Instrumentation and Methods for Astrophysics
Supporting users in their observation preparation - the ESO ObsPrep tool
Monika G. Petr-Gotzens, Vincenzo Forchi, Andrea Mehner et al. (+6 more)
Ground based observatories are experiencing significant technological advances and
telescopes are getting equipped with highly complex instruments to enable cutting-edge astronomical research. The increasing complexity of such instruments displays a challenge to their users when they want to plan and prepare specific observation programmes, that often request to define large amount of detailed instrument-specific information. Therefore, at ESO we developed an Observation Preparation tool (in short ObsPrep tool), which provides a layer of abstraction over the instrument-specific technical details and tries to harmonize the users experience when being faced with the preparation of observation blocks for different complex instruments. The ObsPrep tool allows interactive planning of the observations by visualization of various actions and observing strategies. In a joint approach by software engineers and astronomers, ObsPrep was started as a stand-alone java desktop application and over the years has evolved into an angular based web-application. It is now fully integrated in ESOs general use phase2 user interface (p2) that allows ESO users to create, modify, or delete observation blocks. Here we present the core functionalities of ObsPrep, as well as its special features and how the user interface integrates into ESOs generic phase2 observation preparation tool. We also outline the upcoming plans to incorporate the observation preparation for the instruments of the next generation of ESOs large
telescopes, the ELT, into ObsPrep.
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All authors Monika G. Petr-Gotzens, Vincenzo Forchi, Andrea Mehner, Thomas Bierwirth, John Pritchard, Ahmed M. Khan, Olivier R. Hainaut, Kevin Knecht, Andre Graca
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Shadow and Polarized Images of Schwarzschild-MOG Black Hole Illuminated by Thick Accretion Disk
Cheng Hu, Huan Ye, Hong Lei et al. (+1 more)
Recent EHT polarimetric observations provide a powerful probe of near-horizon physics and modified
gravity. We investigate the shadow and polarization images of a static Schwarzschild-MOG black hole illuminated by geometrically thick, optically thin
accretion flows. Adopting a phenomenological model and the Hou disk model, and solving null geodesics and relativistic radiative transfer, we study how the MOG parameter, inclination angle, anisotropic synchrotron emission, and flow geometry affect the total intensity and linear polarization. It is found that the MOG parameter mainly enlarges and brightens higher-order
photon rings and broadens the shadow, while the inclination angle breaks axial
symmetry and enhances polarized emission inside the shadow. The Hou disk model suppresses off-equatorial radiative interference and localizes polarization signals within higher-order rings. Electric vector position angle (EVPA) patterns are mostly azimuthal but vary rapidly near lensed images. These results provide theoretical diagnostics for constraining MOG with EHT/ngEHT polarimetric observations.
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All authors Cheng Hu, Huan Ye, Hong Lei, Zi-Chao Lin
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Reheating Bounds from Thermal GUT Monopole Production
Donald Liveoak, Arielle Schutz and James D. Wells
Magnetic monopoles are a generic prediction of Grand Unified Theories (GUTs) that are in tension with modern cosmological and observational bounds. In this paper, we calculate the present-day abundance of GUT monopoles produced thermally in the early Universe. We improve on previous calculations by accounting for full relativistic corrections to the thermal abundance and enhanced monopole annihilation due to the emission of radiation and scattering off massive gauge
bosons, the Standard Model
fermions and their superpartners. To obtain a present-day energy density less than that of dark matter, we show that the reheating temperature of the Universe, $T_{\rm RH}$, must be less than $0.55$ times the GUT
symmetry breaking scale $T_{\rm GUT}$ for the canonical 't Hooft-Polyakov monopole mass. Accounting for Parker bounds on the present-day
magnetic monopole abundance, the bound is tightened to $T_{\text{RH}}/T_{\text{GUT}} \lesssim 0.45$. Furthermore, experimental bounds from Super-Kamiokande require $T_{\text{RH}}/T_{\text{GUT}} \lesssim 0.35$ in our scenario.
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Solar and Stellar Astrophysics
Spectral classification of OB-type stars using tree-based ensemble methods and evaluation of their explainability
J.E. Gonzales, S. Simón-Díaz, S. Cuellar et al. (+3 more)
[Abridged] The advent of large-scale spectroscopic surveys will deliver tens of thousands of spectra of blue massive
stars. This data volume renders traditional spectral classification techniques increasingly impractical. We aim to develop a robust ML framework for the automated spectral classification of massive OB
stars by assessing several tree-based ensemble
algorithms. Using a large catalog of high-quality optical spectra of OB
stars, we design 3 hierarchical experiments of increasing complexity: classification into broad SpT; fine-grained classification within the O and B domains; and joint classification of SpT and LC. We evaluate 6
algorithms, ranging from single Decision Trees to ensemble methods and gradient boosting techniques. We further analyze model consensus and probabilistic outputs, and employ SHAP value analysis to provide an interpretation of the model decisions by identifying the features that drive each classification. Models achieve excellent performance for broad SpT classification, with LGBM reaching an accuracy of 98%. For fine-grained SpT, RF provides the most robust results (89%). For the most challenging task combining SpT subtype and LC the XGB reaches a 77% accuracy. Decrease in performance is primarily driven by intrinsic degeneracies in the classical spectral classification scheme. SHAP analysis confirms that the models rely on meaningful spectral features. We also find a high level of agreement among different
algorithms, indicating that current performance limits are largely set by the intrinsic complexity of the classification problem rather than by model choice. Tree-based ensemble methods provide a reliable and interpretable framework for the automated spectral classification of OB
stars. The combination of full-spectrum modeling,
algorithm comparison, and model interpretability offers a robust approach for future large-scale spectroscopic surveys.
