Solar and Stellar Astrophysics
Frequent X-class Far UV Flares from a Young Solar Analog DS Tucanae A
Tristen Sextro, Kevin France, Vladimir Airapetian et al. (+4 more)
The young solar analog DS Tuc A (~45 million years old, spectral type G6V) serves as an excellent proxy to the Sun during early stages of the Earth's
evolution. The young Sun's enhanced
magnetic activity in the form of X-ray and extreme UV emission, stellar wind, and
flares likely affected the magnetospheric and atmospheric environments of early Venus, Earth and Mars. Studies of DS Tuc A help constrain
evolution of magnetospheric and atmospheric environments of early Venus, Earth, and Mars and create opportunities to study the impact of
flares on the transiting
exoplanet, DS Tuc Ab. We analyze ~11 hours of Far-ultraviolet (FUV; 1130 - 1450 $\mathring{A}$) observations taken by the Hubble Space
Telescope Cosmic Origins Spectrograph during late 2023 and early 2024. We find DS Tuc A exhibited 26
flares over ~11.1 hours of observations in the transition region lines Si IV (1394 $\mathring{A}$ + 1402 $\mathring{A}$), with durations ranging 90 - 960 seconds and FUV absolute energies ranging ~ 10$^{29}$ - 10$^{31}$ erg over the observed bandpass. Si IV
flares are accompanied by increases of other chromospheric and transition region lines, however the strongest Si IV
flares show no enhanced coronal emission traced by Fe XXI 1354 $\mathring{A}$. We present an analysis of each detected
flare, including X-ray and bolometric luminosities scaled from FUV
flare energies, electron density measurements for the strongest
flares, and the Far-UV continuum response to flaring. These results provide constraints on the frequency and energetics of
flares comparable to X100-class solar
flares and FUV-emitting regions in young solar analogs.
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All authors Tristen Sextro, Kevin France, Vladimir Airapetian, Grace Sweetak, Randall McEntaffer, Kosuke Namekata, Yuta Notsu
Astrophysics of Galaxies
A dense, metal-rich absorber driven by a heavily dust-obscured galaxy: The direct evidence of CGM enrichment at $z\sim7$
Qinyue Fei, Seiji Fujimoto, Gabriel Brammer et al. (+22 more)
We report the serendipitous discovery of a dense, metal-enriched circumgalactic medium (CGM) absorber at z=7.03, together with its host
galaxy, identified along the sightline toward a red
quasar. The absorber exhibits the largest rest-frame equivalent widths and column densities observed to date at z>5, tracing a metal-enriched gaseous
halo. Using deep JWST/NIRSpec and NOEMA observations, we characterize the absorber's physical properties and identify its host, ND1, as a vigorously
star-forming
galaxy at an exceptionally close impact parameter of ~16kpc, so heavily dust-obscured that it is detected only in the longest-wavelength NIRCam bands. Detections of [OIII]$\lambda$5007, H$\alpha$, and [CII]$\lambda 158\,\mu$m emission anchor the systemic
redshift to z~7.0321, revealing a coherent ~50km/s blueshift of the absorbing gas relative to the host, suggesting outflow-driven metal transport into the
halo. The outflow velocity, combined with the measured column density, implies an outflow rate of $\dot{M}_{\rm out}=64 M_\odot\,yr^{-1}$ and a mass loading factor $\eta=3$, indicating an energetic, chemically-enriched wind launched from a dust-obscured starburst. While the overall ionization state and [Mg/Fe] ratio align with empirical
cosmic evolutionary trends, the absorber displays an enhanced carbon-to-oxygen ([C/O]) ratio. This abundance pattern suggests the nucleosynthetic yields of Population~III stellar explosions, and aligns with the host's
star-formation history extending to $z \gtrsim 8$, potentially offering a rare fossil record of primordial metal enrichment. Our findings demonstrate that intense
star-formation feedback can rapidly and efficiently pollute the CGM/IGM well into the Epoch of Reionization. The NIR-dark nature of the host further implies that rest-UV surveys may systematically miss the dusty sources that drive CGM- and IGM-scale metal enrichment in the early Universe.
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All authors Qinyue Fei, Seiji Fujimoto, Gabriel Brammer, Lise Christensen, Marianne Vestergaard, Rohan P. Naidu, Robert A. Simcoe, Norman Murray, Luis C. Ho, Ruancun Li, Volker Bromm, Javier Álvarez-Márquez, Hollis B. Akins, Yoshihisa Asada, Simona Di Stefano, Kohei Inayoshi, Vasily Kokorev, Jorryt Matthee, Romain A. Meyer, Ava Polzin, Francesco Valentino, Fabian Walter, Marcel Neeleman, Yunjing Wu, Mengyuan Xiao
Cosmology and Nongalactic Astrophysics
The galaxy-electron cross-spectrum with ACT, SPT-3G and DESILS LRGs
Selim C. Hotinli
The
galaxy–electron cross-power spectrum $P_{ge}(k)$ measures the small-scale distribution of gas around
galaxies, the quantity reshaped by feedback. We measure $P_{ge}$ from the kinetic Sunyaev–Zel'dovich (kSZ) signal of the photometric DESI Legacy Imaging Surveys luminous red
galaxies, cross-correlating a velocity-weighted
galaxy momentum template with the CMB temperature from ACT DR6 and, for the first time, SPT-3G. The absolute normalization of the cross-spectrum is fixed by a surrogate-field Monte Carlo that propagates the survey mask, lightcone
evolution, and photometric-
redshift weights, converting the measured pseudo-spectrum into $P_{ge}(k)$ in physical units. We detect $P_{ge}$ at $11.7\sigma$ with ACT and $8.4\sigma$ with SPT-3G, and at $12.3\sigma$ combining SPT-3G with the ACT northern cap, which it does not overlap. The two surveys have independent optics, beams, filtering and noise and share about two thirds of the SPT-3G
galaxies; their amplitudes agree channel by channel, the largest difference being $0.7\sigma$. All $26$ null tests on the adopted night maps are consistent with zero signal, among them the six ACT frequency differences, the three SPT-3G frequency differences, and the four ACT cap differences of the main selection. Turning the amplitude into a gas fraction requires the host
halo masses of the sample, which the cross-spectrum does not itself measure; taking them from its measured number density and from a published CMB-
lensing calibration of the same
galaxies, the gas within the virial radius is $25$–$33\%$ of the
cosmic baryon budget of the
halo.
