Papers for Wednesday, Sep 10 2025

Planets have maximum radii close to that of Jupiter. Qualitatively, the reason for this maximum size is that, as one adds mass, the force of gravity becomes sufficiently strong to cause the radius to decrease. We show that this effect can be understood quantitatively using a simple variational principle very similar to that used to compute the size of the hydrogen atom.

The next generation of Extremely Large Telescopes (ELTs), with their wide apertures and advanced Multi-Conjugate Adaptive Optics (MCAO) systems, will provide unprecedented sharp and deep observations, even surpassing the capabilities of James Webb Space Telescope (JWST). SHARP, a near-infrared (0.95-2.45 {\mu}m) spectrograph, is designed to optimally exploit the collecting area and angular resolution of these forthcoming ELTs, and specifically optimized for the MCAO unit MORFEO at the ELT. SHARP includes two main units: NEXUS, a Multi-Object Spectrograph (MOS), and VESPER, a multi-Integral Field Unit. This paper outlines the opto-mechanical design of SHARP based on the scientific requirements of the project. The optical design is engineered to meet project specifications, featuring a compact mechanical structure that minimizes the required cryogenic power while ensuring ease of access for maintenance and straightforward assembly procedures.

Observations from the Imaging X-ray Polarimetry Explorer (IXPE) have revealed electric vector position angle (EVPA) rotation in several neutron star low-mass X-ray binaries, including the galactic X-ray burster GX 13+1. We developed a novel Bayesian nested sampling framework-"Q-U Event-by-Event Nested sampling for Bayesian EVPA Evolution" (QUEEN-BEE)-to model unbinned Stokes parameters and infer optimal EVPA rotation rates in IXPE data. We then applied this framework to three previous IXPE observations of GX 13+1. In the first observation, QUEEN-BEE recovers a rotation rate of 42+/-4 degrees/day, consistent with prior binned analysis. Energy-binned QUEEN-BEE analysis of this first observation suggests a slab-like coronal geometry, providing the first constraints between slab and shell coronae for this source. We also explore alternative EVPA rotation scenarios in GX 13+1 including variable disk wind behavior. The second observation of this source shows no evidence of rotation, and the third observation shows transient rotating behavior with an EVPA rotation rate when exiting a light curve dip of 170 +20/-40 degrees/day. The results show marginal but consistent increases in the overall measured polarization degree (PD) for epochs where the EVPA rotation is identified. These results demonstrate that QUEEN-BEE can identify evolving polarization signatures in both time- and energy-resolved regimes, even where binned methods fall below detection thresholds. Our findings highlight the diagnostic potential of QUEEN-BEE as a tool for discriminating between competing physical models of coronal geometry and probing disk-wind-related polarization behavior, highlighting the promising potential for application of this framework in a variety of other IXPE observations.

By opening up new avenues to statistically constrain astrophysics and cosmology with large-scale structure observations, the line intensity mapping (LIM) technique calls for novel tools for efficient forward modeling and inference. Implicit likelihood inference (ILI) from semi-numerical simulations provides a powerful setup for investigating a large model parameter space in a data-driven manner, therefore gaining significant recent attention. Using simulations of high-redshift 158$\mu$m [CII] and 88$\mu$m [OIII] LIM signals created by the LIMFAST code, we develop an ILI framework in a case study of learning the physics of early galaxy formation from the auto-power spectra of these lines or their cross-correlation with galaxy surveys. We leverage neural density estimation with normalizing flows to learn the mapping between the simulated power spectra and parameters that characterize the physics governing the star formation efficiency and the $\dot{\Sigma}_{\star}$-$\Sigma_\mathrm{g}$ relation of high-redshift galaxies. Our results show that their partially degenerate effects can be unambiguously constrained when combining [CII] with [OIII] measurements to be made by new-generation mm/sub-mm LIM experiments.

Brown dwarfs that are short period ($<10\,$day) companions to actively flaring M dwarfs may provide a context to directly observe flare-driven photochemistry and structural changes in an extrasolar planet-like atmosphere. To assess the viability of directly observing flare impacts in the atmosphere of a brown dwarf, we perform self-consistent temperature-chemistry modeling of the atmospheric response to individual energetic superflares. We modified the existing open-source \texttt{VULCAN} chemical-kinetics and \texttt{HELIOS} radiative-transfer codes for this purpose. Similar to previous studies of flare impacts on hydrogen dominated atmospheres, we find flares are capable of orders-of-magnitude changes in the mixing abundances of many chemical species, including important opacity sources like CH$_4$ and CO$_2$. However, due to fast chemical timescales resulting from high temperatures and densities in brown dwarf atmospheres, these changes last for a short-period of time, generally less than a day, and are only plausibly observable via high resolution emission spectroscopy. We find that the most observable, short-term spectral changes in hot (T$_{\text{eff}}\sim2000\,$K), high-gravity ($\log{\text{g}}\sim5$), cloudless brown dwarfs are the photolysis of H$_2$O and enhancement of CO$_2$, which can result in part-per-thousands spectral changes in the hours after a flare.

The James Webb Space Telescope (\textit{JWST}) opened a new observational window on the primordial Universe. Here we present new JWST NIRSpec integral field spectroscopy (IFS) observations of the $z=7.54$ quasar ULAS J1342+0928 obtained as part of the Galaxy Assembly with NIRSpec IFS (GA-NIFS) GTO programme. The new data-set obtained with both the prism ($R\sim100$) and the high-resolution grating ($R\sim2700$) allow for a complete description of the quasar emission from the rest-frame UV to optical bands. The low-resolution data reveal the presence of [\ion{O}{iii}] emission on $\sim$7 kpc scales, well above the typical galaxy size at this redshift, likely associated with a past outflow event. Additionally, the high-resolution observations show a more energetic ionised outflow on nuclear scales ($\lesssim 0.6$ kpc). The total ionised mass outflow rate ranges between 50 and 300 $\rm M_{\odot} \, yr^{-1}$ where the significant spread is mostly due to the lack of tight constraints on the electron density. This range overlaps in part with the star formation rate range (85--545 $\rm M_{\odot} \, yr^{-1}$), implying that the nuclear outflow could ultimately lead to an early star formation quenching. By employing an accretion disc modelling, for the first time on \textit{JWST} data, we manage to robustly estimate the black hole mass and the bolometric luminosity, $\rm \log(M_{BH}/(M_{\odot}))=9.2\pm 0.2$ and $\rm \log(L_{bol}/(erg \, s^{-1}))=46.8\pm 0.1$, respectively. We derive an Eddington ratio of $\rm \lambda_{Edd}\sim 0.4$, challenging the paradigm of widespread super-Eddington accretion in quasars at the epoch of reionisation.

Recent imaging of supermassive black holes by the Event Horizon Telescope (EHT) has relied on exhaustive parameter-space searches, matching observations to large, precomputed libraries of theoretical models. As observational data become increasingly precise, the limitations of this computationally expensive approach grow more acute, creating a pressing need for more efficient methods. In this work, we present $\texttt{Jipole}$, an automatically differentiable (AD), $\texttt{ipole}$-based code for radiative transfer in curved spacetimes, designed to compute image gradients with respect to underlying model parameters. These gradients quantify how parameter changes-such as the black hole's spin or the observer's inclination-affect the image, enabling more efficient parameter estimation and reducing the number of required images. We validate $\texttt{Jipole}$ against $\texttt{ipole}$ in two analytical tests and then compare pixel-wise intensity derivatives from AD with those from finite-difference methods. We then demonstrate the utility of these gradients by performing parameter recovery for an analytical model using a conjugate gradient optimizer in three increasingly complex cases for the injected image: ideal, blurred, and blurred with added noise. In most cases, high-accuracy fits are obtained in only a few optimization steps, failing only in cases with extremely low signal-to-noise ratios and large blurring size kernels. These results highlight the potential of AD-based methods to accelerate robust, high-fidelity model-data comparisons in current and future black hole imaging efforts.

The satellite population of the Milky Way is shaped by a range of astrophysical processes including mergers, star formation, feedback, and cosmic reionisation. Determining which processes most strongly influence its properties is challenging and a key test of galaxy formation models. We train a neural network on the GALFORM semi-analytic model and apply a variance-based sensitivity analysis to characterise the influence of 11 astrophysical parameters on two key observables: the satellite luminosity function, and the mass-metallicity relation. We find that: (1) the abundance of bright satellites ($\mathrm{M}_V \lesssim -13$) is regulated primarily by supernova feedback; (2) the faint end of the luminosity function is shaped by the interplay between feedback and reionisation; and (3) the mass-metallicity relation is governed almost exclusively by feedback at all masses. We are unable to find a combination of parameters in the fiducial model that fits the observed data for both statistics simultaneously. To understand why, we employ SHapley Additive exPlanations to capture the directionality of each parameter variation. This enables us to pinpoint the origin of tensions in the model, showing that parameter adjustments that regulate the abundance of faint satellites drive stellar metallicities to be an order of magnitude too low and vice versa. This internal "tug-of-war" leads us to consider extensions to the baseline model, such as metal loading in winds, or allowing the feedback strength to evolve with redshift. Our study highlights the value of interrogating complex physical models through a sensitivity analysis framework by revealing high-order parameter interactions and non-linear responses that traditional one-at-a-time variations would miss.

Dense young star clusters (YSCs) are ideal environments for dynamical interactions between stars and stellar mass black holes (BHs). In such dense environments, stars can undergo close encounters with BHs and fall within their tidal radius, resulting in micro-tidal disruption events (micro-TDEs), transient phenomena with potential multi-messenger signatures. We performed a suite of direct N-body simulations using the PETAR code, to which we implemented new prescriptions for modeling micro-TDEs. We constructed a set of realistic YSC models including primordial binaries, based on the observed Milky Way population. Our simulations incorporate stellar and binary evolution, supernova kicks, and stellar winds using the BSE code, and account for the Galactic tidal field via the GALPY library. We identify three dynamical channels for micro-TDE production: single star-single BH encounters, binary-mediated interactions (including supernova-kick triggers), and interactions involving higher-order multiple systems such as hierarchical triples and quadruples, as well as chaotic few-body interactions. Multiple encounters are the most efficient production channel, which dominates the total rate: 350-450 Gpc$^{-3}$ yr$^{-1}$. Micro-TDEs from YSCs are expected to be detectable by upcoming surveys, particularly the Legacy Survey of Space and Time, with detection rates potentially up to hundreds per year. The gravitational wave (GW) signals expected from micro-TDEs peak in the deci-Hertz band, making them accessible to future instruments such as the Lunar Gravitational Wave Antenna and the Deci-Hertz Interferometer Gravitational-wave Observatory. Micro-TDEs emerge as promising multi-messenger sources, potentially offering unique insights into star cluster dynamics, stellar collisions, and the population of dormant stellar-mass BHs, through both electromagnetic and GW observations.

We report the discovery of a faint (M_1700 ~ -12.2), oxygen-deficient strongly-lensed ionizing source -- dubbed LAP2 (Lensed And Pristine 2) -- at a spectroscopic redshift of z=4.19. LAP2 appears to be isolated and lies very close to the caustic produced by the lensing galaxy cluster Abell 2744. It was observed with the James Webb Space Telescope (JWST) NIRSpec MSA in prism mode as part of the UNCOVER program. The NIRSpec spectrum reveals prominent Lya emission (7.1 sigma), clear Ha emission (6.2 sigma), tentative Hb emission (2.8 sigma), and no detectable [OIII]4959,5007 (~ 7 times fainter than Ha). The inferred [OIII] 2 sigma upper limit corresponds to an R3 index <0.85 (assuming the Ha/Hb ~ 2.86 case~B recombination ratio), which, under high-ionization conditions, implies a metallicity of Z < 6 X 10^(-3) Z_sun. The combination of faint ultraviolet luminosity, large rest-frame Ha equivalent width (~ 650 A), and extremely compact size (< 10 pc) suggests that LAP2 is being caught in an early, pristine formation phase consistent with an instantaneous-burst scenario, with an estimated stellar mass of at most a few 10^4 Msun. Deep VLT/MUSE observations further reveal copious Lya emission forming an arclet that straddles the critical line. LAP2 thus joins the rare class of extremely metal-poor star-forming complexes that JWST has started to unveil at redshifts 3 - 7, and provides a rare glimpse into a still very poorly explored faint-luminosity regime.

Recent findings from several Pulsar Timing Array (PTA) collaborations point to the existence of a Gravitational Wave Background (GWB) at nanohertz frequencies. A key next step towards characterizing this signal and identifying its origin is to map the sky distribution of its power. Several strategies have been proposed to reconstruct this distribution using PTA data. In this work, we compare these different strategies to determine which one is best suited to detect GWB anisotropies of different topologies. We find that, for both localized and large-scale anisotropies, reconstruction methods based on pixel and radiometer maps are the most promising. However, in both scenarios, even the optimistically large anisotropic signals discussed in this work remain challenging to detect with near-future PTA sensitivities. For example, we find that for a GWB hotspot contributing to $80\%$ of the GWB power in the second frequency bin, detection probabilities reach at most $\mathcal{O}(10\%)$ for a PTA with noise properties comparable with the ones of the upcoming IPTA third data release. Finally, we consider the fundamental limitations that cosmic variance poses to these kinds of searches by deriving the smallest deviations from isotropy that could be detected by an idealized PTA with no experimental or pulsar noise.

We studied 12 disk streams found in a 250$^3$ pc$^3$ volume in the solar neighborhood, which we define as coeval and comoving stellar structures with aspect ratios greater than 3:1. Using \emph{Gaia} Data Release 3 data and the advanced clustering algorithms \texttt{SigMA} and \texttt{Uncover}, we identified and characterized these streams beyond the search volume, doubling, on average, their known populations. We estimate the number density of disk streams to be $\approx 820$ objects\,/\,kpc$^3$ (for $|Z| < 100$\,pc), or surface densities of $\approx 160$ objects\,/\,kpc$^2$. These estimates surpass N-body estimates by one to two orders of magnitude and challenge the prevailing understanding of their destruction mechanisms. Our analysis reveals that these 12 disk streams are dynamically cold with 3D velocity dispersions between 2 and 5\,km\,s$^{-1}$, exhibit narrow sequences in the Hertzsprung-Russell diagram, and are highly elongated with average aspect ratios of 7:1, extending up to several hundred parsecs. We find evidence suggesting that one of the disk streams, currently embedded in the Scorpius-Centaurus association, is experiencing disruption, likely due to the primordial gas mass of the association.

