Papers for Wednesday, Apr 08 2026

Bruehl & Villarroel (2025) reported a correlation (p = 0.008, 2.6 sigma) between atmospheric nuclear weapon tests and photographic plate transient detection rates in the Palomar Observatory Sky Survey (POSS-I) archive, independently replicated by Doherty (2026) using negative binomial regression with weather controls. I identify geomagnetic storm activity, measured by the planetary Kp index, as an additional independent variable modulating transient rates in the same dataset. Transient detection rates follow a monotonic dose-response across five Kp intensity bins, from 17.4% during geomagnetically quiet periods to 2.4% at Kp 8-9 (Cochran-Armitage trend: Z = -3.391, p = 0.0007). Nuclear test days are not geomagnetically quieter than the baseline; they are slightly more storm-influenced. A multivariate logistic regression including Kp and lunar-phase controls strengthens the nuclear-transient correlation from 2.6 sigma (p = 0.009, OR = 1.53) to 3.1 sigma (p = 0.002, OR = 1.70). The dose-response rules out emulsion defects and spectrally inert orbital debris as the primary transient source, indicating a population physically coupled to the radiation belt environment at geosynchronous altitude. A self-contained reproduction script is provided as supplementary material.

Bayesian inference in the physical sciences faces a fundamental challenge: the imperative for high-fidelity physical modeling often clashes with the intrinsic limitations of stochastic sampling algorithms. Complex, high-dimensional parameter spaces expose the universal vulnerability of conventional methods, e.g., Markov Chain Monte Carlo (MCMC), which struggle with the prohibitive costs of likelihood evaluations and the risk of entrapment in local optima. To resolve this impasse, we introduce FluxMC (Flow-guided Unbiased eXploration Monte Carlo), a machine learning-enhanced framework designed to shift the inference paradigm from blind local search to globally guided transport. It integrates Flow Matching with Parallel Tempering MCMC, effectively combining the global foresight of generative AI with the rigorous asymptotic convergence and local robustness of temperature-based sampling. We showcase the efficacy of this framework through the lens of space-based gravitational-wave (GW) astronomy -- a field representing the frontier of challenging parameter inversion. In the analysis of massive black hole binaries using high-fidelity waveforms (IMRPhenomHM), FluxMC achieves robust convergence in under five hours, whereas traditional Parallel Tempering MCMC fails to converge even after hundreds of hours, yielding high Jensen-Shannon divergences (JSD) of $O(10^{-1})$. Our method reduces the distributional error by two to three orders of magnitude. Furthermore, for computationally efficient models (IMRPhenomD), it eliminates systematic biases caused by local-optima entrapment. Ultimately, FluxMC removes the necessity to compromise between model accuracy and analysis speed, establishing a new computational foundation where scientific discovery is limited only by observational data quality, not by algorithmic capacity.

Stellar collapse models predict that some stars more massive than $\sim$15$M_\odot$ may collapse directly to a black hole, sometimes with a weak optical transient, a phenomenon known as a failed supernova. Detecting such events is challenging, but searches of vanishing stars have found two promising candidates, N6946-BH1 and M31-2014-DS1. We re-analyze the JWST data of N6946-BH1 to characterize the remnant emission of the object and its surrounding sources. We found four near-infrared stellar neighbors not related to the mid-infrared emission of the candidate. The SED of N6946-BH1 is well modeled by a $\sim$10$^{4.7}L_\odot$ source obscured by a silicate dust shell with a maximum grain size of $\sim$3 $\mu$m and producing negligible emission at $\lesssim$2 $\mu$m. We model the progenitor and remnant emission of four Galactic and seven extragalactic stellar mergers to compare their properties with those of failed supernova candidates. We found that the merger remnants are 10-100 times more luminous than their progenitors at these late phases while the remnants of failed supernovae are $\sim$10 times dimmer than their progenitors. Asymmetric (disky) dust distributions cannot explain the factor of $\sim$100 difference in the ratios of the progenitor and remnant luminosities.

Accretion disks in active galactic nuclei (AGN) are promising sites for mergers of stellar-mass black holes (BHs) detectable via gravitational waves (GWs). These environments facilitate both in-situ formation and dynamical capture of compact objects, and their subsequent mergers. The uncertain origin of GW events detected by LIGO, Virgo and KAGRA motivates searching for accompanying electromagnetic (EM) signatures. Here we investigate post-merger EM flares associated with jets launched from merger remnants, as well as from the shocked ambient gas as the jet breaks out of the disk. We find that jet breakout produces luminous gamma-ray emission, detectable with MeV-band telescopes. Cooling emission from a shocked circum-BH minidisk, winds and background AGN-disk peaks in the UV and optical, with durations ranging from about an hour to a month, and can be identified through year-long monitoring of $\sim10^3$ AGNs with luminosities ranging from $\sim 10^{44}$ to $\sim 10^{45}~{\rm erg~s^{-1}}$. With a single set of parameters, this post-merger jet model produces gamma-ray, hard X-ray and optical flares similar to those claimed to be associated with GW events. Furthermore, by incorporating a transition from a high- to low-angular-momentum accretion state after the merger, the model avoids excessive BH growth, alleviating tensions with hyper-Eddington accretion scenarios.

A majority of the active galactic nuclei (AGN) in the local Universe are classified as low-luminosity AGN (LLAGN), having bolometric luminosities $\lesssim 10^{42} \ \mathrm{erg \ s^{-1}}$. Although high-energy gamma-ray emission is predicted from both the jets and disks of LLAGN, to date only four have been detected by the Fermi Large Area Telescope (Fermi-LAT). In this work, we therefore conduct a comprehensive study of all the LLAGN from the Palomar spectroscopic survey of bright, northern galaxies, including both subthreshold and detected gamma-ray sources, using 14.4 years of LAT data. Our analysis results in a new detection of one LLAGN, as well as a detection of the subthreshold population using a stacking technique. We find that the signal from the subthreshold sample is consistent with being dominated by star-formation activity, although a contribution from compact jets or a mixed contribution from jetted and non-jetted systems is also feasible. On the other hand, the individually detected LLAGN are likely dominated by jet emission. We perform detailed spectral modeling for a subset of these sources and find that the gamma-ray signal can be explained by synchrotron self-Compton radiation, if the inner jet emission region is weakly magnetized with its total energy density being strongly particle dominated, and only slowly moving. With this work we also publicly release our Python-based stacking library for analyzing subthreshold source populations with the LAT, based on a proven technique used in numerous studies.

To measure precise distances beyond the Magellanic Clouds and determine an accurate value of the Hubble constant, eclipsing binary systems composed of early-type stars can play a crucial role. However, it is fundamental to first obtain a reliable empirical surface brightness-color relation (SBCR) for the hottest possible stars. Based on our previous study of six detached eclipsing binaries composed of O- and B-type stars in the Large Magellanic Cloud, we calibrated the SBCR using 12 stars with $V-K_{s} < -0.6$ mag. We found a significant difference between O-type and B-type stars in SBCRs, which are clearly separated in mass. The relation based on B-type stars is consistent with the relation for redder stars from the literature. This allowed us to provide a combined relation valid for stars less massive than $\sim 16\,M_\odot$ in the wide color range $-0.9 < V-K_{s} < 2.1$ mag, with $\sigma = 0.025$ mag. Such a relation can provide extragalactic distances precise to as high as $\sim$1.2% given the sufficient quality and number of target objects. The relation for O-type stars ($\sigma = 0.055$ mag) remains uncertain due to its strong dependence on the method used to determine reddening and requires further study. However, we tested it on the only known eclipsing system in M33, and obtained distance modulus DM=$24.90 \pm 0.17 $ mag, which perfectly agrees with the published distance to the system.

We present a comprehensive analysis of the radial dark-matter (DM) density profiles of cosmic filaments in the hydrodynamical simulation TNG50. The cosmic web is extracted from high-resolution density grids at redshifts $z =$ 0, 0.5, 1, 2 and 3 using the DisPerSE algorithm. We show that the filament spine locations returned directly by DisPerSE do not accurately reflect the true density ridges. To address this issue, we introduce a "shrinking-cylinder" re-centering algorithm, which significantly increases the inferred central densities and restores the inner power-law behavior of the profiles. When the radial coordinate is scaled by the virial radii of the terminal nodes, the filament density profiles exhibit a nearly universal form that depends only weakly on redshift, node mass, and filament length. This result suggests that cosmic filaments, much like dark-matter halos, obey a form of structural self-similarity once an appropriate characteristic scale is introduced. By repeating the measurement using only smoothly distributed, unbound DM particles, we find that the apparent central cusp of the full profile is primarily produced by low-mass halos embedded along the filament spines, while the smooth component develops a flat core within $R/R_{\rm vir}\lesssim0.1$. The redshift evolution of this smooth component further suggests a transition from predominantly smooth filamentary accretion at high redshift to increasingly clumpy accretion at late times. Finally, we show that the universal filament profile is accurately described by a generalized triple-power-law model.

TESS has made clear that most close-in planets were born in chains of mean-motion resonances that break on a characteristic timescale of 100 Myr. This observation is surprising because the same dissipative forces that capture planets into resonance render their orbits long-term stable. We explore a two-stage disruption scenario for resonant chains of super-Earths. First, the chains have their (free) eccentricities excited by some mechanism. We show that any such mechanism that seeds eccentricities of a few percent sets in motion a second stage of dynamical instability on a ~100 Myr timescale. A possible stage-one mechanism is the accretion of a handful of Mercury-sized bodies totaling a few percent of the planetary system mass, which excites the requisite eccentricities and triggers a stage two that reproduces the observed decline in the incidence of resonance. Impacts from such bodies can also explain why some young systems have period ratios narrow of commensurability. We sketch how these impactors may have grown out of debris left over from an earlier epoch of planet formation. We also identify two new trends in the observational data: a decline in multiplicity on the same timescale as the decline in the incidence of resonance, and an increase in the occupation of resonances with multiplicity.

(Abridged) We contribute to our understanding of the evolution of young intermediate-mass stars by providing a comprehensive analysis of their lithium (Li) content. A sample of 71 intermediate-mass T Tauri (IMTT) and Herbig stars within the mass range 1.5 -- 3.5 M$_{\odot}$ was carefully selected for the analysis. Metallicities, rotational velocities, and accretion rates were obtained from spectra. The curves of growth for stars hotter than 8000 K were built to infer the Li abundances, which were interpreted considering standard models of stellar interiors and non-standard processes affecting Li depletion. Li is generally less strongly depleted in intermediate-mass stars than in their lower-mass counterparts, as expected from standard evolution models. However, Li abundances significantly below the cosmic value are observed in 25 -- 30$\%$ of intermediate-mass stars. It is also unexpected that the results show no significant difference between the 1.5 --2.5 M$_{\odot}$ and 2.5 -- 3.5 M$_{\odot}$ subsamples. Evidence is provided showing that disk-locking works in young intermediate-mass stars. This constitutes independent support for the hypothesis that magnetospheric accretion scenario operates in these sources. We found that disk-locking is effective for a timescale that is about twice shorter than for lower-mass stars, before magnetospheres reduce their sizes during the transition from the IMTT to the Herbig regime. This contraction of the magnetosphere can explain the increase in rotation by a factor of about 3 and in accretion by a factor of about 4 that is observed during this transition. We propose a complex scenario linking rotation, accretion, and the surface Li abundance. Finally, we tentatively suggest that the known relation between the presence of planets and Li depletion might also be present in intermediate-mass main sequence (MS) stars and might originate in the pre-MS.

Gravitational wave (GW) and short Gamma Ray Burst (sGRB) observations provide us with complementary views of compact object mergers. The paucity of binary neutron star merger (BNS) detections in the latest LIGO/Virgo/KAGRA (LVK) observing run raises the question of whether the GW merger rates are sufficient to explain the observed sGRB rate with compact object mergers alone. We investigate this connection using the latest merger rate constraints from the fourth LVK observing run (O4) and published estimates of the local sGRB rate density. For an observed sGRB rate density of $ \sim 1-7~\mathrm{Gpc^{-3}\,yr^{-1}}$, if $>55\%$ of BNS mergers can successfully launch a jet, we find that the current LVK BNS merger rate can be reconciled with a sGRB merger population containing a significant fraction of relatively wide jets with core half-opening angles $\theta_j \geq 10^\circ$. Meanwhile, a narrow jet population ($\theta_j \sim 6^\circ$) can only be matched with the O4 neutron star merger rate estimates for an observed sGRB rate density of $\lesssim 1~\mathrm{Gpc^{-3}\,yr^{-1}}$, which is broadly consistent with several of the latest available estimates. We also find that neutron star-black hole mergers (NSBH) are expected to be a subdominant component of the sGRB population compared to BNS mergers, and they cannot help reconcile some of the highest available sGRB rate ($ >7~\mathrm{Gpc^{-3}\,yr^{-1}}$) with the GW rate estimates. However, they can still substantially contribute to the sGRB population, comprising $\sim 6-16\%$ of it for an observed sGRB rate density of $\sim 1-3~\mathrm{Gpc^{-3}\,yr^{-1}}$. Overall, our results indicate that present GW and sGRB observations remain broadly consistent with BNS mergers as the main progenitors of sGRBs.

