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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 16 July

High Energy Astrophysical Phenomena

When will T Coronae Borealis next erupt as a nova? Constraints from recurrence, orbital phase, and accretion-state evolution

Songpeng Pei, Xiaowan Zhang, Renzhi Su et al. (+6 more)

T Coronae Borealis (T CrB) is the nearest symbiotic recurrent nova and is now intensively monitored for its next eruption. We combine three constraints on the eruption time: historical recurrence, orbital phase, and recent accretion-state evolution. Conditioning on no eruption by 2026 July 11, the three effective historical intervals give illustrative survival-conditioned probabilities of 30.2% for the rest of 2026 and 56.9% within the following year; these are empirical indicators, not physical prediction probabilities. The four adopted historical eruption phases do not select a unique ignition phase, but form two loose pairs near $\phi\simeq0.44$ and $\phi\simeq0.62$, used here only as monitoring windows. The 1946 pre-eruption dip is difficult to explain by either a pure accretion-rate decline or standard dust extinction, and may have involved both accretion restructuring and source-dependent obscuration. If the renewed 2026 decline is the true pre-1946 analogue, an eruption around 2026 December remains plausible. Conversely, if post-2024 brightness remains below the 2014–2023 high state, an accretion-deficit estimate gives an earliest lower limit near 2029 May. The data therefore support conditional monitoring windows, not a unique date. These are conditional diagnostic scenarios rather than competing point predictions; the eventual eruption epoch will test their underlying assumptions.
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All authors Songpeng Pei, Xiaowan Zhang, Renzhi Su, Ziwei Ou, Yongzhi Cai, Qiang Li, Yu Liu, Xiaoqin Ren, Taozhi Yang

Cosmology and Nongalactic Astrophysics

Cosmic string gravitational wave backgrounds at LISA: II. Reconstruction of conventional signals over astrophysical foregrounds

Androniki Dimitriou, Daniel G. Figueroa, Peera Simakachorn et al. (+2 more)

We study the reconstruction of conventional cosmic-string signals with LISA in the presence of all major known astrophysical foregrounds expected in the LISA band. These include stellar-origin black-hole binaries (SOBHBs), galactic (WDs) and extragalactic (ExWDs) white dwarfs, extreme-mass-ratio-inspirals (EMRIs), and massive black-hole binaries (MBHBs). Using the Simulation-based Inference package GWBackFinder, we perform a joint inference on the LISA noise, foregrounds, and signal, across a range of injected string tensions $G\mu$. We find that reconstructing tensions with an error $\lesssim 10\%$ requires values as large as $G\mu \gtrsim 10^{-11}$, i.e. a factor $\sim10^5$ larger than previous estimates with no foregrounds, and $\sim 10^2$ larger compared to estimates accounting only for SOBHB and WD foregrounds. This work is the second in a series initiated in Ref. arXiv:2508.05395, which aims to quantify LISA's ability to measure representative cosmic-string models.
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All authors Androniki Dimitriou, Daniel G. Figueroa, Peera Simakachorn, Isak Stomberg, Bryan Zaldivar

Earth and Planetary Astrophysics

Sulfur photochemistry observationally traces mantle redox states of rocky planets

Ioannis Panagiotou, Tim Lichtenberg, Shang-Min Tsai et al. (+1 more)

Volatile outgassing from planetary interiors controls the composition of rocky exoplanets' secondary atmospheres. However, observations indicate that disequilibrium processes, such as photochemistry and vertical transport, can strongly alter the chemical structure of Hot Jupiters. Which process dominates under different types of rocky planets, and how outgassing and photochemistry jointly determine the atmospheric composition, remain open questions. Sulfur species are promising tracers of interior-atmosphere coupling because their atmospheric abundances are sensitive to both mantle redox state and stellar irradiation. The PROTEUS planetary interior-atmosphere evolution modelling framework is coupled to two chemical models, FastChem and VULCAN, for post-processed chemistry calculations. We run a grid of planetary evolution simulations spanning diverse mantle redox states, instellation fluxes, and Solar versus M-star host-star spectra. For each case, we compare atmospheric compositions under thermochemical equilibrium, only vertical transport, and vertical transport plus photochemistry. The bulk atmospheric composition remains controlled by the redox state of the mantle and outgassing history, even when disequilibrium chemistry is included. Reduced mantles produce atmospheres rich in H2, and oxidised mantles are dominated by CO2. Photochemistry affects the upper atmosphere, strongly depleting neutral volatiles and enhancing radicals, especially for highly irradiated cases. SO2 is strongly enhanced at intermediate-to-oxidised redox states. Synthetic emission spectra show that photochemical SO2 can generate absorption features at 4 um and at 7.3 / 8.7 um, reaching ~60 ppm and ~100 ppm, before sequentially returning to the outgassed signatures of ~30 ppm and ~50 ppm for the oxidised mantle redox state. These signatures are detectable with JWST, motivating targeted observational campaigns.
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All authors Ioannis Panagiotou, Tim Lichtenberg, Shang-Min Tsai, Harrison Nicholls

High Energy Astrophysical Phenomena

Spectral study of the outburst decay of the accreting millisecond X-ray pulsar SRGA J144459.2-604207