The stellar haloes and intra-cluster light around galaxies are crucial test beds for dark matter (DM) physics and galaxy formation models. We consider the role that the numerical resolution plays in the modelling of these systems by studying the stripping of satellites in the IllustrisTNG cosmological simulations. We focus on host haloes of total halo mass $M_\mathrm{200c}=10^{12-15}M_{\odot}$ and satellites of stellar mass $>10^{7}$$M_{\odot}$, and compare stellar halo / satellite properties across 9 IllustrisTNG runs with baryonic particle mass resolution between $8.5\times10^4M_{\odot}$ and $7\times10^8$$M_{\odot}$, using a Lagrangian-region technique to identify counterpart satellites across different resolution simulations of the same volume. We publish the corresponding catalogues alongside this paper. We demonstrate that the stripping of DM from satellites that orbit in group- and cluster-mass hosts is largely independent of resolution at least until 90 per cent of their initial mass at infall has been stripped. We do not find evidence for spurious disruption of galaxies due to insufficient resolution for the satellite masses we consider. By contrast, the stripping of stellar mass is strongly resolution-dependent: each factor of 8 improvement in particle stellar mass typically adds 2~Gyr to the stripping time. Improved numerical resolution within the IllustrisTNG model generally results in more compact satellites with larger stellar masses, which in turn generate more centrally concentrated stellar haloes and intra-cluster mass profiles. However, the concomitant increase in stellar mass of both satellites and hosts may still be the cause for the overprediction of the stellar halo mass at large host radii relative to observations seen in some previous studies.

Supernovae that interact with hydrogen-poor, helium-rich circumstellar material (CSM), known as Type Ibn supernovae (SNe Ibn), present a unique opportunity to probe mass-loss processes in massive stars. In this work, we report the first radio detection of a SN Ibn, SN 2023fyq, and characterize the mass-loss history of its stellar progenitor using the radio and X-ray observations obtained over 18 months post-explosion. We find that the radio emission from 58--185 days is best modeled by synchrotron radiation attenuated by free-free absorption from a CSM of density $\sim$ $10^{-18}$ g/$\rm{cm^{3}}$ ($\sim 10^{6} \mathrm{\rho_{ISM}}$) at a radius of $10^{16}$ cm, corresponding to a mass-loss rate of $\sim$ $4 \times 10^{-3} \ \mathrm{M_{\odot} \ yr^{-1}}$ (for a wind velocity of 1700 km/s from optical spectroscopy) from 0.7 to 3 years before the explosion. This timescale is consistent with the time frame over which pre-explosion optical outbursts were observed. However, our late-time observations at 525 days post-explosion yield non-detections, and the 3$\sigma$ upper limits (along with an X-ray non-detection) allow us to infer lower-density CSM at $2\times 10^{16}$ cm with $\rm{\dot{M}}$ $< 2.5\times 10^{-3} \ \mathrm{M_{\odot} \ yr^{-1}}$. These results suggest a shell-like CSM from at most $4 \times 10^{15}$ to $2 \times 10^{16}$ cm ($\sim 10^{5} R_{\rm{\odot}}$) with an elevated CSM density (0.004 $\mathrm{M_{\odot} \ yr^{-1}}$) that is roughly consistent with predictions from a merger model for this object. Future radio observations of a larger sample of SNe Ibn will provide key details on the extent and density of their helium-rich CSM.

Following a binary neutron star (BNS) merger, the transient remnant is often a fast-spinning, differentially rotating, magnetised hypermassive neutron star (HMNS). This object is prone to the magnetorotational instability (MRI) which drives magnetohydrodynamic turbulence that significantly influences the HMNS global dynamics. A key consequence of turbulence is the outward transport of angular momentum which impacts the remnant's stability and lifetime. Most numerical simulations of BNS mergers are unable to resolve the MRI due to its inherently small wavelength. To overcome this limitation, subgrid models have been proposed to capture the effects of unresolved small-scale physics in terms of large-scale quantities. We present the first implementation of our MHD-Instability-Induced Turbulence (MInIT) model in global Newtonian simulations of MRI-sensitive, differentially rotating, magnetised neutron stars. Here, we show that by adding the corresponding turbulent stress tensors to the momentum equation, MInIT successfully reproduces the angular momentum transport in neutron stars driven by small-scale turbulence.

The Alfvén surface -- where the solar wind exceeds the local Alfvén speed as it expands into interplanetary space -- is now routinely probed by NASA's Parker Solar Probe (PSP) in the near-Sun environment. The size of the Alfvén surface governs how efficiently the solar wind braking torque causes the Sun to spin-down. We aimed to characterise the size and evolution of the Alfvén surface as magnetic activity increased during solar cycle 25. The Alfvén surface was extrapolated from the solar wind mass and magnetic flux measured by the SWEAP and FIELDS instrument suites onboard PSP. We accounted for the acceleration of the solar wind along Parker spiral magnetic field lines and used potential field source surface modelling to determine the sources of the solar wind. The longitudinally averaged Alfvén radius measured by PSP grew from 11 to 16 solar radii as solar activity increased. Accordingly, the solar wind angular momentum-loss rate grew from $\sim$1.4$\times 10^{30}$ erg to 3$\times 10^{30}$ erg. Both the radial and longitudinal scans of the solar wind contained fluctuations of 10-40\% from the average Alfvén radius in each encounter. Structure in the solar corona influenced the morphology of the Alfvén surface, which was smallest around the heliospheric current sheet and pseudostreamers. The Alfvén surface was highly structured and time-varying however, at large-scales, organised by the coronal magnetic field. The evolution of the solar corona over the solar cycle systematically shifted the magnetic connectivity of PSP and influenced our perception of the Alfvén surface. The Alfvén surface was 30\% larger than both thermally-driven and Alfvén wave-driven wind simulations with the same mass-loss rate and open magnetic flux, but had a similar dependence on the wind magnetisation parameter.

With pulsar timing arrays (PTAs) having observed a gravitational wave background (GWB) at nanohertz frequencies, the focus of the field is shifting towards determining and characterizing its origin. While the primary candidate is a population of GW-emitting supermassive black hole binaries (SMBHBs), many other cosmological processes could produce a GWB with similar spectral properties as have been measured. One key argument to help differentiate an SMBHB GWB from a cosmologically sourced one is its level of anisotropy; a GWB sourced by a finite population will likely exhibit greater anisotropy than a cosmological GWB through finite source effects (``shot noise'') and potentially large-scale structure. Current PTA GWB anisotropy detection methods often use the frequentist PTA optimal statistic for its fast estimation of pulsar pair correlations and relatively low computational overhead compared to spatially-correlated Bayesian analyses. However, there are critical limitations with the status quo approach. In this paper, we improve this technique by incorporating three recent advancements: accounting for covariance between pulsar pairwise estimates of correlated GWB power; the per-frequency optimal statistic to dissect the GWB across the spectrum; and constructing null-hypothesis statistical distributions that include cosmic variance. By combining these methods, our new pipeline can localize GWB anisotropies to specific frequencies, through which anisotropy detection prospects -- while impacted by cosmic variance -- are shown to improve in our simulations from a $p$-value of $\sim0.2$ in a broadband search to $\sim0.01$ in the per-frequency search. Our methods are already incorporated in community-available code and ready to deploy on forthcoming PTA datasets.

We present a comprehensive spectroscopic and kinematic analysis of the very metal-poor ([Fe/H] = -2.60 $\pm$ 0.20 dex) giant star HE2159-0551. By investigating the star's chemodynamic characteristics, we seek to address its formation, evolution, and role in the chemical enrichment of the early cosmos and the possible connection to known merger events. From high-resolution data we perform a one dimension, local thermodynamic equilibrium analysis using PyMoogi. We conduct a detailed abundance analysis of 23 elements (C, N, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Sr, Y, Zr, Ba, and Eu), allowing us to derive abundances or place limits. Finally, we compute orbital parameters to investigate the kinematics and thus the nucleosynthetic origin of HE2159-0551. The analysis yields significant insights into the chemical composition of HE2159-0551, highlighting its peculiarities among very metal-poor stars. The star shows signs of internal mixing and a peculiar abundance pattern, particular regarding the heavy elements. We find a low Ba abundance (s-process element) and a suppressed contamination of r-process elements, even though r-process enrichment may be expected in very metal-poor stars. The orbital parameters and kinematic properties indicate that HE2159-0551 is a thick disc star, connected to the old and metal-poor LMS-1/Wukong progenitor resulting from an early merger. Our kinematic analysis suggests a potential connection of HE2159-0551 to the merger LMS-1/Wukong. We conclude that the nucleosynthesis processes responsible for the star's enrichment in heavy elements are different from those observed in many other metal-poor stars as neither the main r- nor s-process can explain the derived abundance pattern. A possible weak-r or $\nu$p-process forming Sr-Zr but not Ba might have mixed into a low level of underlying r-process material in the low-mass LMS-1/Wukong system.

In this paper, the suitability of fast-declining Type Ia supernovae (SNe Ia) as cosmological standard candles is examined utilizing a Hubble Flow sample of 43 of these objects observed by the Carnegie Supernova Project (CSP). We confirm previous suggestions that fast-declining SNe Ia offer a viable method for estimating distances to early-type galaxies when the color-stretch parameter, $s_{BV}$, is used as a measure of the light curve shape. As a test, we employ the Tripp (1998) method, which models the absolute magnitude at maximum as a function of light curve shape and color. We calibrate the sample using 12 distance moduli based on published Infrared Surface Brightness Fluctuations to derive a value of the Hubble constant that is in close agreement with the value found by Uddin et al. (2024), using the same methodology, but with the full sample of CSP SNe Ia. We also develop a new and simple method of estimating the distances of fast decliners only based on their colors at maximum (and not light curve shape) and find that it has a precision similar to the Tripp method. This "Color" technique is a powerful tool that is unique to fast-declining SNe Ia. We show that the colors of the fast decliners at maximum light are strongly affected by photospheric temperature differences and not solely due to dust extinction, and provide a physical rationale for this effect.

Galaxy clusters exhibit heterogeneity in their pressure profiles, even after rescaling, highlighting the need for adequately sized samples to accurately capture variations across the cluster population. We present a Bayesian hierarchical model that simultaneously fits individual cluster parameters and the underlying population distribution, providing estimates of the population-averaged pressure profile and the intrinsic scatter, as well as accurate pressure estimates for individual objects. We introduce a highly flexible, low-covariance, and interpretable parameterization of the pressure profile based on restricted cubic splines. We model the scatter properly accounting for outliers, and we incorporate corrections for beam and transfer function, as required for SZ data. Our model is applied to the largest non-stacked sample of individual cluster radial profiles, extracted from SPT+Planck Compton-y maps. This is a complete sample of 55 clusters, with $0.05<z<0.30$ and $M_{500}>4\times 10^{14}M_\odot$, enabling subdivision into sizable morphological classes based on eROSITA data. The shape of the population-averaged profile, at our 250 kpc FWHM resolution, closely resembles the universal pressure profile, despite the flexibility of our model to accommodate alternative shapes, with a ~12% lower normalization, similar to what is needed to alleviate the tension between cosmological parameters derived from the CMB and Planck SZ cluster counts. Beyond $r_{500}$, our profile is steeper than previous determinations. The intrinsic scatter is consistent with or lower than previous estimates, despite the broader diversity expected from our SZ selection. Our flexible pressure modelization identifies a few clusters with non-standard concavity in their radial profiles but no outliers in amplitude. When dividing the sample by morphology, we find remarkably similar pressure profiles across classes.

Fast radio bursts (FRBs) provide a sensitive probe of diffuse baryons: their dispersion measures (DMs) measure electron density independent of temperature and scale linearly with gas density. This makes them particularly well suited to studying the intragroup medium (IGrM), where traditional probes such as X-ray emission and the SZ effect are weak. Evidence suggests that the baryon content of group mass halos ($M_{500}\sim10^{13}-10^{14}$ M$_{\odot}$) is strongly affected by galactic feedback, creating deviations from cluster scaling relations. Three FRBs from the first CHIME/FRB Outrigger sample come from host galaxies found within or behind galaxy clusters and groups. Using integrated halo density models, we estimate the DM contribution of each ICM/IGrM, accounting for uncertainties in halo mass and the distance to the host galaxy relative to the cluster center. For the more massive halos, predicted cluster DMs agree with the extragalactic DM budget. One burst, FRB 20230703A, intersects three groups yet has a low extragalactic DM. By comparing model predictions with the measured DM, we constrain the baryon fraction $f_g(R)$ in these halos. Comparing with published $M-f_g$ relations, we find consistency with recent eROSITA results at $R_{500}$, mild tension at $R_{200}$, and strong tensions with earlier X-ray-based relations. As CHIME/FRB Outriggers build a large catalog of localized FRBs, many additional sightlines through groups and clusters will be obtained. These will enable systematic tests of intragroup and intracluster gas properties and sharpen constraints on the distribution of baryons in massive halos.

Little Red Dots (LRDs) are a puzzling population of extragalactic sources whose origin is highly debated. In this Letter, we stack NIRCam, MIRI and ALMA images of a large and homogeneously-selected sample of LRDs from multiple JWST Legacy fields. We find clear evidence for hot-dust emission, seen as a rising mid-infrared continuum up to rest-frame $\lambda_{\rm rest}$$\sim$ 3$\mu$m, that is best explained by a standard dusty AGN structure. This scenario holds regardless of whether the Optical/Ultraviolet (UV) continuum is stellar or AGN-dominated. Either ways, we argue that AGN-heated dust must have a geometry that leaves at least part of the Optical/UV continuum and broad-line region emission unobscured, which explains the observed blue UV slopes and prominent Balmer features. Lack of detections in the deep stack of X-ray images suggests that Compton-thick ($N_{\rm H}$$>$3$\times$10$^{24}$ cm$^{-2}$) gas obscuration is common, and likely confined within the dust sublimation radius ($R$$_{\rm sub}$$\sim$0.1 pc). While this gas-dust displacement is in line with recent models (e.g. the ``Black Hole Star''), how pre-enriched hot dust can form around a nearly-pristine black hole environment remains to be explained.