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Earth and Planetary Astrophysics
Evidence for an Extended Hydrogen Outflow on WASP-12 b
Morgan Saidel, Shreyas Vissapragada, Heather A. Knutson et al. (+6 more)
Recent observations of atmospheric escape from
planets orbiting early-type
stars indicate that
planets with higher Roche filling factors have significantly higher mass loss rates. For three of these
planets, full-orbit observations have revealed the presence of large leading and trailing tails of escaping planetary material. These 3D outflow geometries encode information about the underlying outflow physics, and can also be used to constrain their stellar wind properties and to predict their long-term orbital
evolution. We present new evidence for extended H$\alpha$ and H$\beta$ absorption from escaping hydrogen for a fourth
planet, WASP-12 b. We observed WASP-12 b with the Keck
Planet Finder on Keck I over a period of approximately eight hours centered on the transit. We find a H$\alpha$ and H$\beta$ absorption signal in the stellar rest frame that is strongest during the transit (H$\alpha$ amplitude: $2.66\pm0.25\%$, H$\beta$ amplitude: $2.88\pm0.43\%$), with evidence of both pre- and post-transit absorption. This measurement is consistent with outflow models where the escaping gas overflows the
planet's Roche lobe and is advected into the stellar rest frame before being tidally sheared into extended tails. This outflow behavior is qualitatively similar to previous H$\alpha$ observations of this
planet as well as observations of extended outflows from other gas giants orbiting early-type
stars.
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All authors Morgan Saidel, Shreyas Vissapragada, Heather A. Knutson, Aaron Householder, Morgan MacLeod, Adam Jensen, Howard Isaacson, Judah Van Zandt, Fei Dai
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Massively parallel transdimensional sampling with data assimilation: an application to LISA galactic binaries
Gabriele Demasi and Walter Del Pozzo
Transdimensional
Bayesian inference is becoming a key ingredient in gravitational-wave astronomy. In many relevant applications, the number of components needed to describe the data is not known a priori and must be inferred jointly with their parameters. We present a transdimensional Sequential Monte Carlo (SMC) framework designed to exploit massive parallelism. The method evolves a population of particles through a sequence of tempered distributions and uses the No-U-Turn Sampler for the exploration of fixed-dimensional parameter space while reversible-jump birth and death moves allow the number of components to vary. The same SMC construction also enables posterior samples obtained from a shorter data segment to be updated as additional data become available, enhancing the overall efficiency of the analysis. We validate the approach on two proof-of-concept problems: the recovery of a sequence of Gaussian pulses and a simplified LISA Galactic-binary inference problem. In both cases, the method recovers the injected number of components and produces consistent posterior estimates. These results indicate that the proposed method is a promising avenue toward scalable and parallel
Bayesian transdimensional inference for current and future gravitational-wave astronomy.
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Astrophysics of Galaxies
Chandra Lensing-cluster Ultradeep Extragalactic Survey (CLUES) I: A 2 Ms Point-Source Catalog of the Abell 2744 Field
Shouyi Wang, Fan Zou, Elena Gallo et al. (+10 more)
In the first paper of the Chandra
Lensing-cluster Ultradeep Extragalactic Survey (CLUES), we present an ultradeep 2 Ms X-ray survey of the Abell 2744 field constructed from 101 archival Chandra ACIS-I observations. With an exposure comparable to the Chandra Deep Fields and further boosted by strong-
lensing magnification from the Abell 2744 cluster at $z=0.3$, this field represents the third deepest extragalactic X-ray survey of the sky and also has rich synergy with extensive coverage by the Hubble Space
Telescope and James Webb Space
Telescope. We present the Chandra data reduction and detect sources in the soft (0.5-2 keV), hard (2-7 keV), and full (0.5-7 keV) bands over a total area of $369~\mathrm{arcmin^2}$. We perform dedicated image fitting with Chandra point spread functions to optimize point-source detections and improve X-ray positions and further screen the detections to address the impact of the central bright, structured intracluster medium. A total of 327 X-ray point sources are detected and cataloged, including their X-ray photometry and basic spectral properties. Detailed simulations are also conducted, based on which the expected 50% flux completeness reaches $6.3\times10^{-16}$, $2.8\times10^{-16}$, and $4.9\times10^{-16}~\mathrm{erg~cm^{-2}~s^{-1}}$ in the full, soft, and hard bands, respectively. The source number density as a function of flux is consistent with those in blank-field surveys within a factor of $\approx2$, with a slight excess above $\approx10^{-14}~\mathrm{erg~cm^{-2}~s^{-1}}$. All X-ray data products are publicly released, including the catalog, X-ray images, exposure maps, background maps, and sensitivity maps.
