relevance for global infrasound monitoring of diverse phenomena (e.g., re-entry capsules, rocket launches, and large-scale explosions).

Recent observations with the James Webb Space Telescope (JWST) of massive galaxies at ages below 1 Gyr pose a challenge to standard models of galaxy formation, which predict significantly longer assembly timescales. One possible explanation is that active galactic nuclei (AGN) drive large scale outflows that accelerate galaxy growth. To test this scenario in the local Universe, we analyzed Gaia DR3 data for stars within 5 kpc of the Galactic center, computing galactocentric radial velocities (v_radial_gc) in 27 spatial sectors covering the entire Galaxy, with radial binning of 0.25 kpc. Coordinate transformations and velocity calculations were performed using the Astropy library. We find that 21 of 27 sectors exhibit statistically significant outward motions of 3-50 km/s, while one quadrant shows negative velocities, likely related to the configuration of an activity zone and/or the Galactic bar. Both disk and halo populations also display small but significant mean expansion of 3-9 km/s (p<0.01). These results are consistent with our previous studies, where globular clusters showed outward velocities of 17-31 km/s up to 12 kpc, and axisymmetric analyses of Gaia DR3 stars indicated expansion of ~19 km/s to 5 kpc. Taken together, the evidence suggests that the Milky Way exhibits measurable central expansion, potentially reflecting AGN-driven feedback. This interpretation departs from standard theory and should be regarded as preliminary, requiring further study. However, if confirmed, such expansion could provide a natural explanation for the rapid appearance of massive galaxies observed by JWST.

Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based gamma-ray observatory operating in the energy range from 20 GeV up to 300 TeV, with two sites in La Palma (Spain) and Paranal (Chile). It will consist of telescopes of three sizes, covering different parts of the large energy range. We report on the performance of Large-Sized Telescope prototype (LST-1) in the detection and characterization of extragalactic gamma-ray sources, with a focus on the reconstructed gamma-ray spectra and variability of classical bright BL Lacertae objects, which were observed during the early commissioning phase of the instrument. LST-1 data from known bright gamma-ray blazars - Markarian 421, Markarian 501, 1ES 1959+650, 1ES 0647+250, and PG 1553+113 - were collected between July 10, 2020, and May 23, 2022, covering a zenith angle range of 4 deg to 57 deg. The reconstructed light curves were analyzed using a Bayesian block algorithm to distinguish the different activity phases of each blazar. Simultaneous Fermi-LAT data were utilized to reconstruct the broadband $\gamma$-ray spectra for the sources during each activity phase. High-level reconstructed data in a format compatible with gammapy are provided together with measured light curves and spectral energy distributions (SEDs) for several bright blazars and an interpretation of the observed variability in long and short timescales. Simulations of historical flares are generated to evaluate the sensitivity of LST-1. This work represents the first milestone in monitoring bright BL Lacertae objects with a CTAO telescope.

Recent near- and mid-infrared (IR) observations reveal the existence of appreciable amounts of aromatic and aliphatic hydrocarbon dust in the harsh environments of active galactic nuclei (AGNs), the origins of which are still under discussion. In this paper, we analyze the near-IR spectra of AGNs obtained with AKARI to systematically study the properties of the aromatic and aliphatic hydrocarbon dust a ected by the AGN activity. We perform the spectral fitting and the spectral energy distribution fitting for our sample of 102 AGNs to obtain the fluxes of the aromatic and aliphatic spectral features, the total IR luminosity (L_IR), and the fractional luminosity of AGN components (L_AGN/L_IR). As a result, we find that L_aromatic/L_IR is systematically lower for the AGN sample, especially much lower for AGNs with the aliphatic feature seen in the absorption, than for star-forming galaxies (SFGs), while L_aliphatic/L_aromatic is systematically higher for the AGN sample than for the SFG sample, increasing with the AGN activity indicated by L_AGN/L_IR. In addition, the profiles of the aliphatic emission features of the AGN sample are significantly di erent from those of the SFG sample in that the AGNs have the feature intensities systematically stronger at longer wavelengths. We conclude that both aromatic and aliphatic hydrocarbon dust are likely of circumnuclear origins, suggesting that a significant amount of the aliphatic hydrocarbon dust may come from a new population created through processes such as shattering of large carbonaceous grains by AGN outflows.

We investigate uncertainties in the estimation of the Hubble constant ($H_0$) arising from Gaussian Process (GP) reconstruction, demonstrating that the choice of kernel introduces systematic variations comparable to those arising from different cosmological models. To address this limitation, we introduce the Generalized Gaussian Process (Gen GP) framework, in which the Matérn smoothness parameter $\nu$ is treated as a free parameter, allowing for data-driven kernel optimization. Using the cosmic chronometer Hubble data, we find that while standard GP with $\Lambda$CDM mean function exhibits noticeable reconstruction differences between optimized and marginalized approaches, particularly at $z > 1$, Gen GP maintains methodological consistency. In Gen GP, slight increases in $\chi^2$ per degree of freedom relative to standard GP, for both the zero-mean and $\Lambda$CDM prior mean cases, reflect added flexibility rather than performance degradation. Our results emphasize that robust cosmological inference requires treating kernel parameters as free variables and implementing full Bayesian marginalization to avoid artificial precision from fixed hyperparameters. As machine learning becomes central to cosmological discovery, the Gen GP framework provides a principled approach to model-independent inference that properly accounts for methodological uncertainties while maintaining necessary flexibility for reliable parameter estimation.

Dense star clusters are promising nurseries for the formation and growth of intermediate-mass black holes (IMBHs; $\sim 10^2-10^5\,\mathrm{M}_{\odot}$), with increasing observational evidence pointing to their presence in massive star clusters and stripped dwarf-galaxy nuclei. During the early evolution of compact clusters, massive stars can rapidly segregate to the center, where frequent collisions may trigger the runaway growth of a very massive star (VMS). This object can subsequently collapse to form an IMBH or merge with a stellar-mass black hole. We carried out direct $N$-body and Monte Carlo simulations of star clusters with initial core densities between $10^6$ to $4\times 10^8\,\mathrm{M}_{\odot}\,\mathrm{pc}^{-3}$ and total masses of $5.9\times 10^5$ and $1.3\times 10^6\,\mathrm{M}_{\odot}$. These models show that IMBHs of $10^3-10^4\,\mathrm{M}_{\odot}$ can form within $\leq 5$ Myr through the runaway collision channel. At later times, the IMBHs continue to grow through mergers with black holes, stars, and compact remnants, providing predictions testable with future gravitational-wave and transient surveys.

We introduce three-parameter extensions of the two-parameter minimal Akhtar-Hossain (mAH) parametrization, termed modified minimal AH (MmAH1,2), which provide greater flexibility in the dynamics of dark energy. These models are compared with $\Lambda$CDM, $w$CDM, mAH, CPL, and three-parameter CPL (CPL-$w_{\rm b}$) using a joint data set of the CMB compressed likelihood, DESI DR2, Pantheon$+$ supernovae, $H(z)$ measurements, and redshift-space distortions. While the common cosmological parameters remain stable across models, CPL and the MmAH1,2 yield modest improvements in fit, with $\Delta\chi^2\simeq -6$ to $-7$ and corresponding $\Delta{\rm AIC}\simeq -1$ to $-2$ relative to $\Lambda$CDM, suggesting a mild preference for dynamical dark energy. Statistical consistency with $\Lambda$CDM is quantified via the Mahalanobis distance in one, two, and three dimensional parameter subspaces. In 1D, the strongest deviation occurs for MmAH1 ($2.5\sigma$), followed by CPL ($2.3\sigma$). In 2D, CPL-$w_{\rm b}$ shows the highest discrepancy ($2.3\sigma$), while other models remain at the $1.7$-$2.1\sigma$ level. In 3D, CPL-$w_{\rm b}$ continues to exhibit the largest tension ($\sim2\sigma$), though this arises in the presence of very strong correlations, particularly between $w_{\rm a}$ and $w_{\rm b}$, whereas the MmAH extensions display slightly weaker but still non-negligible discrepancies ($1.4$-$1.8\sigma$). Overall, these results indicate consistent evidence for departures from $\Lambda$CDM.

The atmospheres of low-temperature brown dwarfs and gas giant planets are expected to contain the phosphine molecule, PH$_3$ However, previous observations have shown much lower abundances of this molecule than predicted by atmospheric chemistry models. We report JWST spectroscopic observations of phosphine in the atmosphere of the brown dwarf Wolf 1130C. Multiple absorption lines due to phosphine are detected around 4.3 ${\mu}$m, from which we calculate a phosphine abundance of 0.100$\pm$0.009 parts per million. This abundance is consistent with disequilibrium atmospheric chemistry models that reproduce the phosphine abundances in Jupiter and Saturn, and is much higher than abundances previously reported for other brown dwarfs or exoplanets.

As a continuation of DRAGON-II, we present the DRAGON-III project, which focuses on the simulations of million-body globular clusters and nuclear clusters over 10 Gyr. We report on its preliminary results on globular clusters. The first 100 Myr of the simulations have produced 41 pulsars, 191 X-ray binaries, 17 gravitational wave sources, and one black hole-black hole merger due to the loss of orbital energy in the form of gravitational wave emission. The inclusion of initial soft binaries brings surprisingly interesting results, including one IMBH in a binary black hole, and compact object binaries resembling the Gaia-BH1 and the wide black hole-giant binary reported in Wang et al. (2024, Nat. Astro.).

Methanol (CH$_{3}$OH) ice is abundant in space and is a key feedstock for seeding chemical complexity in interstellar and circumstellar environments. Despite its ubiquity, gas-phase methanol has only been detected in one disk around a Solar-type star to date, TW Hya. Here we present new high sensitivity (~1 mJy/beam) observations of TW Hya with ALMA that detect four individual transitions of gas-phase methanol spanning upper level energies from 17 to 38 K. We confirm the presence of gas-phase methanol in the luke-warm molecular layer of the disk ($35.9^{+25.9}_{-10.6}$ K) and with a disk-integrated column density of $1.8^{+1.3}_{-0.5}\times 10^{12}$ cm$^{-2}$. A radially-resolved analysis suggests that the gas-phase methanol is centrally compact, peaking within the spatial extent of the mm-sized dust grains ($\lesssim 80$ au). Static gas-grain chemical disk models confirm photodesorption as an important mechanism releasing methanol into the gas phase, with the column density further boosted by the inclusion of grain-surface chemistry, reactive desorption, and an increase in dust-grain surface area assuming fractal grains. However, no model can fully reproduce the observed column density nor the radial distribution, and we suggest that the inclusion of dynamic processes such as vertical mixing and radial drift would be required to do so. Our results demonstrate that the abundance and distribution of the precursors for complex chemistry in the planet-forming regions around Solar-type stars is ultimately controlled by the interplay of grain surface chemistry coupled with the evolution of dust in their disks.