Recent years have seen many arguments for cosmic rays (CRs) as an important influence on galactic and circumgalactic (CGM) physics, star and galaxy formation. We present a pedagogical overview of state-of-the-art modeling of CR-magnetohydrodynamics (CR-MHD) on macro scales (~kpc), highlighting their fundamental dependence on the micro (< au) scales of CR gyro orbits and meso (~pc) scales of CR mean-free-paths, intended to connect the extragalactic, Galactic, and plasma CR transport modeling communities. We note the pitfalls and systematic errors that arise from older assumptions in CR modeling, including: use of a simple Fokker-Planck equation or ad-hoc two-moment formalisms for transport; assumption of leaky boxes or plane-parallel or shear-periodic boundaries for comparison to local interstellar medium (LISM) observations; ignoring detailed LISM constraints on CR spectra (e.g. focusing only on extragalactic observables or spectrally integrated models); assuming CR transport is mediated by classical models of advection, streaming from self-confinement (super-Alfvenic or Alfvenic), or extrinsic turbulence. We emphasize recent progress addressing these: development of rigorously-derived CR-MHD equations; use of global, 3D galaxy+halo models for LISM comparisons; new methods for full-spectrum dynamics; novel models for intermittent scattering and/or new drivers. We compile extragalactic+LISM observations to show how ~GeV CR transport is being rapidly constrained in the CGM, and present phenomenological models which can be used in future simulations. We conclude by highlighting critical open questions for micro, meso, and macro-scale CR-MHD simulations.

We study the infrared/radio correlation of galaxies in the IRAS Revised Bright Galaxy Sample using new MeerKAT observations at $\rm\nu = 1.28\, GHz$, complemented with VLA data. We classify the objects by primary energy source (Active Galactic Nuclei vs. Star-Forming) and take into account their merger status. With this, we aim to explore the effect of galaxy-galaxy interaction on the total-infrared (TIR)/radio correlation ($q_\mathrm{TIR}$) of star-forming galaxies by comparing the $q_\mathrm{TIR}$ distribution between isolated and interacting/merging sources. We found the median $q_\mathrm{TIR}$ to be $2.61 \pm 0.01$ (scatter = 0.16) for isolated galaxies and $2.51 \pm 0.08$ (scatter = 0.26) for interacting/merging galaxies. Our analysis reveals that interacting/merging galaxies exhibit lower $q_\mathrm{TIR}$ and higher dispersion compared to isolated galaxies, and the difference is marginally significant. Interacting/merging galaxies have redder $W2-W3$ colours, higher star formation rates (SFR) and specific SFR compared to isolated objects. We observe a significant decrease in $q_\mathrm{TIR}$ with increasing radio luminosity for isolated galaxies. Additionally, we find the median ratio of TIR ($8 \,\mu m < \lambda < 1000\, \mu m$) to far-infrared (FIR; $40 \,\mu m < \lambda < 120\, \mu m$) luminosities to be $\left<L_\mathrm{TIR}/L_\mathrm{FIR}\right>\approx2.29$. By examining the relation between $L_\mathrm{TIR}$ and the mid-infrared (MIR) star-formation rate indicator ($L_\mathrm{12\,\mu m}$) employed for our interacting/merging sample, we note a strong and consistent (similar non-linear behaviour) relationship between the TIR/radio and TIR/MIR ratios. Finally, we show that already at $z<0.1$, $q_\mathrm{TIR}$ exhibits a dependence on stellar mass, with more massive galaxies displaying a lower $q_\mathrm{TIR}$.

Understanding how shocks interact with coronal structures is crucial for understanding the mechanisms of particle acceleration in the solar corona and inner heliosphere. Using simultaneous radio and white-light observations, we investigate the interaction between a CME-driven shock and a plasmoid. LASCO and STEREO-A COR-2 white-light images are analyzed to track the evolution of the plasmoid, CME and its associated shock, while the Wind/WAVES and STEREO/WAVES dynamic spectra provide complementary radio signatures of the shock-plasmoid interaction at $\approx$7 R$_\odot$. An interplanetary Type II radio burst was detected as the shock propagated through the plasmoid. The merging of the plasmoid into the CME was accompanied by interplanetary Type III radio bursts, suggesting escaping electron beams during the reconnection process. These observations clearly demonstrate that shock-plasmoid interactions can enhance the efficiency of particle acceleration associated with CMEs, with implications for electron acceleration in flare and heliospheric current sheets as well.

When directly imaging a cold giant exoplanet hosting a ring system, the reflected light from the rings can outshine the planet's thermal emission and reflected-light in the near-infrared. Consequently, an exoring may be detectable at a significantly lower contrasts than is required to image the exoplanet itself. Here we investigate the detectability of exorings in near-infrared reflected light using NIRCam coronagraphy PanCAKE simulations of two nearby mature stars, Proxima Centauri and Tau Ceti. Under the most favorable assumptions, we find JWST 2$\mu$m NIRCam coronagraphy (F200W + MASK335R) is capable of detecting an exoring system with a radius of 2.8 times that of Saturn's A-ring for planets on an orbit with a = 1.3-1.9 AU. Broader simulations indicate that NIRCam can probe large planetary ring systems around mature exoplanets comparable in size to circumplanetary disks, which can reach up to 1000 times the radius of Saturn's A-ring. These results suggest that NIRCam F200W coronagraphy could serendipitously detect large exorings in reflected light under the right conditions. A combined analysis of F200W coronagraphic observations of confirmed exoplanets could provide the first empirical constraints on the occurrence rate of large exorings. Confirming the existence and frequency of exorings spanning the scale between circumplanetary disks and the rings of the Solar System giant planet could offer new insight into the formation, evolution, and architecture of planetary systems.

Cosmic rays (CRs) are a non-thermal energy component in the interstellar and circumgalactic medium (CGM) that can act as an additional feedback channel beyond thermal and kinetic feedback from stars and AGN. They influence galaxy evolution by altering gas properties, regulating star formation, and shaping galactic outflows. We investigate these effects using a suite of cosmological zoom-in simulations, which incorporate CR transport and feedback on top of the Auriga galaxy formation model. Our simulations span a wide range of halo masses, from dwarf galaxies to small groups ($M_{200\mathrm{c}}= 10^{10} - 10^{13}~\mathrm{M}_\odot$), allowing us to assess the mass-dependent impact of CRs in a cosmological setting. We find that CRs have the strongest impact in lower-mass galaxies ($M_{200\mathrm{c}} < 10^{12}~\mathrm{M}_\odot$), where they suppress star formation rates by up to 50\%, reduce gas and stellar half-light radii, and drive outflows that reach higher velocities at the virial radius compared to simulations without CRs. These CR-enhanced outflows also transport more metals and magnetic fields into the CGM, leading to higher CGM metallicities, stronger magnetisation, and lower CGM temperatures. In more massive galaxies, CRs do not significantly affect star formation or outflow properties, likely because thermal and kinetic feedback from stars and AGN dominate in this regime. However, CRs still influence galaxy morphology across all halo masses by reducing the gas half-mass radius and stellar half-light radius. Finally, variations in CR transport properties, such as different diffusion coefficients or the exclusion of Alfvén cooling, significantly affect star formation, CGM properties, and outflows in lower-mass galaxies. This sensitivity makes these galaxies key environments for testing CR transport models and refining our understanding of their role in galaxy evolution.

The most common instrument used by the exoplanet/brown dwarf direct imaging community at the W.M. Keck Observatory is currently the NIRC2 near-infrared imager. We performed on-sky testing to investigate three effects which may be limiting the performance of NIRC2 when conducting high-contrast imaging observations from $3-5\mu$m. First, we report the measurements of an on-sky test of the throughput of the L/M vector vortex coronagraph. We quantify the throughput and additional background flux penalties, noting that the performance effects of using the vector vortex coronagraph in the Ms-filter are greater than in the Lp-filter. Second, we utilize the recently commissioned NIRC2 electronics upgrade to measure the sky variability at sub-second speeds. We find that the background varies at timescales of less than 30s, indicating that the electronics upgrade may open an opportunity to improve the sky-background subtraction of future surveys. Third, we document the contribution of the image derotator to the spatial non-uniformity in the background flux. We conclude by giving a set of recommendations of how the Keck-NIRC2 high-contrast imaging community can adapt their observing strategies to improve the sensitivity of future surveys.

The launch of the \textit{Einstein Probe} unleashed a new era of high-energy transient discovery in the largely unexplored soft X-ray band. The \textit{Einstein Probe} has detected a significant number of fast X-ray transients that display no gamma-ray emission, complicating their robust association to more common gamma-ray bursts. To explore their possible connection, we analyzed the redshift distribution of both \textit{Einstein Probe} fast X-ray transients and long duration gamma-ray bursts. A comparative analysis of their cumulative redshift distributions using non-parametric two-sample tests, namely the Kolmogorov-Smirnov and Anderson-Darling tests, finds no statistically significant difference. These tests favor that their redshifts are drawn from the same underlying distribution. This empirical connection between \textit{Einstein Probe} transients and long gamma-ray bursts is further supported by their agreement with the so-called ``Amati relation'' between the spectral peak energy and the isotropic-equivalent energy. Together, these results indicate that most extragalactic \textit{Einstein Probe} fast X-ray transients are closely related to long gamma-ray bursts and originate from a massive star (collapsar) progenitor channel. Our findings highlight the role of the \textit{Einstein Probe} in uncovering the missing population of failed jets and dirty fireballs that emit primarily at soft X-ray wavelengths.

Protohalos, primordial regions in the initial cosmic density field that evolve into dark matter halos, are crucial for understanding cosmic structure formation. Motivated by the potential to reconstruct protohalo positions and shapes from observed galaxies using a novel approach grounded in optimal transport theory, we revisit the relationship between the structural properties of protohalos and the formation histories, concentrations, and final morphologies of their associated dark matter halos. To better understand halo assembly, we introduce a new estimator defined by an integral over redshifts and compare its performance to $z_{50}$, the commonly used redshift at which half of the final halo mass is formed. We quantify protohalo structure using the three invariants of the inertia, deformation, and energy shear tensors. Although past research has correlated the first two invariants of the deformation and energy tensors with halo formation, our findings reveal that the third invariant also significantly correlates with the final halo shape. We discuss the prospect of using optimal transport to connect our protohalo results to observations of high-redshift protoclusters to better align theoretical models with observational data.

CLEAN is a well-established deconvolution approach to Fourier imaging at both radio wavelwengths and hard X-ray energies. However, specifically for hard X-ray imaging, CLEAN suffers two significant drawbacks: a rather limited degree of automation, and a tendency to under-resolution. This paper introduces a multi-scale version of CLEAN specifically tailored to the reconstruction of images from measurements observed by the Spectrometer/Telescope for Imaging X-rays (STIX) on-board Solar Orbiter. Using synthetic STIX data, this study shows that multi-scale CLEAN may represent a reliable solution to the two previously mentioned CLEAN limitations. Further, this paper shows the performances of CLEAN and its multi-scale release in reconstructing experimental real scenarios characterized by complex emission morphologies.

The coming years of gravitational wave astrophysics promises thousands of new detections, which can unlock fundamental scientific insights if the information in each observation can be properly synthesized into a coherent picture. State-of-the-art approaches often accomplish this with hierarchical Bayesian inference. However, this typically relies on Monte Carlo approximations that are already very expensive in current data, and may become prohibitively so in the future. In this paper we show how this process can be understood from a first-principles statistical approach. We derive an error estimator $\hat{E}$ for quantifying the amount of information that is lost due to the Monte Carlo approximation and recommend that this error is limited to no more than $\hat{E} \lesssim 0.2$ bits for reliable inference. We also show that the hierarchical likelihood estimator is biased but may be corrected. Finally, we show some practical examples for inference on synthetic gravitational-wave population inference, demonstrating that simple models with strong assumptions can be much more stable to Monte Carlo uncertainty than those with weaker assumptions. We also provide a \texttt{pip}-installable package \texttt{population-error} with which analysts can calculate the error statistics $\hat{E}$.

Numerical calculations of planetary system formation are very demanding in terms of computing power. These synthetic planetary systems can however provide access to correlations, as predicted in a given numerical framework, between the properties of planets in the same system. Such correlations can, in return, be used in order to guide and prioritize observational campaigns aiming at discovering some types of planets, as Earth-like planets. Our goal is to develop a generative model which is capable of capturing correlations and statistical relationships between planets in the same system. Such a model, trained on the Bern model, offers the possibility to generate large number of synthetic planetary systems with little computational cost, that can be used, for example, to guide observational campaigns. Our generative model is based on the transformer architecture which is well-known to efficiently capture correlations in sequences and is at the basis of all modern Large Language Models. To assess the validity of the generative model, we perform visual and statistical comparisons, as well as a machine learning driven tests. Finally, as a use case example, we consider the TOI-469 system, in which we aim at predicting the possible properties of planets c and d, based on the properties of planet b (the first that has been detected). We show using different comparison methods that the properties of systems generated by our model are very similar to the ones of the systems computed directly by the Bern model. We also show in the case of the TOI-469 system, that using the generative model allows to predict the properties of planets not yet observed, based on the properties of the already observed planet. We provide our model to the community on our website this http URL.

High-Mass X-ray Binaries (HMXBs) serve as useful laboratories for exploring the behaviour of accreted matter onto compact objects and for probing the complex wind environments of massive stars. These investigations are essential for understanding stellar life cycles and the dynamics of the Milky Way, and they are prominent topics in the science cases for XRISM and NewAthena. We report, for the first time, a XRISM observation of the HMXB Vela X-1, conducted during the first cycle of the XRISM general observer programme and complemented by simultaneous XMM-Newton and NuSTAR coverage. This campaign targeted a critical orbital phase -- when the neutron star is in inferior conjunction -- during which significant changes in absorption are expected. We performed absorption-resolved spectral analyses during two time intervals of interest: the soft and hard hardness ratio (HR) intervals, as it is strongly correlated with absorption variability. We observed a sudden transition in the HR from a soft to a hard state, coinciding with an increase in the absorption column density. This is likely attributed to the onset of the accretion structure crossing our line of sight. With XRISM/Resolve, we also investigated the Fe K region, and we report for the first time the presence of a Fe K$\alpha$ doublet in the spectrum of Vela X-1, together with the presence of already known Fe K$\beta$ and Ni K$\alpha$ lines that are produced in cold clumps embedded in the hot ionised wind. The measured line velocities of the order of $10^2 \ \mathrm{km\,s^{-1}}$ are consistent with production sites in the vicinity of the neutron star. This precursor study with Vela X-1 shows the potential of XRISM in studying in unprecedented details the spectral evolution of wind-accreting X-ray binaries.