With its expanded wavelength coverage and increased precision compared to previous space-based observatories, JWST provides the opportunity to revisit benchmark planets and view them in a new light. Here, we conduct an in-depth study of the atmosphere of the hot-Saturn WASP-96b combining a new JWST NIRSpec/G395H transit with archival NIRISS/SOSS and VLT/FORS2 transmission spectra. The combined spectrum shows clearly-visible features from H2O, CO2, and Na. CO, though, remains unconstrained, precluding a firm metallicity derivation from free retrievals alone. However, self-consistent grids yield a broadly super-stellar atmospheric metallicity of 2-6x stellar. When combined with a roughly stellar C/O ratio ($0.41^{+0.10}_{-0.09}$ from self-consistent grids), we find that WASP-96b potentially formed via core-accretion beyond the H2O snowline and subsequently accreted volatile-rich material. Free retrievals also find a moderate preference (ln B=2.69) for models with SO2 versus without. WASP-96b falls directly on the proposed "SO2 shoreline" and the retrieved SO2 abundance is well-matched to predictions from photochemical models. Our combined spectrum displays an optical slope, which our models fit with opacity from scattering aerosols -- either small-particle condensate clouds or photochemical hazes -- though we cannot completely rule out the broad wings of Na or the effects of stellar contamination. Future observations are necessary to disentangle these effects. Finally, we explore the possibility for limb asymmetry in WASP-96b's transmission spectrum and provide several tests to identify asymmetries in our data. We encourage the community to prioritize the development of a robust pathway to quantify the presence of limb asymmetry -- particularly for low signal-to-noise cases.

The Crab pulsar (PSR B0531+21) provides an unusually rich test bed for statistical studies of high-energy photon-counting data, owing to its extreme brightness and the contrasting behavior of its main pulse (MP) and interpulse (IP) components. Using 78.8 ks of Neutron star Interior Composition Explorer (NICER; Gendreau and Arzoumanian 2017) data-over two million individual X-ray pulses- we construct the single-pulse photon-count distributions of the MP and IP at keV energies. We find that the IP is well described by the Skellam distribution expected for the difference of two Poisson processes, providing a rare, high-statistics empirical demonstration of Skellam behavior in an astrophysical photon-counting context. The MP also shows pulse-by-pulse variability best described by a Skellam framework when compared to Gaussian alternatives, but exhibits a significant excess variance driven by high-count events. When photon counts are summed over successive pulses, this excess averages out and the MP distribution becomes consistent with Skellam expectations, indicating that the enhanced variability does not persist across rotations. We further search for short-lag (memory) correlations between successive X-ray pulses and find no statistically significant lag-1 correlation. Although giant radio pulses occur in the MP phase window, their contribution is insufficient to account for the observed excess variability. Together, these results highlight a clear statistical distinction between the MP and IP and underscore the importance of using statistically appropriate models for high-energy photon-counting analyses. The distributional fits and memory limits reported here provide quantitative constraints on pulsar emission models and illustrate the broader utility of Skellam-based approaches.

The first multimessenger discovery of a binary neutron star (BNS) merger, GW170817, proved that such mergers can source short gamma-ray bursts (SGRBs) and produce \rprocess elements. The initial merger rate from this single event in the first two observing runs of the LIGO-Virgo observatory network, $110$--$3840\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$, was found to be broadly consistent with the SGRB rate, the Milky Way (MW) r-process mass, and the Galactic population of double neutron star (DNS) systems that will merge in a Hubble time. However, only one additional BNS merger has been detected since, and the BNS merger rate has been consistently revised downwards with the past few gravitational wave (GW) catalog updates. Analyzing GW data from the latest catalog GWTC-4, we find a total BNS merger rate of $28$--$300\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$ (consistent with the most recently published values from LIGO-Virgo-KAGRA) consisting of $53^{+176}_{-49}\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$ in GW170817-like $\sim(1.3,1.3)\,M_\odot$ BNSs (90\% credibility). In light of this updated GW rate, we revisit the consistency of the BNS merger rate with SGRBs, r-process and Galactic DNSs. In all cases, there is an emerging tension with the BNS (and EM-bright neutron star--black hole, NSBH) merger rate. Comparing to a BNS merger rate of $100\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$, the cosmological SGRB rate is a factor of 3.6--18 higher, the r-process rate is a factor of 0.9--4.1 higher, and the rate inferred from Galactic DNSs is a factor of 2.3--5.1 higher than the BNS rate. We discuss how various uncertainties in the inferred rates either alleviate or exacerbate this tension, which point to the various physical processes that can be constrained by such rate comparisons.

The classical Penrose process and the collisional Penrose processes involve particles decaying or interacting very close to a spinning black hole, in which some particles acquire negative energy and fall into the black hole while others acquire that energy and can leave the system. Both processes involve an extreme form of frame dragging, i.e. the spinning black hole drags spacetime with it, and the spacetime ejects some of the particles with a large energy gain, similar to a projectile in a slingshot. Such extreme forms of frame dragging had long been believed to be unobservable as the efficiency for a black hole energizing particles in this way is very low. Here we report a new observational signature of this extreme sort of frame dragging. In rapidly spinning black holes in X-ray binaries, processes similar to collisional Penrose processes, but slightly less extreme, can give rise to a new spectral component with distinct spectral and polarimetric properties. Observations of this new spectral component with current or future broadband X-ray polarimeters will open a new window into testing Einstein's theory of gravity close to the edge of a black hole and can be used to measure the black hole spin.

The dispersion measures (DMs) of fast radio bursts (FRBs) encode the total ionized-gas column densities along their sightlines. Most observed FRBs originate at distances where the cosmological principle applies. Thus, variations in the DM distribution of FRBs observed in different regions on the sky trace local sources of anisotropy, such as the warm ionized medium and circum-galactic medium of the Milky Way, and local large-scale structure. We present a map of extragalactic DM variations across the Northern sky using a few thousand FRBs from the second \chime{} catalog. We detect a $\gtrsim 4\sigma$ excess of $\sim$150 pc cm$^{-3}$ above the global mean, extended over $\sim$30$^\circ$ scales and centered near $\alpha \approx$ $12^{\rm h}$, $\delta \approx$ $55^\circ$. This excess, termed Wall 1, is robust to variations in sample selection and jackknife resampling, and cannot be explained by Galactic-disk DM-model uncertainties. The excess is likely too large to correspond to anisotropy in the Milky Way halo. The signal spatially coincides with the Ursa Major supercluster and associated large-scale structures. A secondary, more tentative Wall 2 near $\alpha \approx 2^{\rm h}$, $\delta \approx$ $45^\circ$ is spatially coincident with the Perseus-Pisces supercluster. Although the spatial coincidences suggest that the Walls may correspond to baryons in the local large-scale structure, the probability of chance coincidence is likely too high ($\sim10-20\%$) to claim confident associations. These results highlight the potential of using FRB DMs to detect baryon overdensities associated with local large-scale structure, and have important implications for near-field baryon mapping and FRB cosmology.

I show that early-time (pre-recombination) solutions to the Hubble tension are generically expected to increase the preferred baryon density $\omega_b$. This puts these models in tension with Big Bang Nucleosynthesis (BBN), as measurements of primordial deuterium constrain $\omega_b$ at percent level. I show that existing analyses are in tension with the BBN determination of $\omega_b$, and that including a likelihood component for primordial deuterium deters two representative models from recovering a high $H_0$, and leads to worse fits to CMB, BAO, supernova, and BBN data than $\Lambda$CDM.

We present a uniform atmospheric retrieval analysis of 22 late-T and Y-type brown dwarfs within 20 pc, observed with the James Webb Space Telescope NIRSpec PRISM and MIRI LRS. This dataset provides the first continuous 0.95-12 um spectroscopic coverage of late-T and Y-type brown dwarfs, which in turn enables precise constraints on their thermal structures and volume mixing ratios (VMRs) of H2O, CH4, CO, CO2, NH3, H2S, K, Na, and PH3. We find positive correlations between the VMR of H2O and CH4, and CO and CO2, consistent with thermochemical equilibrium chemistry. Using the VMRs, we derive atmospheric metallicity, which is positively correlated with H2O and CH4, showing H2O and CH4 trace oxygen and carbon content, respectively, allowing us to effectively measure (O/H)bulk and (C/H)bulk. We also report tentative PH3 detections in roughly half the sample, suggesting potential vertical mixing or non-equilibrium chemistry. Apart from chemical properties, we retrieve masses and radii spanning approximately 6-77 M_Jup and 0.66-1.53 R_Jup, respectively. We compare the derived log10(g) values of about 4-5.5 cm s^-2 and Teff values of about 350-1100 K with Sonora Bobcat evolutionary models and find an age range of 0.4 to 10 Gyr across the sample. Comparing our retrieved thermal profiles with the Elf-Owl forward-model thermal profiles, we find a systematic difference between the two, likely arising from differences in chemistry treatment.

(Sub)millimeter dust polarization in protoplanetary disks has revealed the presence of large (~ 100 um) dust grains that are aligned along their long axis following the azimuthal direction of the disk. The novel Badminton Birdie-like Aerodynamic Alignment predicts large grains to align with their long axes following the direction of gas flow experienced by the dust, denoted as the A-field. With 3D streaming instability (SI) simulations, we find that the A-field is predominantly in the radial direction in regions of low dust-to-gas ratio, but in the azimuthal direction in regions of high dust-to-gas ratio. Through polarized radiation transfer, we find that the resulting polarization angle indeed follows the disk azimuthal direction in the high dust density regions. Therefore, the azimuthal dust polarization pattern, as observed in an increasing number of disks, especially at relatively long millimeter wavelengths, offers evidence of ongoing SI in protoplanetary disks.

On 2025 August 18, the LIGO-Virgo-KAGRA collaboration reported S250818k, a sub-threshold gravitational-wave (GW) candidate consistent with a binary neutron star (NS) merger potentially involving a sub-solar-mass NS. Optical follow-up by the Zwicky Transient Facility identified AT2025ulz, a transient temporally coincident with the GW trigger that initially resembled a kilonova but was later classified as a young stripped-envelope Type IIb supernova (SN), dubbed SN 2025ulz. A key question is whether SN 2025ulz harbors fast, possibly collimated, non-thermal ejecta indicative of a central engine, as invoked in "superkilonova" scenarios linking sub-solar-mass NSs to accretion-disk fragmentation or core fission. We present early-to-late-time multi-band radio observations of SN 2025ulz obtained with the Karl G. Jansky Very Large Array as part of the JAGWAR program, complemented by observations with the upgraded Giant Metrewave Radio Telescope and MeerKAT. We detect a faint but significant radio counterpart to SN 2025ulz at 6-10 GHz. The data are consistent with non-thermal emission from SN ejecta interacting with circumstellar material, favoring a compact progenitor and relatively fast ejecta akin to those of Type cIIb SNe. Our data are also consistent with emission from an off-axis jet peaking at about 50-100 days after the GW trigger. Overall, our radio detection is compatible with a superkilonova scenario and would motivate future systematic multi-wavelength follow-up of core-collapse events coincident with sub-solar NS GW candidates, should the association between S250818k and SN 2025ulz be supported by offline GW analyses.

Isolated star-forming galaxies require inflows of fresh gas from the surrounding medium to sustain episodes of star formation over time. However, there are very few direct detections of accretion onto external galaxies. Studies in absorption can only observe along limited sightlines, while those in emission can have difficulty distinguishing inflowing gas in the foreground of the galactic disk from similarly Doppler-shifted outflowing gas in the background. We explore the possibility of using the Balmer decrement (H$\alpha$/H$\beta$) in low-inclination systems as a diagnostic for disentangling the flow geometry in disk-like galaxies. We leverage mock spatial-spectral observations of an isolated Milky Way-mass galaxy simulated using the radiation-hydrodynamics code AREPO-RT and post-processed with the Monte Carlo radiative transfer code COLT. We find that gas components located in front of the disk exhibit systematically lower Balmer decrements than gas embedded in or behind the disk, with a mean front-back offset of $\Delta(\text{H}\alpha/\text{H}\beta) \approx -0.14$. The ability to differentiate between the disk and far-side components is limited by the extremely clumpy, multiphase dust distribution along the line of sight introducing substantial scatter. Overall, the results provide a useful observational diagnostic of inflow and outflow in dusty face-on galaxies.

SN2023ixf, a Type II supernova (SN) showing early signs of interaction with circumstellar material (CSM), has been observed with unprecedented detail across the electromagnetic spectrum since shock breakout. Here, we present nonlocal thermodynamic equilibrium time-dependent radiative-transfer calculations of its photospheric-phase evolution (i.e., ~20 to ~120d), and for the first time encompassing from the ultraviolet (UV) to the infrared (IR). The explosion of a 15Msun progenitor star, evolved with enhanced mass loss during the red-supergiant phase, yielding an ejecta of 7-8Msun, a kinetic energy of 1.2x10^51 erg, and a 56Ni mass of 0.05Msun, yields a satisfactory match to the photospheric-phase duration and brightness. Prolonged interaction with a decreasing CSM density is required to match a number of salient features of SN2023ixf during the photospheric phase, including the persistent UV continuum and line fluxes, the optical brightness and line profiles (in particular Halpha), as well as the IR flux (interaction boosts the free-free emission at long wavelengths). The presence of a cold dense shell (CDS), which is hard to infer at early times when the CDS and photosphere lie at similar velocities, becomes evident at later times and more so in the IR - we find no evidence for material faster than the CDS at ~8000km/s. Exploratory two-dimensional radiative-transfer calculations based on axially symmetric CSM or ejecta suggest that asymmetry can produce a diversity of profile shapes, with absorption troughs exhibiting a flat bottom or notches at any Doppler velocity. We emphasize the complexity of UV spectra influenced by complex metal-line blanketing at these phases. We document the sensitivity of model results to the adopted clumping in the CDS, though the largest offset is obtained here in the unlikely case of a smooth CDS.