Amar Deo Chandra

We study the spectra of the accreting X-ray millisecond pulsar SRGA J144459.2-604207 during the 2024 outburst using the Neutron star Interior Composition Explorer (NICER) and Swift observations. The spectra during the outburst decay, reflares, and quiescent state are explored using the absorbed Comptonized model. We find that the spectra during the quiescent state can also be explained using the absorbed power-law and absorbed blackbody model. The spectral evolution of the source is explored as the outburst decays into quiescence. We study the long-term quiescent X-ray activity of the source spanning roughly 45 years and find that the long-term quiescent luminosity may be explained using the deep crustal heating model. We also find that the coronal activity of the companion star alone cannot power the quiescent X-ray luminosity of the source. We place the source on the radio-X-ray luminosity plane and compare its position with other sources. We estimate the propeller luminosity of the source and find that it is smaller than the estimated luminosity during reflares and the quiescent state during the 2024 outburst. Several reflares are detected during the outburst decay, one of which is near-simultaneous with the detection of an ultrafast outflow and radio emission. We explore plausible mechanisms that may power outflow, radio emission and associated jet formation in this accreting binary.
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Astrophysics of Galaxies

Cluster characteristics of Galactic open clusters

K. Neumannová, J. Supíková, N. Faltová et al. (+4 more)

Star clusters are perfectly suited for studying the formation, evolution, and dynamics of stars and their host galaxies. For this, we need to estimate total masses, radii and shapes of star clusters. These parameters strongly influence their fates in the host galaxies. However, there is no agreement about these characteristics in the literature. The published values widely disagree. We estimated total masses and cluster radii using a very conservative approach: calculating member masses and summing them. Furthermore, we investigated the three-dimensional characteristics of open clusters and their limitations. We used a commonly used grid of evolutionary tracks for different photometric sources, including 2MASS, Gaia, and Pan-STARRS. The interpolation method was tested using synthetic clusters built with ASteCA. To estimate three-dimensional shapes, we used the distribution of the well-known Galactic coordinates and inverse parallaxes. We estimated the total masses and radii of about 7000 open clusters and observed traces of tidal tails. Individual values can be used in future $Gaia$ data releases to obtain even more precise values. The current DR3 allows the study of only three-dimensional shapes up to 500 pc. Beyond this distance, we find a significant needle-like shape due to uncertainties in observed parallaxes.
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All authors K. Neumannová, J. Supíková, N. Faltová, P. Mondal, E. Paunzen, T. Ramezani, G. Szász

Earth and Planetary Astrophysics

The majority of hot Jupiters formed beyond the water ice line

Yaxing He, Bertram Bitsch, Adrien Houge et al. (+2 more)

Atmospheric compositions of giant exoplanets can retain information about their formation environments, as volatile species condense at different temperatures in protoplanetary discs. We investigated whether the atmospheric compositions of hot Jupiters can constrain their formation locations. We performed planet formation simulations using the ChemComp code, including pebble drift, pebble and gas accretion, planet migration, stellar abundances, and two additional chemical processes: thermal decomposition of refractory organics and CO/CO2 trapping in water ice. We applied this framework to nine observed hot Jupiter systems and compared the resulting atmospheric metallicities (C/H and O/H) with observational constraints. We found that the observed atmospheric abundances of the nine hot Jupiter systems can be reproduced by planets forming at different locations relative to the H2O and CO2 snowlines. Our results suggest that at least six of the nine systems are consistent with formation beyond the H2O snowline. Combined with the observed orbital separations, eccentricities, and spin-orbit obliquities, these inferred formation locations indicate that many systems likely experienced dynamical scattering followed by tidal evolution. Atmospheric abundances, in combination with detailed orbital parameters, can provide a powerful diagnostic of the formation and migration histories of hot Jupiter systems, opening up avenues to understand the origin of giant planets in general.
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All authors Yaxing He, Bertram Bitsch, Adrien Houge, Joe Williams, Masahiro Ogihara

Astrophysics of Galaxies

Berkeley 32: A Metal-poor and Dynamically Evolved Open Cluster with Evidence of Radial Migration

Deniz Cennet Ç{\i}nar, D. Bisht, Ing-Guey Jiang et al. (+3 more)

We present a comprehensive chemo-dynamical analysis of the old, metal-poor open cluster Berkeley 32 based on Gaia DR3 astrometry and Gaia-ESO Survey DR5.1 spectroscopy. Cluster membership is determined using a Gaussian Mixture Model applied to proper-motion components and trigonometric parallaxes. Isochrone fitting yields an age of 4.9 +/- 0.5 Gyr, a heliocentric distance of 3325 pc, and an extinction of A_V = 0.38 +/- 0.12 mag. Spectroscopic member stars exhibit a mean metallicity of [Fe/H] = -0.39 +/- 0.02 dex, near-solar alpha-element abundances, and a weighted mean radial velocity of V_rad = 106.26 +/- 0.03 km s^-1. The [Y/Mg] chemical clock yields an age of 4.73 +/- 2.39 Gyr, consistent with the isochrone estimate. Orbital integration indicates a moderately eccentric orbit (e = 0.268 +/- 0.004) with a guiding radius of R_g = 8.82 kpc. The inferred chemical birth radius, R_b = 9.82 kpc, together with DeltaR ~ -1 kpc, suggests moderate inward radial migration, while the offsets among R_b, R_g, and R_GC are consistent with both churning and blurring processes. A photometric analysis identifies a binary fraction of f_b = 0.449 +/- 0.017 for systems with mass ratios q >= 0.5, implying a substantial unresolved binary population. Radial cumulative distribution functions further reveal significant mass segregation, with evolved stars more centrally concentrated than main-sequence stars. These results indicate that Berkeley 32 is a dynamically evolved old-disk cluster whose present-day structure and orbit preserve signatures of both internal dynamical evolution and radial migration within the Galactic disk.
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All authors Deniz Cennet Ç{\i}nar, D. Bisht, Ing-Guey Jiang, W. H. Elsanhoury, K. Belwal, Selçuk Bilir