The standard cosmological model assumes the Cosmological Principle. However, recent observations hint at possible violations of isotropy on large scales, possibly through late-time anisotropic expansion. Here we investigate the potential of cross-correlations between CMB lensing convergence $\kappa$ and galaxy cosmic shear $B$-modes as a novel probe of such late-time anisotropies. Our signal-to-noise forecasts reveal that information from the $\kappa$-$B$ cross-correlation is primarily contained on large angular scales ($\ell \lesssim 200$). We find that this cross-correlation for a Euclid-like galaxy survey is sensitive to anisotropy at the percent level. Making use of tomography yields a modest improvement of $\sim 20\%$ in detection power. Incorporating the galaxy $E$-$B$ cross-correlations would further enhance these constraints.

Dual-phase xenon time projection chambers achieve optimal sensitivity for dark matter in the $10$--$1000~\mathrm{GeV}/c^2$ mass range, but sub-GeV dark matter particles lack sufficient energy to produce nuclear recoils above detection thresholds in these detectors. Blazar-boosted dark matter offers a way to overcome this limitation: relativistic jets in active galactic nuclei can accelerate light dark matter in their host-galaxy halos to energies capable of producing detectable nuclear recoil signals in xenon-based detectors on Earth. We present the first blazar-boosted dark matter search incorporating detector response modeling, using public data from XENON1T and LZ for the blazar TXS~0506+056. We model dark matter--proton scattering in the jet environment, covering the full process from jet acceleration to detector response. We explore how the host-galaxy dark matter density profile impacts our analysis. Using XENON1T data, we exclude dark matter--nucleon cross sections for $m_\chi \sim 1~\mathrm{MeV}$ in the range $5.8\times 10^{-31}~\mathrm{cm^2} \lesssim \sigma_{\chi n} \lesssim 6.3\times 10^{-29}~\mathrm{cm^2}$, and using LZ EFT searches we constrain $9.9\times 10^{-32}~\mathrm{cm^2} \lesssim \sigma_{\chi n} \lesssim 2.5\times 10^{-28}~\mathrm{cm^2}$. Our results show that astrophysical uncertainties, especially the dark matter density profile near the supermassive black hole, set the primary limitation on the sensitivity rather than detector systematics. These findings highlight blazar-boosted dark matter as a promising probe of light dark matter and motivate further astrophysical modeling.

The Legacy Survey of Space and Time (LSST) will provide a ground-breaking data set for cosmology, but to achieve the precision needed, the data, data reduction, and algorithms measuring the cosmological data vectors must be thoroughly validated and calibrated. In this note, we focus on clusters of galaxies and present a set of validation tests for optical cluster finding algorithms through comparison to X-ray and Sunyaev-Zel'dovich effect cluster catalogs. As an example, we apply our pipeline to compare the performance of the redMaPPer (red-sequence Matched filter Probabilistic Percolation) and WaZP (Wavelet Z Photometric) cluster finding algorithms on Dark Energy Survey (DES) data.

Will future direct imaging missions such as NASA's upcoming Habitable Worlds Observatory (HWO) be able to understand Earth-sized planets as a population? In this study, we simulate the ability of space-based coronagraphy missions to uncover trends in planetary albedo as a function of instellation, and potentially constrain the boundaries of the habitable zone. We adapt the Bioverse statistical comparative planetology framework to simulate the scientific output of possible designs for HWO. With this tool, we generate a synthetic planetary population with injected population-level trends in albedo and simulate the observability of planets. We then determine the statistical power to which these trends can be recovered as a function of the strength of the injected trend and the sample size of Earth-sized planets in the habitable zone (exoEarths). The strongest trends in albedo require a sample size of roughly 25-30 exoEarths to recover with high confidence. However, for weaker albedo trends, the required number of planets increases rapidly. If a mission is designed to meet the Decadal Survey's requirement of 25 exoEarths, it would be able to recover very strong trends in albedo associated with the habitable zone, but would struggle to confidently detect weaker trends. We explore multiple strategies to increase one's ability to recover weak trends, such as reducing the uncertainties in observables, incorporating additional observables such as planet colors, and obtaining direct constraints on planetary albedo from full spectral retrievals.

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will provide a windfall of new transients and variable sources. Here we have performed mock observation simulations to understand LSST's expected detection rates for cataclysmic variables (CVs) with known large amplitude variations. Under the thin-disk approximation for the distribution of CVs in our Galaxy, we found that only 20% of WZ Sge-type dwarf novae systems, representing the most energetic disk-driven outbursts in CVs, will be detected during outbursts by the LSST. Given their large amplitude (7-9 mag), {only those} brighter than $17.5$ mag at outburst maximum are expected to have an r-band quiescence counterpart in individual scans. Thanks to the planned cadence of the LSST towards the Galactic center, ~70% of the simulated outbursts will be detected twice or more on the discovery night, and two-thirds will be observed in different bands. CVs of the Polar class, which display luminosity changes up to 4 mag, can be unbiasedly recovered to 22.5 mag with more than 100 detections over 10 years of the LSST operation. Finally, we attempt to characterize the detection rate of micronovae bursts, and find that about 2.6%} of the simulated sample will be observed as a >= 0.4 mag-amplitude and <= 1-d duration spike in the long-term light curve. Overall, our results consolidate LSST's capability to studying time-domain phenomena in CVs, and inform on how to plan and organize follow-up observation strategies on transients discovered by LSST.

While bars are commonly observed in disk galaxies, the precise conditions governing their formation remain incompletely understood. To investigate these conditions, we perform a suite of N-body simulations of bulgeless disk galaxies with stellar masses in the range $10^9 \leq M_d \leq 10^{11} \;M_\odot$. Our galaxy models are constructed based on the observed properties of nearby barred galaxies from the S4G survey, and we systematically vary the halo scale radius to isolate its dynamical influence. Bars in our simulations form via repeated swing amplifications of disk perturbations, sustained by feedback loops. The amplification factor $\Gamma$ depends on both the Toomre stability parameter $Q_T$ and the dimensionless wavelength $X$. Based on our simulation results, we propose a two-parameter bar formation criterion, $Q_T + 0.4(X - 1.4)^2 \leq 1.8$, corresponding to $\Gamma = 10$, which better captures the onset of bar formation than traditional one-parameter conditions. Bars in low-mass galaxies tend to be shorter and weaker, and are more susceptible to disruption by outer spiral arms. In contrast, bars in high-mass galaxies are longer, stronger, and more resilient to spiral interference. Bars in low-mass galaxies undergo only slight vertical thickening over time, whereas those in high-mass galaxies thicken rapidly via buckling instability.

One of the primary mission goals of the Kepler space telescope is to detect Earth-like terrestrial planets in the habitable zone around Sun-like stars. Unfortunately, such planets are at the detection limit. Estimating their statistical significance via false alarm probability (FAP) is crucial for their validation, and has a large impact on the estimate of their occurrence rate, which is of central importance for future spectroscopic missions searching for life signatures. Current methods estimate FAP by light curve inverting or scrambling, but we show that both of these approaches are unsatisfactory. Here we propose to modify the planet transit template by randomly shifting the transit times by small amounts. We show that the exoplanet search with the resulting Null Signal Template (NST) has the same statistical properties as with the true periodic template, which enables assigning a reliable star-specific FAP to every candidate. We show on simulations and on the real data that the method is robust to unmodeled noise contamination. We reevaluate the statistical significance of all 47 previously proposed habitable Earth-like and super Earth Kepler candidates and assign them star-specific NST based FAP. We identify 29 candidates with FAP below 1%, 7 of whom are currently not considered confirmed. Among these are Kepler 452b with radius $1.5 R{\oplus}$, a period of 384 days, and KOI 2194.03 with radius $1.8 R{\oplus}$ and a period of 445 days, both around Sun-like G stars. Several well-known candidates should be considered marginal or likely false alarms, including Kepler 186f with 20% FAP.

We compute the 3D cross-correlation between the absorption of the $z\sim 2.3$ Lyman-alpha forest measured by the COSMOS Lyman-Alpha Mapping And Tomography Observations (CLAMATO) survey, and 1642 foreground galaxies with spectroscopic redshifts from several different surveys, including 3D-HST, CLAMATO, zCOSMOS-Deep, MOSDEF, and VUDS. For each survey, we compare the measured cross-correlation with models incorporating the galaxy linear bias as well as observed redshift dispersion and systematic redshift offset. The derived redshift dispersion and offsets are generally consistent with those expected from, e.g., spectroscopic redshifts measured with UV absorption lines or NIR emission lines observed with specific instruments, but we find hints of `fingers-of-god' caused by overdensities in the field. We combine our foreground galaxy sample, and split them into 3 bins of robustly-estimated stellar mass in order to study the stellar mass-halo mass relationship. For sub-samples with median stellar masses of $\log_{10}(M_* / M_\odot) = [9.23,9.71,10.21]$, we find galaxy biases of $b_g\approx [2.9, 3.3,4.7]$, respectively. A comparison with mock measurements from the Bolshoi-Planck $N$-body simulation yields corresponding halo masses of $\log_{10}(M_* / M_\odot) \approx [10.3,11.6,12.1]$ for these stellar mass bins. At the low mass end, our results suggest enhanced star formation histories in mild tension with predictions from previous angular correlation and abundance matching-based observations, and the IllustrisTNG simulation.

Diffuse $\gamma$-ray emission is a key probe of cosmic rays (CRs) distribution within the Galaxy. However, the discrepancies between observations and theoretical model expectations highlight the need for refined uncertainty estimates. In the literature, spatial and temporal variability of lepton flux has been discussed as an uncertainty in diffuse $\gamma$-ray estimation. In the present work, we demonstrate that variability in the high energy CR hadron flux is an important, yet previously underappreciated, source of uncertainty in diffuse $\gamma$-ray estimates. To assess this effect, we perform fully three-dimensional, time-dependent GALPROP simulations of CR protons injected from discrete Galactic sources. Our results reveal that the uncertainty in the hadronic component of diffuse $\gamma$ rays is non-negligible and can be comparable to, or even exceed, current experimental uncertainties at very high energies. This finding challenges the conventional assumption that only leptonic fluctuations are relevant to diffuse $\gamma$-ray modeling.

The Large High Altitude Air Shower Observatory recently detected TeV emission from the low-luminosity active galactic nucleus (LLAGN) NGC 4278. Integral-field spectroscopy with MEGARA revealed ionized outflows on hundred-parsec scales with kinetic power $\dot E_{\rm shock} \sim 10^{38}$ erg s$^{-1}$, well below the TeV luminosity $L_{\gamma} \gtrsim 10^{41}$ erg s$^{-1}$. The implied efficiencies, $\eta \gtrsim 1000$, are far above unity, showing that shocks cannot account for the TeV emission. Contemporaneous Fermi-Large Area Telescope and Swift data, consistent with a compact synchrotron self-Compton jet component, favor a nuclear origin. NGC 4278 is the first low-ionization nuclear emission-line region (LINER)/LLAGN of its class detected at TeV energies, a benchmark for LINERs with outflows and a prime target for the Cherenkov Telescope Array Observatory. I conclude that the TeV photons arise from a compact nuclear accelerator, while optical outflows trace larger-scale jet--ISM interactions that coexist but do not power the TeV radiation.

Tidal disruption events (TDEs) in active galactic nuclei (AGNs) mark a regime where traditional vacuum models fail to capture the full dynamics, especially due to interaction between stellar debris and pre-existing accretion disks. We perform meshless hydrodynamic simulations incorporating both general relativistic (GR) effects and radiative cooling to study TDEs in AGNs with different orbital inclinations ($\theta_{\rm inc}$) of the disrupted star, ranging from projected prograde to retrograde orbits. We post-process the simulations to derive multi-wavelength light curves and identify several distinct features in the light curves, including a precursor flare from early debris-disk collision and a major flare driven by fallback. The dynamics of the stellar debris and accretion disk, and subsequently the light curve features, are strongly affected by $\theta_{\rm inc}$ and GR effects. Retrograde orbits ($\theta_{\rm inc}=135^\circ$) yield a more luminous, shorter major flare and a more prominent precursor than prograde ones ($\theta_{\rm inc}=22.5^\circ$). During fallback, prograde cases ($\theta_{\rm inc} = 22.5^\circ$, $45^\circ$) develop a central cavity with spirals in the inner region of the AGN disk, leading to transient UV/X-ray suppression accompanied by oscillations, while higher inclinations ($\theta_{\rm inc}=90^\circ$, $135^\circ$) form a gradually tilting inner disk, potentially causing UV/X-ray dips via geometric effects at certain viewing angles. Relativistic apsidal precession alters stream collisions, producing structural differences in the inner disk, outer disk, and debris compared to Newtonian cases, and drives quasi-periodic signals in prograde configurations. These results provide predictive diagnostics for identifying AGN TDEs and interpreting observed light-curve diversity.

This study presents a statistical analysis of optical light curves (LCs) of 200 UVOT-detected GRBs from 2005 to 2018. We have categorised these LCs based on their distinct morphological features, including early flares, bumps, breaks, plateaus, etc. Additionally, to compare features across different wavelengths, we have also included XRT LCs in our sample. The early observation capability of UVOT has allowed us to identify very early flares in 21 GRBs preceding the normal decay or bump, consistent with predictions of external reverse or internal shock. The decay indices of optical LCs following a simple power-law (PL) are shallower than corresponding X-ray LCs, indicative of a spectral break between two wavelengths. Not all LCs with PL decay align with the forward shock model and require additional components such as energy injection or a structured jet. Further, plateaus in the optical LCs are primarily consistent with energy injection from the central engine to the external medium. However, in four cases, plateaus followed by steep decay may have an internal origin. The optical luminosity observed during the plateau is tightly correlated with the break time, indicative of a magnetar as their possible central engine. For LCs with early bumps, the peak position, correlations between the parameters, and observed achromaticity allowed us to constrain their origin as the onset of afterglow, off-axis jet, late re-brightening, etc. In conclusion, the ensemble of observed features is explained through diverse physical mechanisms or emissions observed from different outflow locations and, in turn, diversity among possible progenitors.

Optical transient surveys continue to generate increasingly large datasets, prompting the introduction of machine-learning algorithms to search for quality transient candidates efficiently. Existing machine-learning infrastructure can be leveraged in novel ways to search these datasets for new classes of transients. We present a machine-learning accelerated search pipeline for the Deeper, Wider, Faster (DWF) programme designed to identify high-quality astrophysical transient candidates that contain a single detection. Given the rapid observing cadence of the DWF programme, these single-detection transient candidates have durations on sub-minute timescales. This work marks the first time optical transients have been systematically explored on these timescales, to a depth of m$\sim$23. We report the discovery of two high-quality sub-minute transient candidates from a pilot study of 671,761 light curves and investigate their potential origins with multiwavelength data. We discuss, in detail, possible non-astrophysical false positives, confidently reject electronic artefacts and asteroids, ruling out glints from satellites below 800 km and strongly disfavouring those at higher altitudes. We calculate a rate on the sky of $4.72^{+6.39}_{-3.28}\times10^5$ per day for these sub-minute transient candidates.