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All authors J.E. Gonzales, S. Simón-Díaz, S. Cuellar, J.A. Conejero, G. Holgado, A. de Burgos
Astrophysics of Galaxies
Signatures of dark subhaloes in dwarf spheroidal galaxies: II. Transient and localised kinematic features
Eduardo Vitral, Jorge Penarrubia, Roeland P. van der Marel et al. (+1 more)
We use controlled N-body simulations to investigate whether dark matter subhaloes leave detectable signatures in the internal kinematics of dwarf spheroidal
galaxies. At each snapshot, we fit a velocity distribution function to stellar line-of-sight velocities and proper motions, construct normalised residual fields for the projected velocity components, and analyse their power-spectra. We show that subhalo encounters generate a plethora of kinematic features. Amongst the most prominent are rotation-like signals, which arise in our models even though the stellar component is initialised without intrinsic rotation. In line-of-sight velocity alone, several snapshots resemble the classical blueshift–
redshift pattern associated with stationary rotation. The plane-of-sky components, however, bring complexity, with alternating regions of expansion and contraction, as well as clockwise and anticlockwise streaming. Although we observe coherent streaming globally, these structures depart from typical
equilibrium configurations, while their residual power-spectra quantify the characteristic spatial scales involved. This signal strengthens in models containing more massive subhaloes and becomes difficult to recover for small stellar samples: robust power-spectrum recovery of the full velocity-space signature usually requires O(10^{4}) tracers, although a rotation signal alone can be recovered with considerably smaller samples. These results suggest that dwarf spheroidal velocity fields can retain signatures of subhalo heating. Future spectroscopy, improved Gaia astrometry, and chemo-dynamical information should turn these diagnostics into population-level probes of dark matter substructure.
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All authors Eduardo Vitral, Jorge Penarrubia, Roeland P. van der Marel, Matthew G. Walker
Astrophysics of Galaxies
Challenging the archetypal intermittent radio galaxy J0111+3906. New insights from optical GTC/OSIRIS and radio VLA and LOFAR observations
M. Orienti, J.A. Acosta-Pulido, E. De Rubeis et al. (+5 more)
We present results on new optical Gran Telescopio CANARIAS OSIRIS+ spectroscopy and
radio Very Large Array (VLA) observations at 360 MHz of the optical object behind the
radio emission 20 arcseconds east of the archetypal restarted compact symmetric object (CSO) J0111+3906. The optical counterpart is a post-starburst
galaxy at
redshift $z$ = 1.042, ruling out any physical relation between this object and the CSO
radio galaxy J0111+3906 at
redshift $z$ = 0.668. The
radio emission is therefore not the remnant of a past activity of the CSO J0111+3906 that took place around 10$^7$ years ago. When observed with the high angular resolution of VLA and the International LOw Frequency ARray
telescope the East
radio source is resolved in a compact component with spectral index 0.7, centred on the optical
galaxy, surrounded by diffuse emission with a slightly steeper spectrum. The upper limit to the radiative age of the East
radio source is a few million years. If the trigger of the
radio emission and the recent burst of
star formation observed in the East
radio source are causally connected, there must be a long time gap between the two phenomena. The multi-frequency analysis of the CSO
radio galaxy J0111+3906 pointed out excess flux density at 150 MHz, which may indicate the presence of fossil
plasma confined within the host
galaxy. In this scenario, the past activity of the CSO J0111+3906 switched off not long after its trigger, suggesting a duty cycle of about 10$^4$ yr.