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All authors Shouyi Wang, Fan Zou, Elena Gallo, Bin Luo, W. N. Brandt, Yuxuan Pang, Tommaso Treu, Xue-Bing Wu, Dieu D. Nguyen, Guido Roberts-Borsani, Shengzhe Wang, Weiwei Xu, Zihao Zuo
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
WIMPs with Enhanced Annihilation from a Feebly Interacting Unstable Partner
Chance Hoskinson, Pearl Sandick and Barmak Shams Es Haghi
Weakly interacting massive particles (WIMPs) constitute one of the best-motivated dark matter (DM) candidates. In this study, we consider a simple extension of the WIMP paradigm in which WIMPs are coupled to a heavier particle that interacts only with them and can decay into WIMPs. In the early Universe, when WIMPs are in thermal
equilibrium with the Standard Model (SM) bath, they serve as a portal to populate the heavy partner through inverse decays. Depending on the lifetime of the partner particle, its eventual decay into WIMPs can significantly alter the WIMP abundance. If the partner decays into WIMPs before their freeze-out from
equilibrium, the standard thermal history remains unchanged. When the decay occurs after WIMP freeze-out, however, the injected non-thermal population of WIMPs can result in an overproduction of DM, therefore requiring a larger WIMP annihilation cross section relative to the standard scenario without the partner. For a given partner lifetime and WIMP annihilation cross section, freeze-out may be delayed due to re-annihilation or followed by a freeze-in phase. By solving the Boltzmann equations both semi-analytically and numerically, we explore these thermal histories and study the required enhancement in the WIMP annihilation cross section compared to the canonical value. This enhancement, which can reach up to three orders of magnitude, leads to stronger annihilation signals in the late Universe. As a result, current and upcoming indirect detection experiments are able to probe the lifetime of the partner particle. We briefly explore possible connections between our scenario and the baryon asymmetry of the Universe. As an example, we show that the Next-to-Minimal Supersymmetric Standard Model (NMSSM) can provide a realization of our scenario, with the possibility of accommodating light higgsino DM with the correct relic abundance.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Proper Time Shifts in Pulsar Timing Arrays
Vincent S. H. Lee
Pulsar timing arrays are a powerful tool for probing low-frequency gravitational phenomena and physics beyond the Standard Model. We establish a general, gauge-invariant framework for the timing residual by identifying the measurable quantity as the proper time interval between consecutive pulse arrivals at Earth. In linearized general relativity, we derive a general expression for this proper time shift and show that it decomposes into Doppler, Shapiro, and Einstein delay contributions whose sum is gauge invariant, similar to frameworks that have been developed for other gravitational-wave detectors such as
laser and atom interferometers. We also provide a recipe for computing the resulting timing residual for any specified perturbation, and we illustrate the method with several physically well-motivated sources, recovering known results where they exist in the literature. This recipe can be directly applied to search for new physics from real
pulsar timing data using existing numerical software.
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Astrophysics of Galaxies
On the clumpy nature of super-early galaxies
A. Ferrara, B. Das, M. Kohandel et al. (+2 more)
JWST has revealed that
galaxies during the Epoch of Reionization are composed of compact stellar clumps spanning more than two orders of magnitude in mass and size. We present an analytical framework that connects the global properties of high-
redshift galactic disks to the formation, dynamical
evolution and visibility of these systems. Starting from the classical Toomre instability, we derive analytical mass-size and surface density-size relations together with, for the first time, the intrinsic clump mass spectrum obtained by integrating over the entire unstable branch of the dispersion relation. The observed clumps are naturally reproduced for turbulent velocity dispersions $\sigma\simeq 10-80\,{\rm km\,s^{-1}}$, while their location along the mass-size relation is determined by the compactness of the parent disk. The intrinsic spectrum extends over nearly two decades in mass, $5.5\lesssim\log(M_{\rm cl}/M_\odot)\lesssim7.3$, and is transformed by gas dynamical friction, which suppresses the high-mass tail ($t_{\rm df}\propto M_{\rm cl}^{-1}$) and reproduces the observed clump mass-function slope, $dN/dM\propto M^{-1.89}$.
Supernova feedback is insufficient to clear the dense natal gas, whereas radiation pressure provides a robust clearing mechanism: Ly$\alpha$ trapping dominates in dust-poor clumps and infrared trapping takes over as they become enriched. The results provide the first self-consistent analytical framework connecting the formation, statistical properties and visibility of stellar clumps in super-early
galaxies.
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All authors A. Ferrara, B. Das, M. Kohandel, A. Pallottini, E. Ntormousi
High Energy Astrophysical Phenomena
Unifying spatial correlation with hierarchical population inference to constrain the AGN channel for binary black hole mergers
Lucas Pouw, Lorenzo Speri, Niccolò Veronesi et al. (+1 more)
The origin of the stellar-mass binary black holes (BBHs) observed in gravitational wave (GW) events by the LIGO-Virgo-KAGRA (LVK) detectors remains uncertain. One promising formation pathway is the active galactic
nucleus (AGN) channel, in which BBHs embedded in AGN
accretion discs experience enhanced merger rates and may produce rapidly spinning black holes in the upper mass gap. Previous constraints on the AGN contribution to the LVK merger population have relied either on spatial correlations between GW localisations and AGN catalogues or on modelling the intrinsic properties of GW sources. We develop a hierarchical
Bayesian framework that unifies these approaches within a single likelihood for the fraction of AGN-hosted GW events, $f_{\rm agn}$. This framework, combined with the latest gravitational wave transient catalogue GWTC-5.0 and the electromagnetic Quaia AGN catalogue, cannot exclude an AGN contribution to the observed merger rate. For unobscured AGN in the optical and infrared bands with bolometric luminosities $L_{\rm bol}\geq\{10^{44.5},10^{45.5},10^{46.5}\}\,\mathrm{erg\,s^{-1}}$, we exclude $f_{\rm agn} \geq \{0.52,0.41, 0.61\}$ at the 95 percent credible level under our fiducial model. The methodology and results presented in this work lay down the pathway for combining the full GW posterior with electromagnetic observations to infer the properties of GW populations and AGN discs.
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All authors Lucas Pouw, Lorenzo Speri, Niccolò Veronesi, Elena Maria Rossi
Astrophysics of Galaxies
The relationship between morphology, density, and location in the cosmic web from massive to dwarf galaxies
Ilin Lazar, Sugata Kaviraj, Aaron E. Watkins et al. (+5 more)
We study how morphology relates to environment from massive to dwarf
galaxies using, for the first time, a mass-complete sample of ~13,000
galaxies, in the stellar-mass and
redshift ranges 10^8 MSun < Mstar < 10^11.5 MSun and 0.2<z<0.4, respectively. By combining HST-derived visual morphological classifications with local density and
galaxy distances from nodes and filaments, we quantify how early-type and late-type
galaxies (ETGs and LTGs) differ with respect to environment. The overall ETG fraction decreases from ~65 per cent at Mstar ~ 10^11 MSun to ~20 per cent at Mstar ~ 10^8 MSun. Regardless of morphology, lower stellar mass
galaxies lie further away from nodes and filaments than their more massive counterparts. While, at Mstar > 10^9 MSun, ETGs reside further away from nodes and filaments than LTGs, this segregation weakens as stellar mass decreases, with ETGs and LTGs exhibiting similar locations at Mstar < 10^9 MSun. This diminishing difference at lower stellar mass is likely driven by the fact that filaments have a finite extent and lower mass
galaxies, of all morphologies, lie further away from filament cores and are therefore confined to a smaller region of the filament itself. For high-mass
galaxies (where ETGs and LTGs show strong environmental segregation), greater proximity to nodes likely inhibits coherent angular momentum acquisition, while residing closer to filament cores increases the likelihood of interactions and mergers. Both make it easier to create dispersion-dominated systems, driving the sharp rise of the ETG fraction, in the high-mass regime, close to nodes (and, to a lesser extent) filaments. Our results show that
galaxy evolution is increasingly driven by internal processes as stellar mass decreases.