While C IV is the most common absorption line in Broad Absorption Line Quasar spectra, Balmer absorption lines are among the rarest. We present analysis of Balmer absorption in a sample of fourteen iron low-ionization BAL quasars (FeLoBALQs); eight are new identifications. We measured velocity offset, width, and apparent optical depth. The partial covering ubiquitous in BAL quasar spectra alters the measured Balmer optical depth ratios; taking that into account, we estimated the true H(n= 2) column density. We found the anticipated correlation between Eddington ratio and outflow speed, but it is weak in this sample because nearly all of the objects have the low outflow speeds characterizing loitering outflow FeLoBAL quasars (H. Choi et al. 2022b), objects that are also found to have low accretion rates (K. M. Leighly et al. 2022; H. Choi et al. 2022a). Measures of dN/dv, the differential column density with respect to the outflow speed, are anticorrelated with the luminosity and Eddington ratio: the strongest absorption is observed at the lowest speeds in the lowest luminosity objects. The absorption line width is correlated with {\alpha}oi, the F{\lambda} point-to-point slope between 5100A and 3 microns. This parameter is strongly correlated with the Eddington ratio among low-redshift quasars (K. M. Leighly et al. 2024). Balmer absorption lines have been recently found in the spectra of Little Red Dots (LRDs), a class of high-redshift objects discovered by JWST. We note suggestive similarities between LRDs and FeLoBAL quasars in the emission line shape, the presence of steep reddening and a scattered blue continuum, the lack of hot dust emission, and X-ray weakness.

We present a comprehensive 3D dust reddening map covering the entire Milky Way, constructed by combining reddening estimates based on LAMOST low-resolution spectra (E(B$-$V)$_{\rm LAMOST}$) with those derived from $Gaia$ XP spectra (E(B$-$V)$_{\rm XP}$), along with revised $Gaia$ distances. E(B$-$V)$_{\rm LAMOST}$ values of $\sim$ 4.6 million unique sources were obtained with the standard-pair analysis using LAMOST DR11 stellar parameters and synthesized $B/V$-band photometry from $Gaia$ XP spectra, showing a typical precision of $\sim$ 0.01 mag. The E(B$-$V)$_{\rm XP}$ from the catalog of \citet{zhang2023}, which was derived using forward modeling of $Gaia$ XP spectra, were cross-validated with E(B$-$V)$_{\rm LAMOST}$, leading to the selection of $\sim$ 150 million high-reliability measurements. The combined dataset achieves a median precision of $\sim$ 0.03 mag for E(B$-$V). To model the reddening -- distance relationship along various lines-of-sight, we implemented a parametric approach that accounts for contributions from the local bubble, diffuse interstellar-medium, and multiple potential molecular clouds. The sky was adaptively partitioned based on stellar density, resulting in angular resolutions ranging from 3.4$^{\prime}$ to 58$^{\prime}$, with about half of the sky having a resolution better than 6.9$^{\prime}$. The reddening precision of our 3D map for individual stars reaches $\sim$ 0.01 mag in most regions at $|b| > 20^\circ$, but degrades to 0.01-0.05 mag at $|b| < 20^\circ$. The map reaches a maximum distance of 3-5 kpc in high-extinction regions with $|b| < 5^\circ$, and extends to 10-15 kpc elsewhere. An interactive platform and Python package have been developed for utilization of the 3D dust map. Available online: this https URL.

The characterization of exoplanet atmospheres is one of the key topics in modern astrophysics. To date, transmission spectroscopy has been the primary method used, but upcoming instruments will lay the foundation for advancing reflected-light spectroscopy. The main challenge in this area of research is the high contrast ratio between the planet and its star. RISTRETTO, a high-resolution integral-field spectrograph designed for ESO's VLT, aims to address these limitations through a combination of extreme AO, coronagraphy, and high-resolution spectroscopy. The goal of this paper is to demonstrate the detectability of the temperate rocky planet Proxima b with RISTRETTO, using realistic end-to-end simulations and a specifically developed data analysis methodology. We created high-resolution star and planet spectra, selecting realistic observational epochs and incorporating the predicted performance of the AO and coronagraphic systems. We implemented noise and spectrograph effects through the Pyechelle spectrograph simulator. We then applied a new methodology to isolate the signal of the planet from the stellar one and proceeded to fit several planetary models in order of increasing complexity. We also introduced a method to determine the sky orientation of the stellar spin axis, which constrains the orientation of the planetary orbit for aligned systems. Assuming an Earth-like atmosphere, our results show that RISTRETTO can detect Proxima b in reflected light in about 55 hours of observing time, offering the ability to characterize the planet orbital inclination, true mass, and broadband albedo. In addition, molecular absorption by O$_2$ and H$_2$O can be detected in about 85 hours of observations. These findings highlight the potential of RISTRETTO to significantly advance the field of exoplanetary science by enabling reflected-light spectroscopy of a sample of nearby exoplanets.

The Fermi Gamma-ray Space Telescope is currently celebrating its 15th anniversary of operation. Since its launch, the Fermi-Large Area Telescope (LAT), the main instrument onboard the Fermi satellite, has remarkably unveiled the sky at GeV energies providing outstanding results in time-domain gamma-ray astrophysics. In particular, LAT has observed some of the most powerful transient phenomena in the Universe (such as gamma-ray bursts, blazar flares, magnetar flares, ...) enabling the possibility to test our current understanding of the laws of physics in extreme conditions. In this paper I will review some of the main recent results with a focus on the transient phenomena seen by LAT with a multi-wavelength and multi-messenger connection.

Understanding the distribution and properties of molecular clouds is crucial for tracing the structure and evolution of the interstellar medium and the large-scale morphology of the Milky Way. Here we present an all-sky catalog of 3,345 molecular clouds identified from our previous three-dimensional dust reddening map using a dendrogram-based clustering method with distance-adaptive parameters. The catalog spans heliocentric distances from 90 pc to 4.3 kpc and includes key physical properties for each cloud, including position, size, mass, surface density, and dust density. Approximately 650 clouds in our catalog are associated with the boundary of the Local Bubble, while around 740 clouds (excluding those associated with the Local Bubble) are located at high Galactic latitudes ($|b| > 20^\circ$). The spatial distribution of the cataloged clouds reveals prominent large-scale features in the Galactic disk, including coherent spur-like structures, large-scale cavities, and a more detailed view of the Local Bubble shell. These findings refine our understanding of how molecular clouds trace the Galactic spiral arm network and provide new insight into the spatial structure of the Local Bubble. The catalog serves as a valuable resource for future studies of star formation, Galactic structure, and the interaction between molecular clouds and large-scale ISM features.

3I/ATLAS is the third interstellar object discovered to date, following 1I/'Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires tracing its past trajectory through the Galaxy and assessing the possible role of stellar encounters, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together with a sample of Gaia DR3 stars with high-quality astrometry and radial velocities, to identify close passages within 2 pc. We identify 93 nominal encounters, 62 of which are significant at the $2\sigma$ level. However, none of these encounters produced any meaningful perturbation. The strongest perturber Gaia DR3 6863591389529611264 at 0.30 pc and with a relative velocity of 35 km s$^{-1}$, imparted only a velocity change of $|\Delta v| \simeq 5\times10^{-4}$ km s$^{-1}$ to the orbit of 3I/ATLAS. Our results indicate that no stellar flybys within the past 10 Myr and 500 pc contained in Gaia DR3 can account for the present trajectory of 3I/ATLAS or be associated with its origin. We further show that 3I/ATLAS is kinematically consistent with a thin-disk population, despite its large peculiar velocity.

JWST has identified some of the Universe's earliest galaxies, repeatedly pushing the frontier to ever higher redshifts and stellar masses. The presence of such extreme galaxies at such early times, with large stellar populations and high star-formation rates, naturally results in a tension between observation and theory. This tension between numerical models and observations can be either due to our underlying cosmological models or due to a gap in our understanding of early Universe astrophysics. In a prelude to this letter, we showed how the Renaissance simulations, which focused on high redshift galaxy formation were able to reconstruct similar stellar masses to the earliest and highest mass galaxies that had been discovered by JWST at the time of its publication (McCaffrey et al.2023). Since then many more galaxies have been discovered by JWST, in particular the "Mirage-or-Miracle" (MoM) survey broke the record recently with the highest redshift galaxy MoM-z14, which has a spectroscopically confirmed redshift of $z \sim 14.44$ followed closely by GS-z14 with a spectroscopically confirmed redshift of $z \sim 14.3$. We investigate in this letter whether these newly discovered galaxies are in conflict with the Renaissance simulations and thus whether they are causing tension with our established models of cosmology and/or high-redshift astrophysics. We discover that MoM-z14's high mass at early redshift can be explained by the Renaissance simulation suite, whereas the extremely high stellar mass of GS-z14 remains an outlier when compared to previous measurements of high-redshift galaxies detected by JWST and our numerical models (even after accounting for cosmic variance).

A number of theories have been put forward to explain the bi-modal stellar rotational distribution observed in young massive clusters. These include stellar mergers and interactions induced in binary systems, and the role of angular momentum transfer between a star and its circumstellar disk in its early evolution. Each theory predicts unique rotation distributions in various locations of the colour-magnitude diagram. Specifically, the stellar merger hypothesis posits that the upper end of the main sequence will host a significant number of slowly rotating merger products, essentially that the blue straggler stars are an extension of the blue main sequence. In the present work, we use observations of three massive ($\sim10^5$~\msun) young ($100-300$~Myr) clusters in the Large Magellanic Cloud using a combination of HST photometry and VLT/MUSE spectroscopy. We show that in all three clusters, these bright blue stars have stellar rotational distributions that differ significantly from that measured on the blue main sequence. We conclude that stellar mergers do not play a significant role in the formation of the split main sequence/bi-modal rotational distribution. As a corollary, we show that blue straggler stars in these YMCs display a wide range of rotational velocities.

Light curves of young stars exhibit photometric variability over hours to decades and across a wide range of amplitudes. On time scales beyond a few rotation periods, these light curves are typically stochastic. The variability arises from a combination of accretion rate changes, line-of-sight extinction variations, and evolving spotted stellar surfaces. We aim to develop a methodology to quantitatively compare the full variability statistics of these inhomogeneously sampled light curves with model calculations. To achieve this, we converted the light curves into variability fingerprints. They map the probability of variation by a given amount over a given timescale. Applying principal component analysis to these fingerprints produces a stable distribution of the first two principal components. We show that this distribution is a continuum without clusters. Adding a model-generated fingerprint to an observational sample does not significantly alter the distribution of the sample, allowing a robust comparison between the model and observed light curves to assess statistical realism. We show that photometric uncertainties, timing, and observing cadence have a minimal impact on model placement within the observational distribution. The main source of variance among highly variable light curves of young stars is the timescale of the onset of significant variability (above 0.3mag), with 1-3month timescales being the most critical. The secondary cause of variance are long-term (above 1.5yr) dimming or rising trends.

We present a detailed analysis of type Iax supernova SN 2022xlp. With a V-band absolute magnitude light curve peaking at $M_{max}(V) = -16.04 \pm 0.25$ mag, this object is regarded as the second determined well-observed Iax supernova in the intermediate luminosity range after SN 2019muj. Our research aims to explore the question of whether the physical properties vary continuously across the entire luminosity range. We also investigate the chemical abundance profiles and the characteristic physical quantities of the ejecta, followed by tests of the predictions of hydro simulations. The pseudo-bolometric light curve was calculated using optical and UV (Swift UVOT ) light curves and fits with a radiation diffusion Arnett model to constrain the average optical opacity, ejected mass, and initial nickel mass produced in the explosion. We analyzed the color evolution of SN 2022xlp and compared it with that of other Iax supernovae with different peak luminosities. We used the spectral tomography method to determine the radial profiles of physical properties and abundances of the ejecta, comparing them with a set of hydrodynamic pure deflagration models. The estimated bolometric flux peaks at $8.87\times 10^{41}$ erg/s and indicates the production of radioactive nickel as $M(^{56}$Ni) = $0.0215 \pm 0.009\,M_{\odot}$. According to the best-fit model, the explosion energy is $(2.066 \pm 0.236) \times 10^{49}$ erg and the ejecta mass is $0.142 \pm 0.015\,M_{\odot}$. The performed spectral tomography analysis shows that the determined physical quantities agree well with the predictions of the deflagration simulations, with modifications regarding the increased Na abundance and the more massive outer layers. SN 2022xlp bridges the previously existing luminosity gap, and supports the assumption of continuous variation in the physical properties across the SN Iax subclass.

Intrinsic alignments of galaxies are measured and modelled to gain cosmological information, to further understand the interactions between galaxies and to mitigate their effects on gravitational weak lensing studies. Hydrodynamical simulations are often used to constrain priors or calibrate models. Therefore, obtaining the maximum amount of information possible from these simulations is imperative. In this work, we have combined the information of shapes projected over two or three axes ($x,y,z$), for intrinsic alignment signals ($w_{g+},\ \tilde{\xi}_{g+,2}$), showing a consistent gain in signal-to-noise ratio (SNR) for all cases studied using TNG300-1. The gain in SNR is found to be higher for the addition of the second projection than for the third, and higher for shapes calculated using the reduced inertia tensor rather than the simple one. The two shape samples studied, $n_\star>300$ and $\mathrm{log}(M_\star \ h/\mathrm{M_\odot})>10.5$, where the latter has a much higher signal amplitude, show similar gains in SNR when more projections are added. We also model the correlation functions with the non-linear alignment model. The SNR gains from the measurements are higher but consistent with the constraints on the non-linear alignment amplitude $A_{\rm IA}$ and galaxy bias $b_{\rm g}$. Using multiple projection axes increases SNR overall, enabling more efficient use of numerically expensive hydrodynamical simulations.