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All authors M. Orienti, J.A. Acosta-Pulido, E. De Rubeis, C. Stanghellini, M. Bondi, F. D'Ammando, L. Coccato, I. Alemán-Martín
High Energy Astrophysical Phenomena
WFST Follow-up of S251112cm: Searching for an Optical Counterpart to a Subsolar-mass Compact-binary Merger Candidate
Zhengyan Liu, Zelin Xu, Ji-an Jiang et al. (+20 more)
Electromagnetic counterparts to gravitational-wave (GW) sources probe the properties, environments, and
evolution of compact-object mergers. S251112cm belongs to an emerging class of GW candidates with possible subsolar-mass components. We present an optical counterpart search for S251112cm with the Wide Field Survey
Telescope (WFST). The observations began 20.2 hr after the GW trigger and continued for three nights, covering approximately $780~\mathrm{deg}^{2}$ and $51\%$ of the localization probability in the updated skymap. We searched for newly emerging, rapidly evolving, off-nuclear optical transients and identified four candidates whose host-
galaxy distances are broadly consistent with the GW distance estimate. However, all four evolve substantially more slowly than AT 2017gfo, ruling out an AT 2017gfo-like origin and disfavoring their association with S251112cm as rapidly evolving kilonova counterparts. Combining WFST and DECam observations increases the covered localization probability to approximately 67%. Conditional on the counterpart lying within this footprint, we constrain a grid of binary-
neutron-
star kilonova models. For viewing angles $\theta_{\rm obs}<60^{\circ}$, with the other parameters fixed to the best-fitting values for AT 2017gfo, models with dynamical ejecta mass $M_{\rm dyn}\gtrsim0.01\,M_{\odot}$ or wind ejecta mass $M_{\rm wind}\gtrsim0.05\,M_{\odot}$ are disfavored over most of the covered GW probability. Beyond kilonova models, our phenomenological analysis constrains rapidly evolving optical transients with $T_{\rm rise,1/2}\leq2$ days to peak absolute magnitudes fainter than approximately -13 mag. To our knowledge, the coordinated WFST and DECam observations provide the strongest optical constraints to date on possible rapidly evolving counterparts to this new class of GW candidates involving subsolar-mass compact objects.
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All authors Zhengyan Liu, Zelin Xu, Ji-an Jiang, Wen Zhao, Zhiping Jin, Zigao Dai, Dezheng Meng, Yefei Yuan, Xuefeng Wu, Lulu Fan, Xu Kong, Xander J. Hall, Brendan O'Connor, Feng Li, Ming Liang, Binyang Liu, Zhen Wan, Hairen Wang, Jian Wang, Tinggui Wang, Hongfei Zhang, Xianzhong Zheng, Qingfeng Zhu
Instrumentation and Methods for Astrophysics
The GOTO Telescope Control System
Martin J. Dyer, Vik S. Dhillon, Stuart Littlefair et al. (+21 more)
The Gravitational-wave Optical Transient Observer (GOTO) operates a network of robotic, wide-field survey
telescopes searching for optical transients to gravitational-wave signals and other astronomical events. Since 2023, the network has comprised two antipodal sites in the Canary Islands and Australia, each hosting two independent robotic mounts. The GOTO
Telescope Control System (G-TeCS) is a custom Python software package that manages all operational aspects of the network; from alert processing and target scheduling to onsite hardware operations and monitoring. The central system consists of an alert monitor, observation database and scheduler, which issues targets to the four nodes. Each
telescope operates using a system of independent control daemons, with a pilot master control program to coordinate nightly operations. This architecture, in development since 2015, provides a flexible and robust system that now successfully operates the fully autonomous network.
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All authors Martin J. Dyer, Vik S. Dhillon, Stuart Littlefair, Kendall Ackley, Sergey Belkin, Lisa Kelsey, Tom Killestein, Amit Kumar, Joseph Lyman, David O'Neill, Krzysztof Ulaczyk, Ben Godson, Dan Jarvis, Danny Steeghs, Duncan K. Galloway, Paul O'Brien, Gavin Ramsay, Kanthanakorn Noysena, Rubina Kotak, Rene Breton, Laura Nuttall, Ben Gompertz, Jorge Casares Velázquez, Don Pollacco
Earth and Planetary Astrophysics
Characterisation of chaos in meteoroid streams. Application to the Taurids
Ariane Courtot, Melaine Saillenfest, Marc Fouchard et al. (+1 more)
Aims. We explore the dynamics of the Northern and Southern Taurid meteoroid streams to identify major mechanisms structuring the
evolution of the streams. Methods. We use chaos maps and numerical simulations to explore the dynamics of the streams. We also perform some semi-analytical analysis to confirm the mechanisms we identified in the maps. Results. We show how Northern Taurids are structured by the von Zeipel-Lidov-Kozai mechanism and how it interacts with several mean-motion resonances with Jupiter. This mechanism is visible as an increase in inclination for most particles, which is less prominent for those trapped in mean-motion resonances. It is especially strong for larger initial semi-major axis within the stream. We specifically study the 7:2 mean-motion resonance with Jupiter to confirm it leads to observable swarms. Furthermore, we explore the influence of non-gravitational forces, showing that they blur the influence of mean-motion resonances but not the von Zeipel-Lidov-Kozai mechanism. We also show that the dynamics of the Southern Taurids are very similar to the Northern Taurids.