High Energy Astrophysical Phenomena

Swift gives a new BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs

S. Ronchini, T. Parsotan, J. DeLaunay et al. (+1 more)

The Burst Alert Telescope (BAT) onboard the Neil Gehrels Swift Observatory is capable of localizing gamma-ray transients with arcminute precision, enabling rapid multi-wavelength follow-up. However, onboard triggering is disabled during spacecraft slews, preventing the autonomous detection and localization of transients occurring during these intervals. We present here BAT-GLIMPSE, a fully autonomous, open-source pipeline for the low-latency localization of transient gamma-ray sources in Swift-BAT data. Making use of the BatAnalysis package, the pipeline combines coded-mask imaging and mosaic techniques, automatically selecting the appropriate analysis according to the spacecraft attitude and enabling localization searches during both pointing observations and spacecraft slews. We validate the performance of BAT-GLIMPSE on a sample of 66 GRBs reported in GUANO circulars. The pipeline successfully recovers arcminute positions for 43 events, consistent with published localizations, with typical offsets of $\lesssim5$ arcminutes. Approximately $88\%$ of the GRBs occurring during spacecraft slews are recovered through imaging or mosaic analyses. During the fourth LIGO-Virgo-KAGRA observing run, the role of BAT-GLIMPSE was crucial in the search for gamma-ray counterparts of gravitational waves, particularly in response to pre-merger alerts which triggered the slew of the Swift spacecraft with extremely low latency. Operating synergistically with NITRATES, BAT-GLIMPSE fills the critical gap left by slew intervals and, together, the two pipelines are estimated to double the onboard arcminute-localization rate of Swift-BAT, unlocking the full potential of the Swift mission for time-domain and multi-messenger astrophysics.
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All authors S. Ronchini, T. Parsotan, J. DeLaunay, J. A. Kennea

Instrumentation and Methods for Astrophysics

Low-Frequency VLBI Network Using SKA-LOW

Hideyuki Kobayashi, Tomoaki Oyama, Kazuma Fujita et al. (+17 more)

We propose the development of a low-frequency Very Long Baseline Interferometry (VLBI) network operating in the 100-350 MHz range, incorporating the Square Kilometre Array Low (SKA-LOW). SKA-LOW is expected to achieve exceptionally high sensitivity within this frequency band. By integrating SKA-LOW with other high-sensitivity radio telescopes located across the Asia-Pacific region, the proposed network is anticipated to deliver up to two orders of magnitude improvement in sensitivity compared to the existing VLBA. While several scientific themes utilizing low-frequency VLBI have already been proposed, we specifically advocate for astrometric studies employing existing VLBI stations to demonstrate the feasibility and scientific potential of this frequency regime. Furthermore, the combination of SKA-LOW with additional radio telescopes will enable high-fidelity imaging observations, significantly enhancing the quality and scope of low-frequency VLBI science.
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All authors Hideyuki Kobayashi, Tomoaki Oyama, Kazuma Fujita, Syunsaku Suzuki, Shintaro Yoshiura, Hiroaki Misawa, Fuminori Tsuchiya, Kazuhiro Takefuji, Kenta Fujisawa, Kohtaro Niinuma, Keitaro Takahashi, Yashwant Gupta, Bhal Chandra Joshi, Vishwesh Marthi, M. A. Krishnakumar, Zhiqiang Shen, Wu Jiang, Yihua Yan, Wei Wang, Linjie Chen

High Energy Astrophysical Phenomena

PeV extended emission around Galactic PeVatrons and echos of their flares

A.Neronov and Ie.Vovk

We notice that Galactic sources of PeV gamma-rays are generally expected to be surrounded by multi-degree-scale extended emission produced as a result of injection of electron-positron pairs in the interstellar medium from interactions of PeV gamma-rays with microwave photons. The surface brightness of such emission may be variable in time because of variability of the PeV emission power of its parent source. A flare of the parent source produces an “echo” spreading across the extended emission region that may be detectable on the time scales from decades to millennia. We consider a possibility that the very extended PeV source in the Cygnus region is the produced by the Cygnus X-3 PeV gamma-ray source, possibly being an echo of its past flare.
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Cosmology and Nongalactic Astrophysics

Galactic constraints on spinning primordial black hole dark matter from interstellar dust heating

Shaobin Hu, Yupeng Yang, Chengjie Sun et al. (+5 more)

Primordial black holes (PBHs) are compelling dark matter candidates. PBHs with masses between $10^{15}$ and $10^{18}\,\mathrm{g}$ can heat interstellar dust via Hawking radiation. Previous studies of this dust heating mechanism mostly neglected PBH spin and adopted a single dark matter halo profile. In this work, we incorporate PBH spin, which substantially enhances the emitted radiation flux, and systematically investigate the dependence of constraints on the dark matter density distribution by considering five different halo models. We compute the complete photon spectra, including both primary and secondary emissions. Our results show that, for a fixed profile and mass function, larger spin parameters yield stronger constraints on the PBH fraction $f_{\mathrm{PBH}}$. Among the halo models, the Isothermal profile gives the most stringent limits, followed by Einasto, then NFW and Moore, while the Burkert profile yields the weakest constraints. For silicate grains, which cool less efficiently than graphite, the upper limits reach $\mathcal{O}(10^{-4})$ for high spin cases. We consider both monochromatic and lognormal mass functions, and find consistent trends between them. For the lognormal case, larger values of the width $\sigma$ lead to a broader mass range being excluded, in particular ruling out massive PBHs as the sole dark matter component. Our bounds are generally weaker than other existing limits, but they provide a complementary and independent constraint.
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All authors Shaobin Hu, Yupeng Yang, Chengjie Sun, Zihan Li, Jiafan Sun, Yuzhu Tong, Yankun Qu, Shuangxi Yi