Based on the updated M giant star catalog selected from LAMOST DR9, we iden-tify substructures within the integrals-of-motion space through Friends-of-Friends cluster-ing algorithm. We obtain members belonging to several known substructures: the Sagittarius stream, Galactic Anticenter Substructure (GASS), Gaia-Enceladus-Sausage (GES), Splash, and the high-{\alpha} disk. Furthermore, we also identify two groups which cannot be clearly asso-ciated with previously known substructures. Our findings confirm the existence of metal-rich constituents within the GES, representing newly formed stars that originated from the metal-enriched gas delivered during the GES merger event and subsequently evolved. Additionally, this study further expands the sample of GASS, high-{\alpha} disk, and Splash stars. Analysis of these metal-rich M giant stars as members of the GES, Splash, and high-{\alpha} disk compo-nents supports an evolution scenario for the early Milky Way, as proposed by previous stud-ies. In this scenario, stars initially formed in a high-{\alpha} primordial disk were dynamically heated by the massive accretion event (GES). This process redistributed stellar orbits, creat-ing the Splash population, while the undisturbed portion of the primordial disk persisted as the present-day high-{\alpha} disk component.

In this two-part series, we present a multi-probe mass modelling method for massive galaxy clusters, designed to disentangle the contributions of individual mass components (Dark matter, intra-cluster gas, stellar masses). In this first paper, we focus on recovering the mass constraint datasets required for the modelling approach introduced in the second paper. Specifically, we measure the light distribution, stellar mass, and kinematics of the cluster members, the brightest cluster galaxy (BCG), and the intra-cluster light (ICL) in Abell S1063. To that end, we developed a new method to extract the light profiles of the cluster members, BCG, and ICL, while accounting for contamination from nearby foreground and background galaxies in \textsc{Hubble Space Telescope} (HST) imaging. We obtained light profiles for $289$ cluster members using a dual Pseudo-Isothermal Elliptical (dPIE) model based on the HST F160W filter, while the BCG \& ICL is modelled as a single component using a multi-Gaussian expansion. To estimate stellar masses and velocity dispersions, we rely on multi-band HST photometry and \textsc{VLT/MUSE} integral field spectroscopy, respectively. Stellar masses are derived using three different spectral energy distribution (SED) models. We measure the line-of-sight velocity dispersions of the cluster members at their half-light radii, as determined from their light profiles, while for the BCG \& ICL components, we use elliptical annular apertures. Thanks to these measurements, we will be able to constrain the cluster stellar mass content, which is detailed in the second paper of the series. We publicly release these measurements with intermediary data products.

We investigate how simultaneous mass and radius measurements of massive neutron stars (NSs) can help constrain properties of dark matter (DM) possibly admixed in them. Within a fermionic DM model that interacts only through gravitation, along with a well-constrained nuclear matter equation of state, we show that the simultaneous mass and radius measurement of PSRJ0740+6620 reduces the uncertainty of DM central energy density by more than 50\% compared to the results obtained from using the two observables independently, while other DM parameters remain unconstrained. Additionally, we find that the DM fraction $f_D$ should be smaller than 2\% when constrained by the observed NS maximum mass alone, and it could be even smaller than 0.3\% with the simultaneous measurement of mass and radius, supporting the conclusion that only a small amount of DM exists in DM admixed neutron stars (DANS).

Observations of interstellar comet 3I/ATLAS at 3.8 au show an elongated coma similar to a cometary tail but pointing in the direction of the Sun. This type of anti-tail, not a result of perspective, may not have been previously observed. We explain the anti-tail as an anisotropic extension of the snow line, or survival radius of a sublimating ice grain, in the direction of the Sun. The anisotropy is due to the difference in the sublimation mass flux in the solar and perpendicular directions caused by the change in the illumination angle of the cometary surface. The stronger sublimation mass flux in the solar direction results in ice grains with larger sizes, longer sublimation lifetimes, and a snow line at a larger radial distance with respect to other directions. The observed radial surface brightness profiles as a function of illumination angle are well reproduced by a Haser-type spherical outflow with constant velocity and sublimating ice grains with angularly dependent survival lengths.

In the first paper of this series, we derived mass constraints on the total mass and the baryonic components of the galaxy cluster Abell S1063. The main focus was to recover stellar masses and kinematics for cluster members, the brightest cluster galaxy (BCG) and the intra-cluster light (ICL). In this second paper, we introduce a multi-probe mass modelling approach that incorporates constraints on both the total mass and the individual baryonic components. We obtain comprehensive mass models of Abell S1063, in which the dark matter distribution is disentangled from the baryonic mass at both cluster and galaxy scales. The best-fitting mass model achieves an RMS of $0.50"$ on the multiple image positions. The kinematic profiles of the BCG \& ICL, as well as the X-ray surface brightness of the intra-cluster gas, are accurately reproduced within observational uncertainties. However, a $35~\mathrm{km/s}$ scatter is required for the cluster member line-of-sight dispersions. This method yields the most complex parametric mass model with consistency among almost all available mass constraints. We find a $1\sigma$ agreement between the inferred stellar-to-subhalo mass relation and that predicted by large-scale cosmological simulations. The ICL stellar mass derived from our model is consistent with estimates from stellar population modelling. We present the first multi-probe mass modelling method capable of disentangling the dark matter from the baryonic mass distributions in massive galaxy clusters. Its results, such as the stellar-to-subhalo mass relation or the distribution of each mass component, can be directly compared to hydrodynamical cosmological simulations such as illustrisTNG.

Magnetohydrodynamic (MHD) waves play a key role in heating the solar corona and driving the solar wind. Recent observations have shown the presence of slow magneto-acoustic and Alfvénic waves in polar plumes and inter-plumes. However, a complete understanding of wave dynamics in the polar regions has long been limited by the lack of simultaneous, high-resolution observations. In this study, we utilize high spatial (210 km per pixel) and high cadence (5s) dataset from the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter, acquired on 14 September 2021. Our findings reveal the simultaneous presence of slow magneto-acoustic and Alfvénic waves within the same polar plumes. For slow magneto-acoustic waves, the amplitudes of propagating disturbances are 1.4 to 3.2$\%$ of background intensity, with periodicities of 9 min, and the projected speed of these disturbances ranges between 115 to 125 kms$^{-1}$. The corresponding electron temperature in plumes ranges between 0.58 and 0.69 MK. The damping length of these propagating disturbances for five plumes is $\approx$2.4 to 7.1 Mm. The propagating disturbances are also detected in the fine-scale substructures within the plumes. Alfvénic waves, on the other hand, are detected with average displacement amplitude, periodicity, and velocity amplitudes of 165$\pm$82 km, 93$\pm$39 s, and 12$\pm$7 kms$^{-1}$ respectively. The ranges for displacement amplitude, period, and velocity amplitude are 50-600 km, 50-250 s, and 3-32 kms$^{-1}$ respectively. These results mark the first demonstration of Solar Orbiter/EUI's ability to simultaneously detect both slow magneto-acoustic and Alfvénic wave modes extending up to 20 Mm in polar plumes.

The nature of dark matter remains unknown, motivating the study of fuzzy/wave dark matter (FDM/$\psi$DM) and self-interacting dark matter (SIDM) as alternative frameworks to address small-scale discrepancies in halo profiles inferred from observations. This study presents a non-parametric reconstruction of the mass distribution of the previously-found, dark subhalo in the strong-lensing system JVAS B1938+666. Compared with the standard Navarro-Frenk-White (NFW) profile, both SIDM and $\psi$DM ($m_{\psi}=1.32^{+0.22}_{-0.31}\times 10^{-22} \, \rm eV$) provide significantly better fits to the resulting density profile. Moreover, the SIDM model is favored over $\psi$DM with a Bayes factor of 14.44. The reconstructed density profile features a characteristic kiloparsec-scale core ($r_c \approx 0.5 \, \rm kpc$) with central density $\rho_c \approx 2.5\times 10^{7}\, \rm M_{\odot} \, kpc^{-3} $, exhibiting remarkable consistency with the core-halo mass scaling relations observed in Local Group dwarf spheroidals. These findings offer insights that may help address the core-cusp discrepancy in $\Lambda$CDM substructure predictions.

NGC 5253 is a nearby (D=3.6 Mpc) Blue Compact Dwarf galaxy, notable for its three massive young super star clusters (SSCs) and nitrogen enrichment. Its similarity to extreme star-forming galaxies at high redshift makes it a good local analogue for studying chemical enrichment at high spatial resolution. We characterise the ionised gas and dust in the giant HII region in the proximity of the three SSCs in the centre of NGC 5253 using new Multi-Unit Spectroscopic Explorer Narrow Field Mode adaptive optics-assisted data at unprecedented spatial resolution of 0."15$\sim$2.3 pc. We derive the attenuation for the central SSCs and, for the first time, map the extinction parameter ($R_V$) in an extragalactic object. $R_V$ varies among SSCs, suggesting differences in dust physics. Electron temperature and density diagnostics yield flat temperature distributions $T_\mathrm{e,median}$([NII])$=12000 \pm 1700$ K and $T_\mathrm{e,median}$([SIII])$ = 11000 \pm 600$ K, and a structured $n_e$([SII]) of maximum $1930 \pm 40$ cm$^{-3}$. The direct method gives a flat helium abundance ($10^3y^+ = 81 \pm 4$) and uniform oxygen abundance ($12 + \log(\text{O/H}) = 8.22 \pm 0.05$). N/O shows a factor 2-3 enhancement around the SSCs, mapped here for the first time at such high spatial resolution. The total excess nitrogen mass is $\sim$0.3 $M_\odot$, which we estimate is producible by the observed WN-type Wolf-Rayet (WR) stars. Because there is no direct spatial overlap between the enrichment and WR star positions, the N-rich material appears to have been expelled from the original sites.

In this work, we revisit and evaluate new source terms which contribute to the induced gravitational wave background. We study their respective contributions to the stochastic gravitational wave background by computing their spectral densities in a radiation-dominated universe. These terms appear at third order in cosmological perturbation theory, however, their correlations with primordial gravitational waves are non-trivial and appear at the same order as so-called scalar induced and scalar-tensor induced gravitational waves. We find that these gravitational wave sources suppress the spectral density at the scales we consider. Furthermore, similarly to scalar-tensor source terms at second order, we find that some terms are enhanced when the input primordial power spectrum of scalar fluctuations is not sufficiently peaked. Hence, where possible, we show that under certain limits the integrands of these terms diverge in the UV sector.

We test the validity of the cosmic distance duality relation (CDDR) by combining angular diameter distance and luminosity distance measurements from recent cosmological observations. For the angular diameter distance, we use data from transverse baryon acoustic oscillations and galaxy clusters. On the other hand, the luminosity distance is obtained from Type Ia supernovae in the Pantheon+ sample and from quasar catalogs. To reduce the large dispersion in quasar luminosity distances, we apply a selection criterion based on their deviation from the $\Lambda$CDM model and implement a binning procedure to suppress statistical noise. We reconstruct the CDDR using Gaussian Processes, a non-parametric supervised machine learning method. Our results show no significant deviation from the CDDR within the $2\sigma$ confidence level across the redshift range explored, supporting its validity even at high redshifts.

Stellar magnetic fields are thought to truncate the inner regions of protoplanetary disks around T Tauri stars, creating a magnetospheric cavity near the star. As the disk evolves and disperses, the truncation radius is expected to move outward as the balance between magnetic and viscous forces shifts. Planets migrating inward can become trapped near the inner edge, but as the edge itself moves outward, the evolving disk torques can drive planets to migrate outward as well. We employ N-body simulations to assess the influence of magnetospheric cavity expansion on the dynamical evolution and orbital architectures of compact resonant chains of super-Earths and mini-Neptunes. Our results show that rebound-driven expansion of the disk's inner edge plays a pivotal role in destabilizing resonant chains by spreading planetary systems outward, thereby triggering early dynamical instabilities and giant impacts. Despite this dynamical evolution, key observable properties of close-in planetary systems -- such as the distribution of orbital period ratio, the intra-system similarity in planet sizes (``radius uniformity''), and the bimodal distribution of planet radii known as the ``radius valley'' -- remain largely consistent with those of systems formed without the rebound effect, in which the inner edge of the disk remains fixed. Thus, the primary consequence of the rebound appears to be the early disruption of resonant chains, rather than any significant alteration to the statistical properties of the resulting super-Earth and mini-Neptune populations.

We measure and compare the size of the dusty torus with active galactic nucleus (AGN) luminosity and the size of the broad-line region (BLR), using a sample of 182 AGNs with the best H$\beta$ lag measurements. After correcting for accretion-disk contamination, torus sizes are determined from the time lags of the WISE W1 and W2 band light curves relative to the optical band variability based on the interpolated cross-correlation function (ICCF) analysis and the Multiple and Inhomogeneous Component Analysis (MICA). We find that the torus size from the W1-band (W2-band) tightly correlates with the 5100~Å continuum luminosity with an intrinsic scatter of 0.15-0.16 dex and the best-fit slope of $0.35 \pm 0.03$ ($0.33 \pm 0.03$), which is clearly shallower than the expected 0.5 slope from the sublimation radius-luminosity relation. We find a moderate negative trend that higher Eddington AGNs tend to have smaller torus sizes than expected from the best-fit, suggesting the Eddington ratio plays a role in flattening the torus size-luminosity relation. By comparing the torus size with the H$\beta$ reverberation time lag for a subsample of 67 AGNs, we find that the torus size is a factor of $\sim 10$ and $\sim 14$ larger than the BLR size, respectively for W1 and W2 bands. The torus size based on the W1 (W2) band correlates with the BLR size with the best-fit slope of $1.26 \pm 0.17$ ($1.10 \pm 0.16$), which is comparable but slightly steeper than a linear correlation.

We analyze the morphology of 125 submillimeter galaxies (SMGs) in the PRIMER-COSMOS field using double Sersic modeling on JWST NIRCam images across six bands (F150W, F200W, F277W, F356W, F410M and F444W), with SMGs being classified by bulge Sersic index (n_bulge) and bulge-to-total luminosity ratio (B/T). The Kolmogorov-Smirnov test between the bright (SFR > 175 M_sun yr^{-1}) and the faint group (SFR < 175 M_sun yr^{-1}) reveals no significant statistical differences in morphology across bands. However, we notice that SMGs skew towards higher B/T ratios and lower n_bulge from shorter to longer wavelengths. In F444W, bright SMGs exhibit higher B/T and lower n_bulge, indicating flatter, disturbed bulges, while faint SMGs show lower B/T and higher n_bulge. Notably, SMGs with higher B/T tend to have low Sersic index, challenging the local universe dichotomy of classical bulges (B/T > 0.5, n > 4) versus pseudo-bulges (B/T < 0.35, n < 2). In the F277W band, non-parametric measurements indicate predominantly disk-dominated patterns, with only 24 percent of SMGs demonstrating merger signatures. After the removal of SMGs with disturbed morphology, the bulge classification scheme in F277W shows pseudo-bulges (21 percent) and clump migration bulges (16 percent) from secular evolution, compared to 4 percent merger-built bulges. Surprisingly, 48 percent of SMGs defy the classification scheme, showing high B/T (approximately 0.7) but low Sersic index (n_bulge <= 1). Bars are confirmed in 7 percent of SMGs. This work suggests that secular evolution takes precedence over major mergers, supporting the idea that isolated evolution fueled by filamentary gas inflow plays a non-negligible role in the SMG bulge formation.