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All authors Ariane Courtot, Melaine Saillenfest, Marc Fouchard, Jérémie Vaubaillon
Astrophysics of Galaxies
Low Star Formation Efficiency in M31: Evidence for a Deficit of Bound Gas
Fangyuan Deng, Sihan Jiao, Hauyu Baobab Liu et al. (+14 more)
The Andromeda
galaxy (M31) exhibits a systematically low
star formation efficiency (SFE) compared to other
star-forming
galaxies.
Star formation is thought to be regulated by the mass of gravitationally bound gas. To investigate whether the low SFE in M31 originates from a scarcity of such bound gas, we analyze the dynamical state of its giant molecular cloud (GMC) population by estimating their virial parameters ($\alpha_{\rm vir}$). Using a JCMT-SCUBA2 850 micron dust-continuum GMC catalog as the parent sample, we combine it with IRAM 30 m CO(1-0) data to define a working sample of 173 GMCs and derive their kinematic properties. Most analyzed GMCs exhibit high $\alpha_{\rm vir}$, indicating that they are predominantly gravitationally unbound at the approximately 86 pc resolution of our observations. While no statistically significant global correlation is found between SFE and $\alpha_{\rm vir}$ for the full cloud sample, the upper
quantiles of the SFE distribution show progressively stronger negative trends with increasing $\alpha_{\rm vir}$. This upper-tail trend may arise from the combined effects of the virial parameter limiting the upper range of SFE values accessible to the GMC population and feedback-driven disruption reducing the number of high-SFE, high-$\alpha_{\rm vir}$ CO-bright clouds in the observed sample. The substantial scatter in the SFE-$\alpha_{\rm vir}$ plane likely reflects the diverse evolutionary stages of GMCs, the temporal mismatch between gas and
star formation tracers, and the limitations of a cloud-averaged virial parameter as a tracer of internal dynamical structure, making a simple one-to-one correspondence between $\alpha_{\rm vir}$ and instantaneous SFE difficult to recover for individual GMCs.
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All authors Fangyuan Deng, Sihan Jiao, Hauyu Baobab Liu, Jingwen Wu, Henrik Beuther, Fanyi Meng, Caroline Gieser, Yuxin Lin, Di Li, Chao-Wei Tsai, Junzhi Wang, Zhi-Yu Zhang, Fengwei Xu, Jakob den Brok, Linjing Feng, Zongnan Li, Yuxiang Liu
High Energy Astrophysical Phenomena
The unidentified PeV source LHAASO J2108+5157: A microquasar remnant?
Josep Martí, Pedro L. Luque-Escamilla, Leandro Abaroa et al. (+4 more)
Context. LHAASO~J2108+5157 is one of the most intriguing Galactic ultra-high-energy $\gamma$-ray sources. It is detected up to hundreds of TeV but lacks a clear counterpart at lower frequencies. Fermi-LAT observations have revealed a compact GeV source spatially coincident with the PeV emission, while VERITAS and LST-1 impose stringent upper limits in the intermediate TeV band, producing a pronounced spectral suppression between the GeV and TeV domains. Aims. We investigate a time-dependent hadronic scenario in which a past episode of microquasar jet activity injected relativistic
protons that are now observed in a relic phase. Methods. Energy-dependent
diffusion naturally segregates the particle population: Lower-energy
protons remain confined near dense molecular gas and account for the GeV emission, whereas higher-energy particles reach more distant material, producing the hard TeV–PeV component. Results. For representative interstellar conditions, the model is simultaneously consistent with the broadband spectral energy distribution, the spatial compact–extended dichotomy, and the lack of detectable
radio or X-ray counterparts. Conclusions. The observed bimodal $\gamma$-ray phenomenology thus emerges as a transport effect of a single injected
proton population, supporting the interpretation of LHAASO~J2108+5157 as a fossil microquasar remnant observed at an intermediate evolutionary stage and highlighting relic jet systems as a viable class of Galactic PeVatrons.