Characterizing the atmospheric compositions of exoplanets, along with determining properties such as their mass, mean density, and orbital configuration, is thought to be an effective means for differentiating between various formation and evolution scenarios. Exoplanet atmospheric C/O ratios, when compared to host star C/O ratios, have been advanced as discriminators of gas giant formation and evolution scenarios in the context of the core accretion mechanism. Gas giants formed by gas disk gravitational instability (GDGI), on the other hand, are thought to have atmospheres with C/O ratios identical to their host stars. We examine this assumption through analysis of fully three dimensional radiative hydrodynamics models of the GDGI in the flux-limited diffusion approximation. We show here that GDGI protoplanets may be able to form and accrete disk gas with super-stellar C/O ratios, as a result of their formation and orbital evolution in a disk with midplane temperatures in the range of the evaporation temperatures of water ($\sim$ 135 K) and CO$_2$ ($\sim$ 47 K) ices. Solids that avoid fragmentation and grow rapidly to cm-size could be transported inward to the central protostar or outward to the edge of the disk considerably faster than the disk gas is dissipated, leading to the preferential accretion of C-rich disk gas compared to the O-rich ices, provided that the protoplanet's orbit remains outside $\sim$ 7 au from a solar-mass protostar. Orbits inside $\sim$ 7 au, however, could result in the accretion of disk gas with nearly stellar C/O.

We derive and showcase a novel approach to approximating Fourier transforms in higher dimensions, focusing specifically on the case of 2D radially concentrated ('ring-like') functions. We first reduce the problem to that of evaluating the Hankel transforms of each angular mode of the image and then use our focal expansion to approximate these remaining Hankel transforms. Our method provides a single approximation that remains accurate from small to large spatial frequencies, bridging regimes where moment-based or large-frequency asymptotic expansions are individually reliable. We explore a series of examples, showing that the leading focal term provides an accurate global approximation for a broad range of functions. We demonstrate the utility of this approximation by examining the interferometric response for toy models of a black hole's "photon ring," highlighting the application to experiments designed to measure this feature such as the Black Hole Explorer.

We constrain local primordial non-Gaussianity by a combined analysis of auto and cross-correlations of DESI DR1 tracers, leveraging LRGs and QSOs as well as ELGs between $0.8<z<3.1$. By cross-validating the signal across different clustering tracers within the same redshift range, we evaluate potential systematics in the $f^\mathrm{loc}_\mathrm{NL}$ measurements, capitalizing on the reduced susceptibility of cross-correlations to non-common systematics. We find that the cross-correlation between LRG and quasars can robustly improve the DESI DR1 $f^\mathrm{loc}_\mathrm{NL}$ constraints, by $\sim9\%$ to a measurement of $f^\mathrm{loc}_\mathrm{NL}=2.1_{-8.3}^{+8.8}$ at 68\% confidence. On the other hand, we do not find a clear improvement when including the DESI DR1 ELG sample. Mock tests predict an additional $\sim8\%$ gain with statistical scatter, and the lack of improvement in the data remains consistent with this expectation. This project serves as an exploratory analysis of DESI ELG clustering for $f^\mathrm{loc}_\mathrm{NL}$ through its cross-correlation in preparation for future DESI data analyses.

We present the first stellar elemental abundance study for two very low-mass stars, similar in mass to TRAPPIST-1, in the $\sim5-10$\,Myr-old Upper-Sco association. Their mid-infrared JWST/MIRI spectra, like those of many very low-mass stars, are hydrocarbon-rich, indicating C/O ratios greater than unity in the inner disk gas inside their snowlines. By fitting synthetic spectra to high-resolution APOGEE near-infrared stellar spectra, we show that, unlike their inner disks, both stars have solar C/O ratios. Their Fe, C, O, Mg, and Ca abundances are likewise consistent with solar values, placing them within the Galactic thin-disk population, as expected for nearby star-forming regions. This contrast between stellar and inner disk C/O ratios provides the first direct evidence that the inner disk's supersolar values are not inherited from the natal cloud but arise from disk processes. If these enhanced C/O ratios are primarily driven by inward drift of icy pebbles, there are major implications for disk evolution and planet formation, which we also discuss.

While no conclusive detections of exomoons have been reported to date, planet formation theories predict that satellites should be a common outcome of the collisional dynamics in early extrasolar systems. Such satellites have the potential to unlock new avenues to learn about exoplanet systems, speaking to topics of habitability, tidal heating, planet formation, late-stage growth, planetary compositions, and more. Here we describe the results of our JWST program to search for Luna-analog exomoons around the rocky, habitable-zone M-dwarf planets TOI 700 d and e. We refine the ephemerides of both worlds, providing an order-of-magnitude improvement in period precision and a factor of 2-3 improvement in planetary radii. We identify a strong correlated noise signal with a timescale of $16\pm4$ minutes and an amplitude of $46\pm4$ ppm; similar signals have been observed in previous JWST analyses of other stars and have been ascribed to stellar granulation. This noise source inflates our error by a factor of 4 relative to photon-noise expectations in 10-minute bins and limits our sensitivity to moons: we determine that our observations are sensitive mainly to moons larger than Ganymede on periods longer than 2 days (i.e., moons larger than our solar system's natural satellites). If this noise could be corrected, we would be sensitive to Luna-analog moons. Future work to address this noise source will thus be critical for detecting exomoons in stellar transits, as well as for all other science cases that hope to take advantage of JWST white-light curves in the photon-noise limit.

We explore the lowest mass limit that can be placed on the halo mass function in CDM using 28 strong gravitational lenses. For this purpose, we study an extreme model in which the halo mass function and mass-concentration relation follow CDM, with a sharp cutoff at some mass scale, $m_{\rm{low}}$. Lensing provides a unique window into this quantity as it does not depend on the presence of baryons in dark matter halos and also allows the detection of low mass halos at cosmological distances, both in the lens galaxies and along the line-of-sight. Our model incorporates the effects of tidal stripping of subhalos, leading to the presence of many subhalos below a given model cutoff scale. We place an upper limit on the low-mass cutoff of the halo mass function of $m_{\rm{low}}<10^{8.3}$ M$_\odot$ at 10:1 odds using a prior for the normalization of the subhalo mass function from the semi-analytic model {\tt galacticus} and $m_{\rm{low}}<10^{8.2}$ M$_\odot$ at 10:1 odds using a prior from $N$-body simulations. These limits are comparable to, or stronger than, existing constraints based on Milky Way satellite galaxies. Based on these results, we forecast more than an order of magnitude improvement with a sample of 200 quadruply imaged quasar lenses. This number represents a small subset of the thousands that are anticipated to be discovered by Rubin, Euclid, and Roman. Furthermore, with this larger sample of lenses we expect to directly constrain the normalization of the subhalo mass function, thereby eliminating a major source of uncertainty in our current measurements.

We consider the generic injection of radiation (both dark and electromagnetic) during the epoch between big bang nucleosynthesis (BBN) and recombination. The contribution of the additional radiation to the number of effective neutrinos may be quite small in this scenario, since dark radiation and electromagnetic radiation provide contributions of opposite sign. However, the injection of electromagnetic radiation dilutes the baryon-to-entropy ratio, which is measured both at BBN and at recombination. As a result, this scenario is expected to be tightly constrained. Indeed, performing a numerical study, we find that the allowed amount of extra radiation may be no more than $\sim 25\%$ greater than in the case where it is assumed to be entirely dark radiation.

Cepheids are key distance indicators and benchmarks for stellar evolution, yet most of them are members of binary or multiple systems. While spectroscopic surveys and Gaia proper-motion anomalies reveal a high binary fraction, the population of resolved companions remains poorly characterised. We aim to search for and characterise visual companions to bright Galactic Cepheids using high-contrast imaging and to derive quantitative limits on undetected companions to constrain the architecture of Cepheid multiple systems. We observed 47 Cepheids with SPHERE using the ZIMPOL instrument in classical imaging mode and the V, R, and I filters. The data were obtained in pupil-stabilised mode and analysed using PCA-based imaging technique. For detected companions, we injected negative fake companions in a Monte Carlo approach to measure the relative astrometry. For non-detections, synthetic companions were injected to compute 5sigma contrast curves as a function of separation. We detected companions with a signal-to-noise ratio of > 5 for 8 Cepheids, corresponding to about 17% of the sample. Our SPHERE imaging confirms previously known visual companions with improved astrometry and reveals new wide components for AP Pup, T Vel, and TX Del) at projected separations of 0.16-0.9". For the remaining Cepheids, we derived typical maximum contrasts of 10, 11, and 12mag at 0.25", 0.5", and > 1, respectively. For a sub-set of targets, these limits ruled out main sequence companions more massive than late-K dwarfs beyond 0.5". Our SPHERE survey provides the first homogeneous set of high-contrast optical constraints on wide companions of Galactic Cepheids. The low detection rate of visual companions compared to the high overall binary fraction implies that most companions inferred from radial velocities and Gaia astrometry are either closer than 20mas or significantly fainter than the limits reached here.

We present a framework for cosmological model selection using Neural Networks (NNs) trained directly on simulated Cosmic Microwave Background (CMB) temperature and polarisation maps. By operating at the map level rather than on compressed angular power spectra, our approach retains the full spatial information of temperature and polarisation anisotropies, enabling the identification of subtle signatures of primordial features beyond the standard $\Lambda$CDM model. We describe the generation of Planck-like CMB maps, and the hybrid architecture that combines principal component analysis and neural networks, optimised for classification tasks. To understand how the classifier reaches its decisions, we apply Shapley Additive exPlanations (SHAP) as a post-hoc interpretability tool, identifying which regions of the sky and which scales contribute most to the distinction between $\Lambda$CDM and feature models. This work serves as a follow-up to previous analyses at the level of summary statistics and as a proof-of-concept for using interpretable machine learning to uncover higher-order information in CMB data, with the potential to enhance the detection of nontrivial inflationary signals and improve cosmological model discrimination. Results for model classification performance, calibration, and interpretability are presented as a placeholder for the full analysis. In addition, we introduce the Open Science project, providing public access to the full pipeline for simulation, training, and interpretability of CMB map-based neural networks.

Integrated-light star cluster catalogues in external galaxies are subject to complex, often poorly-characterised selection effects that can bias inferred cluster demographics and introduce significant uncertainties, limiting the physical parameter space accessible to analysis. To mitigate this problem, here we introduce the Cluster Completeness Correction Calculator (C-4): a new software tool to quantify and predict these effects in both physical and photometric parameter spaces. C-4 adds artificial star clusters to observed galaxy images, processes these images through the same detection and filtering steps used to construct the original cluster catalogue, and then trains multilayer perceptron neural networks to learn the resulting selection function. The trained neural networks provide continuous, differentiable completeness functions that can be used for direct completeness corrections or incorporated into forward models. We present a pilot application of C-4 to NGC~628, demonstrating that the learned selection operator is highly accurate and successfully captures the strongly non-separable dependence of completeness on mass, age, and extinction. Applying the completeness correction to NGC 628 extends the range of cluster demographic analyses by roughly an order of magnitude in both mass and age, and removes artificial flattening in the observed cluster mass and age distributions. These results establish neural-network-based completeness modelling as a powerful and general approach for recovering intrinsic cluster populations, and provide a scalable framework for modelling high-dimensional selection functions in resolved stellar population studies.

Previous studies have shown that a streamer blob might originate in the lower corona and thus be affected by activity in that region. While the base of one streamer might differ from that of another, it can be cataloged into two distinct types: active region streamers (ARSs) that have active regions at their base, and quiet equatorial streamers (QESs) that do not have an active region this http URL difference between the blob properties in ARSs and those in QESs remains unknown. By analyzing the whole-year observations from SOHO/LASCO/C2 in 2018, we carried out a statistical analysis of the properties of propagating blobs in ARSs and QESs. We found that the properties of streamer blobs are very different from one blob to another. The occurrence rate of blobs in ARSs is about twice as high as that in QESs. On average, the ARS blobs have significantly higher initial velocities and slightly higher accelerations, but slightly lower heights of first appearance than the QES blobs. There is a weak positive correlation between the initial velocities and heights of first appearance in the two groups of streamer blobs. The correlation between the accelerations and heights of first appearance in ARS blobs is negative, while that in QES blobs is positive. Our results provide statistical evidence that a higher degree of activity at the coronal base of a streamer can cause more dynamic blobs higher up, and that it affects the structures of the solar wind originating in the region.