The TOI-178 system hosts six planets with five of them locked in a :4:6:9:12 Laplace resonance chain. We perform N-body simulations to investigate the dynamics of test particles in this system. We observe that co-orbital regions around each planet are approximately 30\% wider than predicted by classical theory for planets in the resonance chain, while TOI-178b, which lies outside the chain, shows a 52\% enhancement. The region between TOI-178e and TOI-178f reveals Kirkwood gap-like structures created by mean-motion resonances with TOI-178f (4:3, 5:4, 6:5) and TOI-178g (5:3), where particle clearing occurs on 500-year timescales. An extended integration of the innermost region (0.015-0.025 au) shows periodic inclination oscillations with period 196 years, coincident with TOI-178b's own oscillation period, with maximum amplitude occurring near the 3:2 resonance location. These structures are consistent with the system's resonant architecture and provide a baseline characterization that enables future comparative studies of similar phenomena in other multi-planet systems with resonant configurations.

The observed architecture and modeled evolution of close-in exoplanets provide crucial insights into their formation pathways and survival mechanisms. To investigate these fundamental questions, we employed JADE, a comprehensive numerical code that models the coupled evolution of atmospheres and dynamics over secular timescales, rooted in present-day observations. JADE integrates photoevaporation with migration driven by von Zeipel-Lidov-Kozai (ZLK) cycles from an external perturber, allowing us to explore evolutionary scenarios where dynamical and atmospheric processes influence each other. Here, we specifically considered GJ 436 b, a warm Neptune with an eccentric orbit and polar spin-orbit angle that has survived within the "hot Neptune desert" despite ongoing atmospheric escape. Our extensive exploration included over 500 000 simulations in a framework that combines precomputed grids with Bayesian inference. This allowed us to constrain GJ 436 b's initial conditions and the properties of its putative companion within a ZLK hypothesis. Our results suggest that GJ 436 b formed at ~ 0.3 AU and, despite its current substantial atmospheric erosion, has experienced minimal cumulative mass loss throughout its history, thanks to a late inward migration triggered by a distant companion inducing ZLK oscillations. We find that initial mutual inclinations of 80° - 100° with this companion best reproduce the observed polar orbit. By combining our explored constraints with radial velocity detection limits, we identified the viable parameter space for the hypothetical GJ 436 c. We found that it strongly disfavors stellar and brown dwarf masses, which offers a useful guide for future observational searches. This work demonstrates how coupled modeling can shed light on the interplay shaping close-in exoplanets and explain the survival of volatile-rich worlds near the edges of the desert.

We investigate the evolution of the galaxy stellar mass function (GSMF) and star formation rates (SFRs) across cosmic time in the COLIBRE simulations of galaxy formation. COLIBRE includes a multiphase interstellar medium, radiative cooling rates coupled to a model for the evolution of dust grains, and employs prescriptions for stellar and AGN feedback calibrated to reproduce the $z=0$ observed GSMF and stellar mass - size relation. We present the evolution of the GSMF from simulations at three resolutions: $m_{\rm gas}\approx m_{\rm dm}\sim 10^7$, $10^6$, and $10^5~\mathrm{M_\odot}$, in cosmological volumes of up to $400^3$, $200^3$, and $50^3$ cMpc$^3$, respectively. We demonstrate that COLIBRE is consistent with the observed GSMF over the full redshift range for which there are observations to compare with ($0<z<12$), with maximum systematic deviations of $\approx 0.3$ dex reached at $2<z<4$. We also examine the evolution of the star-forming main sequence, cosmic SFR density, stellar mass density, and galaxy quenched fraction, making predictions for both the fiducial COLIBRE model with thermally-driven AGN feedback and its variant with hybrid (thermal + kinetic jet) AGN feedback, and finding good agreement with observations. Notably, we show that COLIBRE matches the number density of massive quiescent galaxies at high redshifts reported by JWST, while predicting a stellar-to-halo mass relation that evolves little with redshift. We conclude that neither a redshift-dependent star formation efficiency, nor a variable stellar initial mass function, nor a deviation from $\Lambda\mathrm{CDM}$ is necessary to reproduce the high-redshift JWST stellar masses and SFRs.

Gravitational lensing of gravitational waves (GWs) can be leveraged to provide early-warning times of $\mathcal{O}({\rm hours})$ to $\mathcal{O}({\rm days})$ before the merger of Binary Neutron Stars (BNSs) and Neutron Star Black Holes (NSBHs). This in turn could enable electromagnetic (EM) telescopes to capture emissions surrounding the time of the merger. In this work, we assess the practicability of lensing-driven early-warning by analysing optical images of the lensed host galaxy to predict the arrival time of subsequent BNS/NSBH signals following the observation of the first signal. We produce mock lenses with image quality and resolution similar to images taken with the Hubble Space Telescope (HST) and the ground-based Hyper Suprime-Cam (HSC) on the Subaru telescope. We compare the time delay uncertainties between these two cases for typical lensed image configurations and multiplicity. These include doubles and quads, and among quads: the fold, cusp, cross image configurations. We find that time delay uncertainties for doubles are comparable for both HST and HSC mocks. On the other hand, quads tend to provide accurate time-delay predictions (typical relative error $\sim0.1$) with HST. Analysis of a real lens led to a difference in time-delay estimates of $\mathcal{O}(\rm days)$ between the predictions derived from HST and HSC data. Our work therefore strongly advocates the need for high-resolution EM observations of lensed host galaxies to feasibly enable lensing-driven early-warning.

Higher-order shear statistics contain part of the non-Gaussian information of the projected matter field and therefore can provide additional constraints on the cosmological parameters when combined with second-order statistics. We aim to provide the theoretical framework for studying shear four-point correlation functions (4PCF) using fourth-order aperture statistics and develop a numerical integration pipeline to compute them. Finally, we forecast the information content of fourth-order aperture statistics. We begin by giving the relation of the $n$-th order aperture statistics, $\langle M_\mathrm{ap}^n\rangle$, to the shear $n$PCF and to the convergence polyspectra. We then focus on the fourth-order case, where we derive the functional form of their filters and test the behavior of these filters by numerically integrating over the 4PCF of a Gaussian random shear field (GRF). Finally, we perform a Fisher forecast on the constraining power of $\langle M_\mathrm{ap}^4\rangle_\rm{c}$, where we develop a novel method to estimate derivatives from a simulation suite with arbitrarily distributed cosmological sets. By analyzing and mitigating numerical effects within the integration pipeline, we achieve a two-percent-level precision on the fourth-order aperture statistics for a GRF, which remains well below the noise budget of Stage IV surveys. We report a minimal improvement in the constraining power of the aperture statistics when including fourth-order statistics to a $\langle M_\mathrm{ap}^2\rangle + \langle M_\mathrm{ap}^3\rangle$ joint analysis for a DES-Y3-like setup, using non-tomographic equal-scale aperture statistics.

Higher-order lensing statistics contain a wealth of cosmological information that is not captured by second-order statistics. Stage-III lensing surveys have sufficient statistical power to significantly detect cumulant-based statistics up to fourth order. We derive and validate an efficient estimation procedure for the four-point correlation function (4PCF) of polar fields such as weak lensing shear. We then use our approach to measure the shear 4PCF and the fourth-order aperture mass statistics in the DES Y3 survey. We construct an efficient estimator for fourth-order shear statistics which builds on the multipole decomposition of the shear 4PCF. We then validate our estimator on mock ellipticity catalogues obtained from Gaussian random fields and on realistic $N$-body simulations. Finally, we apply our estimator to the DES Y3 data and present a measurement of the fourth-order aperture statistics in a non-tomographic setup. Due to its quadratic scaling, our estimator provides a significant speed-up over hypothetical brute force or tree-based estimation methods of the shear 4PCF. We report a significant detection of the connected part of the fourth-order aperture mass in the DES Y3 data. We find the sampling distribution of the fourth-order aperture mass to be significantly skewed. We make our estimator code available on GitHub as part of the orpheus package.

As the Imaging X-ray Polarimetry Explorer (IXPE) measures increasingly faint sources, the need for precise polarimetry extraction becomes paramount. In addition to previously described neural-net (NN) weights, we introduce here point-spread function weights and particle background weights, which can be critical for faint sources. In some cases these can be augmented by time/phase and energy weights. We provide a publicly available analysis tool to incorporate these new weights, validate our method on simulated data, and test it on archival IXPE observations. Together these weights decrease the area of the polarization uncertainty contour by a factor of two and will be essential for background-limited IXPE observations.

The persistent null results at dark matter (DM) direct detection experiments have pushed the popular weakly interacting massive particle (WIMP) DM to tight corners. Generic WIMP models with direct detection rate below the current upper limits often lead to thermally overproduced relic abundance after freeze-out. To resolve this conundrum, we propose a novel scenario where DM has temperature-dependent couplings with the standard model (SM) bath. A scalar field having a large vacuum expectation value (VEV) at high temperatures generates sizeable DM-SM interactions leading to efficient DM annihilations responsible for generating the desired thermal relic. At lower temperatures, the scalar field VEV settles down to a small value as a result of a first-order phase transition (FOPT), effectively leading to suppressed DM-SM interaction rate at low temperature, consistent with null results at direct detection experiments. Upper bound on thermal DM mass forces the FOPT to occur at scales such that the corresponding gravitational wave signal remains within reach of future experiments like LISA.

A first-order phase transition could occur in the late universe when vacuum energy begins dominating the energy density ($z \lesssim 0.3$) and convert some latent heat into other forms such as invisible radiation. This generic possibility also has concrete motivation in particle physics models which invoke a multitude of vacua to address theoretical puzzles. The naïve constraint on such an event comes from measurements of the Hubble expansion rate, but this can only probe transitions involving $\mathcal{O}(10)\%$ of the dark energy. In this work, we show that significantly tighter constraints appear when accounting for phase transition fluctuations affecting CMB photon propagation anisotropically, akin to the integrated Sachs-Wolfe effect. For instance, if a completed phase transition has $\beta/H_\star\lesssim 25$, current CMB data limits the associated vacuum energy released to less than $1\%$ of the dark energy. A transition to negative vacuum energy (quasi-anti-de Sitter) is allowed only for $\beta/H_\star \gtrsim 300$. For $\beta/H_\star \lesssim 500$, the universe will not crunch for at least $14$ Gyr.

Using magnetic white dwarfs as a case study, we show that the emission of sub-MeV bosons from stellar plasmas can be substantially modified in the presence of a magnetic field. In particular, the magnetic field-induced anisotropy and cyclotron resonance both significantly affect the in-medium dispersion relations of the Standard Model photon. As a result, resonant level crossing between photons and other light bosons occurs under environmental conditions that differ from the resonance criteria in unmagnetized environments. We find that the magnetic field opens additional regions within magnetic white dwarfs where resonance can occur. These findings motivate revisiting astrophysical constraints on light bosons in systems where the cyclotron frequency is comparable to or larger than the plasma frequency.

We perform a comprehensive Bayesian analysis to constrain the neutron star (NS) equation of state (EoS) using a wide range of terrestrial and astrophysical data. The terrestrial inputs include quantities related to symmetric nuclear matter (SNM) and symmetry energy up to two times saturation density ($\rho_0\sim$0.16 fm$^{-3}$), derived from finite nuclei and heavy-ion collisions (HICs). The astrophysical constraints incorporate NS radii and tidal deformabilities from recent NICER observations and GW170817, respectively. We consider five different EoS models: Taylor, $n/3$, Skyrme, RMF, and sound speed(CS), are analyzed by sequentially updating the priors with (i) $\chi$EFT based pure neutron matter, (ii) terrestrial, empirical and earlier astrophysical data, (iii) case (ii) including NICER radii of PSR J0437+4715 and J0614+3329, (iv) all data combined, and (v) excluding empirical nuclear inputs. We also perform Bayesian model comparison which favors the Skyrme model under all combined data (scenario (iv)), yielding tight constraints on symmetry energy parameters: $L_0 = 56 \pm 3$~MeV, $K_{\mathrm{sym}0} = -132 \pm 15$~MeV and also on SNM parameters: $K_0 = 265 \pm 12$~MeV, $Q_0 = -366 \pm 43$~MeV. The mass-radius and mass-tidal deformability posterior distributions are also well constrained. The radius and tidal deformability of a $1.4\,M_\odot$ neutron star are found to be $R_{1.4} = 11.85 \pm 0.11$~km and $\Lambda_{1.4} = 354 \pm 25$, respectively.

The Martian magnetosheath acts as a conduit for mass and energy transfer between the upstream solar wind and its induced magnetosphere. However, our understanding of its global properties remains limited. Using nine years of data from NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we performed a quantitative statistical analysis to explore the spatial distribution of the magnetic fields, solar wind and planetary ions in the magnetosheath. We discovered significant asymmetries in the magnetic field, solar wind protons, and planetary ions between the quasi-perpendicular and quasi-parallel magnetosheaths. The asymmetries in the Martian magnetosheath exhibit both similarities and differences compared to those in the Earth's and Venus' magnetosheaths. These results indicate that the Martian magnetosheath is distinctly shaped by both shock geometry and planetary ions.

Critical collapse is a well-studied subject for a variety of self-gravitating matter. One of the most intensively examined models is that of perfect fluids, which have been used extensively to describe compact objects such as stars, as well as being of cosmological interest. However, neutron stars are believed to possess an elastic crust, thus departing from a perfect fluid body, and critical collapse with elastic materials is an entirely unexplored topic. In this work, we employ a scale-invariant elastic matter model to study self-similar collapse with elasticity. As with perfect fluid models, we show that including elasticity allows for continuous self-similar configurations, which we determine numerically by solving the associated boundary value problem. The set of solutions is discrete and we focus on the fundamental mode, but also present some results for overtones. Similarly to the perfect fluid case, the existence of a sonic point plays a central role. We find that the addition of elasticity, by either increasing the shear index $\mathrm{s}$ or decreasing the Poisson ratio $\nu$, leads to an increase in compressibility and can yield negative radial pressures around the sonic point. Simultaneously, the elastic longitudinal wave speed ceases to be constant, while the two possible transverse wave speeds grow further apart. The departure from the perfect fluid case can be so dramatic as to generate a second sonic point, which does not seem to be regular. This, in turn, imposes bounds on the elasticity parameters of the material. This study represents the first step in the analysis of critical collapse with elastic materials.