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All authors Ilin Lazar, Sugata Kaviraj, Aaron E. Watkins, Christopher J. Conselice, Darshan Kakkad, Thomas M. Sedgwick, Garreth Martin, Sophie Koudmani
High Energy Astrophysical Phenomena
1D PIC Simulations of Resonant Scattering-Driven Pair Cascades in Magnetar Magnetospheres
Jens F. Mahlmann, Alexander A. Philippov, Adrien Soudais et al. (+2 more)
Hard X-rays in persistent magnetar emission originate from radiative processes in pair-loaded magnetospheric
plasma, yet self-consistent kinetic simulations of such radiation-rich systems remain limited. We perform 1D particle-in-
cell simulations of pair creation mediated by resonant inverse Compton scattering (RICS) along isolated field lines in twisted magnetospheres, capturing particle acceleration and radiative drag from first principles. The drag force, which strongly depends on the particle Lorentz factor and location, plays a key role in the magnetospheric
circuit. Strong RICS drag impedes the flow of electrons and positrons, particularly along extended field lines. Nevertheless, the
plasma sustains the
circuit by self-organizing into a single accelerating gap near the
star in one hemisphere. The accelerated
plasma flow from the gap becomes loaded with copious electron-positron pairs in extended RICS zones, and also carries ions extracted from the
star and accelerated in the gap. When radiative drag stops the pair-loaded flow at the
magnetic equator, the ion component transfers momentum through streaming instabilities, delivering a small lepton population into the opposite hemisphere and sustaining the
circuit. The gap confined to a single (anode) hemisphere implies asymmetric hard X-ray production, possibly detectable in phase-resolved magnetar spectra.
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All authors Jens F. Mahlmann, Alexander A. Philippov, Adrien Soudais, Andrei M. Beloborodov, Lorenzo Sironi
Instrumentation and Methods for Astrophysics
The OpenGadget3 Code for Cosmological Simulations
Klaus Dolag, Geray S. Karademir, Luca Tornatore et al. (+28 more)
We present the public release of OpenGadget3 (OG3), a substantially extended and re-organised version of the widely used Gadget-2/3 family of cosmological simulation codes. Since G2 was made publicly available, the absence of continued official development led to the creation of numerous, mutually incompatible developer versions of G3 across the community. This made it effectively impossible to track bug fixes, reproduce published results, or consistently credit the many individual contributors. OG3 addresses this by consolidating these disparate developments into a single, documented, and continuously maintained code base, released under the GNU GPLv3 through a GitLab repository (with an accompanying wiki), regularly synchronised with the active developer branch, and supported by a dedicated continuous-integration (CI) pipeline. OG3 retains the core algorithmic backbone of its predecessors, a Barnes&Hut oct-tree combined with a Particle-Mesh method for
gravity, and a choice of Smoothed Particle Hydrodynamics or Meshless-Finite-Mass solvers for gas dynamics, within a hybrid MPI/OpenMP parallelisation framework, extended with GPU offloading via OpenACC and OpenMP. The code integrates an extensive suite of sub-resolution and physical modules, including primordial chemistry, radiative cooling,
star formation, stellar feedback and chemical enrichment, dust formation and
evolution, black hole growth and AGN feedback, MHD, thermal conduction, physical viscosity, SIDM, and massive
neutrinos. OG3 introduces new features improving robustness, reproducibility, and usability: a flexible mixed-precision framework spanning 16- to 128-bit representations; expert-level tagged parameters with restart-time change log; extensive consistency checks against invalid configurations; and FAIR-compliant reporting of all settings, parameters, and specific publications. (shortened and abridged)
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All authors Klaus Dolag, Geray S. Karademir, Luca Tornatore, Antonio Ragagnin, Milena Valentini, Ludwig M. Böss, Frederick Groth, Giuseppe Murante, Stefano Borgani, Volker Springel, Cenanda Arido, Javier Badía, Tiago Castro, Alice Damiano, Laura Di Federico, Moritz S. Fischer, Gian Luigi Granato, Nitya Hariharan, David Klemmer, Umberto Maio, Tirso Marin-Gilabert, Ilaria Marini, Yashraj Patil, Margarita Egelhofer, Cinthia Ragone-Figueroa, Luca Sala, Cecilia Scannapieco, Ludwig D. Schmidt, Ulrich P. Steinwandel, Giovanni Tedeschi-Prades, Marc Wiertel
Instrumentation and Methods for Astrophysics
Rethinking Domain Specialization for Open-Ended Scientific Reasoning in Astronomy Language Models
Vanessa Lama, Sanjay Das, Emily Herron et al. (+5 more)
Domain-specialized
language models are widely used for scientific question answering, but stronger general-purpose systems raise a sharper question: when does domain-specific fine-tuning remain valuable for open-ended scientific
reasoning? We study this in astronomy with a curated QA
benchmark from publicly available 2017–2026 Olympiad-style materials. The free-response subset contains 300 questions, including 204 text-only and 96 image-linked examples. We compare open-weight and API-served general-purpose,
multimodal, and astronomy-specialized models using judge-based correctness and complementary reference metrics. Strong general-purpose models establish the highest correctness baseline in this testbed, while analyses of metric agreement, judge sensitivity,
benchmark composition, and modality reveal variation not captured by a single leaderboard. These results motivate treating domain specialization as a task- and deployment-dependent property and highlight the role of domain-specific evaluation in determining which models, capabilities, and evaluation criteria are appropriate for scientific workflows.