We perform a consistency check of DESI DR2 BAO constraints ($D_M/r_d, D_H/r_d)$ by reconstructing the same quantities from DES supernovae (SNe) in bins with the same effective redshift $z_{\textrm{eff}}$. We find that the ratio of $D_M/r_d$ values are consistent with a horizontal, thus confirming that the distance duality relation holds up to calibration. However, the $D_H/r_d$ ratio shows a decreasing trend with $z_{\textrm{eff}}$ at $2.3 \sigma$ to $2.5 \sigma$ that cannot be explained by physics. We demonstrate that the result does not depend on the choice of cosmological model, but the radius of the sound horizon $r_d$ has a much greater influence. Studying ratios of $D_H/r_d$ is a stronger test than the distance duality relation, and the rejection of a horizontal confirms systematics in either DESI BAO or DES SNe. Claims of new physics based on combined data still have rudimentary hurdles to clear.

Recent observations from the Dark Energy Spectroscopic Instrument (DESI) raise doubts about the standard cosmological model, $\Lambda$CDM, suggesting a preference for an inherently dynamical dark energy component. The Chevallier-Polarski-Linder (CPL) parameterization -- a widely used two-parameter model for the dark energy equation of state -- displays marked early-time phantom behavior and a recent crossing of the phantom divide. These features suggest the convenience to check observationally the robustness of such evolution. To address this, we design two alternative families of two-parameter dark energy parameterizations which remain close to the original CPL but aim to soften its phantom character. Specifically, these models reproduce CPL-like behavior at low redshift but mitigate early phantom behavior through the use of smooth sigmoid transitions, yielding a more gradual evolution. By combining recent DESI data with constraints from the cosmic microwave background and Type Ia supernovae, we assess the viability of these models. Our analysis shows that CPL remains a strong and competitive parameterization, with the proposed alternatives only marginally favored or disfavored. We conclude that current observational data lack the statistical precision to decisively distinguish between CPL and similarly constructed parameterizations across the redshift range probed by late-time observables.

We investigate the origin of warps in stellar disks using high-resolution Milky Way analogs from the IllustrisTNG50 simulation. Focusing on galaxies that experienced a major merger, we identify a characteristic azimuthal misalignment between the warp structures of stellar populations formed before and after the merger. This misalignment persists even after correcting for differential rotation, suggesting it is a dynamical imprint of the merger rather than a consequence of internal kinematics. In contrast, galaxies without significant merger events show no such offset between stellar populations of different ages. These findings support the scenario in which mergers can induce long-lived warps and leave detectable structural signatures in stellar disks. Applied to the Milky Way, this approach offers a potential way to test whether the Gaia-Sausage-Enceladus merger contributed to the formation of the Galactic warp. It may also provide an independent means to constrain the timing of such merger events by examining the phase offsets in the stellar warp as a function of stellar age.

Recently, the \textit{EHT} collaboration unveiled the shadow images of the supermassive black hole (SMBH) M87* and Sgr A*, with angular radii of $42\pm3$\,$\mu$as and $48.7\pm7.0$\,$\mu$as, respectively. These observations are consistent with the shadow of a Kerr black hole in general relativity (GR). Observations of the shadow of SMBHs can be used to test modified gravity theories, including Yukawa gravity, in extremely strong fields. In this paper, we illustrate the shadows of Yukawa black holes, showing that their sizes are significantly influenced by the Yukawa parameters $\lambda$ and $\kappa$. Using the EHT observations of M87* and Sgr A*, we obtain constraints on the Yukawa parameters. For Sgr A*, Keck and VLTI provide different priors on its gravitational radius. The Sgr A* shadow yields $\kappa=-0.04^{+0.09}_{-0.10}$ for $\lambda>1$\,AU with the Keck prior, while $\kappa=-0.08^{+0.09}_{-0.06}$ with the VLTI prior. As $\lambda$ decreases, the constraints weaken, reaching $-0.37<\kappa <0.17$ (Keck prior) and $-0.47<\kappa<0.04$ (VLTI prior) at $\lambda=0.1$\,AU. For M87*, with a mass significantly larger than Sgr A*, this system can only put constraints on $\kappa$ at larger $\lambda$. For $\lambda>1.5\times10^4$\,AU, the \textit{EHT} observation of M87* yields $\kappa=-0.01^{+0.17}_{-0.17}$. No significant deviation from GR is detected in our analysis. Additionally, we explore potential constraints using the next-generation VLBI, like \textit{ngEHT} and the Black Hole Explorer (BHEX), which promise the detection of the second ring of photons. The improved angular resolution and the measurements of the second ring could substantially refine constraints on the Yukawa parameters, enhancing our ability to test deviations from GR in the strong-field regime.

This review surveys recent advances in the numerical modeling of solar prominences and coronal rain achieved with the fully open-source adaptive-grid, parallelized Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC). We examine how these models have contributed to our understanding of the formation and evolution of cool plasma structures in the solar corona. We first discuss prominence models that focus on prominence formation and their dynamic behavior. We then turn to coronal rain, highlighting its connection to thermal instability and its role in the exchange of mass and energy between the corona and chromosphere. Particular attention is given to the growing efforts to connect simulations with observations through synthetic emission and spectral diagnostics.

The role of spiral arms in galaxies -- whether they enhance star formation efficiency or primarily act as material gatherers -- remains an open question. Observational studies have yielded ambiguous results, in part due to the choice of star formation rate (SFR) tracers and their inherent limitations. These limitations are addressed here by applying multi-wavelength spectral energy distribution (SED) fitting to individual arm and interarm regions. We expand on our previous study of two galaxies to include six diverse galaxies, spanning over an order of magnitude in total stellar mass and factors of several in total SFR, for which spiral arms have been mapped. We find that the specific star formation rate (sSFR = SFR/M$_{star}$) can be used as a proxy for the star formation efficiency (SFE=SFR/M$_{gas}$), since the two quantities are directly proportional to each other in our regions. In our analysis of both tracers (sSFR and SFE) no significant difference is found the between arm and interarm regions, except for one galaxy (NGC 1097), supporting the gatherers scenario.

CTA 1 is a shell-type supernova remnant (SNR) with a central pulsar wind nebula (PWN), visible at very-high-energy (VHE) from 50 GeV to 100 TeV from a moderately extended emission region. While general consensus concludes the VHE emission originates from relativistic leptons accelerated by the PWN and undergoing inverse Compton scattering, questions remain about electron escape and propagation, as well as the evolutionary stage of this particular PWN. CTA 1 is on the cusp of middle age (~13 kyr) and spatially resolvable at energies visible to imaging atmospheric Cherenkov telescopes (IACTs), such as the Very Energetic Radiation Imaging Telescope Array System (VERITAS) (PSF < 0.1 deg). Therefore, this remnant is an excellent candidate to study lepton propagation and escape between different PWN evolutionary stages. Since the initial VERITAS publication on CTA 1 in 2013, VERITAS has performed new observations, adding to a total exposure of about 120 hours. We have analyzed the entire VERITAS CTA 1 dataset to date and report results.

There is increasing observational evidence for a failed galaxy formation pathway for some ultradiffuse galaxies (UDGs) at low redshift however they currently lack simulated counterparts. We attempt to identify dark matter halos at high redshift within the MAGNETICUM cosmological simulations that could plausibly be their progenitors. We build a toy model of passive galaxy evolution within the stellar mass-halo mass relation to trace z = 0 observations of UDGs back to their z = 2 locations. We identify a population of 443 galaxies that match these parameter space positions within the simulation. We build two comparison samples within the simulation that follow the stellar mass-halo mass relationship at z = 2, one of which is stellar mass matched (with varying smaller halo masses) and the other is halo mass matched (with varying larger stellar masses) to our sample. We identify that our failed galaxy progenitor candidates have 1) flatter, cored dark matter halos; 2) more extended stellar bodies; 3) a larger fraction of their gas in the outskirts of their halos; 4) lower metallicities and 5) higher star formation rates than the control samples. Findings 1) and 2) are similar to low redshift observations of UDGs. Finding 3) will aid the removal of gas and permanent quenching of star formation which is a requirement of the failed galaxy formation scenario. The low metallicities of finding 4) match those observed in low redshift failed galaxy UDGs. Comparing the high star formation rates of finding 5) to recent JWST observations suggests that a starburst would naturally explain the high globular cluster richness of the UDGs. Many of the properties we find for these failed galaxy progenitors can be explained by an assembly bias of their dark matter halo to later formation times. We conclude by proposing that the fraction of failed galaxy UDGs is expected to increase with environmental density.

We aim to spectroscopically confirm the nature of VVV-J181258.71-314346.7, a candidate counterpart to the unassociated gamma-ray source 4FGLJ1812.8-3144. This object was selected based on its near-infrared photometric properties and moderate variability, as part of a broader effort to identify active galactic nuclei (AGN) behind the Galactic bulge and disc. We obtained near-infrared spectra using the Flamingos-2 instrument at Gemini South, covering the $1.1 $--$ 1.8~\mu$m range with a spectral resolution of $R \sim 1200$. Standard data reduction procedures were applied, including telluric correction and wavelength calibration. The analysis focused on the identification of emission lines and the estimation of the redshift using cross-correlation techniques and spectral template fitting. Despite a relatively low signal-to-noise ratio, the spectrum reveals the presence of Pa$\beta$ and Fe\,\textsc{ii} emission lines. The measured redshift is $z = 0.206 \pm 0.001$, which confirms the extragalactic nature of the source. The spectral features such as line ratios and full width at half maximum are consistent with those typically observed in type-1 AGNs, particularly Seyfert 1 galaxies. This study demonstrates the ability of near-infrared spectroscopy to reveal AGNs that are obscured by highly extincted and crowded galactic fields. The confirmation of an AGN at low Galactic latitude ($b\sim -6.5$°) shows that near-IR surveys like VVV can successfully penetrate the zone of avoidance. Extending this approach to additional candidates is crucial for improving the census of AGNs hidden behind the Milky Way, as well as for constraining the population of unassociated gamma-ray sources in these troublesome regions.