The Integrating Miniature Piggyback for Impulsive Solar Hard X-rays (IMPISH) is a piggyback mission originally designed for the second flight of the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS-2) Antarctic balloon. IMPISH will take measurements of collimated, full-Sun X-ray spectra with the goal of detecting sub-second variations (order of tens of milliseconds) of nonthermal X-ray emission during the impulsive phase of large solar flares to probe particle acceleration mechanisms driven by magnetic reconnection. The IMPISH detector system, made up of four identical detectors totaling 64 cm$^2$ effective area, is capable of measuring from ~10 keV to over 200 keV through the use of silicon photomultipliers (SiPMs) and LYSO scintillators. At the stratospheric altitude of GRIPS-2, the effective lower energy limit is ~20-30 keV. The geometry of the LYSO crystal has been optimized to balance the light collection efficiency with the effective area required for stratospheric X-ray measurements. Development of the IMPISH detectors has introduced a path for a low-cost solution to fast solar X-ray measurements across a large energy range utilizing commercially available components. The payload has a 3U form factor and has been designed so that both the electronics and detectors may be easily adaptable for space-based missions.

The problem of minimizing the transfer time between periodic orbits in the Earth-Moon elliptic restricted three-body problem using a multi-mode propulsion system is considered. By employing the true anomaly on the primary orbit as the independent variable and introducing normalized time as an additional state, the need to repeatedly solve Kepler's equation at arbitrary epochs is eliminated. Furthermore, a propellant constraint is imposed on the high-thrust mode to activate the multi-mode capabilities of the system and balance efficiency with maneuverability. The minimum-time optimal control problem is formulated as a three-phase trajectory consisting of a coast along the initial periodic orbit, a controlled transfer, and a coast along the terminal periodic orbit. The three-phase optimal control problem is then solved using an adaptive Gaussian quadrature direct collocation method. Case studies are presented for transfers from an L2 southern halo orbit to a near-rectilinear halo orbit, analyzing the impact of different single- and multi-mode propulsion architectures and varying propellant constraint values. Finally, the methodology developed in this paper provides a systematic framework for generating periodic orbit transfers in three-body systems using single- and multi-mode propulsion systems.

GW230814 was detected by the LIGO Livingston observatory with a signal-to-noise ratio of 42.4 making it the loudest gravitational-wave signal in the GWTC-4.0 catalog. The source is consistent with a binary black hole coalescence similar to those in the previously observed population, with component masses $m_1 = 33.7^{+2.9}_{-2.2}$ $\mathrm{M}_\odot$, $m_2 = 28.2^{+2.2}_{-3.1} M_\odot$, and small effective inspiral spin $\chi_{\mathrm{eff}}= -0.01^{+0.06}_{-0.07}$. The high signal-to-noise ratio enabled us to confidently detect an $\ell = |m| = 4$ mode in the inspiral signal for the first time, and enables a range of tests of consistency between theoretical predictions and the observed waveform. Most of these tests show good agreement with expectations from general relativity. However, a few indicate deviations, particularly in the ringdown part of the signal. We find that deviations comparable to those observed can be obtained from similar simulated signals based on general relativity and detector noise effects. Therefore, the apparent deviations do not provide evidence for a violation of general relativity. The observation of GW230814 demonstrates that while the unprecedented sensitivity of the detectors enable highly significant detections with a single observatory, drawing robust inferences about fundamental physics remains limited without data from a multiple observatory network.

We present the first directed searches for long-transient and continuous gravitational waves from ultralight vector boson clouds around known black holes (BHs). We use LIGO data from the first part of the fourth LIGO-Virgo-KAGRA observing run. The searches target two distinct types of BHs and use two new semicoherent methods: hidden Markov model (HMM) tracking for the remnant BHs of the mergers GW230814_230901 and GW231123_135430 (referred to as GW230814 and GW231123 in this study), and a dedicated method using the Band Sampled Data (BSD) framework for the galactic BH in the Cygnus X-1 binary system. Without finding evidence of a signal from vector bosons in the data, we estimate the mass range that can be constrained. For the HMM searches targeting the remnants from GW231123 and GW230814, we disfavor vector boson masses in the ranges $[0.94, 1.08]$ and $[2.75, 3.28] \times 10^{-13}$ eV, respectively, at 30% confidence, assuming a 1% false alarm probability. Although these searches are only marginally sensitive to signals from merger remnants at relatively large distances, future observations are expected to yield more stringent constraints with high confidence. For the BSD search targeting the BH in Cygnus X-1, we exclude vector boson masses in the range $[0.85, 1.59] \times 10^{-13}$ eV at 95% confidence, assuming an initial BH spin larger than 0.5.

We explore the possibility that the high energy neutrino flux observed by terrestrial telescopes originates from dark matter (DM) annihilation. Specifically, we study a minimal, UV-complete $U(1)$ extension of the Standard Model with a Dirac DM candidate, whose annihilation into neutrinos proceeds exclusively through a $Z^\prime$ boson. By computing the annihilation cross section and comparing with the observed flux, we derive bounds on the model parameters. Additional constraints are obtained within the freeze-in framework, where the observed relic abundance is reproduced, leading to the strongest bounds. Considering cosmic string vibrations as a source of gravitational waves, we further constrain the vacuum expectation value of the $U(1)$ breaking. All results are contrasted with perturbativity limits and existing constraints from low- and high-energy experiments.

Magnetic reconnection is an explosive process that accelerates particles to high energies in Earth's magnetosphere, offering a unique natural laboratory to study this phenomenon. We performed fully kinetic 2D simulations of a reconnection event observed by the Magnetospheric Multiscale mission and compared the resulting ion and electron energy distributions with observations. The simulations capture the overall shape and evolution of non-thermal energy distributions for both species, but generally underestimate the very-high-energy tail of the electron spectrum. Variations in numerical parameters have negligible effects on the resulting spectra, while the initial upstream temperatures instead play a critical role in reproducing the observed distributions. This work presents a novel analysis of particle acceleration in fully kinetic modeling of reconnection directly informed by observed, realistic parameters; highlights the limitations of 2D simulations and underlines the need for more realistic simulations (e.g. employing 3D setups) to capture the observed particle energization more accurately.

The discovery of gravitational waves from a neutron star merger in 2017 (GW170817) and the associated kilonova (AT2017gfo) confirmed these events as key sites for heavy element production through the r-process. Subsequent observations, including late-time spectra with \textit{JWST}, have highlighted the need for accurate modeling of kilonova ejecta. In the photospheric phase, atomic level populations can be estimated under LTE using Boltzmann and Saha relations, but about a week after the merger the ejecta enters the nebular phase where non-LTE effects dominate. Modeling nebular spectra therefore requires a detailed treatment of radiative and collisional processes that affect the population of atomic levels. This work focuses on electron-impact excitation in Sr II, a heavy ion relevant for kilonova spectra. Two computational approaches are employed: the Plane Wave Born approximation within the pseudo-relativistic Hartree-Fock method, and a Distorted Waves method using AUTOSTRUCTURE. The resulting collision strengths are compared against reference R-matrix data to evaluate the accuracy of these approximations and their suitability for large-scale applications to all heavy elements. In addition, radiative parameters for forbidden transitions are computed. These results provide an essential benchmark of approximations that could be used to compute atomic data for nebular-phase kilonova modeling.

We unveil the dynamical equivalence of field theories with non-canonical kinetic terms and canonical theories with a volume element invariant under transverse diffeomorphisms. The proof of the equivalence also reveals a subtle connection between the standard Legendre transformation and the so-called Clairaut equation. Explicit examples of canonizable theories include classes of $k$-essence, non-linear electrodynamics, or $f(R)$ theories. The equivalence can also be extended to the class of mimetic theories.

With the significantly improved sensitivity and a wider frequency band, the next-generation gravitational-wave (GW) detectors are anticipated to detect $\sim 10^5$ GW signals per year with durations from hours to days, leading to inevitable signal overlaps in the data stream. While a direct fitting for all signals is infeasible, extracting only one signal will be biased by its overlap with other signals. From this perspective, understanding how the biases arise from the overlapping and their dependence on the signal parameters is crucial for developing effective algorithms. In this work, we extend the anatomy of biases in single-detector cases to a detector network. Specifically, we focus on the bias dependence on the sky location, polarization and inclination angles, as well as the coalescence time and phase. We propose a new quantity, named the bias integral, as a useful tool, and establish relationship between the biases in a single detector and that in the entire network, with explicit dependence on extrinsic parameters. Using a 3-detector network as an example, we further explore the potential of a network to suppress biases due to the detectors' different locations and orientations. We find that location generally has a smaller effect than orientation, and becomes significant only when the time separation between signals is below sub-seconds. Through a population-level simulation over the extrinsic parameters, we find that nearly half of overlapping signals will lead to larger biases in the network compared to a single detector, highlighting the need to cope with overlapping biases in a detector network.

We re-examine the decoherence rate of primordial fluctuations within minimal inflationary models, using only the gravitational interactions required for the underlying fluctuation-generation mechanism itself. Since gravity provides the weakest interactions the result provides a plausible floor on the rate of primordial decoherence. Previous calculations (arXiv:2211.11046) did so using only a subset of these interactions, motivated by assuming both system and environment were super-Hubble. We extend this by including the effects on super-Hubble modes of {\it all} gravitational interactions at leading order in H/Mp (and so need not restrict the decohering environment to being super-Hubble). We show how the decohering evolution becomes Markovian for super-Hubble modes, without the need to appeal to truncations (like the `rotating wave' approximation) that are often used in optics but can be inapprorpriate for cosmology. We find that the dominant contribution comes from the nonlocal cubic interactions obtained by solving the constraints. We identify UV divergences systematically and verify thereby that the leading part of the purity evolution is UV finite. In the end we find a decoherence rate that grows in the super-Hubble regime significantly {\it faster} than found earlier. We take the preliminary steps to resum this result to late times and briefly discuss why they are more complicated than for earlier calculations.

We propose a novel sparsity enhancement strategy for regression tasks, based on learning a data-adaptive kernel metric, i.e., a shape matrix, through 2-Layered kernel machines. The resulting shape matrix, which defines a Mahalanobis-type deformation of the input space, is then factorized via an eigen-decomposition, allowing us to identify the most informative directions in the space of features. This data-driven approach provides a flexible, interpretable and accurate feature reduction scheme. Numerical experiments on synthetic and applications to real datasets of geomagnetic storms demonstrate that our approach achieves minimal yet highly informative feature sets without losing predictive performance.

A particularly compelling aspect of the GW190521 event detected by the LIGO-Virgo collaboration is that it has an extremely short duration, and lacks a clearly identifiable inspiral phase usually observed in the binary black holes (BBHs) coalescence. In this work, we hypothesize that GW190521 might represent a single, isolated gravitational wave (GW) echo pulse from the wormhole, which is the postmerger remnant of BBHs in another universe and connected to our universe through a throat. The ringdown signal after BBHs merged in another universe can pass through the throat of wormhole and be detected in our universe as a short-duration echo pulse. Our analysis results indicate that our model yields a network signal-to-noise ratio comparable to that of the standard BBHs merger model reported by the LIGO-Virgo collaboration. Though the Bayesian factor slightly prefers the standard BBHs merger model, it is not significant enough to rule out the possibility that the echo-for-wormhole model is a viable hypothesis for the GW190521 event.

The Lunar Gravitational Wave Antenna (LGWA) is a proposed gravitational-wave detector that will observe in the decihertz (dHz) frequency region. In this band, binary white dwarf systems are expected to merge, emitting gravitational waves. Detecting this emission opens new perspectives for understanding the Type Ia supernova progenitors and for investigating dense matter physics. In this work, we present the capabilities of LGWA to detect and localize short-period double white dwarfs in terms of sky locations and distances. The analysis is performed using a realistic spatial distribution of sources, merger rates, and binary-mass distributions derived from current population synthesis models. The simulated population of double white dwarfs is generated using the SeBa stellar-evolution code, coupled with dedicated sampling algorithms. The performance of the LGWA detector, both in terms of signal detectability and parameter estimation, is assessed using standard gravitational-wave data analysis techniques, including Fisher matrix methods, as implemented in the GWFish and Legwork codes. The analysis indicates that LGWA could detect approximately O(30) monochromatic galactic sources and O(10) extragalactic mergers, demonstrating the unique potential of decihertz gravitational-wave detectors to access and characterize extragalactic DWD populations. This will open new avenues for understanding Type Ia supernova progenitors and the physics of DWDs.

We introduce the first oscillation-independent astrophysical method to probe non-standard neutrino interactions (NSI) in core-collapse supernovae. Using a self-consistent treatment of NSI effects in both supernova neutrino emission simulations and flavor independent neutral-current scattering in detectors, we show that anti-correlated coincidence signatures between liquid scintillator experiments such as JUNO and dark matter detectors such as DARWIN/XLZD, ARGO, or RES-NOVA break degeneracy between NSI and flavor conversions effects. For a Galactic supernova within $\lesssim1$ kpc this approach enables independent probes of neutrino-quark NSI couplings in parameter space overlapping and extending beyond existing terrestrial limits. Our results establish a novel oscillation-independent avenue to test fundamental neutrino interactions in extreme astrophysical environments.

We discuss the implications of the most recent DESI Baryon Acoustic Oscillations (BAO) DR2 and DESyr5 compilation of supernovae (SNe) datasets for modified gravity focusing on non-metricity based $f(Q)$ theory, by employing a `model-independent' approach. We reconstruct of dark energy density which is then extended to estimate the perturbation-level quantities, sourced by the modified gravity, namely the effective gravitational coupling, $\mu$, and the amplitude damping parameter of gravitational wave propagation, $\nu$. In light of the remarkable hints for a dynamical dark energy emerging from the analysis of background cosmological data, we discuss the possibility to distinguish between dark energy and modified gravity scenarios from their scalar and tensor perturbation-level signatures. We contrast our findings between the older Pantheon+ and the newer DESyr5 compilations of SNe datasets, which predict a significant distinct signature in the damping parameter of the gravitational wave propagation amplitude. On the other hand, the prediction for the effective gravitational coupling remains insensitive to the choice of the SNe datasets. Our results provide a strong case for the study of gravitational wave propagation in modified gravity theories, in light of the new generation of gravitational wave detectors such as LISA, Einstein Telescope and Cosmic Explorer.