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All authors Vanessa Lama, Sanjay Das, Emily Herron, Yuan-Sen Ting, Tijmen de Haan, Junqi Yin, Tirthankar Ghosal, Feiyi Wang
Instrumentation and Methods for Astrophysics
IViS: Interferometric Visibility-domain inversion Software - A GPU-accelerated Python framework for joint deconvolution with ASKAP
A. Marchal, N. M. McClure-Griffiths, J. Dempsey et al. (+9 more)
Wide-field spectral-line imaging with modern
radio interferometers remains challenging when the emission is extended, multiscale, and distributed over many overlapping pointings. Accurate reconstruction requires joint treatment of the calibrated visibilities, control of image-domain regularity, and recovery of missing short spacings from single-dish data. We present IViS (Interferometric Visibility-domain Inversion Software), a GPU-accelerated Python framework for visibility-domain joint deconvolution, and assess its performance for wide-field HI imaging with the Australian Square Kilometre Array Pathfinder (ASKAP). The current model, Classic3D, reconstructs a non-parametric sky cube directly from calibrated visibilities by minimizing a regularized least-squares criterion. The forward model relies on a non-uniform fast
Fourier transform (NUFFT), supports joint deconvolution across mosaic pointings and positivity constraints, and can incorporate single-dish data through a fusion term. We validate the method using point-source, noise-only, and multiscale diffuse-emission simulations, and apply it to ASKAP observations toward the Large Magellanic Cloud (LMC). The simulations show that IViS recovers point-source flux accurately without regularization and that regularization sets the trade-off between noise suppression and effective resolution. Joint deconvolution can recover more large-scale power than linear mosaicking of independently deconvolved pointings. With single-dish information, the reconstructed power spectra closely reproduce the input sky statistics. Applied to ASKAP data, IViS yields 10h mosaics with an effective resolution of 22” and reduced residual side-lobe structure. Compared with ASKAPSoft multi-scale CLEAN for a single observing block, Classic3D exhibits fewer residual side-lobes and recovers substantially more power at low spatial frequencies.
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All authors A. Marchal, N. M. McClure-Griffiths, J. Dempsey, H. Nguyen, H. Dénes, J. Dickey, C. Lynn, Y. K. Ma, D. McConnell, M.-A. Miville-Deschênes, N. Pingel, J. Th. van Loon
Cosmology and Nongalactic Astrophysics
$B$-sure. Part II. Scattering transforms as robustness test for tensor-to-scalar ratio detection from CMB observations
Claudio Ranucci, Sébastien Pierre, Léo Vacher et al. (+7 more)
Galactic foregrounds represent a major contamination to the measurement of primordial $B$-modes from observations of the
Cosmic Microwave Background polarisation. Even after the application of component separation
algorithms, foreground residuals may potentially still bias the estimate of the tensor-to-scalar ratio $r$, causing a false detection. In this work, we present the methodology of a robustness test for the validation of an eventual detection of primordial $B$-modes, as obtained by a future, LiteBIRD-like satellite experiment. The goal of the test is to identify the foreground residuals contamination by looking for non-Gaussian properties in the CMB $B$-modes map, recovered through blind component separation
algorithms. We adopt scattering transforms (ST) as our summary statistics sensitive to the non-Gaussian features of foreground residuals and to their correlation with foregrounds tracer maps. We characterise and validate the methodology on realistic sky simulations with different levels of foregrounds complexity. The proposed test is able to identify a bias on the tensor-to-scalar ratio of $\gtrsim 10^{-3}$ in $\sim 90\%$ of our simulations, with this bias value being of the same order of the accuracy targeted by LiteBIRD. Additionally, for our particular experimental configuration, the test is passed when the bias is lower than the sensitivity on the $r$ parameter, and no warning is raised. These results provide an important step forward in the development of statistical tools for validating future measurement of cosmological parameters, against foregrounds contamination.
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All authors Claudio Ranucci, Sébastien Pierre, Léo Vacher, Alessandro Carones, Nicoletta Krachmalnicoff, Erwan Allys, Jean-Marc Delouis, Paolo Campeti, Giuseppe Puglisi, Carlo Baccigalupi
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Vanilla Scotogenic Model at the future Muon Collider
Niloy Mondal, Dipankar Pradhan, Abhik Sarkar et al. (+2 more)
The vanilla scotogenic model (VSM) featuring three right-handed
neutrinos and an inert scalar doublet, offers a unified explanation of
neutrino masses, dark matter (DM), and the baryon asymmetry of the Universe through leptogenesis. The typical mass scale of such a scenario lies in the vicinity of $\sim$ 10 TeV and above, whereas enhanced second-generation Yukawa couplings lower the leptogenesis scale to $\sim 1$ \TeV, allowing the model to be probed at the future
muon colliders. Adhering to DM,
neutrino mass, Leptogenesis, and flavour dependent constraints, the charged scalar is likely to be a long-lived particle (LLP). We analyse both the
prompt and displaced vertex signatures of the model to find that,
prompt mono-
photon signals remain challenging, but LLP searches offer a promising avenue to probe such a framework, subject to the timing resolutions, and displaced-vertex reconstruction efficiency.
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All authors Niloy Mondal, Dipankar Pradhan, Abhik Sarkar, Biplob Bhattacherjee, Subhaditya Bhattacharya
Earth and Planetary Astrophysics
Secular evolution of viscous and self-gravitating protoplanetary discs with magnetic winds
Evgenii R. Redkin, Eduard I. Vorobyov, Paola Pinilla et al. (+2 more)
Traditionally, the disc is believed to evolve under the influence of turbulent viscosity, although the importance of this mechanism has recently been questioned. Alternatively,
magnetic disc wind or gravitational instability could be considered, but which of these three mechanisms contributes the most at a given evolutionary stage remains an open question. We present global numerical hydrodynamic simulations of protoplanetary disc
evolution in the thin-disc limit on disc lifetime timescales, including all three mechanisms of mass and angular momentum transport. We calculate the gravitational, viscous, and
magnetic torques to assess the contribution of each mechanism. We found that these transport mechanisms occupy distinct zones of influence in the disc depending on the stage of
evolution: the dominance of disc self-
gravity during the early phase is replaced by the prevalence of
magnetic disc wind and viscosity, with the latter being especially relevant at the disc periphery. We show that a noticeable decrease in disc mass occurs only after the termination of the embedded phase. The suppression of disc viscous spreading is achieved only for the most intense wind; otherwise, the disc continues to grow in size till the end of simulations. The spiral structure contributes to the temporary retention of dust in the disc. However, this is insufficient to prevent the depletion of dust on long timescales. The results emphasize the importance of a comprehensive approach to long-term simulations of protoplanetary discs with no single mechanism of mass and angular momentum transport regarded as exclusive.