We present measurements of the dusty torus sizes of 51 active galactic nuclei (AGNs) with a redshift of $z<$ 0.8. Our analysis utilizes about 16 years of optical photometric data of 146 AGNs from various time-domain surveys, including ASAS-SN, CRTS, and ZTF, along with 14 years of infrared data in the $W$1 ($\sim$ 3.4 $\mu$m) and $W$2 ($\sim$ 4.6 $\mu$m) bands obtained from the Wide-Field Infrared Survey Explorer (WISE). The estimated dust torus size ranges from 1000 to 3000 days, using both the cross-correlation analysis and lightcurve modeling through `MICA'. The measured lag has been corrected by $(1+z)^{-0.37}$, to account for cosmological time dilation and the torus temperature-gradient scaling. We conduct a linear regression analysis for both the $W$1 and $W$2 bands to examine the radius--luminosity ($R$--$L_{BOL}$) relationship under two conditions: one where the slope is fixed at 0.5 and one where it is allowed to vary. For the fixed slope of 0.5, we find the ratio of R$_{\mathrm{BLR}}$: R$_{W1}$: R$_{W2}$ to be 1: 9: 12, indicating that the torus lies outside the BLR and that its size increases with wavelength. Furthermore, we determine the relationship between torus size and L$_{BOL}$, yielding best-fit slopes of $0.413\pm0.047$ for the $W$1 band and $0.397\pm0.058$ for the $W$2 band. Both slopes are shallower than predicted by the dust radiation equilibrium model. Furthermore, our findings indicate that the torus size systematically decreases as the Eddington ratio increases, a trend that can be explained by the self-shadowing effects of slim disks.

We present an analysis of Suzaku observations of 14 nearby galaxy clusters and groups (z < 0.06), extending radial coverage out to the virial radius (approximately r200). The sample spans a wide mass range, from M500 about 2x10^13 to 7x10^14 solar masses, and includes well-studied systems such as Coma, Perseus, and Virgo. We carefully modeled all background components, including the soft X-ray foregrounds (the Local Hot Bubble, Milky Way Halo, and super-virial temperature components), the cosmic X-ray background, and the non-X-ray background, and assessed their effects on the derived properties of the intracluster medium (ICM). We constructed radial profiles of emission measure, electron density, and temperature. Temperatures decrease smoothly with radius, typically dropping to about one-third to half of their peak values near r200. For relaxed clusters, the emission measure profiles outside the core regions are well described by a beta model with beta around 0.6-0.7, while groups show slightly flatter slopes of beta around 0.4-0.65. Beyond r2500, electron density profiles follow a power-law decline with a slope close to 2. At r500 and r200, the electron density and the gas mass fraction show a tight correlation with the system mass, except for three clusters with bright subclusters. In massive clusters, the gas fraction increases with radius and approaches the cosmic baryon fraction near r200. In contrast, lower-mass systems exhibit gas fractions of around 0.1 at r200. The observed mass dependence of gas fractions suggests that feedback and related processes play an increasingly important role toward the group scale, shaping the connection between baryons and dark matter halos.

Galaxy observations suggest there is about one merger of supermassive black hole binaries (SMBHB) throughout the observable universe in a year. Here, we introduce the methodology to search for gravitational waves from these events with Pulsar Timing Arrays (PTAs). Modelling the inspiral, the merger, the ringdown, and the gravitational wave memory components of the signal in simulated data, we demonstrate a proof of principle for detection and parameter estimation. We study a few representative SMBHB mergers with chirp masses spanning $10^{8} - 10^{10}~M_\odot$ at distances from a few Mpc to 100~Mpc to asses their detectability in PTA observations. Assuming the fixed binary inclination angle of $90^{\circ}$ corresponding to the maximum displacement memory signal, these signals appear distinct for a PTA with 25 pulsars timed for 13 years with 100 ns precision. We demonstrate the capabilities of PTAs to constrain chirp masses and distances of detected merging binaries, as well as to place limits. The sky position uncertainties of the order of $1^{\circ}$, which we find in this optimistic example, could potentially enable electromagnetic follow-up and multi-messenger observations of SMBHB mergers. Finally, we show that the measurement uncertainties on the parameters of simulated merging binaries depend weakly on the presence of the gravitational wave background with Hellings-Downs correlations in our simulated data.

We have identified more than a hundred close triply eclipsing hierarchical triple star systems from data taken with the space telescope TESS. Many of them have outer periods less than or, close to 100 days, hence, we call them `ultracompact hierarchical triples'. These systems are noteworthy in that we can potentially determine their dynamical and astrophysical parameters with a high precision, in many cases even without radial velocity data. In the present paper we report the comprehensive study of ten new ultracompact triply eclipsing triple star systems, located in the northern ecliptic hemisphere, taken from this larger sample: TICs 198581208, 265274458, 283846096, 337993842, 351404069, 378270875, 403792414, 403916758, 405789362, 461500036. Most of the data for this study come from TESS observations, but we obtained supplemental ground-based photometric measurements for two of the systems. The eclipse timing variation curves extracted from the TESS and the ground-based follow up data, the photometric light curves, and the spectral energy distribution are combined in a complex photodynamical analysis to yield the stellar and orbital parameters of all ten systems. The outer periods are in the range of 46.8-101.4 days. We found third-body forced, rapid apsidal motion in four systems. Moreover, TIC 403916758 was found to be a double twin triple (i.e. both the inner and the outer mass ratios are close to unity). All of the systems are substantially flat, with mutual inclination angles of $<5^o$. Finally, we have taken the results for the ten systems in the present paper, and combined them with the system parameters for more than 30 other compact triples that we have reported on in previous work, in order to examine some of the global properties of these systems on a statistical basis.

Jets in active galactic nuclei have to cross significant distances within their host galaxies, meeting large numbers of stars of different masses and evolution stages in their paths. Given enough time, supernova explosions within the jet will eventually happen, and may have a strong impact on its dynamics, potentially triggering powerful non-thermal activity. We carried out a detailed numerical study to explore the dynamics of the interaction between the ejecta of a supernova explosion and a relativistic extragalactic jet. By means of relativistic hydrodynamics simulations using the code RATPENAT, we simulated the jet-ejecta interaction in two different geometries or scenarios: a two-dimensional, axisymmetric simulation, and a three-dimensional one, which includes the orbital velocity of the exploding star. Although initially filling a region much smaller than the jet radius, the ejecta expands and eventually covers most of the jet cross section. The expansion is enhanced as more energy from the jet is converted into kinetic and internal energy of the ejecta, which also favors the ejecta disruption, all this occurring on timescales ~ 10^4 yr. Although a complete numerical convergence of the results is unattainable given the subsonic, turbulent nature of the interaction region, the simulations are consistent in their description of the gross morphological and dynamical properties of the interaction process. At the end of the simulations, the supernova ejecta has already partially mixed with the relativistic jet. The results also suggest that the jet-ejecta interaction may be a non-negligible non-thermal emitter. Moreover, due to efficient mixing, the interaction region can be a potential source of ultra-high-energy cosmic rays of heavy composition.

Type II solar radio bursts are commonly associated with shocks generated by coronal mass ejections (CMEs), where plasma waves are excited by magnetohydrodynamic (MHD) processes and converted into radio waves at the local plasma frequency or its harmonics. However, there are instances where type II bursts occur in the absence of whitelight CMEs. We analysed one such metric type II radio burst observed on November 2, 2023, characterized by split band features and fundamental-harmonic lanes. Notably, no CME was detected with space-based coronagraphs during this event. However, an intense M1.6 class flare was observed just before the type II burst and an extreme ultraviolet (EUV) disturbance was observed expanding into surrounding regions. The absence of any whitelight CME seen in any coronagraph field of view even though the EUV shock had a moderate speed of $\approx500~km/s$, which was close to the shock speed derived from radio observations, %indicates that the shock in the inner corona was most-likely produced by the very intense solar flare and the type II was associated with the EUV disturbance seen in the lower corona. These observations indicate that the shock in the inner corona was most-likely driven by the EUV ejecta seen in the lower corona, but the ejecta did not survive as a CME in the coronagraph field of view.

These notes review theoretical models of massive black hole formation, growth and observables. They start with a brief summary of basic properties of massive black hole properties. The current view on massive black holes and active galactic nuclei at high redshift is then summarized, highlighting the JWST ``revolution'' and the questions raised by the recent observations. The notes then touch on massive black hole formation and growth mechanisms, emphasizing the processes at play at early cosmic times. Then techniques for modeling the cosmic massive black hole evolution, are reviewed with an emphasis on cosmological simulations, before approaching how observables are derived from models. They conclude with a section reflecting on the main questions on the JWST-discovered population in light of the material presented in the earlier sections.

Over the past decades, there has been growing observational and theoretical evidence that cosmic-ray-induced instabilities play an important role in both acceleration and transport of cosmic rays (CRs). For instance, the efficient acceleration of charged particles at supernova remnant shocks requires rapidly growing instabilities, so much so that none of the proposed processes seem sufficient to warrant acceleration to PeV energies. In this work, we investigate whether an acoustic instability triggered by the presence of a CR pressure gradient can lead to significant self-confinement of charged particles in the vicinity of shocks. We validate the expected growth rates and obtain the scale and energy of magnetic field perturbations induced by such system using magnetohydrodynamical simulations. Our results suggest a strong suppression of the diffusion coefficient for particles with Larmor radius around a thousandth of the precursor scale length.

Low-frequency radio data improve the sensitivity of pulsar timing arrays (PTAs) to propagation effects such as dispersion measure (DM) variations, enabling better noise characterization essential for detecting the stochastic gravitational wave background (GWB). We combined LOFAR (100-200 MHz) and NenuFAR (30-90 MHz) observations with the recent European and Indian PTA release (DR2new+) into a new dataset, DR2low, spanning ~11 years for 12 pulsars. DR2low allows updated noise models, increasing PTA sensitivity to the GWB. Using Libstempo and Enterprise, we applied standard noise models including red noise (RN) and time-variable DM (DMv) as power laws, and performed Bayesian model selection over RN, DMv, and an additional chromatic noise term (CN4). Compared to DR2new+, DR2low improves DM constraints and separates DM and RN contributions. We found that the RN is required in the final model for 10 out of 12 pulsars, compared to only 5 in the DR2new+ dataset. The improved sensitivity to plasma effects provided by DR2low also favors the identification of significant CN4 in eight pulsars, while none showed such evidence in DR2new+. The analysis also reveals unmodelled solar wind effects, particularly near solar conjunction, with residual delays absorbed into the DM component, highlighting the importance of accurately modelling the solar wind in PTA datasets.