High-cadence multi-band imaging and polarimetry have important scientific applications in astronomy. Observations of transits of exoplanets are a particular application that requires robust data reduction and analysis. We present the SPARC4 Pipeline, a suite of routines developed to process photometric and polarimetric data obtained with the instrument SPARC4 installed on the 1.6 m telescope at Pico dos Dias Observatory, Brazil. The scientific data products, up to the generation of high-cadence time series, are demonstrated using observations of several transiting exoplanetary systems in both photometric and polarimetric modes. These observations are used to produce stacked calibrated images, yielding sub-arcsecond astrometric accuracy even in sparse fields. The time series of these fields enabled a photometric characterization of the instrument. Observations of polarimetric standard stars yield an instrumental polarization below 0.06% and a linear polarization accuracy of 0.2%. Furthermore, transit observations of seven exoplanets with host-star magnitudes in the range 10.2 < V < 13.9 demonstrate that SPARC4 achieves an average photometric precision of 0.02% for a 15-minute cadence and a polarimetric precision of ~0.02% over hours-long time series. Finally, we jointly model the SPARC4 light curves together with TESS data (or K2 data in the case of HATS-9) using a Bayesian MCMC framework to refine constraints on the physical parameters of the exoplanets, enabling a more accurate determination of orbital periods and planetary radii, and providing improved constraints on the orbital and physical parameters of these hot Jupiters.

We construct a catalog of mid-infrared (MIR) variable sources using the multi-epoch 3.6 (W1) and 4.5 $\mu$m (W2) dataset from the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) at the north and south ecliptic poles (NEP and SEP). The catalog provides well-sampled light curves that cover areas within a radius of 5 degrees from the poles, which are frequently observed by current and forthcoming missions. By carefully processing the NEOWISE data to secure reliable photometric measurements, we identified 2764 and 27581 variables in the NEP and SEP, respectively, using the probability deviating from the non-variable and the correlation coefficient between W1 and W2. Cross-correlation with various complementary datasets reveals that, in the NEP, variability is dominated by active galactic nuclei, whereas stellar objects are more common in the SEP due to its proximity to the Large Magellanic Cloud. In particular, proper motion measurements from Gaia and MIR color-color diagrams are ideal for narrowing down the physical origin of the MIR variable sources. We identify three MIR transients in the NEP. Interestingly, all coincide with obscured QSOs, suggesting a physical connection between transient events and circumnuclear obscuration. Finally, we discuss the potential applications of our catalog in synergy with existing and future time-domain surveys.

An accurate polarization calibration is essential for a spectral data analysis and Zeeman splitting measurements. Two anomalies challenge our understanding of OH megamasers in IRAS 02524+2046: an unexplained 1667/1665 MHz flux-ratio deviation, and complex Stokes V signatures. Well-calibrated sensitive polarization observations are required to understand them. We develop a polarization calibration solution for the L-band 19-beam receiver installed on the Five-hundred-meter aperture spherical radio telescope (FAST) to achieve a high calibration accuracy and thus enable accurate measurements of the OH megamaser properties in IRAS 02524+2046. We determined the Mueller matrix solution for spectral observations across the 1050-1450 MHz frequency range with an accuracy of about 0.01%-0.08% for circular polarization. We then applied it to FAST observational data of IRAS 02524+2046. Our results show narrower emission line components in the OH megamasers than previously reported, which are indistinguishable in the total power spectrum, but are detected in the circular polarization spectrum. The 1667 MHz OH megamaser emissions probably span a wide velocity range from ~54750 to ~53580 km/s, indicating greater complexity than previously recognized. Our fit of the total power and circular polarization spectra for IRAS 02524+2046 revealed ten line components with significant Zeeman splitting (>3sigma), indicating in situ magnetic fields with a strength of approximately -24.5 mG to +20.6 mG, most of which (8/10) have positive values.

The stability of binary mass transfer is a critical problem for binary evolution. We systematically calculate the adiabatic mass-loss model for naked helium stars with masses ranging from 10\,$M_{\odot}$ to 80\,$M_{\odot}$ to study the critical mass ratio ($q_\textrm{crit}$) of Wolf-Rayet binaries. We set up two prescriptions about Wolf-Rayet stellar wind and consider the isotropic re-emission effect during adiabatic mass loss. Results of the critical mass ratio for conserved dynamically unstable mass transfer show that most of the no-wind helium stars on the main sequence (HeMS) have $0.7<q_\textrm{crit}<3.0$ and on the Hertzsprung gap (HeHG) have $1.5<q_\textrm{crit}<27$. With the Wolf-Rayet star wind effect, the $q_\textrm{crit}$ gets lower on a certain evolutionary stage. With the isotropic re-emission effect, the $q_\textrm{crit}$ gets larger for early-evolutionary stage helium stars and lower for late-evolutionary stage helium stars. Based on fully non-conserved mass transfer, the criteria for HeMS stars are $1.0<q_\textrm{crit}<2.8$ and HeHG stars are $1.5<q_\textrm{crit}<5.0$. Compared with the widely used criterion $q_\textrm{crit}=3$ (HeMS) and $q_\textrm{crit}=4$ (HeHG), our result becomes more unstable for the HeMS stars and more stable for the HeHG stars. Our work could be applied to the binary mass transfer stage of massive helium binaries, such as Wolf-Rayet star binaries and high mass X-ray binaries with Wolf-Rayet star companions. It can be applied to the binary population synthesis studies for the formation of special objects, such as double black hole mergers.

Binary systems with ultrashort-period planetary-mass companions are expected to radiate continuous gravitational waves (GWs). However, earlier studies found that the detectability of such systems by the Laser Interferometer Space Antenna (LISA) is unlikely. In this study, we investigate the detectability of GWs from planetary-mass companions orbiting pulsars (PSRs) or white dwarfs (WDs) whose fundamental parameters, essential for calculating GW properties, have been measured. We compare the GW signals from our sample with the sensitivity curves of space-based GW detectors. We find that fourteen sources achieve a signal-to-noise ratio (\(\text{S/N}\)) of \(\gtrsim 5\) within four years of observations. Among these, three sources have PSR primaries (2S 0918-549 b, 4U 0513-40 b, and 4U 1543-62), and eleven systems possess WD primaries (BW Scl b, CP Eri b, CR Boo b, EF Eri b, GP Com b, GW Lib b, SDSS J0926+3624 b, SDSS J1507+5230 b, SMSS J1606-1000 b, SRGeJ0453 b, and WZ Sge b). We note that their detectability is less probable with near-term missions such as LISA, TianQin, and Taiji. Nevertheless, they could be detected by more advanced, future-generation observatories, such as the Deci-hertz Interferometer Gravitational wave Observatory (DECIGO) and the Big Bang Observer (BBO). This offers the potential to investigate the formation and evolution of ultrashort-period planetary-mass companions around compact stars through joint GW and electromagnetic surveys.

Rotation can significantly affect neutron-star (NS) properties, but accurate modeling of rapidly rotating NSs requires solving a two-dimensional, axially symmetric system, making traditional calculations too expensive for inference analyses that demand a large amount of model evaluations. We develop a causal convolutional neural networks that preserve the chronological-like dependence of NS properties on the equation of state (EoS) and rapidly reconstruct observables for static, Keplerian, and rotating configurations. Using \texttt{RNS}, we generate a dataset of NS observables and use it to train our networks. We validate our networks with three representative EoS (SFHo, SLy4, and DD2) and find that the they accurately reproduce the \texttt{RNS} results. The trained networks evaluate NS configurations for a single EoS in $\sim 50$ms, providing a substantial speedup over typical \texttt{RNS} runtimes of $\sim 30$ min and enabling efficient inference analyses involving rapidly rotating NSs.

The average pulse shape of a pulsar is typically stable over decadal timescales, enabling estimation of pulse times of arrival to better than a small fraction of the pulse width using matched filtering techniques. However, in North American Nanohertz Observatory for Gravitational Waves (NANOGrav) observations of PSR J1713+0747, three discrete timing events that depart from the prevailing timing model have been seen in the last 20 yr. All three correspond to morphological changes in pulse shape. Using principal component analysis, we analyze the pulse profiles of nine NANOGrav pulsars, including seven with profiles from the 15 yr dataset and two with additional profiles from the forthcoming 20 yr dataset. We recover the three known pulse shape change events in PSR J1713+0747 and another previously known event in PSR J1643$-$1224. We implement a ranking metric for candidate events and address four highly ranked candidates in this nine-pulsar sample. We also recover known slow pulse shape variations in PSR J1643$-$1224, PSR J1903+0327, and PSR B1937+21 and report an unexpected recurrence after ~10 yr of one such variation in PSR B1937+21.

The Hubble parameters measured by the DESI DR2 BAO observations show a significant discrepancy from the prediction of the standard cosmological model. This discrepancy, together with the long-discussed Hubble tension, may originate from large-scale inhomogeneities in the matter distribution. This interpretation is motivated by infrared galaxy surveys, which suggest that our galaxy resides within the $\sim300$ Mpc under-dense region known as the KBC void. In this study, we apply a linear order relation -- relating the horizon-scale Hubble parameter inferred from CMB observations and the local-scale Hubble parameter -- to the Pantheon+ Type Ia supernovae and the DESI DR2 BAO data. We show that a simple inhomogeneous cosmological model consisting of eight top-hat shells can consistently explain the Hubble parameters inferred from both observations. Based on the matter-density distribution, we also briefly discuss its possible impact on cosmological observables, including the magnitude--redshift relation, the kinematic Sunyaev--Zel'dovich effect, and the integrated Sachs--Wolfe effect.

Extragalactic jets exhibit a wide range of propagation orientations relative to the host galaxy's principal axis. This study investigate the spatiotemporal evolution of jets as a function of their propagation direction within their triaxial hosts-introducing varying degrees of environmental hindrance-and as a function of internal jet properties (while maintaining identical jet power)-introducing varying collimation and thrust. Observational data on extended radio sources are re-analyzed to identify key traits arising from variations in jet orientation and intrinsic properties. These findings are then systematically tested using a suite of 3D RMHD simulations. When a jet propagates along host's major axis (path of maximal environmental resistance), it produces an X-shaped morphology with secondary lobe aligns along the minor axis, co-evolving actively alongside the active jet. At intermediate angles to the major axis, the jet morphology transitions into a double-boomerang structure with notably curved lobes. Such lobes are interestingly regenerative through both backflow and jet precession mechanisms, making it difficult to disentangle their origin. Jets propagating along the minor axis (path of minimal resistance) exhibit faster propagation, forming classical double-lobed sources. With increased thrust and improved collimation (keeping jet power constant), these jets advance even more rapidly, potentially evolving into giant radio galaxy candidates. Counterexample sources that deviate from these traits were also modeled. The spatial variation of internal turbulence shows significant fluctuations below 1 kpc, with stronger magnetic fields further suppressing these irregularities. Magnetic field plays a key role in the radiative appearance of these sources, modulating features like missing or one-sided (wing) lobe emission, filamentary structures, and warmspot versus hotspot formation.

We study the equation of state of neutron-star matter with color-spin molecular dynamics. The calculation includes the internal color and spin degrees of freedom and their time evolution. The matter composition, including strangeness under beta equilibrium, is determined by energy minimization. We find two main trends. First, within the present CSMD framework and under the adopted clustering criterion along the stable neutron-star branch, isolated quark-like configurations do not appear; instead, color-magnetic interactions favor the self-consistent formation of multi-quark clusters. Within the same criterion, the cluster-size distribution is concentrated at quark numbers that are multiples of three, corresponding to integer baryon numbers. Second, the interaction between strange and light quarks has a strong impact on neutron-star radii. This suggests that future radius measurements may help constrain flavor-sector interactions, including those involving strangeness.

We report the discovery of an intervening 21\,cm absorption line at z = 0.882 towards the z = 1.284 quasar PKS 0405-385, identified in the First Large Absorption Survey in HI (FLASH). This quasar once displayed the most rapid known intraday variability at radio frequencies, from which it earned the title of `the smallest radio quasar'. Although its size was revised upwards soon after based on updated scattering theory, PKS 0405-385 remains an important probe of Galactic plasma, and now also of intervening gas discovered through HI absorption. We present new long-slit spectroscopy spanning both PKS 0405-385 and the candidate host of the intervening HI gas. We identify MgII and FeII absorption lines in this spectrum consistent with the redshift of the intervening HI, as well as two additional, independent metal-line systems at z = 0.907 and z = 0.966, but we cannot accurately pinpoint the host(s) of this intervening gas in current data. We revisit the radio variability of PKS 0405-385 in light of advances in scintillation theory, as well as extended monitoring with the Australia Telescope Compact Array and the Australian SKA Pathfinder, and find a revised linear size >0.3 pc, but no new evidence of repeating intraday variability.

Contact binaries (CBs) serve as fundamental laboratories for studying complex stellar interactions, including mass transfer, tidal effects, and angular momentum loss. In this work, we search for CB with high-precision light curves from the Transiting Exoplanet Survey Satellite (TESS) and large radial-velocity variation from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). We derive a sample of 1,281 CB candidates, among which 266 are newly reported. Our sample with both high-precision photometry and medium-resolution spectra may provide new constraints on the physical scales, luminosity calibration, and population distribution of CBs, offering valuable insights into their evolutionary role within the stellar population.