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All authors Evgenii R. Redkin, Eduard I. Vorobyov, Paola Pinilla, Fabiola A. Gerosa, Konstanze Zwintz
High Energy Astrophysical Phenomena
Constraints on the central engine of merger-driven long gamma-ray bursts
Muskan Yadav, Roberto Ricci, Paz Beniamini et al. (+4 more)
Recent observations have identified a new class of long-duration gamma-ray bursts (GRBs) likely produced by compact binary mergers. Using
radio observations and lightcurve modelling, we investigate whether a magnetar remnant can power the long-lasting
prompt emission observed in this merger-driven GRB sample. We derive constraints on the magnetars' rotational energy and
magnetic-field strength, and assess whether the magnetar central-engine model is viable for the observed events. We conducted 2.1 GHz
radio observations of seven nearby merger-driven GRBs ($z<0.25$) using the Australia
Telescope Compact Array (ATCA), obtaining sensitive upper limits on late-time
radio emission 520-6900 days post-burst. We modelled the expected
radio light curves from magnetar-energized ejecta interacting with the circumburst medium and compared them to our observations. We separately tested the magnetar hypothesis against the extended gamma-ray emission using a fallback-accreting magnetar model. No
radio counterpart is detected in any of the observed GRBs, with 3$\sigma$ flux density upper limits of 33-72 $\mu$Jy at 2.1 GHz. Modelling the expected synchrotron emission from magnetar-energized ejecta interacting with the circumburst medium, we find that the
radio non-detections remain compatible with energetic outflows in low-density environments. The analysis of the
prompt gamma-ray emission provides complementary constraints on the
spin period and
magnetic field of the magnetar engine. Once fallback
accretion and jet baryon-loading are considered, the parameter space is narrowly confined.
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All authors Muskan Yadav, Roberto Ricci, Paz Beniamini, Hira Waseem, Tatsuya Matsumoto, Simone Dichiara, Eleonora Troja
Earth and Planetary Astrophysics
Stellar Ages of M Dwarf Hosts of Temperate Sub-Neptunes
Lalitha Sairam and Nikku Madhusudhan
Measuring M dwarf ages is a central challenge in stellar astrophysics. These
stars evolve so slowly that isochrone fitting gives little constraint, requiring alternative methods based on rotation, activity, and kinematics. Reliable ages help constrain the formation and
evolution of planetary systems around M dwarfs, including the temperate sub-Neptunes now being characterised with the James Webb Space
Telescope (JWST). We present an age analysis of six nearby M dwarf
planet hosts (TOI-732, TOI-736, TOI-270, TOI-1468, TOI-1231, and K2-18) using lithium absorption at 6708 Å, rotation periods, and Galactic kinematics. The Li I 6708 Åfeature is absent above 3$\sigma$ in all targets, implying substantial depletion and ages exceeding 200 Myr. Rotation periods of 39-145 days yield ages of 2.8-8.6 Gyr, calibrated against open cluster M dwarfs and including the intrinsic dispersion of the rotation-age relation. Kinematic ages span 0.8-13 Gyr with uncertainties of 4-6 Gyr. These are less precise per
star but help identify outliers such as TOI-1231 (~13 Gyr) and K2-18 ( ~1-2 Gyr) and place the
stars in Galactic context. Rotation yields age constraints 2-6 times tighter than kinematics where periods are measured, and comparable constraints where periods must be inferred from chromospheric activity. Combining multiple indicators enables more secure classification of these
stars' evolutionary states, providing reference points for future comparative studies.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Quasinormal modes of Kerr-Newman-de Sitter black holes from Heun connection formulae
Hideo Furugori, Naotaka Kubo, Hayato Motohashi et al. (+1 more)
We study quasinormal modes governed by the Teukolsky equation in Kerr-Newman-de Sitter spacetime, formally treating the
spin weight and field charge as arbitrary parameters. We use exact Heun connection formulae expressed through classical conformal blocks. We analytically derive the quasinormal mode spectra in the small cosmological constant, near-extremal, and near-Nariai limits. In the small cosmological constant limit, we obtain the leading charged de Sitter spectrum together with its subleading corrections. In both the small cosmological constant and near-extremal limits, solving the full connection condition beyond the leading pole approximation gives rise to generically noninteger-power corrections to the quasinormal mode frequencies, whereas no analogous correction appears in the near-Nariai limit. We also analyze the angular
eigenvalue problem as an illustration of the same connection-formula method.
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All authors Hideo Furugori, Naotaka Kubo, Hayato Motohashi, Daisuke Yoshida
High Energy Astrophysical Phenomena
Spontaneous wandering of the magnetic axis in pulsars: 3D magneto-thermal simulations and the imprint on braking indices
Clara Dehman and Daniele Viganò
Braking index measurements of hundreds of
pulsars, despite observational caveats, show a clear trend: $n<3$ at early ages, $n>3$ at middle ages, and increasingly large, fluctuating values at larger characteristic ages. Crustal
magnetic fields in isolated
neutron stars evolve through Ohmic dissipation and non-linear Hall redistribution across scales, with additional early-time contributions from the chiral
magnetic effect and post-burial re-emergence. Initial conditions are usually assumed dipole-dominated, whereas more complex and realistic fields, with energy spread more evenly over a broad range of scales, have not been explored in this context. We assess how the internal dynamics of initially non-trivial fields change the dipolar field strength and obliquity, and how their combined contribution to the braking index $n$, together with that of the
alignment, compares with the observed values. To this end we perform long-term 3D magneto-thermal simulations, for configurations ranging from the dipole-dominated case to tangled, small-scale-dominated fields. Small-scale dominated configurations with weak dipolar components show rich dynamics: the dipolar mode is continuously fed by the small scales and may grow or decay depending on the initial spectrum, driving $n<3$ or $n>3$, while the obliquity varies on timescales as short as ${\cal O}$(kyr). These spontaneous changes often dominate the
alignment torque and can account for the large values of $n-3$ of either sign observed at characteristic ages $\tau_c\gtrsim10^5$ yr, unlike the dipole-dominated models. However, short-term magnetospheric fluctuations or superfluid-driven variations of the torque may still be needed to explain the measurements and the structured timing residuals quantitatively. Future work comparing these models with the observed timing properties could fine-tune the most promising initial configurations.