Cosmology and Nongalactic Astrophysics

High resolution Lyman-{\alpha} forest constraints on dark matter-neutrino scattering

Markus R. Mosbech, Olga Garcia-Gallego, Vid Iršič et al. (+2 more)

We present new constraints on models of dark matter interacting with neutrino, based on high-resolution Lyman-$\alpha$ forest data. We perform a suite of full hydrodynamical simulations of these models, spanning a range of interaction strengths and thermal histories. We train an emulator on the simulation results. A Monte Carlo Markov Chain analysis yields an upper limit on the interaction strength of $u_{\nu\chi} \leq1.5\times10^{-8}$ (95% C.L.), which is the strongest direct bound to date on such interactions. Our results exclude previous hints of non-zero interactions presented in the literature. We furthermore compare our results to those obtained by mapping warm dark matter constraints to other models with suppressed small-scale structure, and find that these methods would overestimate the constraining power for this model.
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All authors Markus R. Mosbech, Olga Garcia-Gallego, Vid Iršič, Matteo Viel, Julien Lesgourgues

Solar and Stellar Astrophysics

The non-LTE abundances of magnesium and yttrium and asteroseismic ages for the chemical clock calibration

Š. Mikolaitis, G. Tautvaišienė, E. Pakštienė et al. (+11 more)

Building on our previous study, which demonstrated the importance of accounting for departures from local thermodynamic equilibrium (LTE) in elemental-abundance determinations and of using asteroseismic ages, we investigate spatial variations in the empirical [Y/Mg]-age relation across the Galactic disc using a substantially larger stellar sample. We analysed high-resolution stellar spectra and determined Mg and Y abundances through spectral synthesis of multiple spectral features, rigorously accounting for non-LTE (NLTE) effects. We derived asteroseismic ages for stars exhibiting solar-type oscillations and used cross-checked isochrone-based methods for the remaining stars. We determined atmospheric parameters and Mg and Y abundances for 528 Galactic field stars, together with asteroseismic ages for 307 stars and isochronal ages for 221 stars. We also identified two new triple-lined and nine double-lined spectroscopic systems. Combining the present sample with that of our previous study yielded a total of 736 stars, which we used to examine the [Y/Mg]-age relation across the Galactic disc. The relation shows systematic spatial variations that likely reflect differences in star-formation and chemical-enrichment histories. In general, [Y/Mg] tends to increase with metallicity over the investigated age range. At supersolar metallicity, however, this trend may weaken, and the [Y/Mg]-age relations become flatter than those of solar-metallicity stars, which show lower [Y/Mg] values at young ages and higher values at old ages.
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All authors Š. Mikolaitis, G. Tautvaišienė, E. Pakštienė, A. Drazdauskas, V. Bagdonas, C. Viscasillas Vázquez, M. Ambrosch, Y. Chorniy, R. Minkevičiūtė, E. Stonkutė, B. Bale, B. Ćurjurić, A. Sharma, K. Diktanaitė

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Comment on "Non-linear interactions in cosmologies with energy exchange"

Naman Soni

This work provides a critical reassessment of the cosmological models presented in the article "Non-linear interactions in cosmologies with energy exchange" Eur. Phys. J. C 80, 120 (2020) arXiv:1907.06410 . It points out and corrects several mathematical inconsistencies in the original article. These include a flawed simplification of a Liénard-type equation, unjustified omissions of integration constants, and an incorrect use of the variation-of parameters method. By deriving the exact analytical solutions, it is shown that the corrected mathematical framework fundamentally contradicts the claims of the original article.
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Earth and Planetary Astrophysics

Atmospheric evolution through outgassing and escape on young molten rocky exoplanets

Emma Postolec, Tim Lichtenberg, Harrison Nicholls et al. (+2 more)

The earliest rocky planet atmospheres are shaped by competition between initial volatile inventories and atmospheric escape. On young magma ocean planets, outgassing competes with atmospheric escape, controlling volatile retention and atmospheric evolution. We investigate how atmospheric escape and replenishment via outgassing during magma ocean crystallization shape rocky planet atmospheres. We extend a coupled interior-atmosphere model to simulate rocky planet evolution during the magma ocean era by incorporating an energy-limited atmospheric escape module. Comparing radiative-convective and prescribed-convective atmospheres, we quantify how atmospheric energy transport affects escape. We explore a wide range of orbital separations, escape efficiencies, oxidation states, and initial volatile inventories to identify regimes where sustained magma-ocean outgassing or escape dominates. We estimate atmospheric loss and compositions for young rocky planets around Sun-like and M-dwarf stars over geologic timescales. Atmospheric escape shortens magma ocean lifetimes by weakening greenhouse insulation. Radiative-convective atmospheres reduce solidification timescales compared to purely convective cases. Volatile dissolution into the magma ocean interacts with escape to chemically fractionate the planetary volatile budget over time by retaining more soluble species. For Earth-mass planets, atmospheres survive if loss rates remain moderate. Mantle redox state remains a key control on retained atmospheric composition: high oxygen fugacity (fO2) yields heavier, H2O- and CO2-rich atmospheres, while low fO2 produces light, H2- or CO-dominated atmospheres, consistent with previous studies. Orbital separation, initial volatile inventory, and stellar type produce diverse evolutionary pathways, from bare rocky planets to magma oceans with thick atmospheres, ranging from H2- to SO2-dominated.
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All authors Emma Postolec, Tim Lichtenberg, Harrison Nicholls, Laurent Soucasse, Floris van der Tak