Determining the astrophysical origin of binary black holes and whether merger remnants are retained in their birth environments is essential for understanding hierarchical mergers and the growth of intermediate-mass black holes. We identified the gravitational-wave (GW) events most consistent with dynamical formation and assessed whether their merger remnants are retained in globular clusters, nuclear star clusters, or galactic potentials. We considered the 84 events consistent with binary-black-hole (BBH) mergers from the first part of the fourth observing run (O4a) of the LIGO-Virgo-KAGRA (LVK) GW detector network, and 3 selected events from the second part (O4b). We compared parameter-estimation posteriors with synthetic population models for field and cluster binaries using Bayes factors, accounting for the relative abundances of these formation channels in the local Universe. We computed recoil-velocity posteriors for all events using the IMRPhenomXPNR waveform model, which incorporates multipole asymmetries. We identified five events showing preference for a dynamical origin, including the most massive O4a event GW231123_135430, while excluding the high-spinning O4b event GW241011_233834. Typical recoil velocities of analyzed events are of order a few hundred km/s, with extended high-velocity tails. These kicks suggest that merger remnants are likely ejected from typical globular clusters, while retention in nuclear star clusters remains possible but not guaranteed. Our results disfavour efficient hierarchical growth in globular clusters, whereas nuclear star clusters remain viable environments for repeated mergers. Although results depend on the adopted astrophysical population models, this analysis highlights the importance of improved and larger population models, as well as higher-quality detections enabled by future developments in GW detectors.

Neutral atomic hydrogen (HI) reservoirs typically extend far beyond the inner star-forming regions of galaxies, and global HI measurements, which mix these distinct environments, limit our understanding of the gas-star formation cycle. In particular, global HI depletion times combine gas and star formation from different physical scales, contributing to long measured timescales (5-9 Gyr) and large scatter compared to molecular gas. Using 841 gas-rich galaxies from the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) pilot observations, we investigate how HI depletion time and its scaling relations change when HI and star formation are both confined to the stellar disc (R25, the isophotal radius at 25 mag arcsec-2 in i-band). We find that depletion times within this region are on average 1.4 Gyr shorter than global values, though some remain very long, indicating that a substantial fraction of HI remains inactive for star formation. HI depletion times anti-correlate strongly with stellar surface density, and this trend becomes even tighter within the stellar disc. The Kennicutt-Schmidt relation further reveals an almost constant HI depletion time at fixed stellar surface density, similar to the behaviour seen for molecular gas, suggesting that HI and star formation are regulated by conditions that enable HI-to-H2 conversion, traced by stellar surface density. Beyond the stellar disc, HI depletion times are on average almost 10 Gyr longer than within R25, confirming extremely inefficient star formation in low-density outer regions. These results highlight the critical role of spatial location and local conditions for HI to serve as a fuel for star formation.

Subhalo abundance matching (SHAM) is a commonly used framework for modeling the galaxy-halo connection. Yet, its standard implementation has difficulty reproducing the observed galaxy clustering with high accuracy (e.g., $\chi^2/\mathrm{dof} \approx 1$). To overcome this issue, we propose a novel CS-SHAM framework, in which central and satellite galaxies are independently matched to main and satellite subhalos in simulations. Within this scheme, we introduce three free parameters to explicitly characterize the satellite fraction, $f_{\mathrm{sat}}$, as a function of stellar mass or absolute magnitude. To evaluate the performance of CS-SHAM, we apply it to two sets of mock galaxy catalogs built with the conventional SHAM method but using different subhalo mass proxies, $M_{\mathrm{peak}}$ and $V_{\mathrm{peak}}$, as well as two additional galaxy samples generated from a SAM and from TNG-300. We demonstrate that CS-SHAM reliably reproduces galaxy clustering whether $M_{\mathrm{peak}}$ or $V_{\mathrm{peak}}$ is used as the subhalo mass proxy. We also find that the models are unable to place robust constraints on $f_{\mathrm{sat}}$ if different mass proxies are employed. Indeed, within the CS-SHAM framework the halo occupation distribution (HOD) and conditional luminosity or stellar mass function (CLF/CSMF) are accurately recovered. Furthermore, we demonstrate for the first time that galaxy clustering constrains the HOD and CLF/CSMF primarily for relatively massive halos. Because the halo bias is nearly constant for low-mass halos, galaxy clustering is generally not very sensitive to the satellite population residing in these low-mass systems.

WASP-11~b/HAT-P-10~b is an inflated hot Jupiter, which has a low density that makes it a good target for atmospheric studies using the transmission spectroscopy technique. In this work, we present 31 new transit light curves of WASP-11~b/HAT-P-10~b, obtained through the SPEARNET network. These data were analyzed along with previously published ground-based observations and space-based data from \texttt{TESS}. We refine the planetary parameters of WASP-11~b/HAT-P-10~b and perform a transit timing analysis using data spanning 16 years. The updated ($O-C$) diagram shows no significant evidence of orbital decay. The TTV analysis reveals no significant signals indicative of additional planets. Atmospheric analysis using multi-band optical observations indicates a strong Rayleigh scattering slope in the transmission spectra, which may originate from the planetary atmosphere itself or be influenced by contamination such as stellar activity or light from the companion star.

Extremely high-peaked BL Lac objects - also named extreme blazars - are among the most energetic and persistent extragalactic accelerators in the Universe, defined by a synchrotron emission peaking above $10^{17}$ Hz in X-rays. Such emission is then reprocessed and produces radiation extending deeply into very-high-energy (VHE, energy E>100 GeV) gamma rays. Observations in this energy band - optimally investigated by the Imaging Air-Shower Cherenkov telescopes - are crucial for probing the physical processes that drive their extreme behavior. This study extends our investigation of extreme blazars in the VHE gamma-ray range, providing a second new mini-catalog of sources observed by the MAGIC telescopes. We report on the monitoring of seven targets between 2017 and 2025, including four newly observed sources and three that have been part of long-term observation campaigns, for a total of approximately 338 hours of observations. The analysis of MAGIC data reveals two new VHE detections of extreme blazars, along with three additional sources showing hints of VHE emission. Joint observations of MAGIC and the first Large-Sized Telescope (LST-1) also confirmed a new VHE extreme blazar. Our results are complemented by simultaneous multiwavelength observations in other energy bands, including optical-UV, X-rays, and high-energy gamma rays (100 MeV<E<100 GeV). We confirm typical behavior of extreme blazars, such as a modest variability and a ``harder-when-brighter'' trend in X-rays across the sample. This new set increases the population of extreme blazars and their broadband analysis confirms the physical properties of these extreme sources.

We investigate hierarchical mergers among subhalos within a $\Lambda$CDM simulation using the {\hbt} subhalo finder. Unlike previous methods, {\hbt} tracks subhalo evolution across hierarchy levels, identifying the coalescence of subhalo cores in phase-space as a ``sinking" event. This coalescence marks a distinct stalled phase in orbital decay, providing a physically motivated and natural definition of a resolved merger. Our main findings include: 1) Over 90\% of sinking events occur between adjacent subhalo levels, while cross-level pathways arise from tidal stripping, group infall, and numerical constraints. 2) Resolved mergers are predominantly \ major mergers (mass ratios $>$ 1:10), while the occurrence of minor mergers decreases with the dynamical age of the host halo. 3) Although deep-level subhalos have low mass ratios relative to the host halo, their high mass ratios relative to direct parents significantly boost merger statistics. Consequently, the satellite-satellite merger rate can rival or exceed the central-satellite rate at lower mass thresholds. 4) Satellite-satellite mergers are spatially biased toward the outer regions of the host, suggesting that the central tidal field suppresses their orbital decay. 5) A bidirectional sinking detection recovers 32\% more sinking events than the original algorithm, revealing that child-dispersion-driven mergers are dominated by tidal heating at the final stage of sinking, while parent-dispersion-driven and doubly-identified events proceed primarily via orbital decay. Altogether, these results reveal a complex landscape of hierarchical satellite mergers which deviate from the self-similarity of host halo mergers, due to additional physical processes including dynamical friction and the scale-dependent halo growth history.

Galactic outflows are predicted to be ubiquitous in low-mass galaxies, but observational evidence is lacking. Both a low signal-to-noise and a low spectral resolution can severely hamper the detection of galactic outflows, especially in small galaxies that have intrinsically narrow spectral lines. We obtained new, medium-high resolution (FWHM$_\mathrm{inst}\sim50-110$~km/s) optical spectra of 52 local star forming galaxies ($0.01 < z < 0.03$) with stellar masses $10^{8.5}<M_*/[M_{\odot}]<10^{10}$, using the TNG/DOLORES and NTT/EFOSC2 instruments. Our parent sample consists of SDSS galaxies with available heterodyne single-dish molecular (i.e., CO) line data. The targets of this study are selected among those that, based on the comparison between CO line widths, SDSS spectral resolution, and corresponding SDSS-based H$\alpha$ line widths, have a high chance of being unresolved by SDSS spectroscopy. Our new, spectra reveal overall narrower H$\alpha$ and [OIII]$\lambda5007$ lines, with signs of asymmetries and broad wings that are absent in the SDSS spectra of the same galaxies. This confirms that SDSS spectroscopy does not resolve the narrow emission lines of low-M$_*$ galaxies, which hinders the detection of outflows. We identify outflow signatures in $\sim30\%$ of our targets based on the H$\alpha$ line spectra. Assuming a typical bi-conical outflow geometry, this detection rate is consistent with theoretical predictions of ubiquitous outflows in the low-mass regime. The outflow incidence is enhanced ($\sim60\%$) for galaxies with above average star formation rates for the sample (SFR $>10^{-0.74}~\mathrm{M_{\odot}/yr}$). We estimate ionized gas mass outflow rates ranging from $\sim0.1-50\times10^{-3}~\mathrm{M_{\odot}/yr}$ (mean $\sim20\times10^{-3}~\mathrm{M_{\odot}/yr}$) and corresponding mass loading factors between 0.03 and 0.14 (mean $\sim0.07$) for the sample.

Dust in Early-Type galaxies (ETGs) may originate from internal or external sources. In this paper we study the stellar populations of particularly dusty ETGs to search for evidence of the dust's origin. Using the Southern African Large Telescope (SALT), we obtained long-slit optical spectra within the effective radius (R_e), along the major axis of 15 nearby ETGs, selected from the GAMA and Herschel-ATLAS surveys for their high levels of interstellar dust. Using full spectrum fitting and Lick index fitting we analysed their major axis kinematics and stellar population characteristics. We used stellar population models from the newly developed sMILES library and from the empirical MILES library. Kinematic results show that most of our sample of dusty ETGs are rotationally supported and there are no detectable kinematic discontinuities. 12 of our sample of 15 dusty ETGs show evidence of young/intermediate age stellar population components suggesting ongoing/recent star formation. Using simulations, we show that these recent ($\approx$1~Gyr) populations are not artefacts of the fitting process or data. As a check with a control sample we use stacked SDSS spectra and find that dusty ETGs show a component with intermediate age, whereas non-dusty ETGs do not. Age, metallicity and $\alpha$-element abundance ratio increase with increasing central velocity dispersion in the SALT spectra, as seen in previous studies of ETGs, but with larger scatter in our sample. Given our stellar population findings, we discuss formation scenarios that might cause or rule out a high dust/molecular gas content.

The material ejected from a binary neutron star merger produces "kilonova," a radioactively powered emission at ultraviolet, optical, and infrared wavelengths. The early-phase spectra of the kilonova AT2017gfo, following the gravitational wave event GW170817, exhibit a strong absorption feature around $1\,\mathrm{\mu m}$. Helium (He) and strontium (Sr) have been proposed as the candidate elements contributing to this feature. However, due to the lack of consistent modeling including these two elements simultaneously, the exact contributions of each element to this feature remain unclear. In this study, we develop non-local thermodynamic equilibrium ionization models for He and Sr that take into account ionization by high-energy electrons, and estimate the abundances of each element required to reproduce the observed feature. Our modeling indicates that about $1\, \%$ of He or $1\mathrm{-}10\, \%$ of Sr in mass fraction are present in the ejecta moving at $v \sim 0.15 \, c$. This Sr mass fraction nicely agrees with the mass fraction in the solar $r$-process abundance. Based on comparison with nucleosynthesis calculations, our constraints suggest that $r$-process nucleosynthesis in GW170817 occurs at relatively low electron fraction ($Y_{\rm e} \lesssim 0.35$) and low entropy ($s \lesssim 30 \ k_B/\, \mathrm{nucleon}$) conditions. Interestingly, for $Y_{\rm e}$ $\lesssim 0.15$, the observed feature is reproduced by He with a mass fraction expected from $\alpha$ decays of trans-Pb nuclei, which gives an indirect signature for the production of elements beyond the third $r$-process peak.

Gravitational waves from intermediate-mass black-hole (IMBH) binaries is a probe of strong-field gravity and black-hole evolution. Detection of IMBH is challenging because of their typically low frequency where the seismic noise, radiation pressure noise, and thermal noise dominate. The Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS) has been proposed to reach a strain sensitivity of $10^{-18} {\rm Hz}^{-1/2}$ at 2 Hz. It aims to detect GW from IMBH mergers with the mass of $\mathcal{O}(10^4)$ M$_{\odot}$ and to explore stochastic gravitational background of $\Omega_{\rm GW} \sim 2\times 10^{-3}$ at 2 Hz. We present the overview of the CHRONOS hardware which is designed to integrate key techniques for improving low frequency sensitivity; torsion bar, speed meter, and cryogenic mirror. As a demonstration of the interferometer operation, we also report the commissioning status of a Michelson interferometer in National Central University in Taiwan which has been assembled as a partial component of CHRONOS.