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All authors Josep Martí, Pedro L. Luque-Escamilla, Leandro Abaroa, Gustavo E. Romero, Valentí Bosch-Ramon, Josep M. Paredes, Cintia S. Peri
Astrophysics of Galaxies
Self-interacting dark matter delays bar growth in an isolated gas-rich galactic disk: torque-resolved numerical evidence
Dong-Biao kang
We investigate how a dynamically responsive gas disk changes the influence of self-interacting dark matter (SIDM) on stellar-bar formation. In an isolated Milky-Way-mass
galaxy with fixed total baryonic mass, the gas-rich collisionless (CDM) model develops a persistent bar at $1.96\,\Gyr$, whereas the matched SIDM model with $\sigmam=1\,\mathrm{cm^2\,g^{-1}}$ does so at $2.69\,\Gyr$. The final stellar $m=2$ amplitude is 0.437 in CDM and 0.340 in SIDM, a 22 per cent suppression; the corresponding gas-free controls remain weak over the same interval. An independently sampled gas-rich pair preserves the direction of both differences. Direct component-force measurements show that the SIDM stellar disk loses $2.82\times10^{11}\,\Msun\,\kpc\,\kms$ less angular momentum than its CDM counterpart. The integrated torque contrast is dominated by the dark
halo (approximately 74 per cent), with a substantial gas contribution (26 per cent), and is redistributed in radius and time rather than being a uniform reduction of
halo coupling. Conservation, force-accuracy, aperture, threshold, and independent-sampling checks support the ordering as a dynamical effect within this model. The result demonstrates that a live gas component can change both the sign and timing of the early SIDM impact inferred from collisionless disks, providing a mechanism-based constraint for future hydrodynamic SIDM studies.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Searching for gravitational wave echo with group equivariant neural posterior estimation
Jian-Wei Luo and Yun-Song Piao
Current methods for the gravitational-wave (GW) echo searches generally require substantial computational time and resources. Recent advances in group equivariant neural posterior estimation (GNPE) have demonstrated the potential to substantially accelerate posterior inference. In this work, we adopt this framework and train a GNPE model to perform echo searches, significantly improving computational efficiency while maintaining comparable inference accuracy. We apply it to the O4a events and find no significant evidence for the GW echo.
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Earth and Planetary Astrophysics
Bridging magnetothermal winds and photoevaporation to model discs dispersal
Giovanni Picogna and Barbara Ercolano
Protoplanetary disc dispersal is driven by two processes usually modelled separately: photoevaporative and magnetohydrodynamic (MHD) disc winds. Global simulations indicate that in the inner disc these are not distinct outflows but a single magnetothermal wind. We assemble a closed-form, two-phase model that respects it. A single-field-line wind, whose base is fixed by the irradiated temperature and penetration column, supplies the launch and feeds a secular
evolution, with photoevaporation convolved on as a sink. The flux closure $B_z\propto\Sigma^q$ is self-limiting: for $q\le1/2$ depletion alone cannot demagnetise the disc, so dispersal requires independent flux loss, parameterised by the
magnetic Reynolds number $\mathcal{R}_m$. Integrating the coupled system yields two regimes. Efficient flux loss ($\mathcal{R}_m\lesssim1$) lets the magnetisation front recede by over an order of magnitude and opens a photoevaporative gap. Flux retention ($\mathcal{R}_m\gg1$) drives the front outward, sustains
accretion, and defers dispersal by $\approx2.7$~Myr. Deriving the base from stellar irradiation instead of prescribing it, we find that the cold-launch approximation is valid during the early stages of disc
evolution: anchoring the base at
plasma equipartition ($\beta_{\rm base} \sim 1$) confines irradiation's influence on the
magnetic lever arm to the magnetothermal annulus, decoupling the peak
accretion rate from the incident flux. Both regimes clear the disc inside-out, through either a photoevaporatively amplified cavity wall or an expanding magnetothermal front.
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Astrophysics of Galaxies
The Delegate Survey: KOALA/AAOmega-IFU spectroscopy of three nearby dwarf galaxies
Kyungdo Ko, Helmut Jerjen, Sarah M. Sweet et al. (+6 more)
Assessing the cosmological typicality of the Local Group is crucial for establishing whether its dwarf
galaxy population is representative. To this end, the Delegate Survey targets dwarf
galaxies in Local Group analogues for systematic comparison. As a pilot study for the Delegate Survey, we obtained integral-field spectra of three dwarf
galaxies, GAMA 79098, GAMA 569709, and HIPASS J1159-19 S2, in two nearby
galaxy groups using the KOALA instrument on the AAT. The
galaxies were mapped at a spatial sampling of 1.25 arcsec per spaxel, providing two-dimensional spectral coverage of both the stellar and ionised gas components. Using continuum and emission-line maps, we investigate the ionisation structure,
star-forming properties,
metallicity,
star formation histories, and velocity fields of each system. GAMA 79098 exhibits properties closely analogous to the SMC, with ongoing
star formation superimposed on an old stellar population and moderate rotational support. GAMA 569709 resembles transition-type Local Group (LG) dwarfs such as NGC 147 and NGC 185, showing predominantly an old stellar population. HIPASS J1159-19 S2 is dominated by young
stars and intense
star-forming complexes, consistent with a dynamically young, gas-rich
galaxy group environment. The two GAMA dwarfs follow the LG stellar mass-
metallicity relation within uncertainties, while HIPASS J1159-19 S2 appears approximately 0.5 dex more metal-rich for its stellar mass. Overall, the structural, chemical, and kinematic properties of these dwarfs overlap substantially with analogous LG dwarfs.