Astrophysics of Galaxies

The World Cup in space: Finding ionised buckyballs in the ISM with CARMENES

J. Maíz Apellániz

Over a century after the discovery of the first diffuse interstellar bands (DIBs) in absorption in stellar spectra (Heger et al 1922), their origin is still mostly unknown. The exception are four DIBs (out of 600+ known) in the 9300-9700 Angstrom region, for which a possible ascription to C_60^+ (ionised buckminsterfullerene, shaped liked a football, hence buckyballs) has been made. However, those DIBs are located in a spectral region heavily contaminated by telluric H_2O absorption, hampering their detection and study from the ground. I present the results of a study with the CARMENES spectrograph that uses a novel technique with multi-epoch spectroscopy at different times of the year to shift the relative position of the DIBs and the surrounding telluric lines, hence facilitating the analysis of the DIBs. The technique has been applied to 41 sightlines of diverse extinctions and environments, with positive detections in all of them. Our results are consistent with three of those DIBs having C_60^+ as the carrier.
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Solar and Stellar Astrophysics

Stellar Multiplicity in Open Clusters: Investigating Binary Fractions and Their Relationship with Cluster Properties

Ruan P. Alves, Hektor Monteiro, Wilton S. Dias et al. (+1 more)

Stellar multiplicity is key in dynamical evolution of open clusters (OCs) and processes of stellar formation and evolution. Since most stars form in multiple systems, investigating how environmental properties affect their occurrence is crucial. We aim to investigate how binary fraction and mass ratios change across different OC environments. Using a sample of 773 OCs, we identified binary systems and estimated binary fractions, obtaining values in the ranges 0.10-0.85 overall and 0.06-0.79 for high mass-ratio systems. No strong dependence on age or evolutionary stage is found, while an anticorrelation between metallicity and the binary fraction is identified. However, young and old clusters exhibit distinct mass-ratio distributions. We also find that the probability of a star being the primary component increases with stellar mass. In contrast, the probability of a star belonging to a binary system increases with mass for masses below 1 solar mass, and remains between 60% and 70% for high masses. Binary systems are preferentially located in the inner regions of clusters compared to single stars, and the mean mass ratio decreases with increasing distance from the cluster center. These results suggest that the binary fraction appears to be set at early times and remains largely unaffected by cluster dynamical evolution. The concentration of binaries in the inner regions of clusters likely reduces their susceptibility to dynamical escape.
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All authors Ruan P. Alves, Hektor Monteiro, Wilton S. Dias, Gabriel R. Hickel

Astrophysics of Galaxies

Isomer-specific excitation of formic acid in collisions with helium atoms

Karina Sogomonyan, Anzhela Veselinova-Marinova, François Lique et al. (+1 more)

An accurate estimation of the molecular abundances of isomers in the interstellar medium (ISM) is necessary to unravel the underlying chemistry and physics. After the recent detections of both isomers of formic acid ($cis-$ and $trans-$HCOOH) in dense dark cold clouds, their accurate molecular line modeling became of interest. The conditions of these environments do not necessarily follow the local thermodynamic equilibrium, thus taking into account the competition between the radiative and collisional processes is required. This involves the knowledge of the rotational excitation data for collisions with the most abundant interstellar species \textemdash He and H$_2$. In this paper, the first potential energy surfaces (PES) for the interaction of the two rotamers of formic acid with He atoms are computed using the explicitly correlated coupled-cluster theory [CCSD(T)-F12]. The obtained PESs demonstrate qualitative similarities and high anisotropy. The global minima are found with $V=-53.0$ cm$^{-1}$ and $V=-46.0$ cm$^{-1}$ for $cis-$HCOOH and $trans-$HCOOH respectively. Collisional excitation cross sections calculated for total energies up to 100 cm$^{-1}$ demonstrate similar propensity rules for both isomers. Quantitative differences of the cross sections associated with the two rotamers are also discussed.
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All authors Karina Sogomonyan, Anzhela Veselinova-Marinova, François Lique, Jérôme Loreau

High Energy Astrophysical Phenomena

Testing the Isotropy of the Universe with the CHIME/FRB Catalog I

Jun-Yi Shen and Yuan-Chuan Zou

We test the isotropy of the Universe using 536 Fast Radio Bursts (FRBs) from the first CHIME/FRB catalog, employing two complementary statistical methods: the two-point angular correlation function (2PACF) and the sigma-map method, with observational biases corrected using CHIME injection data. Both analyses are consistent with the isotropic expectation, but are limited by the small sample size. The 2PACF suffers from an ill-conditioned covariance matrix, preventing robust parameter inference. The sigma-map angular power spectrum shows no statistically significant directional anisotropy, though the uncertainties at low multipoles remain large. Future FRB surveys are expected to improve these limitations.
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High Energy Astrophysical Phenomena

A self-consistent Higgs-portal framework for dark matter–admixed neutron stars: Collider-motivated benchmarks meet multimessenger constraints