Mergers of neutron stars are believed to be one of the primary sites for the synthesis of the universe's heavy elements via the rapid neutron capture process. AT2017gfo, the kilonova following GW170817 provided the first direct spectroscopic evidence of the $r$-process happening in the universe. A prominent line feature near $1\,\mu$m in its spectrum was attributed to strontium -- a claim that has been independently recovered by several teams. However, in recent years it has been debated whether the feature arises instead from helium. Here, we present non--local thermodynamic equilibrium (NLTE) radiative transfer modelling of the observed kilonova spectra, including detailed radiation-matter interaction physics for both strontium and helium. We make use of freshly calculated strontium atomic data for e$^-$ impact collisions, photoionization, and recombination processes. Our strontium model self-consistently reproduces the temporal evolution of the $1\,\mu$m feature at early times, with its absence at $0.92\,$days to its clear emergence at $1.17\,$days. This transition mimics LTE, because at early epochs ($t\lesssim 1.5\,$days) the radiation field dominates the ionization state of the ejecta over thermal and non-thermal electron collisions. We further test if helium can form the feature under the same plasma conditions. The helium mass required at $1.17\,$days is comparable to the total ejecta mass, while a few percent by mass of helium suffices at 4.4 days. On the other hand, the strength of the strontium lines decrease with time, and may require a radially stratified abundance to consistently produce the feature. We conclude that strontium is required to explain the onset of the feature at early times, but helium can contribute to, or even dominate the feature at later epochs.

Axion-like particles (ALPs) produced via the Primakoff process in the cores of Galactic core-collapse supernovae (SNe) could convert into MeV-energy gamma-rays through interactions with the Milky Way's magnetic field. To evaluate the detection prospects for such signals, we perform sensitivity projections for next-generation MeV telescopes by combining hypothetical instrument responses with realistic background estimates. Our analysis incorporates detailed simulations of the expected ALP flux from nearby SNe, the energy-dependent conversion probability in Galactic magnetic fields, and the telescope's angular/energy resolution based on advanced detector designs. Background components are modeled using data from current MeV missions and extrapolated to future sensitivity regimes. Our simulations demonstrate that next-generation telescopes with improved effective areas and energy resolution could achieve sensitivity to photon-ALP couplings as low as gagamma approx 1.61 x 10^-13 GeV^-1 for ALP masses ma < 10^-9 eV in Galactic Center. These results indicate that future MeV missions will probe unexplored regions of ALP parameter space, with conservative estimates suggesting they could constrain gagamma values two orders of magnitude below current astrophysical limits. Such observations would provide the most stringent tests to date for axion-like particles as a dark matter candidate in the ultra-light mass regime.

The standard $\Lambda$CDM cosmological model faces increasing tensions between key observations, motivating tests that probe its underlying assumptions. In a companion letter, we present a model-independent framework that combines derivatives of the angular diameter distance, $d_A(z)$, and the line-of-sight expansion rate, $\mathcal{H}(z)$, to clarify the physical content of FLRW consistency relations and to construct a general-spacetime estimator of the cosmic density field. Here, we apply these tests to data, introducing a non-parametric reconstruction method based on symbolic regression combined with bootstrapping to provide data-driven uncertainty estimates. Using supernova and BAO data, we reconstruct $d_A$, $\mathcal{H}$, and their derivatives, enabling model-independent evaluation of FLRW relations and recovery of the sky-averaged density field over $z \in [0.38, \sim 2]$. Current data are too sparse to tightly constrain $\mathcal{H}(z)$, and the reconstructed density is consistent with both Planck and SH0ES $\Lambda$CDM. Reconstructed FLRW consistency tests show mild to moderate deviations from FLRW expectations at the $\sim 2$-$4\sigma$ level, although their significance depends on data selection and reconstruction stability. If these indicated deviations from an FLRW geometry are real, it would signify that most of the cosmological solutions considered for solving the cosmological tensions (evolving/interacting dark energy, new types of matter/energy, modified gravity, etc., within the FLRW framework) are ruled out. These preliminary indications highlight the importance of future, denser distance and expansion rate measurements, as well as further work toward standardizing uncertainty estimation for symbolic regression reconstructions.

Cluster catalogs selected by optical properties are subject to selection biases, primarily arising from unresolved systems along the line of sight. These biases affect key observables for cluster cosmology, such as the lensing signal and clustering statistics. In this work, we present a fully predictive forward analytical model to quantify the impact of optical-selection bias due to projection effects on cluster density profiles. This is achieved by introducing a scale-dependent parametrization of the optical cluster bias, whose small- and large-scale behaviour is set by the amplitude of projection effects, and by expressing the two-halo component of the density profile in terms of the contributions from off-axis halos along the line of sight. As a case study, we consider a DES Y3-like cluster catalog and validate our model against simulated samples. Our model successfully captures the dependence of the two-halo component on richness boosts induced by projections, as well as its evolution with richness and redshift. It also recovers the overall bias in the projected density profile relative to a randomly selected sample with the same mass distribution. The framework presented here provides a consistent methodology for modeling the impact of line-of-sight structures on the observed richness and density profiles of optically selected clusters, directly linking selection biases to the underlying cosmology and survey specifications.

The $\Lambda$CDM cosmological model faces increasingly significant and robust tensions among independent cosmological probes, prompting renewed scrutiny of its foundational assumptions. While General Relativity and the nature of dark energy are now routinely tested with cosmological surveys, less progress has been made testing the space-time geometry at the largest scales, and in particular testing the assumption that observables (distances, redshifs, expansion of space, etc.) on the largest scales are described by a single Friedmann-Lema\^ıtre-Robertson-Walker (FLRW) metric. In order to enable such tests, we introduce a model-independent framework that combines successive derivatives of the angular diameter distance, $d_A(z)$, with the line-of-sight expansion rate, $\mathcal{H}(z)$, to expose the physical content of well-known FLRW consistency relations. This allows us to perform diagnostic tests of the large-scale geometry, that are free of assumptions about dark energy and the theory of gravity on large scales. In addition, we derive a new nonparametric estimator for the cosmic density field that is independent of the Friedmann equations. This enables qualitatively new, observationally accessible tests of the FLRW framework and provides a stringent, model-independent diagnostic for departures from standard cosmology using current and forthcoming distance and expansion rate measurements.

We investigate several phenomenological dark energy parameterizations using a joint analysis of late-time cosmological observations, including cosmic-chromatometer measurements of the Hubble parameter, DESI DR2 baryon acoustic oscillation data, and the Pantheon+ Type Ia supernova sample. Our results show that allowing for a time-varying dark energy equation of state significantly improves the overall fit compared to $\Lambda$CDM. The present-day equation-of-state parameter departs from the standard cosmological constant value. In contrast, the evolution parameter in two-parameter models tends to be negative, indicating a possible time dependence of dark energy. However, the constraints on the evolution remain moderate, and current data cannot clearly distinguish the specific functional form of dark energy. Model comparison using information criteria suggests that dynamical dark energy models are favored over $\Lambda$CDM, with the most straightforward one-parameter extension emerging as the most parsimonious scenario. These findings indicate a mild preference for dark energy evolution, though future high-precision observations will be required for definitive conclusions.

In this short comment, I discuss the relationship between the results presented in arXiv:2512.01403 and those previously published in Phys.~Rev.~D~101,~083011~(2020). The 2020 study provides a full Monte Carlo simulation of cosmic-ray interactions with the solar atmosphere using the FLUKA code, including realistic solar-atmosphere models, PFSS/Parker/BIFROST magnetic-field configurations, and predictions for gamma rays, electrons, positrons, neutrons, and neutrinos. Given the substantial scientific overlap -- particularly in the modelling of hadronic interactions, magnetic-field effects, cascade development, and comparison with Fermi-LAT observations -- a direct comparison is relevant to assess consistency and complementarity. Here I summarize the main points of agreement, highlight differences in modeling assumptions, and outline how the two approaches can jointly contribute to understanding high-energy emission from the solar disk.

The first detection of supernova burst neutrinos was achieved through the observation of SN1987A, almost four decades ago. However, neutrinos produced during the burning stages of a star prior to core collapse are yet to be detected. Detection of pre-supernova neutrinos could provide an early warning of an imminent supernova and allow the scientific community time to focus their resources on the observation and study of such an event leading to better understanding of these rare phenomena. Integrating pre-supernova models into a neutrino event generator would help to provide a unified framework for studying these neutrinos in current and next generation detectors. sntools is a neutrino event generator for supernova burst neutrinos, originally developed to study supernova model discrimination with Hyper-Kamiokande. Work to add support for pre-supernova event generation to sntools is presented, detailing the adaptations and additions to the code, with emphasis on how time binning can be optimised for a robust simulation, and also detailing the status of the validation process. The current status and capabilities of the package will be explained alongside plans for any further work and the intended use for the new functionality within the Hyper-Kamiokande Collaboration.

The aim of this study is to investigate the interaction of Earth-mass planets with a planetesimal disk. It is shown that an Earth-mass planet, initially located near the inner boundary of the planetesimal disk, migrates into the disk. The depth of penetration of the planet into the disk is a random quantity determined by the angular momentum distribution of planetesimals approaching the planet. However, at a certain stage, the direction of the planet's migration changes, and the planet returns to the inner boundary of the disk. During such reversible migration, the planet perturbs the orbits of planetesimals and increases their relative velocities in the region of the disk traversed during its migration. The relative velocities of planetesimals increase to values sufficient for their fragmentation in collisions. Our estimates show that, after the passage of an Earth-mass planet through the outer planetesimal disk, the mean relative velocities in the main part of the disk increase to values sufficient to disrupt monolithic basaltic planetesimals with sizes of 40 km. Thus, the interaction of even a relatively low-mass planet (of order an Earth mass) with a planetesimal disk can lead to the formation of dust particles observed in outer debris disks.

PG~1553+113 is the blazar with the most-significantly detected periodic patter in its multiwavelength (MWL) emission, making it one of the most promising candidates for hosting a supermassive black hole binary. However, the presence of this periodic behavior in the X-ray band remains under debate, largely due to the lack of continuous monitoring. This has led to differing conclusions in previous studies. In addition, we aim to examine whether the recently identified linear long-term trends in the gamma-ray and optical bands also exist in the X-ray regime. Here, we evaluate the 2.1-year period in the X-ray light curve of PG 1553+113 using two dedicated monitoring campaigns with Swift-XRT and UVOT, guided by predictions of future oscillation phases. We also examine whether the long-term trend is present in X-rays, the potential periodic behavior of the X-ray power-law photon index, and its potential correlation to the X-ray flux. As a result, we find tentative evidence for a correlation between the predicted high-emission states in the gamma-ray band and those observed in the X-ray and UV bands. Therefore, we do not find a strong evidence of the same periodic pattern in X-ray. In addition, we find that the X-ray light curve is consistent with the presence of a long-term linear trend, in agreement with those previously reported in gamma-ray, optical, and radio. Overall, these results indicate that the X-ray emission is likely to share the same long-term behavior observed in the gamma-ray and optical bands. Nevertheless, the pronounced stochastic variability that characterizes the X-ray light curve limits our ability to draw firm conclusions regarding the presence of the periodic behavior.

We present a new set of 35 transit light curves of the hot Jupiter WASP-43~b, obtained through the SPEARNET network. These datasets were analyzed together with previously published ground-based observations, as well as space-based data from \emph{TESS}, \emph{HST}, and \emph{JWST}, to refine the planetary parameters of WASP-43~b. A total of 188 mid-transit times, measured with \texttt{TransitFit}, were analyzed for potential timing variations. The transit timing variations do not show any significant evidence of orbital decay. Atmospheric retrievals using \emph{HST}/WFC3 G141 transmission spectra suggest that higher-temperature solutions are associated with higher water abundances. However, when these data are combined with observations from ground-based telescopes, \emph{TESS}, and \emph{JWST}, the increased modeling complexity across the broad wavelength baseline presents significant challenges for atmospheric characterization. These results highlight that high-precision, multi-instrument datasets will be necessary to break existing degeneracies in the atmospheric modeling of this target in the future.

We extended the radio K-band spectroscopic survey for organics in southern hemisphere dense cores by observing seven sources using NASA's Deep Space Network 70-m antenna in Canberra, Australia, over the frequency range of 18 to 25 GHz. Molecular column densities of NH$_3$, $c$-C$_3$H$_2$, HC$_3$N, HC$_5$N, CCS, C$_3$S, and $c$-C$_3$HD were derived for each source assuming LTE. The resulting column density ratios were compared with predictions of a state-of-the art astrochemical model to constrain the C/O ratio and chemical age of each source. Most cores have similar C/O ratios of $0.5 - 0.7$, much different from the best studied TMC-1 dense core characterized by a high C/O ratio of $\sim 1.4$. The chemical ages of the cores are also similar and fall between 0.6 and 5~Myr. The less dense cores tend to have the oldest chemical ages, as might be expected given that chemical timescales scale with density. Our results showcase the synergistic approach of combining radio observations using the DSS-43 antenna with state-of-the-art astrochemical models to study the chemical composition of southern hemisphere dense cores, enabling constraints on their C/O ratios and chemical ages, which remain largely unexplored.