When performing X-ray observations with a Wolter-I telescope, the presence of bright off-axis sources can introduce unfocused rays, known as straylight, which contaminate the detector and compromise the scientific analysis. Among the different components of straylight, single reflections off the hyperboloid section of the mirror shells often produce arc-like patterns on the detector. These arcs depend not only on the off-axis angle of the source but also on the geometrical alignment of the individual shells. In this paper, we introduce the SHell misAlignment Detection for straylight Estimation (SHADE) algorithm, a novel and flexible tool designed to infer the misalignment parameters of individual shells, reproduce the geometry of straylight arcs and predict its pattern on the detector. SHADE allows us to model each shell displacement with two parameters: $(\gamma,\xi)$ that represents the tilt amplitude and direction. While the algorithm is general and applicable to any Wolter-like telescope, we demonstrate its effectiveness using a set of XMM-Newton observations of the low-mass X-ray binary GX5-1. As a proof of concept, we recover the best-fit misalignment parameters for a selected shell, obtaining $\gamma = 21.9''^{+10.3}_{-9.02}$ and $\xi = 5.88^{+1.02}_{-0.97}$ rad. SHADE represents a new approach to diagnosing mirror misalignments from straylight patterns and can support both pre and post-launch calibration efforts and future telescope designs.

The exponential growth of data in Astrophysics and Cosmology demands scalable computational tools and intuitive interfaces for analysis and visualization. In this work, we present an innovative integration of the VisIVO scientific visualization framework with the InterActive Computing (IAC) service at Cineca, enabling interactive, high-performance visual workflows directly within HPC environments. Through seamless integration into Jupyter-based science gateways, users can now access GPU-enabled compute nodes to perform complex 3D visualizations using VisIVO via custom Python wrappers and preconfigured interactive notebooks. We demonstrate how this infrastructure simplifies access to advanced HPC resources, enhances reproducibility, and accelerates exploratory workflows in astronomical research. Our approach has been validated through a set of representative use cases involving large-scale simulations from the GADGET code, highlighting the effectiveness of this system in visualizing the large-scale structure of the Universe. This work exemplifies how science gateways can bridge domain-specific tools and advanced infrastructures, fostering user-centric, scalable, and reproducible research environments.

Context. Edge-on disks offer a unique opportunity to directly examine their vertical structure, providing valuable insights into planet formation processes. We investigate the dust properties, as well as the CO and HCO$^+$ gas properties, in the edge-on disk surrounding the T Tauri star 2MASS J04202144+281349 (SSTTau042021). Aims. We estimate the radial and vertical temperature and density profile for the gas and the dust. Methods. We use ALMA archival data of CO isotopologues and continuum emission at 2, 1.3 and 0.9 mm together with new NOEMA HCO$^+$ 3-2 observations. We retrieve the gas and dust disk properties using the tomographic method and the \textsc{DiskFit} model. Results. The vertical CO emission appears very extended, partly tracing the H$_2$ wind observed by JWST. C$^{18}$O, $^{13}$CO and HCO$^+$ emission characterize the bulk of the molecular layer. The dust and gas have a mid-plane temperatures of $\sim 7-11$ K. The temperature of the molecular layer (derived from $^{13}$CO and HCO$^+$) is on the order of 16 K. HCO$^+$ 3-2 being thermalized, we derive a lower limit for the H$_2$ volume density of $\sim 3 \times 10^6$ cm$^{-3}$ at radius 100-200 au between 1 and 2 scale heights. The atmosphere temperature of the CO gas is of the order $\sim$ 31 K at a radius of 100 au. We directly observe CO and HCO$^+$ gas onto the mid-plane beyond the dust outer radius ($\ge 300$ au). The (gas+dust) disk mass estimated up to a radius of 300 au is on the order of $4.6 \times 10^{-2} \mathrm{M}_\odot$. Conclusions. Thanks to the favorable disk inclination, we present the first quantitative evidence for vertical molecular stratification with direct observation of CO and HCO$^+$ gas along the mid-plane. We estimate the temperature profile with temperature of 7-11 K near the mid-plane, and 15-20 K in the dense part of the molecular layer up to $\sim$ 35 K above.

Twisted coronal loops in the solar atmosphere may become kink-unstable when their magnetic field lines are sufficiently twisted. This instability can trigger magnetic reconnection, leading to the emission of electromagnetic radiation, which manifests as a solar flare. Previous research has demonstrated that oscillations in microwave emissions, resembling observed quasi-periodic pulsations (QPPs), can be generated by the reconnecting loop. Our aim is to investigate the relationship between the oscillations of the loop and these microwave pulsations. Using 3D magnetohydrodynamical simulations, we examine two models: a straight loop in a uniform-density atmosphere and a curved loop in a gravitationally stratified atmosphere. Using new methodology, we extract the reconnecting loop-top from both models and identify structural oscillations. We then compare these oscillations with the gyrosynchrotron (GS) radiation emitted from the simulations, which is forward-modelled using a radiative transfer code. We find that oscillations in the GS emissions are driven by sausage and kink-mode oscillations. However, the relationship between the oscillation frequencies of the GS emission and the identified loop oscillation modes is complex. The dominant mode in the former may result from interference between sausage-mode and kink-mode oscillations or entirely different mechanisms. Results such as these increase our understanding of the time-dependent behaviour of solar flares and lay the groundwork for potential diagnostic tools that could be used to determine physical parameters within a flaring loop

Extra radiation injection after neutrino decoupling in the early Universe contributes to the effective number of neutrino species that can be constrained by the cosmic microwave background (CMB). However, any effective neutrino number itself cannot uniquely determine the underlying source. We argue that the degeneracy can be relaxed by CMB spectral distortions, which are caused by energy exchange between the extra radiation and photons. We consider neutrinogenic CMB spectral distortions, where extra energy is released in the form of neutrinos but still creates the CMB spectral distortions via electroweak interactions. The synergy between the effective neutrino number and CMB spectral distortions provides a complementary probe of hidden sectors that dominantly couple to neutrinos, opening up parameter space that can be targeted by joint CMB anisotropy and spectral distortion experiments.

In the "stochastic $\delta N$ formalism", the statistics of the inflationary density perturbation are obtained from the first passage distribution of a stochastic process. We develop a general framework in which to evaluate the rare tail of this distribution, based on an instanton approximation to a path integral representation for the transition probability. We relate our formalism to the Schwinger-Keldysh path integral, by integrating out short wavelength degrees of freedom to produce an influence functional. This provides a principled way to extend the calculation beyond the slow-roll limit, and to models with multiple fields. We argue that our framework has a number of advantages in comparison with existing methods. In particular, it reliably captures the tail behaviour in cases where existing techniques do not apply, including cases where the noise amplitude has strong time dependence. We demonstrate the method by computing the tail probability in a number of scenarios, including a beyond-slow-roll analysis of a linear potential, ultra-slow-roll, and constant-roll inflation. We find close agreement with results already reported in the literature. Finally, we discuss a scenario with exponentially decaying noise amplitude. This is a model for the stochastic evolution of a fixed comoving volume of spacetime on superhorizon scales. In this case we show that the tail reverts to a Gaussian weight.

The James Webb Space Telescope (JWST) has unveiled a population of unexpectedly massive and luminous galaxies at redshifts $z \gtrsim 7$, posing a significant challenge to the standard $\Lambda$CDM cosmological paradigm. In this work, we address the tension between early JWST observations of luminous high-redshift galaxies and predictions of the standard $\Lambda$CDM model by revisiting the physics of dark matter halo formation. Employing refined halo mass functions derived by Del Popolo \textit{et al.} (DP1 and DP2) that incorporate angular momentum, dynamical friction, and redshift-dependent collapse barriers, we demonstrate a significant enhancement in the abundance of massive halos at $z \gtrsim 7$ compared to the conventional Sheth-Tormen (ST) formalism. Using a semi-empirical framework linking halo mass to UV luminosity, we show that the DP2 model reproduces the observed UV luminosity functions from $z = 7$ to $14$ with moderate star formation efficiencies, whereas the ST model requires implausibly high efficiencies. Our results suggest that the JWST overabundance problem stems not from new physics beyond $\Lambda$CDM, but from oversimplified treatments of gravitational collapse, highlighting the critical role of small-scale dissipative dynamics in early structure formation.

Context: Astronomical imaging aims to maximize signal capture while minimizing noise. Enhancing the signal-to-noise ratio directly on detectors is difficult and expensive, leading to extensive research in advanced post-processing techniques. Aims: Removing background noise from images is a valuable pre-processing step catalog-building tasks. We introduce BGRem, a machine learning (ML) based tool to remove background noise from astronomical images. Methods: BGRem uses a diffusion-based model with an attention U-Net as backbone, trained on simulated images for optical and gamma ({\gamma})-ray data from the MeerLICHT and Fermi-LAT telescopes. In a supervised manner, BGRem learns to denoise astronomical images over several diffusion steps. Results: BGRem performance was compared with a widely used tool for cataloging astronomical sources, SourceExtractor (SExtractor). It was shown that the amount of true positive sources using SExtractor increased by about 7% for MeerLICHT data when BGRem was used as a pre-processing step. We also show the generalizability of BGRem by testing it with optical images from different telescopes and also on simulated {\gamma}-ray data representative of the Fermi-LAT telescope. We show that in both cases, BGRem improves the source detection efficiency. Conclusions: BGRem can improve the accuracy in source detection of traditional pixel-based methods by removing complex background noise. Using zero-shot approach, BGRem can generalize well to a wide range of optical images. The successful application of BGRem to simulated {\gamma}-ray images, alongside optical data, demonstrates its adaptability to distinct noise characteristics and observational domains. This cross-wavelength performance highlights its potential as a general-purpose background removal framework for multi-wavelength astronomical surveys.

Aims. We have determined Sr abundance in a sample of 31 red giant branch stars located in the Galactic globular cluster 47 Tuc with the aim to identify potential differences in the Sr abundance between first population (1P, Na-poor) and second population (2P, Na-rich) stars. Methods. We derived the Na and Sr abundances from the archival spectra obtained with the UVES spectrograph. To do this, we used 1D ATLAS9 model atmospheres and a 1D local thermodynamic equilibrium spectral synthesis method. Particular attention was paid to assessing the potential impact of CN line blending on the obtained Sr abundances. Furthermore, we evaluated the potential influence of convection on the Sr line formation by using 3D hydrodynamical model atmospheres computed with the CO5BOLD code. Results. Our results suggest a weak correlation between the abundances of Sr and Na. Together with a similar correlation between the abundances of Zr and Na determined in our previous study, our analysis of Sr suggests that polluters that have enriched 2P stars with light elements may have produced some s-process elements as well. The mean Sr abundance determined in 31 red giant branch stars of 47~Tuc is $\langle {\rm [Sr/Fe]} \rangle = 0.18\pm0.08$ (the error denotes the standard deviation due to the star-to-star abundance scatter). This value is within the range of the Sr abundance variation that is observed in Galactic field stars of similar metallicity. The mean [Sr/Zr] abundance ratio in our sample stars suggests that the two s-process elements could have been synthesized by either low-mass asymptotic giant branch stars ($M=1-4 {\rm M}_{\odot}$) or massive ($M=10-20 {\rm M}_{\odot}$) fast-rotating ($v_{\rm rot}=200-300$ km/s) stars.