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Cosmology and Nongalactic Astrophysics
The Equivalence Principle in the Dark Sector in light of DESI
Andrea Clini, Pierre Zhang, Emanuele Castorina et al. (+1 more)
Recent measurements of the distribution of
galaxies by the Dark Energy Spectroscopic Instrument (DESI) are in mild tension with a standard $\Lambda$-Cold Dark Matter cosmological model inferred from the anisotropies of the
Cosmic Microwave Background (CMB) when extrapolated to low
redshifts. Several solutions to explain this discrepancy in terms of new physics have been put forward, notably from new dynamics in a complex Dark Sector. Here we report on a resolution to this discrepancy that postulates that the inertial and gravitational masses of dark matter particles are not the same. Our best fit to CMB data combined either with Baryon Acoustic Oscillation (BAO) and Full Shape (FS) data from DESI DR1 (Data Release 1), or with BAO DR2 data alone, suggests the presence of a new long-range force in the Dark Sector with strength of $\beta \sim 0.5\% $ relative to
gravity, at the $\sim 2.5\sigma$ level. A preliminary analysis combining FS DR1 and BAO DR2 data confirms the statistical power of DR2 and raises the evidence for dark forces to $\sim 3\sigma$, albeit ignoring the not yet available cross-correlation between the two
datasets.
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All authors Andrea Clini, Pierre Zhang, Emanuele Castorina, Maria Archidiacono
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Cosmological Constrained Axion-Portal Inelastic Dark Matter for the LZ Event
Haipeng An, Fei Gao, Jia Liu et al. (+2 more)
The recent high-recoil candidate event reported by LUX-ZEPLIN (LZ) motivates dark-matter scenarios with nonstandard kinematics and momentum-dependent interactions. We study a two-state inelastic dark-matter model in which $\chi_1$ and $\chi_2$ couple off-diagonally to an
axion-like particle (ALP) that also couples to gluons and
photons. Unlike treatments that assume only one dark-matter state is present today, we track the cosmological
evolution of both states. The excited state $\chi_2$ is sufficiently long-lived to survive to the present, with its relic fraction determined by the dark-sector conversion process $\chi_2\chi_2\leftrightarrow\chi_1\chi_1$. We find that this fraction depends strongly on the Lorentz structure of the DM–ALP interaction: scalar transition couplings efficiently deplete $\chi_2$, favoring endothermic $\chi_1 N\to\chi_2 N$ scattering, whereas pseudoscalar transition couplings preserve $f_2\simeq1/2$, yielding recoil spectra dominated by exothermic $\chi_2 N\to\chi_1 N$ down-scattering.
Benchmark spectra in all four scenarios can peak near the observed recoil energy of $250\,\mathrm{keV}$. Our results demonstrate that the dominant direction of inelastic scattering in direct detection can be dynamically selected by the early-Universe
evolution of the dark sector. With additional data, annual modulation measurements could distinguish these scenarios. We further show that the ALP portal can be directly probed at
colliders.
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All authors Haipeng An, Fei Gao, Jia Liu, Minghao Liu, Changlong Xu
Cosmology and Nongalactic Astrophysics
Running Hubble Constant with the Redshift as a Marker of Evolutionary Dark Energy
Nakia Carlevaro, Giovanni Montani and Maria Giovanna Dainotti
We discuss the interpretation of an observed running Hubble constant with the
redshift, in terms of the possible underlying physical scenario. Assuming, like in the $\Lambda$CDM model, that the matter and dark energy components do not directly interact, we arrive at the conclusion that the physical content of the cosmological dynamics can always be represented with an evolutionary dark energy paradigm. We discuss both the case of the power-law running Hubble constant, and that of an optimized fitting model, both studied with the binned Pantheon Sample of the Type Ia
Supernovae data. These two cases turn out to be associated with a phantom-like evolutionary dark energy.
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High Energy Astrophysical Phenomena
X-ray to Mid-IR Spectral Energy Distributions: A Catalog of X-ray Selected AGNs in the XMM-COSMOS Survey
Şeyda Şen, Eda Sonbas, Ece Kilerci et al. (+4 more)
We present a component-resolved analysis of the IR–X-ray connection in a sample of 104 spectroscopically confirmed Type~1 AGN. By combining \xmm, \swift/UVOT, and new high–angular resolution \jwst/NIRCam imaging for a subset of the sources, we constructed detailed SEDs in which the IR emission was explicitly decomposed into
accretion-disk,
torus, and polar-dust components. This approach enables us to isolate the intrinsic AGN-IR luminosities with minimal host-
galaxy contamination, providing a clean assessment of the physical relationship between the
accretion flow, circumnuclear dust, and the X-ray corona. By incorporating JWST/NIRCam observations into our SED decomposition, we significantly reduce host-
galaxy contamination and isolate the nuclear infrared emission with greater fidelity, particularly at near-infrared (NIR) wavelengths. This improvement is most apparent at 1 $\mu\mathrm{m}$, where sources with JWST coverage exhibit a markedly steeper relation between $\nu$L$_{\nu}$ (2 keV) and the NIR luminosity than those without JWST data. This behavior is naturally explained by starlight dilution, whereby host-
galaxy emission dominates lower-resolution measurements.
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All authors Şeyda Şen, Eda Sonbas, Ece Kilerci, Hasan Avdan, Kalvir S. Dhuga, Ersin Göğüş, W. N. Brandt
Instrumentation and Methods for Astrophysics
Assessing ionospheric effects on image quality in the LOFAR Decametre Sky Survey
Cristina-Maria Cordun, Harish K. Vedantham and Maaijke Mevius
The terrestrial ionosphere is a major limitation for high angular resolution imaging at decametre wavelengths. Its rapidly varying and direction-dependent phase errors can defocus sources, reduce recovered flux densities, and produce strong field-to-field variations in image quality. We investigate these effects using three overlapping pointings from the LOFAR Decametre Sky Survey (LoDeSS), observed under different ionospheric conditions. Using phase-calibration solutions on a bright source, we derive the spatial diffractive scale, the temporal decorrelation time, and the angular scale over which direction-dependent calibration solutions can be transferred before residual phase errors become significant. These metrics are reflected in the final image quality. The field with the weakest ionospheric phase structure has the sharpest compact sources and the most reliable flux-density scale, while the field with the strongest phase structure shows substantial source broadening and flux-density loss. The comparison indicates that spatial ionospheric structure is the dominant limitation in these observations. Calibration-derived ionospheric metrics, therefore, provide a practical way to diagnose and predict image-quality variations in decametre survey data.