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All authors Kyungdo Ko, Helmut Jerjen, Sarah M. Sweet, Ángel R. López-Sánchez, Simon Deeley, Caroline Foster, Holger Baumgardt, Pratyush Kumar Das, Adebusola Alabi
Instrumentation and Methods for Astrophysics
cosmokdtree: a flexible OpenMP-parallelized k-d tree for computational astrophysics applications
Óscar Monllor-Berbegal, David Vallés-Pérez, Susana Planelles et al. (+1 more)
Modern numerical astrophysics applications present a common demand for efficient spatial querying techniques, such as neighbor searches or density estimations over billions of resolution elements. To address the growing need for fast and versatile tools tailored to these tasks, we present cosmokdtree, a fast and flexible multi-purpose k-d tree implementation in Fortran, parallelized with OpenMP directives. Our library supports arbitrary dimensionality and spatial distributions, and is designed for efficient tree construction and fast query performance for moderate-scale applications (performance tested up to 10^9 points). Python bindings coupled to the module are also provided. All these ingredients yield a k-d tree package suitable for analysis purposes. We
benchmark cosmokdtree across a variety of scenarios, including different point distributions, dimensionality, and parallel scaling. We also compare its performance against the widely used scipy implementation and other efficient alternatives such as coretran's and a GPU-based version, showing that cosmokdtree consistently achieves lower construction and query times than CPU alternatives while keeping a reasonable
memory usage. Our tree-building phase implementation, executed on a mid-range workstation-class CPU, approaches the performance of GPU-based implementations when run on high-end consumer graphic cards, although data-center GPUs, out of the scope for our comparison, could still deliver substantially higher performance and a broader conclusion cannot be extracted. We further present some applications tackling common problems in astrophysics, namely, the friends-of-friends clustering
algorithm and the particle-to-mesh assignment process. The code is publicly released and intended to serve as a flexible multi-purpose tool for computational applications in a wide range of scenarios, particularly in astrophysics.
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All authors Óscar Monllor-Berbegal, David Vallés-Pérez, Susana Planelles, Vicent Quilis
Solar and Stellar Astrophysics
Mode Switching in Two Blue Large Amplitude Pulsators observed by OGLE, KMTNet and DREAMS
Hao Ma, Shude Mao, Seung-Lee Kim et al. (+20 more)
Blue large-amplitude pulsators (BLAPs) are rare, hot, short-period pulsating
stars whose rapid oscillations provide a unique probe of stellar interiors and atmospheres. In this paper, we study two short-period BLAPs in the Galactic bulge, OGLE-BLAP-142 ($P \approx 6.6$ min) and OGLE-BLAP-148 ($P \approx 7.5$ min), by combining light curves from the OGLE, KMTNet, and DREAMS surveys, spanning 17 years with cadences ranging from minutes to hours to days. We perform Generalized Lomb-Scargle periodogram analyses of their light curves and identify, for each BLAP, three closely spaced pulsation modes separated by $\sim 1\%$. The dominant mode can switch within timescales of order a year, accompanied by a likely blueward color shift ($\sim 0.1$–$0.2$ mag). The yearly period excursions of the resolved mode families imply apparent $|\dot{P}/P|$ values of order $10^{-6}$–$10^{-4}\,\mathrm{yr^{-1}}$, large enough to mimic or exceed smooth evolutionary period changes. One mode family in OGLE-BLAP-148 shows a coherent decade-long drift at the $\sim10^{-5}\,\mathrm{yr^{-1}}$ level, but its failure to extrapolate to the earliest and latest epochs suggests a transient mode-family drift rather than secular
evolution. Such close-spaced multiple pulsations and mode switching may be common among BLAPs with periods shorter than 10 min, and their physical origin remains unclear.