PG0043+039 has been identified as an extremely X-ray-weak quasar and as a peculiar broad-absorption-line quasar based on UV HST spectra. We took simultaneous deep X-ray observations of PG0043+039 with XMM-Newton and NuSTAR, UV spectra with the HST, and optical spectra with the HET telescope in 2022. PG0043+039 was an extreme low-X-ray-luminosity quasar in 2022. This AGN showed an extreme steep alpha_oX value of -2.47. The X-ray luminosity was a factor of 3.4 higher in the meantime in 2013. The optical and UV continuum only decreased by a factor of 1.3 - 1.5 from 2013 to 2022. Very strong emission-line intensity variations by factors of eight or more were observed in the OVI_1038 and SiIV_1403 lines between 2013 and 2022. The other UV emission lines such as Ly_alpha only decreased by a factor of 1.4. We derived a black hole mass of M=6.95*10^{8} M_solar (based on H_beta). This corresponds to an Eddington ratio of L/L_edd = 0.115. PG0043+039 exhibits strong and broad absorption lines in the UV. The highly ionized absorption lines show the largest velocity blueshifts in their broad absorption lines. The PV absorption is very strong, with equivalent widths of 7 - 10 AA. PG0043+039 shows strong Ly_alpha emission despite strong PV absorption. All the strong absorption-line troughs in the UV varied in unison in velocity space back and forward (-2000.+-this http URL-1, +2740.+-this http URL-1) without any major changes in absorption strength or in their profiles for the years 1991, 2013, and 2022. We found no general correlations of X-ray/opt/UV continuum variations with the broad absorption line variations. However, based on the simultaneous UV and X-ray observations - taken in 2013 and 2022 - we see higher maximum velocities of the blueshifted broad absorption lines in the UV when the X-ray flux was lower.

The infall of the Large Magellanic Cloud (LMC) into the Milky Way (MW) has displaced the MW's centre of mass, manifesting as an observed reflex motion in the velocities of outer halo stars. We use a Simulation Based Inference framework to constrain properties of the MW, LMC and the induced reflex motion using the dynamics of outer MW halo stars. Specifically, we use the mean radial and tangential velocities of outer halo stars calculated in a set of distance and on-sky bins. We train neural networks to estimate parameter posterior distributions using a set of $128,000$ rigid MW--LMC simulations conditioned upon velocity data from the Dark Energy Spectroscopic Instrument (DESI) and the combined H3+SEGUE+MagE outer halo surveys. We constrain the reflex motion velocity and the enclosed MW and LMC masses within $50 \, \rm kpc$ using the DESI or H3+SEGUE+MagE dataset while varying the survey sky coverage and depth. We find the most precise constraints by using the radial and tangential velocity data from the H3+SEGUE+MagE survey and on-sky quadrant sky coverages. We report a reflex motion velocity, the speed at which the MW lurches towards the LMC, of $v_{\rm{travel}} = 26.4^{+5.5}_{-4.4} \, \rm km \, \rm s^{-1}$, while simultaneously finding an enclosed LMC mass of $M_{\rm LMC}(< 50 \, \rm kpc) = 9.2^{+1.9}_{-2.3} \times 10^{10}\, \rm M_{\odot}$ and enclosed MW mass of $M_{\rm MW}(< 50 \, \rm kpc) = 4.4^{+0.7}_{-0.7} \times 10^{11}\, \rm M_{\odot}$. Our results suggest that the LMC's total mass is at least $\approx 10-15 \%$ of that of the MW. This inference framework is flexible such that it can provide rapid and reliable constraints when applied to any future survey measuring the velocities of outer halo stars.

Massive stars exhibit a perplexing mismatch between their inferred masses from different observational techniques, posing a significant challenge to our understanding of stellar evolution and structure. This discrepancy is believed to be caused by the underestimation of the convective core masses. The efficiency of such measurement is usually impaired by a lot of processes at work in the interior of the stars such as convective core overshooting and interior rotation. By integrating the precision of asteroseismology which provides insights into the internal structure and dynamics of stars, with the detailed observational constraints offered by eclipsing binary systems, this study aims to precisely characterize a sample of massive stars in eclipsing binaries to infer their properties and evolutionary state. In this paper, the sample, observed photometrically with TESS and spectroscopically with SALT HRS, CHIRON, HERMES and a spectrograph at Skalnate Pleso Observatory between 2021 and 2024, are analyzed. The orbital elements as well as the basic stellar parameters of the targets in the sample are fitted to derive the geometry of their orbits as well as their absolute parameters. The asteroseismic properties of the targets are also obtained, which unravel their core dynamics and profiles. This is a precursor work that provides detailed characterization of the targets in the sample for future theoretical modeling.

We use the ultra-deep GLIMPSE JWST/NIRCam survey to constrain the faint-end of the H$\beta$+[OIII]$\lambda\lambda$4960,5008 luminosity function (LF) down to $10^{39}$ erg/s at z=7-9 behind the lensed Hubble Frontier Field Abell S1063. We perform SED fitting on a Lyman-Break Galaxy sample, measuring combined H$\beta$+[OIII] fluxes to construct the emission-line LF. The resulting LF ($\alpha$=-1.55 to -1.78) is flatter than the UV LF ($\alpha<-2$), indicating a lower number density of low H$\beta$+[OIII] emitters at fixed MUV. We explore three explanations: (i) bursty star formation histories reducing the H$\beta$+[OIII]-to-UV ratio, (ii) metallicity effects on [OIII]/H$\beta$, or (iii) a faint-end turnover in the UV LF. Assuming an evolving [OIII]/H$\beta$ ratio, we derive a flatter [OIII]$\lambda$5008 LF ($\alpha$=-1.45 to -1.66) and a steeper H$\beta$ LF ($\alpha$=-1.68 to -1.95). The combination of decreasing metallicity and bursty star formation can reconcile the UV and H$\beta$+[OIII] LF differences. Converting the LF to the ionising photon production rate, we find that galaxies with H$\alpha$ flux $>10^{39}$ erg/s (SFR(H$\alpha$)$>5\times10^{-3} M_\odot$/yr) contribute 21-61% and 24-104% of the ionising photon budget at 7<z<8 and 8<z<9, respectively (for $f_{esc}=0.1$). The LF shape suggests faint galaxies contribute minimally to the ionising photon production rate. Our cosmic star formation rate density (CSFRD) estimates align with previous work, but GLIMPSE's sensitivity to low SFRs confirms that very faint galaxies are minor contributors to both the ionising photon production rate and the CSFRD. Our results suggest that GLIMPSE has detected the bulk of the total H$\beta$+[OIII] emission from star-forming galaxies, with fainter sources playing a limited role in cosmic reionisation.

When debris from a star that experienced a tidal disruption events (TDE) after passing too close to a massive black hole returns to pericenter on the second passage, it is compressed, leading to the formation of nozzle shocks (in the orbital plane) and pancake shocks (perpendicular to the orbital plane). Resolving these shocks is a long-standing problem in the hydrodynamic simulations of parabolic TDEs. Excessive numerical energy dissipation or heating unrealistically expands the stream. In this Letter, we apply adaptive particle refinement to our 3D general relativistic smoothed particle simulations to locally increase the resolution near the pericenter. We achieve resolutions equivalent to $6.55\times10^{11}$ particles, allowing us to converge on the true energy dissipation. We conclude that only $4\times10^{-5}$ of the orbital energy is dissipated in nozzle shocks for a Sun-like star tidally disrupted by a $10^6$ solar-mass black hole, therefore the nozzle shocks are unlikely to be important in the evolution of TDEs.

PKS 2155-304 is a well-known high-frequency peaked BL Lac (HBL) at redshift z=0.116, which has been extensively studied across the electromagnetic spectrum due to its rapid and large-amplitude variability. Several violent outbursts in X-rays and $\gamma$-rays have been observed in the past, with intra-night variability in very-high-energy $\gamma$-rays (VHE; E > 100 GeV) detected down to the minute timescale. The alternation of quiescent and enhanced states, observed with a tentative quasi-periodicity of 1.74 $\pm$ 0.13 years in high-energy (HE; 100 MeV < E < 100 GeV) $\gamma$-rays, makes this source a key target also for ground-based $\gamma$-ray instruments and in particular for the Imaging Atmospheric Cherenkov Telescopes. Its brightness, proximity, and well-determined redshift make this $\gamma$-ray source a prime target for fundamental physics studies, including tests of Lorentz Invariance Violation (LIV), searches for axion-like particles (ALPs), and constraints on the distribution of the extragalactic background light (EBL). In the last two years, PKS 2155-304 has been independently monitored by the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes and the first Large-Sized Telescope (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) located at the Roque de Los Muchachos Observatory (La Palma, Spain). The observations were carried out at large zenith angles (LZA; ZA > 55°), and the VHE data have been complemented with simultaneous observations in HE $\gamma$-rays (Fermi-LAT), X-rays (Swift-XRT) and optical wavelengths (ASAS-SN).

Pulsar wind nebulae (PWNe) are prominent sources in the very-high energy (VHE) gamma-ray sky, constituting the most numerous identified source class in the H.E.S.S. Galactic Plane Survey (HGPS). They are comprised of energetic particles originating from the pulsar and expanding into the surrounding medium. As such, PWNe are of very high scientific interest as PeVatron candidates, objects that could potentially accelerate particles up to PeV energies. Additionally other aspects of their acceleration mechanism are being actively investigated, such as the open question of whether they accelerate not only leptonic but also hadronic particles, and the details of their morphology and particle transport mechanism. As PWNe emit photons over a broad range of the electromagnetic spectrum, multiwavelength (MWL) studies are crucial for the investigation and study of their emission. In this vein we present a joint eROSITA X-ray and H.E.S.S. gamma-ray study of the PWN MSH 15-52. We showcase our custom code for integrating the EDR and DR1 eROSITA data into the Gammapy framework, a python package optimised for the analysis of gamma-ray data. We present the first 3D (spatial and spectral) fit to eROSITA data by using Gammapy. We furthermore combine these data with the public H.E.S.S. gamma-ray observations of MSH 15-52, resulting in a joint physical fit of the underlying particle population, and a subsequent discussion of the physical implications of our results. Finally we give an outlook towards future efforts in MWL studies of PWNe and the broader context of MWL data analysis with Gammapy.