The orbital inclination of an eclipsing binary is generally determined through light curve analysis. Binary parameters in the light curve analysis are typically constrained through the use of optimization and sampling techniques. We propose a new simple method, based on the derivatives of light curves, for estimating the orbital inclinations of overcontact systems. Our sample consists of 89670 synthetic light curves for overcontact binaries, covering a parameter space typical of overcontact systems. We classified the sample light curves on the basis of a recently proposed classification scheme: DP, SPp, SPb, SPf, and SPs types. For each type, we found that the orbital inclination is closely associated either with the time interval between local extrema in the derivatives of light curves or with the depth of the local minimum at phase 0.5 in the second derivative. Using regression analysis of the identified associations, we developed empirical formulae to estimate the orbital inclinations for each type of light curve. We also provide the associated uncertainties for the estimated inclinations. Application of the proposed method to real overcontact binary data demonstrated that our method can reasonably estimate both the inclinations and their uncertainties.

Detection of parity violation on cosmological scales would have profound implications for fundamental physics. Motivated in part by recent measurements of parity-odd four-point correlation functions in BOSS and DESI luminous red galaxy samples, which probe parity violation in the scalar sector, we present the first measurement of parity-odd kurto spectra in spectroscopic galaxy survey data. We analyse two composite-field spectra, $\mathcal{P}_{2\times2}$ (vector--pseudo-vector) and $\mathcal{P}_{3\times1}$ (scalar--pseudo-scalar). Compared with parity-odd four-point correlation function analyses, the kurto-spectrum formalism performs physically motivated compression on the trispectrum into a substantially lower-dimensional data vector, allowing direct estimation of covariance matrices from mock catalogues and reducing sensitivity to covariance-modelling systematics. Using null-hypothesis $\chi^2$ tests and cross-patch consistency checks, we find no evidence for a cosmological parity-violating signal in either survey. We examine the impact of the adopted mock catalogues and find that the high-fidelity mocks provide a better match to the data of both surveys than the approximate mocks. The DESI DR1 measurements exhibit a scatter smaller than that of BOSS DR12 by about a factor of four, consistent with the improved statistical precision expected from the higher tracer number density. Future DESI data releases, with larger volume and number density, together with larger suites of high-fidelity mocks, can enable significantly sharper tests of parity violation using kurto spectra.

Plotting the mass-density of a wide range of astronomical objects as a function of their mass reveals that the vast majority of these objects fall along a ``cohesive object sequence'' that extends all the way from asteroids to the largest stars. Trends and features within this sequence reflect fundamental astronomical processes and phenomena, including the gravitational contraction of progressively higher-mass planets and the onset of nuclear reactions within stars. Meanwhile, compact stellar remnants fall well off this sequence, reflecting their extreme natures. This type of plot is therefore useful both for showcasing the relationships and connections between a wide range of astronomical objects and for clarifying the distinctions used to identify particular types of objects.

We present cuRAMSES, a suite of advanced domain decomposition strategies and algorithmic optimizations for the ramses adaptive mesh refinement (AMR) code, designed to overcome the communication, memory, and solver bottlenecks inherent in massive cosmological simulations. The central innovation is a recursive k-section domain decomposition that replaces the traditional Hilbert curve ordering with a hierarchical spatial partitioning. This approach substitutes global all-to-all communications with neighbour-only point-to-point communications. By maintaining a constant number of communication partners regardless of the total rank count, it significantly improves strong scaling at high concurrency. To address critical memory constraints at scale, we introduce a Morton-key hash table for octree-neighbour lookup alongside on-demand array allocation, drastically reducing the per-rank memory footprint. Furthermore, a novel spatial hash-binning algorithm in box-type local domains accelerates supernova and AGN feedback routines by over two orders of magnitude (an about 260 times speedup). For hybrid architectures, an automatic CPU/GPU dispatch model with GPU-resident mesh data is implemented and benchmarked. The multigrid Poisson solver achieves a 1.7 times GPU speedup on H100 and A100 GPUs, although the Godunov solver is currently PCIe-bandwidth-limited. The net improvement is about 20 per cent on current PCIe-connected hardware, and a performance model predicts about 2 times on tightly coupled architectures such as the NVIDIA GH200. Additionally, a variable-Nrank restart capability enables flexible I/O workflows. Extensive diagnostics verify that all modifications preserve mass, momentum, and energy conservation, matching the reference Hilbert-ordering run to within 0.5 per cent in the total energy diagnostic.

We investigate Lyman-alpha forest flux statistics in mixed fuzzy dark matter (FDM) and cold dark matter (CDM) cosmologies using the Fluctuating Gunn-Peterson Approximation (FGPA) applied to hybrid Schrödinger-Poisson and N-body simulations. We evolve the dark matter distribution from z = 120 to z = 2 for an axion mass ( m_22 = 0.01) and FDM fraction (f_A = 0.1), and compare two realizations with identical initial conditions: one evolved with a particle-only approximation and one with full wave--mechanical dynamics. We find that, despite near-degeneracy in the nonlinear matter power spectrum, the corresponding Ly {\alpha} flux power spectra differ at the 10 percent level on intermediate scales. This discrepancy arises from a strong suppression of small-scale velocity power in the Schrödinger--Poisson evolution, which is not captured by N-body treatments with matched initial transfer functions. As a result, the flux statistics cannot be fully characterized by the matter power spectrum alone, but depend sensitively on the dynamical evolution of the velocity field. These results demonstrate that wave-mechanical effects in FDM leave distinct kinematic imprints in Ly {\alpha} observables beyond those associated with initial-condition suppression. While our analysis is based on an idealized FGPA framework, it isolates a mechanism by which mixed dark matter models can break degeneracies present in standard structure-based probes, motivating further investigation with full hydrodynamical simulations.

We present a spectroscopic follow-up program targeting closely-separated dual quasar candidates selected from imaging of SDSS quasars with the Subaru Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Using two-dimensional image decomposition, our selection identifies PSF-like companions within 0.6-4 arcsec separation (< 30 kpc) around the SDSS quasar. We newly confirm six broad-line dual quasars and eleven offset quasars (quasar-galaxy pairs), spanning 1.5 < z < 3.3 for the duals and predominantly z < 0.6 for the offset systems. No obvious lensed quasars were discovered from this program. We obtained 99 spectra of these candidates from NTT/EFOSC2, Gemini/GMOS-N, Keck/NIRES, and Subaru/FOCAS. From the spectra, we measure the emission-line properties of these dual black holes (BH). At z > 1.5, the confirmed duals exhibit high black hole mass ($M_{\rm BH}$ $=10^{8.5}$-$10^{10} M_{\odot}$) with high bolometric luminosities ($L_{bol}$ $=10^{45.5}$-$10^{47.5}$ erg s$^{-1}$), yet accrete at moderate Eddington ratios ($\lambda_{\rm Edd}=$0.01-0.4). From the spectroscopically-confirmed samples, we estimate the dual fraction of SDSS quasars with separations of 0.6-4 arcsec to be 0.2%-1.2% at z<0.8, 0.08%-0.24% at 0.8<z<1.5, and 0.06% at 1.5<z<3.3. These values are broadly consistent with other recent optical studies, but lower than theoretical expectations of a rising dual fraction at cosmic noon. However, we note that these fractions, especially at high $z$, still need a more accurate assessment of selection and observation effects.

Observations of periodic stellar activity near the transit phase of a close-in exoplanet provide evidence of star-planet magnetic interactions (SPMI), similar to the magnetic coupling between Jupiter and its moons. Comparing the power associated with SPMI signals to analytical theories offers a way to constrain exoplanetary magnetic fields, but models based on moon-magnetosphere analogs often underpredict observed energy fluxes. Unlike moons, many close-in exoplanets are extended, highly irradiated gas giants undergoing significant photoevaporation. However, it is not known how atmospheric escape influences the star-planet magnetic coupling. Here, we present three-dimensional radiation magneto-hydrodynamic simulations that simultaneously model planetary evaporation and SPMI in a hot Jupiter planet embedded in a magnetised stellar wind. Our simulations reveal the formation of magnetic structures known as Alfvén wings, which transport magnetic energy away from the planet. When the dayside mass-loss rate $\dot{M}_d$ of the planet lies below a threshold $\dot{M}_0$ defined by pressure balance between the planetary and stellar winds ($\dot{M}_d \leq \dot{M}_0$), the maximal power delivered to the star matches predictions from the Alfvén wing model. For higher escape rates, the planetary outflow opens additional magnetic flux, and the SPMI power increases proportionally with $(\dot{M}_d / \dot{M}_0)^{1/2}$. Applying this scaling law to the HD18973 system, we find that a $30$ G planet could reproduce the observed power if $\dot{M}_d \sim 10^{12}$ g/s. Although this signal likely represents only a fraction of the total power, additional mechanisms could amplify the energy budget. These results show that photoevaporating exoplanets in sub-Alfvénic orbits constitute promising targets for SPMI observations.

Too light primordial black holes evaporate and are therefore strongly constrained by various bounds, e.g. Cosmic Microwave Background distortion. However, if they are formed strongly clustered, the corresponding haloes may collapse in heavier black holes which may form the entirety of the dark matter of the universe. The indirect signal of such scenario is the production of a flat stochastic background of gravitational waves which is detectable by the Einstein Telescope.

Recently, the ACS team applied an Ubercal framework to assess the photometric repeatability of stars observed across the WFC detector using 15 years of post-SM4 calibration data in the globular cluster 47 Tuc (Ryan et al., 2024). A surprising finding was an apparent 0.05 mag global difference in sensitivity between the WFC1 and WFC2 chips, which had not been seen in prior tests of sensitivity variations around the field-of-view. Given the many degenerate variables within the Ubercal framework such as CTE losses, time-dependent sensitivity, and flat-field corrections, we obtained new calibration data to perform a straightforward test of the reported $\sim$5$\%$ flux offset between detectors. We observed three white dwarf standards with three filters at four positions on the detector (each on a different amplifier), but with the same number of x and y pixel transfers to mitigate differential CTE-related effects. For the F606W and F814W filters, the agreements are good to 0.4$\%$ on average, and always 1$\%$ or better in individual cases. The consistency of these two filters over all three stars and the four dither positions provides very strong evidence against the large global sensitivity offset between WFC1 and WFC2 as seen in the Ubercal work. Larger variations seen in the bluer F435W filter are likely a result of a sensitivity of the flat field in that filter to underlying spectral type, warranting a future solution.

Astrophysical black holes appear well-represented by the Kerr metric, but this metric has the philosophical problem of a ring-like curvature singularity. We show that a phenomenological correction to the Kerr metric known as the Kerr-Hayward metric can eliminate the curvature singularity while preserving in detail many features of polarized black hole images now testable by the Event Horizon Telescope (EHT). To establish this, we produce new general relativistic magnetohydrodynamics (GRMHD) simulations of a magnetized plasma in a Kerr-Hayward spacetime, then we extend the EHT analysis framework to perform polarized radiative transfer in this spacetime. We detail our methodology for implementing this modified spacetime into an open-source pipeline. From fluid quantities such as the magnetic flux parameter and jet efficiency, to image quantities such as the polarization pattern and the photon ring structure, our results for the Kerr-Hayward metric appear functionally indistinguishable from the Kerr metric. Our study finds that under certain conditions, the singularity-free correction to the Kerr metric can yield observables that are effectively indistinguishable in EHT measurements.

Simplified, one-dimensional models are necessary to model convection in the context of stellar evolution. By including the non-local effects of convection, turbulent convection models describe convection in a more physical way compared to mixing length theory, which is typically used in one-dimensional stellar evolution models. We recently showed that the 1-equation Kuhfuss turbulent convection model is not sufficient to model the solar convective envelope satisfactorily. Using the Sun as a benchmark, we test the physically more complete 3-equation Kuhfuss turbulent convection model. We calculate a solar calibrated model with the 3-equation Kuhfuss turbulent convection model using the one-dimensional stellar evolution code GARSTEC. We compare the predicted interior structure of the model with helioseismic measurements of the Sun. Furthermore, we investigate how the free parameters and the closure relations of the 3-equation model influence the results. We find that, with the 3-equation model, the temperature gradient at the inner boundary of the convective envelope is modelled more realistically compared to the mixing length theory or the 1-equation model. This also improves the agreement for the sound speed profile between the model and the Sun, and reduces the asteroseismic surface effect. However, close to the surface, the 3-equation model results in a layer having an unphysical, negative temperature gradient. This layer is connected to the closure relations used in the 3-equation model. Our results demonstrate the capabilities of turbulent convection models, and can serve as a next step towards an improved and more realistic modelling of convection in stellar evolution codes.

We consider nearly-integrable Hamiltonian systems defined over a non-resonant domain. In the neighborhood of resonances, we use Nekhoroshev-like estimates to provide effective stability bounds for the action variables over long time. The applicability conditions of these estimates allow some freedom in the choice of parameters. Hence, we develop an optimization algorithm for choosing parameters that maximize the stability time. To further improve the stability estimates, we use perturbation theory to reduce the norm of the perturbing function. We implement this procedure (effective stability estimates and perturbation theory) to analyze the stability of sequences of irrational (Diophantine) frequencies converging to frequencies corresponding to resonances. We consider two applications to models describing problems of rotational dynamics in Celestial Mechanics: the spin-orbit problem, described by a 1D time-dependent Hamiltonian, and the spin-spin-orbit model, described by a 2D time-dependent Hamiltonian. We show stability results for orbits close to the main resonances associated with such models.