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All authors Hao Ma, Shude Mao, Seung-Lee Kim, Hongjing Yang, Weicheng Zang, Tianjun Gan, Steve Heathcote, Chung-Uk Lee, Tao Wu, Dong-Jin Kim, Zhenhao Wang, Yaosong Yu, Qiyue Qian, Yuchen Tang, Yuxin Shang, Zhixing Li, Tomas Ahumada, Timothy Abbott, Guillermo Damke, Konstantina Boutsia, Alfredo Zenteno, Przemek Mróz, Andong Xu
Cosmology and Nongalactic Astrophysics
Cosmological anatomy of interacting dark energy
Miguel A. Sabogal, Sunny Vagnozzi and Eleonora Di Valentino
Interacting dark energy (IDE) models, featuring interactions between dark matter (DM) and dark energy (DE), have received significant renewed interest. However, little
attention has been devoted to understanding their genuine cosmological signatures, with comparisons against $\Lambda$CDM often carried out at fixed cosmological parameters. Considering the widely studied model with energy exchange rate proportional to the DE density, we carry out a three-level sequence of comparisons, starting from the naïve fixed-parameter comparison, then compensating for shifts in $\theta_s$ and $z_{\text{eq}}$, and then removing effects due to the modified background. We show that fixing $\theta_s$ and $z_{\text{eq}}$ leads to pre-recombination evolutions of the Weyl potential,
photon monopole, and baryon velocity which are nearly identical to their $\Lambda$CDM counterparts, and hence virtually indistinguishable
Cosmic Microwave Background (CMB) temperature power spectra. Comparing IDE to a non-interacting $w$CDM model with the same background, we find small scale-dependent signatures in CMB
lensing. We find larger differences in the matter power spectrum, reflecting the different values of $\Omega_m$ resulting from the different partition of the dark sector into DM and DE, with only percent-level differences remaining once we compare $\Omega_m^2P_m(k)$, indicating the importance of high-fidelity determinations of $\Omega_m$. Our controlled comparison strategy can be a powerful tool for a wide range of models beyond $\Lambda$CDM.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Probing Lorentz-violating scalar forces and dark matter with precision matter and antimatter experiments
Yevgeny V. Stadnik
We explore a class of Lorentz-violating scalar-field models where the effects of the scalar field on antimatter can be strongly enhanced compared to matter. Non-trivial differences in phenomenology arise for spectroscopy measurements depending on whether the scalar field changes slowly or rapidly on the atomic scale. We highlight opportunities for precision tests in the laboratory including dark matter searches, in particular with spectroscopy and interferometry measurements, as well as certain types of antimatter experiments.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Probing Feebly Interacting Particles with 511 keV Line from Circumstellar Medium of Supernovae
Yu Cheng, Chui-Fan Kong, Yen-Hsun Lin et al. (+2 more)
Core-collapse
supernovae (CCSNe) are intense sources of feebly interacting particles (FIPs), whose visible decays beyond the stellar envelope can generate distinct electromagnetic signals. We propose the circumstellar medium (CSM) surrounding the CCSNe progenitor as a new target for 511 keV line searches. FIPs escaping the stellar interior may decay into electron-positron pairs and inject positrons into the CSM, where they slow down and subsequently annihilate, giving rise to a 511 keV line as an electromagnetic precursor to the
supernova shock breakout. Using dark
photons as a
benchmark, we calculate the time-dependent signal for CSM profiles motivated by SN 2023ixf and SN 2024ggi. For a Galactic
supernova at 10 kpc, the projected reach of COSI and AMEGO extends beyond existing
supernova limits over part of the MeV-scale dark-
photon parameter space. The same FIP decays can simultaneously heat the CSM and sublimate circumstellar dust, producing a rapid spectral transition from infrared excess to optical or ultraviolet emission [Y. Cheng et al., Phys. Rev. Lett. 137, 111005 (2026)]. The coincident appearance of this transition and the 511 keV line would provide a distinctive correlated multiwavelength signature of FIP decays in the dense presupernova environment.
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All authors Yu Cheng, Chui-Fan Kong, Yen-Hsun Lin, Meng-Ru Wu, Seokhoon Yun
High Energy Astrophysical Phenomena
Toward Autonomous Radio Follow-up of Multi-messenger Transients with RADAR: From Alert Parsing to Inference and Observation Scheduling
Mihael Hategan-Marandiuc, Tanner O'Dwyer, Alessandra Corsi et al. (+6 more)
Multi-messenger astronomy (MMA), the joint study of
cosmic sources through gravitational waves (GWs), electromagnetic (EM) radiation,
neutrinos, and
cosmic rays, is rapidly reshaping time-domain astrophysics. Realizing the promise of MMA will require coordinating heterogeneous observing resources and automating the chain from alert to analysis to follow-up. RADAR (
Radio Afterglow Detection and AI-driven Response) is a
federated,
privacy-enhancing framework for the
radio follow-up of GW events, previously validated on GW170817. Here, we extend it along three axes. First, we
benchmark three large
language models (LLMs; GPT-5.5, Claude-Opus-4.7, and Gemini-3.5-Flash) against the GW170817
radio light curve
dataset. GPT-5.5 attains the highest event-level $F_1$ score, the harmonic mean of precision and recall, at $0.893 \pm 0.010$, and the highest GCN-level recall, $0.794 \pm 0.013$, improving on previous GPT-4.1 results by 16% and 10%, respectively, while Claude-Opus-4.7 achieves the highest precision, $0.978 \pm 0.014$. Second, we introduce concurrent likelihood evaluation, which speeds up the MCMC computation by a factor of $40\times$ over our previous results. Third, we present an LLM-driven scheme that converts natural-
language observing requests into submission-ready scheduling blocks for the Karl G. Jansky Very Large Array. Together, these developments advance RADAR toward a scalable, largely autonomous system for GW
radio follow up.