LTT-9779 b is an ultra-hot Neptune (Rp ~ 4.7 Re, Mp ~ 29 Me) orbiting its Sun-like host star in just 19 hours, placing it deep within the "hot Neptune desert," where Neptunian planets are seldom found. We present new JWST NIRSpec G395H phase-curve observations that probe its atmospheric composition in unprecedented detail. At near-infrared wavelengths, which penetrate the high-altitude clouds inferred from previous NIRISS/SOSS spectra, thermal emission reveals a carbon-rich atmosphere with opacity dominated by carbon monoxide (CO) and carbon dioxide (CO2). Both species are detected at all orbital phases, with retrieved mixing ratios of 10^-1 for CO and 10^-4 for CO2, indicating a globally well-mixed reservoir of carbon-bearing gases. We also moderately detect water vapor (H2O) and tentatively detect sulfur dioxide (SO2), providing insight into its chemistry and possible photochemical production under intense stellar irradiation. From these detections we infer a carbon-to-oxygen ratio near unity (C/O ~ 1) and a metallicity exceeding 500X Solar, consistent with equilibrium chemistry predictions for high-temperature atmospheres. This enrichment raises the mean molecular weight, reducing atmospheric escape, and likely helps LTT-9779 b retain a substantial atmosphere despite extreme irradiation. Our findings show that LTT-9779 b survives where few planets can, maintaining a carbon-rich atmosphere in a region where hot Neptune-class worlds are expected to evaporate. This makes LTT-9779 b a valuable laboratory for studying atmospheric escape and chemical processes under extreme conditions, offering new insight into the survival of planets in the hot Neptune desert.

The observational properties of core-collapse supernovae (CC-SNe) are shaped by the envelopes of their progenitors. In massive binary systems, mass-transfer alters the pre-SN structures compared to single stars, leading to a diversity in SN explosions. Aims. We compute the distribution of CC-SN properties based on comprehensive detailed grids of single and binary stellar evolution models. We conduct a grid-based population synthesis to produce a synthetic population of CC-SNe, and compare it to observed SN samples. We also apply various explodability and merger criteria to our models. In line with earlier results, we identify interacting SN progenitors as those stars that undergo CC during or shortly after a Roche-lobe overflow phase. With an interacting binary fraction of 68%, our models predict two-thirds of all CC-SNe to be of Type IIP/L, and 1/3 of Type Ibc, in agreement with recent volume-limited SN surveys. We find that 76% of the Type Ibc SN progenitors took part in a previous binary mass transfer (mostly as mass donor), but also 63% of the Type IIP/L SN progenitors (mostly as mass gainers), yielding a much broader envelope mass distribution than expected from single stars. We find that mass-transfer induced interacting SNe make up ~5% of all CC-SNe, which is close to the observed fractions of Type IIn and Type Ibn SNe. When assuming a disk or toroidal CSM geometry for Type IIn SNe, our models predict a bimodal distribution of the radiated energies, similar to that deduced from observations. While we find the effect of binary evolution on the relative number of Type Ibc and Type IIP/L SNe to be moderate, it leads to lower average ejecta masses in Type Ibc and Type IIb SNe, and can lead to higher pre-SN masses in Type IIP/L SNe than single stars. Binary models are also able to reproduce the number and properties of interacting SNe.

We developed the full magnetohydrodynamical analytical jet model that allows accurate reproducing of a transversal and longitudinal structure for a highly collimated relativistic jets. This model can be used as a setup for convenient solution of radiative transfer equations and modelling the total intensity and polarization maps. We show that the analytical fits are in excellent agreement with the numerical solutions of full magnetohydrodynamical equations. Our approach allows setting easily different models for an emitting plasma number density. For example, we show that the equipartition number density ranges from several to tens of percent of a total number density. We show that the Doppler-corrected emissivity distribution behave in such a way that we may expect a limb brightened intensity pattern on a sub-parsec scale and a spine-brightened structure downstream. We reproduce the broken power-law dependence of a jet pressure at its boundary from the jet radius. The corresponding power exponents are in agreement with the parabola-to-cone transition observed directly in nearby sources.

The high-frequency resolution of the four-year $\textit{Kepler}$ time series allows detailed study of seismic modes in luminous giants. Seismic observables help infer interior structures via comparisons with stellar models. We aim to investigate differences between H-shell (Red-Giant Branch; RGB) and He-burning (red clump and Asymptotic-Giant Branch; AGB) stars in the He-II ionisation zone and the sensitivity of seismic parameters to input physics in stellar models. We used a grid of stellar models with masses $0.8-2.5M_\odot$ and metallicities $-1.0-0.25$dex, including mass loss, overshooting, thermohaline mixing, and rotation-induced mixing. P-mode frequencies were inferred by suppressing g-modes in the core. The main factors affecting seismic observables are stellar mass and metallicity. The He-II glitch amplitude in the local large frequency separation $\Delta\nu$ correlates with the He-II ionisation zone density, explaining observed differences between RGB and clump/AGB stars. That amplitude exceeds 10% of $\Delta\nu$ in high-luminosity giants, making the asymptotic expansion less accurate when $\Delta\nu \le 0.5\,\mu$Hz. Mass loss on the RGB and rotation-induced mixing from the main sequence to the early-AGB produce phase differences in the He-II glitch modulation signature between RGB and clump/AGB stars. Efficient RGB mass loss (for $M \le 1.5\,M_\odot$) and mixing processes (for $M \ge 1.5\,M_\odot$) leave detectable signatures in p-mode frequencies, enabling classification of red giants.

Galaxy model subtraction removes the smooth light of nearby galaxies so that fainter sources (e.g., stars, star clusters, background galaxies) can be identified and measured. Traditional approaches (isophotal or parametric fitting) are semi-automated and can be challenging for large data sets. We build a convolutional denoising autoencoder (DAE) for galaxy model subtraction: images are compressed to a latent representation and reconstructed to yield the smooth galaxy, suppressing other objects. The DAE is trained on GALFIT-generated model galaxies injected into real sky backgrounds and tested on real images from the Next Generation Virgo Cluster Survey (NGVS). To quantify performance, we conduct an injection-recovery experiment on residual images by adding mock globular clusters (GCs) with known fluxes and positions. Our tests confirm a higher recovery rate of mock GCs near galaxy centers for complex morphologies, while matching ellipse fitting for smooth ellipticals. Overall, the DAE achieves subtraction equivalent to isophotal ellipse fitting for regular ellipticals and superior results for galaxies with high ellipticities or spiral features. Photometry of small-scale sources on DAE residuals is consistent with that on ellipse-subtracted residuals. Once trained, the DAE processes an image cutout in $\lesssim 0.1$ s, enabling fast, fully automatic analysis of large data sets. We make our code available for download and use.

Dark Matter remains a great mystery in modern physics. Among various candidates, the weakly interacting massive particles (WIMPs) scenario stands out and is under extensive study. The detection of the hypothetical gamma-ray emission from WIMP annihilation could act as a direct probe of electroweak-scale interactions, complementing DM collider searches and other direct DM detection techniques. At very high energies (VHE), WIMP self-annihilation is expected to produce gamma rays together with other Standard Model particles. The galactic center (GC), due to its relative proximity to the Earth and its high expected DM density, is a prime target for monoenergetic line searches. IACTs have placed strong constraints on the DM properties at the GC, with the MAGIC providing the most stringent limits from 20 TeV to 100 TeV, exploiting large zenith angle (LZA) observations. However, the limited field of view (FoV) of the MAGIC telescopes (< 3.5° ) prevented a detailed study of the extended region around the GC in which an enhanced DM density is expected. The LST-1 of the CTAO, located at the Roque de Los Muchachos Observatory (La Palma, Spain), close to the MAGIC site, has been observing the GC since 2021. With its wide FoV of 4.5°, LST-1 could contribute significantly to the WIMPs search at the GC. The observations are performed at LZA (ZA > 58°), which, while required due to the source's low altitude, also optimizes the detection of gamma rays up to 100 TeV and beyond. We present a study of the systematic uncertainties in WIMP line emission searches with LST-1. Our work examines the instrument response functions for LZA observations, background rejection in monoscopic mode, and includes updated results from simulations, highlighting new methods for spectral line searches.

Planets and their host stars form from the same cloud of gas and dust, so we assume that their chemical compositions are linked. However, a clear correlation between rocky planet interior properties and host star chemistry remains elusive for planets around FGK dwarfs, and non-existent for planets around M dwarfs because cool stars frequently lack detailed chemical information. Here, we investigate the relationship between small (R$_{P}$ $\leq$ 1.8 R$_{\oplus}$) planet densities and host star elemental abundances. We use the Sloan Digital Sky Survey-V/Milky Way Mapper and an accompanying data-driven framework to obtain abundances for FGK and M dwarf hosts of 22 rocky planets. We find that planet densities exhibit a strong, inverse relationship to [Mg/Fe] abundances of FGK hosts (p = 0.001). This correlation becomes more significant with the addition of M dwarf hosts (p = 0.0005). If we assume that rocky planets have terrestrial-like compositions, this suggests that low [Mg/Fe] environments form planets with larger Fe-rich cores and thus higher densities. The thick disk planets in our sample help anchor this trend, illustrating the importance of sampling exoplanet properties across a range of host star populations. This finding highlights the connection between Galactic chemical evolution and rocky planet formation, and indicates that Earth-like planet compositions may vary significantly across different regions of the Galaxy.

S$H_0$ES 2016-2022 $HVI$ data for classical Cepheids in the keystone galaxy NGC4258 yield doubly discordant Wesenheit Leavitt functions:~$\Delta W_{0,H-VI} = -0.13\pm0^{m}.02$ ($-0^{m}.17$ unweighted) and that is paired with a previously noted $\Delta W_{0,I-VI}\simeq-0^{m}.3$, which in concert with complimentary evidence suggest the 2016 S$H_0$ES NGC4258-anchored $H_0 \pm \sigma_{H_0}$ warrants scrutiny (i.e., $\sigma_{H_0}/{H_0}\gtrsim 6$\%). Cepheid distance uncertainties are further exacerbated by extinction law ambiguities endemic to such Leavitt relations (e.g., NGC4258), particularly for comparatively obscured variables (e.g., $\Delta d \gtrsim 4$\%, reddened Cepheid subsamples in the Milky Way, M31, NGC2442, NGC4424, NGC5643, NGC7250). Lastly, during the analysis it was identified that the 2022 S$H_0$ES database relays incorrect SMC Cepheid photometry.