We propose a novel concept of astrophysical mirroring in the schwarzschild framework, which emerges as a direct consequence of gravitational lensing effects occurring in the immediate vicinity of extremely dense massive objects within spacetime. Through rigorous theoretical calculations and numerical ray-tracing analysis, we demonstrate that sufficiently compact astrophysical objects possess the capability to induce such extreme curvature in spacetime that the resulting gravitational field can bend light rays to extraordinary degrees, creating what we term a "reflection image" or mirror-like appearance of the source in distant regions of space. We discuss the theoretical framework as well as the observational consequences of this phenomenon.

Weakly interacting massive particles provide a well-motivated framework for dark matter, naturally reproducing the observed relic abundance through thermal freeze-out. A recent claim of an indirect-detection signal from the Galactic halo, consistent with dark matter annihilation in the mass range 400--800 GeV, motivates a reexamination of minimal models that can account for such a signal while remaining consistent with existing constraints. In this paper, we analyze the simplest extensions of the Standard Model capable of explaining the signal. We show that electroweak doublet dark matter with Higgs-portal interactions provides a natural and economical explanation. The model predicts annihilation predominantly into longitudinal gauge bosons with characteristic branching fractions and allows for inelastic dark matter with a mass splitting of order 100 keV, intriguingly consistent with a recent direct-detection anomaly. Possible enhancements of the present-day annihilation rate relative to the thermal value are also discussed, including a simple extension with a light scalar field, whose mass can be chosen such that the enhancement is suppressed in dwarf galaxies.

We compute the stochastic gravitational wave background sourced at second order by a spectator scalar field $\chi$ coupled to the inflaton $\phi$ through a portal interaction $\sigma\phi^2\chi^2$ and with quartic self-interaction $\lambda_\chi\chi^4/4!$. In the large portal coupling regime ($\sigma/\lambda \gg 1$, with $\lambda$ the inflaton normalization), parametric resonance during reheating amplifies the spectator power spectrum by many orders of magnitude near the resonance band until Hartree backreaction from the quartic coupling detunes the instability, while the large inflationary effective mass suppresses superhorizon power and ensures compatibility with CMB isocurvature bounds. We focus on the direct field-gradient source $\partial_a\chi\,\partial_b\chi$ in the second-order Einstein equations and derive a master formula that factorizes into a spectral integral over the frozen, vacuum-subtracted spectator spectrum and a time integral encoding the post-inflationary expansion history. For our benchmark reheating history we obtain analytic scaling relations, including a peak amplitude $\Omega_{\rm GW}\propto T_{\rm reh}^{8/3}$, strong dependence on the portal strength, and weak sensitivity to $m_\chi$. We validate the framework against nonlinear lattice simulations, demonstrating complementarity: the Hartree treatment captures superhorizon evolution inaccessible to the lattice, while the lattice resolves rescattering and fragmentation near the spectral peak. For $\sigma/\lambda \simeq 10^4$ and $T_{\rm reh}=2 \times 10^{14}\,\mathrm{GeV}$, the signal reaches $\Omega_{\rm GW}h^2\sim 10^{-11}$ at $f\sim10^{7}$-$10^{8}\,\mathrm{Hz}$. Increasing $\lambda_\chi$ at fixed $\sigma$ has a non-monotonic effect: small values enhance the signal via rescattering, whereas larger values suppress it by detuning the resonance.

We consider a modular-invariant extension of the Standard Model. Assuming that the modulus is the inflaton, the CP-violating phases of the Yukawa couplings evolve during inflation. This dynamics favours a Higgs condensate, so that Standard Model fermions mediate a one-loop cosmological collider signal enhanced by chemical potentials. Next-generation experiments can probe sub-Planckian values of the modulus decay constant. We provide precise expressions for Dirac fermions with chemical potentials in de Sitter.

The Kerr black hole spacetime is symmetric with respect to a well-defined equatorial plane. When such a symmetry is broken, for instance, by some putative effects beyond general relativity, the Keplerian circular orbits around the black hole are distorted vertically away from the equatorial plane by an amount depending on the orbital radius. As a result, the Keplerian thin disk acquires a curved surface. In this work, we extend such results to thick tori configurations by considering non-self-gravitating Polish doughnut models. We show that due to the equatorial asymmetry of the spacetime, the centers and the cusps of tori are distorted away from the original equatorial plane toward the same direction as that experienced by the stable Keplerian orbits, and the entire tori configurations are twisted toward that direction as well. The shape of the distorted tori is demonstrated explicitly using a constant specific angular momentum profile $\ell(r,y)=\ell_0$ of the disk fluid. However, the result also applies to non-constant profiles of $\ell(r,y)$ generically in the sense that any asymmetric profile of $\ell(r,y)$ that attempts to produce a symmetric tori configuration either turns out to be ill-defined near the equatorial plane or suffers from fine-tuning issues.

Despite the fact that electrons observed in situ in space plasmas have three major components-the quasi-thermal core, suprathermal halo, and strahl-the analysis of instabilities triggered by kinetic, velocity-space anisotropies (such as relative drifts and temperature anisotropy) generally considers only two. We demonstrate that realistic modeling with all three components is achievable in the present analysis focusing on heat-flux instabilities. In the absence of particle collisions, these instabilities regulate the heat flux carried mainly by suprathermal electrons. The velocity distributions were modeled according to in situ observations, with a Maxwellian core and Kappa-distributed halo and strahl. We exploited advanced numerical codes capable of solving the linear dispersion and stability properties of plasma systems with Maxwellian and Kappa distributions. The unstable solutions differ significantly from those obtained with simplified two-component models (such as core-strahl or core-beam). The growth rates predict the excitation and interplay of two unstable modes, whistler and/or firehose heat-flux instabilities. The numerical solver 'ALPS' was successfully applied to systems with regularized Kappa distributions, for which analytical derivation of dispersion relations is not straightforward. The two instabilities are triggered by the relative drifts, core-strahl and halo-strahl, and may have new consequences for heat-flux regulation. Particularly important are cases when the core-strahl instability is in competition with the instability driven by the halo-strahl drift, as well as when the two instabilities have the same nature and accumulate. Future studies are motivated to confirm these predictions in quasilinear theories and numerical simulations.

Calculations of the lowest valence {\pi}* as well as the 3s and higher energy 3p{\sigma} Rydberg excited states of the CO2 molecule are carried out using density functionals with variational optimization of the orbitals, an approach involving relatively little computational effort. Five functionals with varying degree of exchange are used in combination with real or complex-valued orbitals that are optimized by finding saddle points on the electronic energy surface corresponding to the excited states. When the PBE functional is used in combination with complex orbitals, the calculated excitation energy is found to be within 0.3 eV of multireference configuration interaction reference values, and the results are further improved with hybrid functionals. In contrast, linear-response time-dependent density functional theory calculations give errors up to 1.9 eV for the most diffuse 3p{\sigma} excitation and exhibit stronger dependence on both the excitation character and the functional used. Calculated C-O dissociation curves using the PBE functional and the orbital-optimized approach compare remarkably well with the reported multireference configuration interaction and equation-of-motion coupled-cluster singles and doubles calculations. Thanks to the low computational cost, these results demonstrate that orbital-optimized density functional calculations can be a promising route for modelling photorelaxation in condensed-phase CO2, for example in the context of interstellar cosmic-ray radiation driven process involving high-energy Rydberg states.

CHRONOS is a proposed gravitational-wave detector designed to operate in the sub-Hz frequency range (0.1 to 10 Hz), a largely unexplored band due to strong noise sources that hamper ground-based detectors. It employs cryogenic operation, a cross torsion-bar configuration, a triangular Sagnac interferometer, and a speed meter readout scheme to overcome key noise limitations, targeting a strain sensitivity of $h \sim 10^{-18} Hz^{-1/2}$ around 2 Hz and a stochastic gravitational wave background of $\Omega_{GW}$ approximately $2 \times 10^{-3}$ at 2 Hz. Using analytical and interferometric simulations with FINESSE3, we evaluate the noise budget of CHRONOS and characterize the relative contributions of quantum, thermal, and environmental noise sources. Our results demonstrate that CHRONOS achieves competitive sensitivity at low frequencies. The feasibility of using CHRONOS in an earthquake early-warning system by detecting prompt gravity-gradient signals is also investigated, and is predicted to be faster by approximately 2.92 to 6.90 seconds within 40 km. These findings highlight the scientific potential of CHRONOS, bridging gravitational-wave astronomy and geophysical monitoring, and motivating further development of low-frequency detector technologies.

Algorithms based on spatial tree traversal are widely regarded as among the most efficient and flexible approaches for many problems in CPU-based high-performance computing (HPC). However, directly transferring these algorithms to GPU architectures often yields substantially smaller performance gains than expected in light of the high computational throughput of modern GPUs. The branching nature of tree algorithms leads to thread divergence and irregular memory access patterns -- both of which may severely limit GPU performance. To address these challenges, we propose a Morton (z-order) 'plane-based tree hierarchy' that is specifically designed for GPU architectures. The resulting flattened data layout enables efficient dual-tree traversal with collaborative execution across thread groups, leading to highly coalesced memory access patterns. Based on this framework we present implementations of two important spatial algorithms -- exact $k$-nearest neighbour search and friends-of-friends (FoF) clustering. For both cases, we observe more than an order-of-magnitude performance improvement over the closest competing GPU libraries for large problem sizes ($N \gtrsim 10^7$), together with strong scaling to distributed multi-GPU systems. We provide an open-source implementation, 'JZ-Tree' (JAX z-order tree), which serves as a foundation for efficient GPU implementations of a broad class of tree-based algorithms.

In this paper we investigate the long range gravitational effect of curvature-scalar field non-minimal coupling, in the form of $\xi R \phi^2$, in the perturbative quantum gravity framework. Such coupling is most naturally motivated from the renormalisation of a scalar field theory with a quartic self interaction in a curved spacetime background. This coupling results in two scalar-$n$ graviton vertices which contain no explicit momenta of the scalar, qualitatively different from the usual, e.g. $\kappa h^{\mu\nu}T_{\mu\nu}$-type minimal matter-graviton vertices. Assuming the dimensionless coupling parameter $\xi$ to be small, we compute the 2-2 scattering Feynman amplitudes between such scalars up to ${\cal O}(G^2 \xi)$. From the non-relativistic limit of these amplitudes, we compute the corresponding long range gravitational potential. There exists no tree level contribution $({\cal O}(\xi G))$ here, and hence the one loop ${\cal O}(G^2 \xi)$ result is leading. Recently, the effect of a cosmological constant in such non-minimal interaction and the subsequent gravitational potential was computed. In this work we take the cosmological constant to be vanishing. The resulting potential is found to have $r^{-4}$ leading behaviour. We further extend these results for scalar-massive spin-1 and massive spin-1/2 scattering. Spin and polarisation dependence of the two body potential have been explicitly demonstrated. We discuss some possible physical implications of these results.

When selecting a model to characterize an astrophysical population, it is crucial to assess whether that model fits the data and, if not, how it can be improved. To this end, posterior predictive checks (PPCs) are a widely-used statistical test of model fit when inferring gravitational-wave source populations. However, PPCs exhibit limitations when assessing single-event parameters with large measurement uncertainty, like the spin tilt angles of the binary black holes (BBHs) observable with the LIGO-Virgo-KAGRA (LVK) detectors. When single-event inference is prior-dominated, traditional PPCs fail to flag even very poor model fits. In this work, we assess the efficacy of various alternative PPCs on poorly-constrained parameters. We compare PPCs conducted on event- vs.~data-level parameters (e.g. posterior samples vs. maximum likelihood points), and explore two additional event-level PPCs: partial predictive checks and split predictive checks. Independent of measurement uncertainty, we find that PPCs on maximum likelihood parameters are always more discerning of model misspecification than any event-level PPC. However, when investigating simulated GWTC-3.0-like catalogs, none of the alternative PPCs show significant improvement over those traditionally used, indicating that at that sensitivity, any limited information in the data about spin tilts is insufficient to diagnose model this http URL, we apply our suite of PPCs to the spin magnitude and tilt distributions inferred in the most recent LVK catalog, GWTC-4.0. We conclude that the Gaussian Component Spins model used therein under-predicts BBHs with large spin magnitudes and over-predicts those with perfectly anti-aligned tilts.

We study the inflationary bispectrum generated by the tree-level exchange of a massive hidden-sector scalar during inflation. When the interaction between the inflaton and the hidden sector arises only from the leading boost-breaking operator of the Effective Field Theory (EFT) of inflation, the equilateral bispectrum for principal-series scalar exchange is known to be universally negative, independent of the sign of the coupling. We revisit this result within the full EFT operator basis. Using bootstrap methods, we construct the de Sitter-invariant seed four-point function and obtain the inflationary bispectrum via weight-shifting operators and a soft-limit procedure. While the equilateral bispectrum remains strictly negative when only the leading interaction is present, additional operators generate independent cubic structures whose contributions compete in the equilateral configuration. As a result, the sign of the bispectrum is no longer universal. We derive a critical ratio of interaction coefficients that separates regions of positive and negative equilateral bispectrum. We further study the effects of reduced sound speed $c_s<1$ and the exchange of multiple particles. In both cases, the critical ratio is modified, and for multi-particle exchange a positive equilateral bispectrum can arise even when the higher-order operator is subdominant. Our results show that the negativity of the equilateral bispectrum from massive exchange is not generic, but reflects a restricted operator structure in the EFT of inflation.