Adamu Issifu

We investigate dark matter (DM)-admixed neutron stars (NSs) within a self-consistent single-fluid relativistic mean-field framework by extending the Higgs-portal model with a massive $Z^\prime$ vector mediator. The resulting density-dependent repulsive interaction dynamically couples the baryonic matter (BM) and DM sectors, allowing the DM content to be characterized by the global particle fraction, $F_\chi=N_\chi/N_B$, with the local DM density determined self-consistently as $n_\chi=F_\chi n_B$, thereby eliminating the need for the externally prescribed DM Fermi momentum adopted in previous single-fluid models. Using the NL3$\omega\rho$, DD2, and FSU2R EOSs, we show that increasing $F_\chi$ systematically softens the nuclear equation of state (EOS), reduces the maximum NS mass by up to $\sim29\%$, increases stellar compactness, and modifies the thermodynamic response of dense matter. We further derive exact analytical expressions for the adiabatic speed of sound, its density derivative, and the adiabatic index, providing a rigorous benchmark for assessing the causality and thermodynamic stability of DM-admixed EOSs. At the microscopic level, the BM–DM interaction is shown to be dominated by the repulsive $Z^\prime$ vector channel. Our framework establishes a direct connection between collider-motivated WIMP models and the multimessenger phenomenology of NSs, with potential implications for future gravitational-wave and X-ray observations.
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Astrophysics of Galaxies

The Goldilocks Molecule: H$_{2}$ Emission Lines Can Identify Elusive Dwarf AGN

Morgan Micharski and Chris Richardson

We propose using H$_{2}$ emission lines as a novel diagnostic to identify dwarf AGN by running photoionization models incorporating active intermediate-mass black holes and using an observed WISE dwarf AGN as a template. Though many dwarf AGN would be incorrectly classified as star-forming if the H$_{2}$~2.12~$\mu$m/Br$\gamma$ ratio is used, ratios between H$_{2}$ emission lines can reveal active IMBHs in cases where log $n_{\text{H}} \gtrsim 4.0$. This includes the case where $M_{\text{BH}} = 10^3~M_{\odot}$, even though the optical strong lines and NIR coronal lines would likely go undetected. We conclude that H$_{2}$ emission lines show promise in detecting the most elusive IMBHs.
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High Energy Astrophysical Phenomena · Cross-listed from physics.hist-ph

Coloring Black Holes: Epistemic and Aesthetic Choices in Astronomical Imaging

Rodrigo Ochigame, Emilie Skulberg and Jeroen van Dongen

In 2019, the first image of a black hole's shadow based on observation was released by the Event Horizon Telescope Collaboration (EHT). This paper shows that despite the EHT's emphasis on a single image as its final result, there were countless plausible ways of rendering the data, among which researchers could not easily choose. To obtain a single image from the extremely noisy and sparse data, it was necessary to select one of multiple plausible approaches, or to average the results from different approaches, at each stage of data processing. We examine the epistemic and aesthetic choices involved at various stages, and explore what the images would have looked like if the EHT had made different choices. We suggest that the most valuable evidence produced by the EHT comes not from the single image it ultimately advertised as its central result, but from the demonstration of the limited variability that emerged from the specific choices made.
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Instrumentation and Methods for Astrophysics

DD4AO control law for RISTRETTO: robustness, real-time performance, and on-sky validation with PAPYRUS

Isaac Dinis, Muskan Schinde, Nicolas Blind et al. (+11 more)

This study presents DD4AO progress towards its implementation in the RISTRETTO instrument. DD4AO is a novel frequency-domain, data-driven controller for adaptive optics that leverages power spectral density estimation for optimization while enforcing stability criteria. It addresses disturbance rejection, command amplitude constraints, and system transfer functions through convex optimization, yielding an optimal controller in Infinite Impulse Response (IIR) filter form. We present the on-sky validation of DD4AO conducted using the PAPYRUS instrument at the Observatoire de Haute-Provence (OHP). The observations were performed on two stars over the night of 24-25 March 2026: the bright star Arcturus, and the faint binary HD137909. DD4AO successfully maintained a closed and stable loop over hour-long exposures while continuously adapting to evolving atmospheric conditions. The pipeline enabled instantaneous switching between DD4AO and standard controllers, namely the Integrator and OMGI, allowing direct statistical comparisons throughout each observation. On Arcturus, DD4AO achieved a 5% Strehl ratio improvement over the integrator at lambda = 1310 nm, from 28.8% to 33.9%. On HD137909, performance differences were smaller due to the low-SNR regime, though DD4AO consistently used less deformable mirror stroke and suppressed vibration peaks present in the residuals of the standard controllers. These results validate DD4AO as a robust on-sky control solution and represent an important milestone towards its deployment in RISTRETTO and SAXO+ at the VLT.
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All authors Isaac Dinis, Muskan Schinde, Nicolas Blind, Bruno Chazelas, Nathanael Restori, Christophe Lovis, Sylvain Cetre, Angelie Alagao, Romain Fetick, Taïssir Héritier, Vincent Chambouleyron, Benoit Neichel, Thierry Fusco, Jean-François Sauvage

Cosmology and Nongalactic Astrophysics

The VST ATLAS Survey IV: Galaxy, LRG and QSO bias and HODs via ACT CMB Lensing

Harshnoor Kaur, T. Shanks, S. Bose et al. (+1 more)