The localization of X-ray counterparts to gravitational wave events requires a telescope with accurate localization capability in a field of view comparable to the region constrained by the gravitational wave detectors. In the context of a small, dedicated, mission, we investigate which optical design could satisfy this capability. We compare the possible optical designs that have been proposed for X-rays: the Lobster Eye design (both in the Angel and Schmidt variant) - inspired by the eyes of crustaceans - consisting of many small capillaries where grazing incidence reflection occurs, the Kirkpatrick-Baez design, where double reflection occurs on two orthogonal parabolic mirrors, and the standard Wolter-I design. We find that the first two designs, compared to the latter, can achieve a significantly larger field of view, and have a good localization capability if the focal length is longer than existing Lobster Eye designs. The Kirkpatrick-Baez design presents the best angular resolution, but the best overall field of view is obtained with a Lobster system: we present a small optical module able to achieve an effective area $>$100 cm$^2$ at 1 keV in a field of view of 10 deg$^2$.

While task-specific demonstrations show early success in applying large language models (LLMs) to automate some astronomical research tasks, they only provide incomplete views of all necessary capabilities in solving astronomy problems, calling for more thorough understanding of LLMs' strengths and limitations. So far, existing benchmarks and evaluations focus on simple question-answering that primarily tests astronomical knowledge and fails to evaluate the complex reasoning required for real-world research in the discipline. Here, we address this gap by systematically benchmarking five state-of-the-art LLMs on the International Olympiad on Astronomy and Astrophysics (IOAA) exams, which are designed to examine deep conceptual understanding, multi-step derivations, and multimodal analysis. With average scores of 85.6% and 84.2%, Gemini 2.5 Pro and GPT-5 (the two top-performing models) not only achieve gold medal level performance but also rank in the top two among ~200-300 participants in all four IOAA theory exams evaluated (2022-2025). In comparison, results on the data analysis exams show more divergence. GPT-5 still excels in the exams with an 88.5% average score, ranking top 10 among the participants in the four most recent IOAAs, while other models' performances drop to 48-76%. Furthermore, our in-depth error analysis underscores conceptual reasoning, geometric reasoning, and spatial visualization (52-79% accuracy) as consistent weaknesses among all LLMs. Hence, although LLMs approach peak human performance in theory exams, critical gaps must be addressed before they can serve as autonomous research agents in astronomy.

If the Universe has non-trivial spatial topology, observables depend on both the parameters of the spatial manifold and the position and orientation of the observer. In infinite Euclidean space, most cosmological observables arise from the amplitudes of Fourier modes of primordial scalar curvature perturbations. Topological boundary conditions replace the full set of Fourier modes with specific linear combinations of selected Fourier modes as the eigenmodes of the scalar Laplacian. In this paper we consider the non-orientable Euclidean topologies \E{7}--\E{10}, \E{13}--\E{15}, and \E{17}, encompassing the full range of manifold parameters and observer positions, generalizing previous treatments. Under the assumption that the amplitudes of primordial scalar curvature eigenmodes are independent random variables, for each topology we obtain the correlation matrices of Fourier-mode amplitudes (of scalar fields linearly related to the scalar curvature) and the correlation matrices of spherical-harmonic coefficients of such fields sampled on a sphere, such as the temperature of the cosmic microwave background (CMB). We evaluate the detectability of these correlations given the cosmic variance of the CMB sky. We find that in manifolds where the distance to our nearest clone is less than about $1.2$ times the diameter of the last scattering surface of the CMB, we expect a correlation signal that is larger than cosmic variance noise in the CMB. Our limited selection of manifold parameters are exemplary of interesting behaviors, but not necessarily representative. Future searches for topology will require a thorough exploration of the parameter space to determine what values of the parameters predict statistical correlations that are convincingly attributable to topology.[Abridged]

We announce V. 2025-08-08 of the Chroma+ suite of stellar atmosphere and spectrum modelling codes for fast, approximate, effectively platform-independent stellar spectrum synthesis, written in a number of free well-supported programming languages. The Chroma+ suite now computes the emergent surface intensity and flux distributions and the hydrostatic pressure structure assuming a spherical atmosphere rather than local flatness by implementing the analytic formal solution of the 1D spherical radiative transfer equation of Chapman (1966} based on an integration factor. We present our adaptation and discretization of the solution and demonstrate the resulting impact of our sphericity treatment on a number of computed observables, including exo-planet transit light-curves. All codes are available from the OpenStars www site: this http URL.

Anomalous Microwave Emission (AME) is a diffuse microwave component thought to arise from spinning dust grains, yet remains poorly understood. We analyze AME in 144 Galactic clouds by combining low-frequency maps from S-PASS (2.3 GHz), C-BASS (4.76 GHz), and QUIJOTE (10-20 GHz) with 21 ancillary maps. Using aperture photometry and parametric SED fitting via MCMC methods without informative priors, we measure AME emissivity, peak frequency, and spectral width. We achieve peak frequency constraints nearly three times tighter than previous work and identify 83 new AME sources. AME spectra are generally broader than predicted by spinning dust models for a single phase of the interstellar medium, suggesting either multiple spinning dust components along the line of sight or incomplete representation of the grain size distribution in current models. However, the narrowest observed widths match theoretical predictions, supporting the spinning dust hypothesis. The AME amplitude correlates most strongly with the thermal dust peak flux and radiance, showing $\sim30$% scatter and sublinear scaling, which suggests reduced AME efficiency in regions with brighter thermal dust emission. AME peak frequency increases with thermal dust temperature in a trend current theoretical models do not reproduce, indicating that spinning dust models must incorporate dust evolution and radiative transfer in a self-consistent framework where environmental parameters and grain properties are interdependent. PAH tracers correlate with AME emissivity, supporting a physical link to small dust grains. Finally, a log-Gaussian function provides a good empirical description of the AME spectrum across the sample, given current data quality and frequency coverage.

Here we use data from multi-scale galactic MHD simulations to observe filaments and star forming clumps on 10's of pc scales and investigate flow rate relationships along, and onto filaments as well as flows towards the clumps. Using the FilFinderPPV identification technique, we identify the prominent filamentary structures in each data cube. Each filament and its corresponding clump are analysed by calculating flow rates along each filament towards the clump, onto each filament from increasing distances, and radially around each clump. This analysis is conducted for two cubes, one feedback dominated region, and one with less feedback. Looking at the face-on inclination of the simulations (0 degrees), we observe different trends depending on the environmental conditions (more or less feedback). The median flow rate in the region with more feedback is 8.9$\times$10$^{-5}$ M$_{sun}\mathrm{yr}^{-1}$ and we see that flow rates along the filaments toward the clumps generally decrease in these regions. In the region with less feedback we have a median flow rate of 2.9$\times$10$^{-4}$ M$_{sun}\mathrm{yr}^{-1}$ and when looking along the filaments here we see the values either increase or remain constant. We find that the flow rates from the environments onto the primary filaments are of an order of magnitude sufficient to sustain the flow rates along these filaments. When discussing the effects of galactic and filamentary inclination, we also observe that viewing the filaments from different galactic inclinations can reveal the presence of feeder structures (smaller filamentary structures aiding in the flow of material). The method used to estimate these flow rates, which has been previously applied to observational data, produced results consistent with those obtained from the simulations themselves, providing high confidence in the flow rate calculation method.

The $^{30}$P$(p,\gamma)^{31}$S reaction plays an important role in understanding nucleosynthesis of $A\geq 30$ nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure $^{31}$Cl $\beta$-delayed proton decay through the key $J^{\pi}=3/2^{+}$, 260-keV resonance. The intensity $I^{260}_{\beta p} = 8.3^{+1.2}_{-0.9} \times 10^{-6}$ represents the weakest $\beta$-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of $\Gamma_p / \Gamma = 2.5^{+0.4}_{-0.3} \times 10^{-4}$. By combining this measurement with shell-model calculations for $\Gamma_{\gamma}$ and past work on other resonances, the total $^{30}$P$(p,\gamma)^{31}$S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of $^{30}$Si/$^{28}$Si excesses in presolar nova grains and the calibration of nuclear thermometers.

The existence of a large primordial neutrino asymmetry is an intriguing possibility, both observationally and theoretically. Such an asymmetry can lead to the resonant production of $\mathrm{keV}$-scale sterile neutrinos, which are a fascinating candidate for dark matter. In this paper, we comprehensively revisit the resonant production processes with a refined numerical analysis, adopting a dynamical discretization of momentum modes to take care of the sharpness of the resonance. We find parameter regions consistent with X-ray and Lyman-$\alpha$ constraints for lepton-to-entropy ratio $\gtrsim \mathcal{O}(10^{-3})$ and $m_{\nu_s}\gtrsim 20$\,keV. We also explore the Affleck-Dine mechanism as a possible origin for such asymmetries. While previous studies considered resonant production after lepton number generation, we numerically investigate cases where a fraction of sterile neutrinos is produced during lepton number injection. In this regime, some parameter sets can shorten the free-streaming length and reduce the required mixing angle to match the observed dark matter abundance, thereby mitigating the observational constraints.

We present comprehensive \textsl{ab initio} calculations of CO$_{\rm 2}$-H$_{\rm 2}$ and CO$_{\rm 2}$-He collisional properties from first principles, employing CCSD(T), potential calculations together with close-coupling dynamical scattering in the \YUMI~framework. We derive (in)elastic cross sections, rate coefficients, and pressure-broadening parameters -- incl., their rotational dependence up to $|m|=50$, and temperature dependence over the range of 100-800 K. We provide Padé fits for the broadening coefficients as a function of rotational quantum number, enabling extrapolation of the results and integration into spectroscopic databases, including HITRAN and HITEMP. The computed potentials for both CO$_{\rm 2}$-H$_{\rm 2}$ and CO$_{\rm 2}$-He have a sub-percent precision, and the dynamics-solving code YUMI ultimately yields the collisional parameters. Among these, the scaled pressure broadening experimental values meet the 10\% precision requirement for exoplanetary sciences with \textit{JWST}. This contrasts with the parameters available before the present calculations, which at higher temperatures (T$>$400 K) deviate as much as 5$\times$ from the desired precision requirement. All derivations and collisional properties are provided with this manuscript, establishing the first of such a comprehensive ab initio foundation for collisional systems with a target molecule having more than two atoms.

Pairing the accuracy of Kohn-Sham density-functional framework with the efficiency of a stochastic algorithmic approach, mixed stochastic-deterministic Density Functional Theory (mDFT) achieves a favorable computational scaling with system sizes and electronic temperatures. We employ the recently developed mDFT formalism to investigate the dynamic charge-transport properties of systems in the warm dense matter regime. The optical conductivity spectra are computed for single- and multi- component mixtures of carbon, hydrogen, and beryllium using two complementary approaches: Kubo-Greenwood in the mDFT picture and real-time Time-Dependent mDFT. We further devise a decomposition of the Onsager coefficients leading up to the Kubo-Greenwood spectra to exhibit contributions from the deterministic, stochastic, and mixed electronic state transitions at different incident photon energies.