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Earth and Planetary Astrophysics
DewTwin-Coin: an onboard autonomous framework for lunar water-ice prospecting using Chandrayaan-3 LIBS and ChaSTE data
Soundarya R. and Debasish Mondal
It is important to locate water-ice in the lunar regolith to build futuristic, sustainable bases there. But communication delays from Earth, limited bandwidth, and power constraints demand an onboard, autonomous, time-efficient decision-making framework for locating volatiles such as water-ice in the lunar regolith. In this work, we present a framework, DewTwin-Coin, that can locate potential water-ice sites in real time without drilling. Its decision-making principle is based on a find-S learning
algorithm that uses surface temperature and the Hydrogen-to-Oxygen intensity ratio at a location. The core idea is a physics-based rule $-$ water-ice is stable only if the temperature is below 110 K and the Hydrogen-to-Oxygen intensity ratio is between 1.7 and 2.3. We validate DewTwin-Coin on Chandrayaan-3's 3165
laser-induced breakdown spectroscopy (LIBS) elemental data with 387 Chandra's surface thermophysical experiment (ChaSTE) data. On a 16 GB RAM system, it classified all 3165 locations within 615 seconds, yielding no strong signatures of water-ice, which matches the Chandrayaan-3 in-situ analysis. This framework is very important for future lunar and other planetary missions in which an onboard rover can autonomously determine feasible drilling locations for water-ice without issuing false drilling commands in warm terrains. Thus, the mission's onboard setup can stretch its technical limits in both power and
memory capacity.
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Instrumentation and Methods for Astrophysics
Characterization of IBEX LmAPD detectors at CEA for future low-noise NIR astronomy instruments
Jean Le Graët, Vincent Affatato, Marion Baumann et al. (+9 more)
Future near-infrared (NIR) astronomy missions dedicated to
photon-starved science cases, in particular an all-sky astrometric survey extending the legacy of Gaia into the NIR, as identified within the ESA Voyage~2050 programme, require large-format detectors combining sub-electron effective read noise with very low dark current. Linear-mode avalanche photodiodes (LmAPDs) based on HgCdTe meet this need by multiplying the photo-generated charge by an avalanche gain before the readout stage, thereby reducing the relative contribution of the read noise. We report the first electro-optical characterization of an IBEX detector, a $2048\times2048$, \SI{15}{\micro\meter}-pitch HgCdTe LmAPD array developed by Leonardo with the European Space Agency and operated at \SI{80}{\kelvin} on a dedicated bench at CEA-IRFU. We first discuss the central difficulty of characterizing an APD array, the degeneracy between avalanche gain,
quantum efficiency (QE), and conversion gain in the measured response, and we then separate the measurements into two categories. Among the quantities that are directly measurable without assumptions, we report a signal-to-noise ratio for a CDS measurement that exceeds that of a Euclid-type H2RG above \SI{8}{\volt} pixel bias under identical low-flux conditions, a photo-response non-uniformity stable at the $\sim$10% level, and a
quantum efficiency-to-excess-noise ratio (QEFR) of \num{0.40} at \SI{10.5}{\volt}. Among the quantities derived under an explicit set of assumptions, we obtain a conversion gain corresponding to a sense-node capacitance of \SI{27}{\femto\farad}, a
quantum efficiency of $46\pm12\%$ at \SI{2.5}{\volt}, and an excess noise factor $F=1.15\pm0.14$ at \SI{10.5}{\volt}. These results establish IBEX as a promising European large-format detector for future ultra-low-flux NIR instruments.
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All authors Jean Le Graët, Vincent Affatato, Marion Baumann, Olivier Boulade, Cyrille Delisle, Eloy Hernandez, Christian Ketchazo, Frederic Lemmel, Vincent Moreau, Salima Mouzali, Thibault Pichon, François Visticot
High Energy Astrophysical Phenomena
Large ${\rm Pm}$ small-scale kinematic dynamo in protoneutron stars
Shipra Verma, Kannabiran Seshasayanan, Raphaël Raynaud et al. (+1 more)
Magnetars are young, isolated
neutron stars that possess an exceptionally strong
magnetic field, with surface dipolar strengths on the order of $10^{15}$ G. One of the plausible scenarios for generating such a strong field is an exponential amplification by a turbulent convective dynamo during the protoneutron
star phase. However, the short expected duration of the convection ($\sim 10$ s) imposes a stringent constraint on the dynamo growth rate. We perform an extensive set of 82 three-dimensional convective dynamo simulations in the anelastic approximation and investigate the kinematic phase to quantify the dynamo growth rate $\gamma$. We find that $\gamma$ increases with both the
magnetic Prandtl number ${\rm Pm}$ and the Rayleigh number ${\rm Ra}$, with the most unstable mode becoming highly non-axisymmetric and multipolar. We further observe a gradual transition from large-scale to small-scale dynamo as the
magnetic Reynolds number ${\rm Rm}$ increases, resulting in a
magnetic field that is predominantly concentrated at small scales. The trend remains unchanged when the outer
magnetic boundary condition is varied. Since resolving the increasingly small scales becomes numerically impractical, we employ the theoretical small-scale Kazantsev dynamo model to explore the large ${\rm Pm}$ regime characteristic of protoneutron
stars. The model qualitatively captures the growth rate behaviour observed in simulations and, upon extrapolation to the large ${\rm Pm}$ limit, indicates that $\gamma$ is only weakly dependent on the resistivity in a PNS. Under conditions relevant to the PNS, this model predicts a
magnetic energy growth rate of the order of $\sim 1$ ms$^{-1}$.
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All authors Shipra Verma, Kannabiran Seshasayanan, Raphaël Raynaud, Jérôme Guilet