We present angular correlation and power spectral analyses of the clustering of VST ATLAS galaxies, LRGs and QSOs and their cross-correlations with the ACT DR6 CMB lensing map with its $\approx3\times$ higher resolution than Planck DR3. We first use $\Lambda$CDM Halofit models at linear scales to estimate galaxy, LRG and QSO bias, $b$, from the ratio of the 3-D power spectra, $b= P_{gg}/P_{gK}$ and hence the mass clustering amplitudes, $\sigma_8$. For galaxies we find $b_G(z=0.15)=1.22\pm0.07$, $\sigma_8(z=0)=0.71\pm0.06$ and for LRGs $b_{LRG}(z=0.26)=2.76\pm0.11$, $\sigma_8(z=0)=0.63\pm0.15$, both consistent with $\Lambda$CDM predictions. But for QSOs, we estimate a bias of $b_Q(z=1.7)=4.44\pm0.24$ and $\sigma_8(z=0)=0.49\pm0.06$, the latter significantly lower than expected for $\Lambda$CDM and leads to an observed $0.15<z<1.7$ gravitational growth rate faster than predicted for $\Lambda$CDM. At smaller non-linear scales, HOD model fits imply a broad halo mass distribution for $z\approx0.15$ galaxies but much narrower mass distributions for LRGs and QSOs. More surprisingly, the HOD fit for QSOs implies $M_{eff}=5\times10^{14}M_\odot$, $\approx10\times$ higher than expected. Finally, while the LRG and QSO HOD models fit $w_{gg}$ and $w_{gK}$ consistently, the same is not true for the $z\approx0.15$ galaxies unless we hypothesise anti-bias with $b_G\approx0.55$. This result supports previous QSO lensing analyses that also found anti-bias at $r<5$h$^{-1}$Mpc. We suggest that while HOD + NFW halo models may well describe LRG mass profiles and clustering, at intermediate scales the dominant galaxy population (and QSOs) may follow the alternative hierarchical clustering model of Peebles(1974) where galaxies trace the mass more closely than in a halo model.
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All authors Harshnoor Kaur, T. Shanks, S. Bose, A.C. Edge

Astrophysics of Galaxies

The COLIBRE-SKIRT pipeline: Calibration-free dust radiative transfer postprocessing for cosmological simulations

Andrea Gebek, Maarten Baes, Nick Andreadis et al. (+16 more)

Context. Three-dimensional dust radiative transfer provides a powerful framework to connect cosmological galaxy simulations to multiwavelength observations. Until recently, in large-volume simulations, the formation of a cold ISM phase was prevented and dust was not evolved self-consistently. This required calibration of dust-to-metal ratios and extra subgrid dust attenuation in birth clouds, thereby reducing the predictive power. Aims. We present the COLIBRE-SKIRT pipeline, a calibration-free dust radiative transfer framework for the novel COLIBRE suite of large-volume cosmological simulations, which include a live dust model and directly simulate the multiphase ISM. Our primary aim is to establish a reference pipeline for generating multiwavelength mock observables from these simulations. As a first application, we produce far-ultraviolet (FUV) to far-infrared (FIR) spatially integrated spectra and assess them by comparison with the observed low-redshift cosmic spectral energy distribution (CSED). Methods. We apply the SKIRT dust radiative transfer code to the COLIBRE simulations. Dust masses and species fractions are taken directly from the simulation, and no birth cloud model is added in postprocessing. We introduce a "split & scale" approach that maps the simulated two-size, multi-species dust distribution onto continuous grain size distributions without introducing free parameters. Results. We find that, for the first time, a large-volume cosmological simulation directly reproduces the local Universe CSED without calibrating the postprocessing routine a priori. Residual tensions in the mid-infrared (~0.2 dex) point towards insufficient heating of the hottest dust components and uncertainties in the modelling of the PAH-emission carriers. This framework can be readily applied at low and high redshift to create synthetic spectra and images from the FUV to the FIR.
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All authors Andrea Gebek, Maarten Baes, Nick Andreadis, Joop Schaye, Anand Utsav Kapoor, Connor Bottrell, Shengdong Lu, Cedric G. Lacey, Alejandro Benítez-Llambay, Peter Camps, Evgenii Chaikin, Anna Durrant, Carlos S. Frenk, Filip Huško, Sylvia Ploeckinger, Alexander J. Richings, Matthieu Schaller, James W. Trayford, Aswin P. Vijayan

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Cosmological Collider Signals at Strong Mixing

Xiangwei Wang, Yi Wang and Yunke Zhao

We study cosmological collider signatures in a two-field inflationary system with constant-turn derivative mixing between the canonically normalized curvature fluctuation and a massive isocurvature field. Building on recently derived exact hypergeometric solutions that treat the quadratic mixing nonperturbatively, we construct the mixed propagators constituting the cosmological correlators. A Mellin-Barnes approach helps isolate the pair of nonanalytic late-time branches carried by a heavy field. For a cubic isocurvature self-interaction, these branches contribute towards a squeezed bispectrum with a power-law envelope and logarithmic oscillations. The oscillation frequency encodes the heavy mass, while the amplitude and phase retain the full mixing dependence rather than a perturbative expansion. We perform the squeezed limit integral analytically and compare it with numerical results across representative masses and mixing strengths. At fixed mixing we derive the large-mass JWKB expansion of the squeezed correlator and its phase. We also give integral representations for the isocurvature Wightman function. The research idea was suggested by ARC, the calculation was performed by GPT, and the results were checked by the authors.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Thermal Masses and Bubble-Wall Friction in Cosmological Phase Transitions

Carlo Branchina, Stefania De Curtis, Luigi Delle Rose et al. (+3 more)