Writing is a critical skill for modern science, enabling collaboration, scientific discourse, public outreach, and more. Accordingly, it is important to consider how physicists and astronomers are trained to write. This study aims to understand the landscape of science writing education, specifically in physics and astronomy, in higher education in the United States. An online survey probing various aspects of their writing training in both undergraduate and graduate school was administered to 515 participants who have obtained training in physics and/or astronomy, or related fields, at the level equal to or beyond upper-division undergraduate study. Humanities and writing requirement courses appear to have a key role in general writing education, while laboratory courses and feedback from mentors are the dominant modes of science writing education in undergraduate and graduate school respectively. There is substantial variation in the quality of writing education in physics and astronomy, often dependent on the student's institution and/or mentor. Some participants also report that their success in disciplinary writing was a result of a solid foundation from K-12 education and/or self-direction towards resources; such reliance on past experiences and student background may contribute to inequality in the field. Many participants also stated a clear desire for more structured writing training to be available in the field. We provide suggestions for how to implement such training to meet the needs of the community identified in the survey.

Resolving the most fundamental questions in cosmology requires simulations that match the scale, fidelity, and physical complexity demanded by next-generation sky surveys. To achieve the realism needed for this critical scientific partnership, detailed gas dynamics, along with a host of astrophysical effects, must be treated self-consistently with gravity for end-to-end modeling of structure formation. As an important step on this roadmap, exascale computing enables simulations that span survey-scale volumes while incorporating key subgrid processes that shape complex cosmic structures. We present results from CRK-HACC, a cosmological hydrodynamics code built for the extreme scalability requirements set by modern cosmological surveys. Using separation-of-scale techniques, GPU-resident tree solvers, in situ analysis pipelines, and multi-tiered I/O, CRK-HACC executed Frontier-E: a four trillion particle full-sky simulation, over an order of magnitude larger than previous efforts. The run achieved 513.1 PFLOPs peak performance, processing 46.6 billion particles per second and writing more than 100 PB of data in just over one week of runtime.

This work tries to establish the theoretical framework for gravitomagnetic-hydrodynamics (GMHD), revealing a fundamental correspondence between geometrodynamics and magnetohydrodynamic phenomena in general relativity. By introducing the gravitoelectromagnetic formalism to relativistic fluids, a set of leading-order GMHD equations is derived that govern the co-evolution of spacetime geometry and matter dynamics in the early Universe. This analysis reveals that, under high-temperature and high-density conditions such as those during the electroweak phase transition, the gravitomagnetic Reynolds number becomes large, leading to a strongly coupled fluid-spacetime system. This coupling supports the emergence of gravitational Alfven waves and a turbulent energy cascade. Our findings suggest that GMHD turbulence may leave imprints on the stochastic gravitational wave background, offering a new window into the nonlinear dynamics of the primordial Universe.

Within the framework of loop quantum cosmology (LQC), we investigate the effect of inverse volume corrections on the low scale spontaneously broken supersymmetric (SB SUSY) and exponential inflationary potentials. The LQC modifications to the Friedmann equations and cosmological perturbation parameters are employed to assess the observational viability of these models against recent data from the Atacama Cosmology Telescope (ACT). Our results indicate that in contrary to the standard model of inflation, in the presence of inverse volume corrections in LQC, the prediction of SB SUSY and exponential potentials in the $r-n_{\rm s}$ plane lie inside the 68\% confidence level interval of the ACT data.

In bouncing cosmological models, either classical or quantum, the big bang singularity is replaced by a regular bounce. A challenging question in such models is how to keep the shear under control in the contracting phase, as it is well-known that the shear grows as fast as $1/a^{6}$ toward the bounce, where $a$ is the expansion factor of the universe. A common approach is to introduce a scalar field with an ekpyrotic-like potential which becomes negative near the bounce, so the effective equation of state of the scalar field will be greater than one, whereby it dominates the shear and other matter fields in the bounce region. As a result, a homogeneous and isotropic universe can be produced. In this paper, we study how the ekpyrotic mechanism affects the inflationary phase in both loop quantum cosmology (LQC) and a modified loop quantum cosmological model (mLQC-I), because in these frameworks the inflation is generic without such a mechanism. After numerically studying various cases in which the potential of the inflaton consists of two parts, an inflationary potential and an ekpyrotic-like one, we find that, despite the fact that the influence is significant, by properly choosing the free parameters involved in the models, the ekpyrotic-like potential dominates in the bounce region, during which the effective equation of state is larger than one, so the shear problem is resolved. As the time continuously increases after the bounce, the inflationary potential grows and ultimately becomes dominant, resulting in an inflationary phase. This phase can last long enough to solve the cosmological problems existing in the big bang model.

Many quantum gravitational frameworks, such as DBI inflation, k-essence, and effective field theories obtained by integrating out heavy modes, can lead to a non-trivial sound speed. Meanwhile, our universe can be described as an open system. Under the non-trivial sound speed, we employ the method of open quantum systems combined with Arnoldi iterations to study the Krylov complexity throughout the early universe, including the inflationary, radiation-dominated, and matter-dominated epochs. A key ingredient in our analysis is the open two-mode squeezed state formalism and the generalized Lanczos algorithm. To numerically compute the Krylov complexity, we are the first time to derive the evolution equations for the parameters $r_k$ and $\phi_k$ within an open two-mode squeezed state. Our results indicate that the Krylov complexity exhibits a similar trend in both the standard case and the case with non-trivial sound speed. To distinguish between these two scenarios, we also investigate the Krylov entropy for completeness. The evolution of the Krylov entropy shows a clear difference between the standard case and the non-trivial sound speed case. Furthermore, based on the behavior of the Lanczos coefficients, we find that the case of non-trivial sound speed behaves as a maximally chaotic system. However, our numerical results suggest that the Krylov complexity does not saturate to a constant value due to the huge expansion of spacetime background. This study offers a new perspective for exploring the early universe through the quantum information.

The prediction of solar flares is typically formulated as a binary classification task, distinguishing events as either Flare (FL) or No-Flare (NF) according to a specified threshold (for example, greater than or equal to C-class, M-class, or X-class). However, this binary framework neglects the inherent ordinal relationships among the sub-classes contained within each category (FL and NF). Several studies on solar flare prediction have empirically shown that the most frequent misclassifications occur near this prediction threshold. This suggests that the models struggle to differentiate events that are similar in intensity but fall on opposite sides of the binary threshold. To mitigate this limitation, we propose a modified loss function that integrates the ordinal information among the sub-classes of the binarized flare labels into the conventional binary cross-entropy (BCE) loss. This approach serves as an ordinality-aware, data-driven regularization method that penalizes the incorrect predictions of flare events in close proximity to the prediction threshold more heavily than those away from the boundary during model optimization. By incorporating ordinal weighting into the loss function, we aim to enhance the model's learning process by leveraging the ordinal characteristics of the data, thereby improving its overall performance.

While the majority of gravitational wave (GW) events observed by the LIGO and Virgo detectors are consistent with mergers of binary black holes (BBHs) on quasi-circular orbits, some events are also consistent with non-zero orbital eccentricity, indicating that the binaries could have formed via dynamical interactions. Moreover, there may be GW events which show support for spin-precession, eccentricity, or both. In this work, we study the interplay of spins and eccentricity on the parameter estimation of GW signals from BBH mergers. We inject eccentric signals with no spins, aligned spins, and precessing spins using hybrids, TEOBResumS-DALI, and new Numerical Relativity (NR) simulations, respectively, and study the biases in the posteriors of source parameters when these signals are recovered with a quasi-circular precessing-spin waveform model, as opposed to an aligned-spin eccentric waveform model. We find significant biases in the source parameters, such as chirp mass and spin-precession ($\chi_p$), when signals from highly-eccentric BBHs are recovered with a quasi-circular waveform model. Moreover, we find that for signals with both eccentricity and spin-precession effects, Bayes factor calculations confirm that an eccentric, aligned-spin model is preferred over a quasi-circular precessing-spin model. Our study highlights the complex nature of GW signals from eccentric, precessing-spin binaries and the need for readily usable inspiral-merger-ringdown eccentric, spin-precessing waveform models for unbiased parameter estimation.

Gravitational wave astronomy has opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. In this study, we examine a series of well-motivated deviations from the classical Kerr solution of General Relativity and employ gravitational wave data to place constraints on possible deviations from the Kerr geometry. The method involves calculating the phase of gravitational waves using the effective one-body formalism and then applying the parameterized post-Einsteinian framework to constrain the parameters appearing in these scenarios beyond General Relativity. The effective one-body method, known for its capability to model complex gravitational waveforms, is used to compute the wave phase, and the post-Einsteinian framework allows for a flexible, model-independent approach to parameter estimation. We demonstrate that gravitational wave data provide evidence supporting the Kerr nature of black holes, showing no significant deviations from General Relativity, thereby affirming its validity within the current observational limits. This work bridges theoretical waveform modeling with observational constraints, providing a pathway to test the no-hair theorem and probe the astrophysical viability of modified black holes.

A generic D-dimensional Gaussian can be conditioned or projected onto the D-1 unit sphere, thereby leading to the well-known Fisher-Bingham (FB) or Angular Gaussian (AG) distribution families, respectively. These are some of the most fundamental distributions on the sphere, yet cannot straightforwardly be written as a normalizing flow except in two special cases: the von-Mises Fisher in D=3 and the central angular Gaussian in any D. In this paper, we describe how to generalize these special cases to a family of normalizing flows that behave similarly to the full FB or AG family in any D. We call them "zoom-linear-project" (ZLP)-Fisher flows. Unlike a normal Fisher-Bingham distribution, their composition allows to gradually add complexity as needed. Furthermore, they can naturally handle conditional density estimation with target distributions that vary by orders of magnitude in scale - a setting that is important in astronomical applications but that existing flows often struggle with. A particularly useful member of the new family is the Kent analogue that can cheaply upgrade any flow in this situation to yield better performance.

We develop a quantum-cosmological framework in which the inflationary potential emerges from the structure of the wave function of the universe rather than being postulated. Starting from the Wheeler-DeWitt equation for a flat Friedmann-Robertson-Walker minisuperspace, we express the wave function in terms of an amplitude and a phase and, in a semiclassical regime where the expansion dominates the field's evolution, separate these into purely geometric and purely field-dependent pieces. This yields a closed expression for an emergent potential that makes transparent the roles of the cosmological constant, the momenta associated with expansion and field dynamics, and quantum corrections from the amplitude. Slow-roll conditions follow from properties of the phase and amplitude, leading to wave-function-level expressions for the usual slow-roll parameters and to direct links between cosmic microwave background observables and derivatives of the phase. The approach ties inflation to the quantum state of the universe and suggests testable relationships between cosmological data and features of the wave function.