Bubble-wall friction controls the dynamics of first-order cosmological phase transitions. In Boltzmann-equation approaches, a major uncertainty arises from infrared gauge bosons, whose contribution is artificially enhanced in the massless approximation. We study the impact of thermal masses by including them consistently in both the Liouville operator and the collision integrals. Thermal masses suppress the source term for out-of-equilibrium perturbations while also reducing interaction rates. These effects largely cancel for top quarks, giving only percent-level changes, but they strongly suppress the infrared gauge-boson contribution, shifting the dominant momenta to scales of order the temperature. As a result, gauge bosons become subleading and wall velocities are close to those obtained from top-quark friction alone. We illustrate this in the singlet-extended Standard Model. Our results show that thermal masses reduce the sensitivity of friction calculations to the poorly controlled infrared sector of the plasma.
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All authors Carlo Branchina, Stefania De Curtis, Luigi Delle Rose, Alessio Notari, Giuliano Panico, Matthew Starbuck

Cosmology and Nongalactic Astrophysics

CAMB v2: cosmological power spectra for high-precision surveys

Antony Lewis

Upcoming cosmic microwave background (CMB) and large-scale-structure surveys require theoretical power spectra with numerical errors well below their observational uncertainties over the scales that carry most of the constraining power. We describe a substantial update to CAMB designed to provide fast, high-precision predictions for two key outputs: the lensed CMB and matter power spectra. The central development is a new treatment of the hyperspherical Bessel functions used for line-of-sight integration in non-flat cosmologies. A leading-order Olver construction maps the curved radial equation onto the flat spherical Bessel equation by matching their actions through the turning point. The resulting approximation is exact in the flat limit, remains smooth through the turning point, and reduces near flatness to a simple rescaling of the flat Bessel argument and amplitude. We also describe updated integrators, a recalibrated fast recombination model, stabilized parameterized post-Friedmann dark-energy evolution, and improvements to CMB lensing accuracy. Numerical convergence is assessed by comparing unboosted default results against more converged calculations. The defaults meet conservative $10^{-3}$ pointwise convergence targets over the main lensed-CMB and quasi-linear matter-power ranges relevant for future surveys. Errors measured in typical runs are substantially smaller than this. We also describe the convention dependence of the nominally linear matter power spectrum when a homogeneous calculation attempts to represent the effects of reionization heating. Essentially all of the new algorithms and code were developed with LLMs or AI agents under human supervision.
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Earth and Planetary Astrophysics

Dust masses of Upper Scorpius disks and their statistics

Huiyi Deng, Yao Liu and Min Fang

The total dust mass of protoplanetary disks is a key property that determines the potential for planet formation. Upper Scorpius (USco), with an age of ~5-12Myr, provides an important laboratory for investigating the evolution of dust reservoirs on timescales comparable to those of planet formation. In this work, we analyze the dust mass distribution of 136 full and transitional disks in USco using the largest ALMA 0.88mm continuum sample currently available for the region. To improve the accuracy of dust mass estimates, we construct a grid of 918 self-consistent radiative transfer models that account for stellar-mass-dependent disk sizes, accretion rates, and porous dust properties. The models yield a new calibration between dust temperature and stellar luminosity, predicting systematically higher dust temperatures for low-mass stars than commonly adopted prescriptions. Using these revised dust temperatures together with porous dust opacities, we derive dust masses for the USco disks and compare them with those of a younger sample in the Chamaeleon~I star-forming region. We find a median dust mass of 0.95M_E for the USco disks, approximately six times lower than that of the Chamaeleon I disks (5.69M_E), providing strong evidence for substantial depletion of millimeter-sized dust grains over the first several Myr of disk evolution. We confirm the previous finding of a highly significant correlation between stellar mass and dust mass, with a slightly steeper relation in USco than in Chamaeleon I. The low dust masses observed in USco, together with their comparison to mature exoplanetary systems, suggest that a large fraction of the primordial solid reservoir has already been incorporated into larger bodies, removed by radial drift, or hidden from millimeter observations by ages of 5-12 Myr.
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Earth and Planetary Astrophysics

Flow-Driven Limb-Asymmetry of Haze Distribution Part I: An Analytical Framework for Predicting the Size Distribution of Photochemical Hazes Across the Two Limbs of hot-Jupiters

Mei Ting Mak, Thaddeus D. Komacek, Nathan J. Mayne et al. (+1 more)

Photochemical haze, a common aerosol type expected to form in the atmospheres of hot-Jupiters, can become concentrated to different extents between the morning and evening limbs depending on the balance between advection, gravitational settling, and radiation pressure. We present a analytical framework incorporating the effect of gravity, planetary radius, and stellar flux, alongside the particle size of the haze on its resulting relative distribution between the two limbs. Using this framework and further comparing with 3D climate simulations, our framework provides a reasonable first-order estimate of the maximum radius of haze particles which would reach the morning limb and subsequently be trapped by the nightside gyres, resulting in a higher or comparable concentration of haze over the morning limb compared to the evening limb for a given hot-Jupiter atmosphere. We find that the framework performs best for higher-gravity planets, where the transport of haze particles is more strongly controlled by gravitational settling and therefore less sensitive to the approximations made in describing the atmospheric circulation. We further show that for low-gravity hot-Jupiters, even large haze particles can be readily transported to the morning limb before being removed by gravitational settling, whereas for high-gravity hot-Jupiters only small particles can survive transport to the morning limb. Our novel framework provides a rapid way to understand the transport of haze and plan limb asymmetry observations with JWST, constraining the parameter space exploration for full-scale computationally expensive 3D simulations.
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All authors Mei Ting Mak, Thaddeus D. Komacek, Nathan J. Mayne, David K. Sing