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All authors Mihael Hategan-Marandiuc, Tanner O'Dwyer, Alessandra Corsi, Eliu Huerta, Zilinghan Li, Ian T. Foster, Kyle Chard, Ryan Chard, Amal Gueroudji
High Energy Astrophysical Phenomena
Detectability of 100 TeV Gamma Rays from PeV Cosmic Rays Accelerated in the Early Phase of a Supernova Shock Wave
Tomotaka Nishikawa, Tsuyoshi Inoue and Alexandre Marcowith
Galactic
cosmic rays (CRs) are thought to be accelerated by diffusive shock acceleration in
supernova remnants (SNRs), but observations of SNRs aged ~100-1000 yr suggest maximum CR energies below the PeV level. Recently, Inoue et al. (2021) showed with kinetic-MHD simulations that CRs can be accelerated to ~3 PeV when a blast wave shock propagates through dense circumstellar material (CSM) within tens of days after explosion. Such CSM can be produced by a red-supergiant (RSG) wind with an observationally motivated mass-loss rate of ~10^-3 Ms/yr. 100 TeV gamma-rays from neutral pion decay can test PeV CR acceleration. However, hadronic gamma-rays from very young SNRs can be significantly attenuated by
supernova photospheric
photons and the
cosmic background radiation. Using the CR distribution functions and CSM density profiles from Inoue et al. (2021), we calculate time-dependent gamma-ray fluxes from Type II-P SNe, including both attenuation processes. We find that photospheric
photons attenuate the intrinsic 1-100 TeV gamma-ray flux by about one order of magnitude. For the dense CSM case with dot{M}_RSG ~ 10^-3 Ms/yr and an outer CSM radius of ~ 3x10^15 cm, CTA can detect 100 TeV gamma-rays with a 50 h observation out to ~ 4 Mpc (this is reduced to 3 Mpc if the spatial extent of the CSM is shrunk to 2x10^15 cm). These results suggest that early 100 TeV observations of nearby Type II-P SNe can probe PeV CR acceleration in sufficiently dense and extended CSM.
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Cosmology and Nongalactic Astrophysics
Void probability function in the Quijote simulations
Snehasish Bhattacharjee
The void probability function (VPF) is the likelihood of finding no tracers (
galaxies or dark-matter
haloes) within a given volume and is sensitive to the large-scale matter distribution. We investigate the VPF of dark matter
haloes and
galaxies using the Quijote N-body simulations across a range of cosmological models, including $\Lambda$CDM and several extensions. We examine its dependence on cosmology,
redshift,
halo mass, morphology, and sample dilution, and compare the results with theoretical predictions from the
geometric hierarchical (GH) and negative binomial (NB) models. We find that the
halo VPF is sensitive to cosmology and
halo mass and follows the GH model at $z=0$, with $\Lambda$CDM showing the smallest deviation and the massive-
neutrino cosmology the largest. At higher
redshift and stronger sample dilution, the VPF departs from the GH model and approaches the NB model. The dependence on
halo mass varies with cosmology, with low-mass
haloes showing the largest deviations in $\Lambda$CDM, while intermediate- and high-mass
haloes show stronger deviations in the modified-
gravity scenario. In
redshift space, the VPF shifts toward the NB model, with primordial non-Gaussianity producing the largest deviations. For
galaxies, the VPF depends on morphology and cosmology, with ellipticals following the GH model and spirals following the NB model. We also find that
cosmic variance introduces non-negligible scatter in the VPF measurements. Overall, these results suggest that the VPF could be useful as a computationally efficient probe to distinguish extensions of the standard $\Lambda$CDM model in upcoming large-volume
galaxy surveys.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Gravitational lensing of neutrinos through the lens of decoherence
Bikash Kumar Acharya and Ujjal Kumar Dey
We propose a new source of
neutrino decoherence arising from
stochastic gravitational
lensing by unresolved mass substructure. Unlike traditional models that treat the
lensing potential as smooth and deterministic, we decompose the
lensing potential into a smooth component and a
stochastic population of compact clumps. The substructure induced fluctuations of the
lensing potential generate
stochastic corrections to the
neutrino time delay, thereby producing random relative phases between different
neutrino mass eigenstates. Averaging over the clump ensemble converts these phase fluctuations into an effective dampening of flavour coherence. This framework connects
stochastic gravitational
lensing with
neutrino phenomenology and offers a novel route to probe dark matter substructure through astrophysical
neutrino flavour transitions.
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High Energy Astrophysical Phenomena
RadioAstron space-VLBI imaging of the jet in M87: II. The parsec-scale structure at 4.8 GHz
Evgeniya V. Kravchenko, Tuomas Savolainen, Alexey S. Nikonov et al. (+9 more)
We present RadioAstron observations of the M87 jet obtained on 2014 February 4-5 at 4.8 GHz ($\lambda=6.2$ cm). The correlated signals between the 10-m space
antenna and ground-based
radio telescopes were detected up to projected baselines of $\thicksim3$\,Earth diameters (0.65~G$\lambda$). The orientation of the jet downstream of the core shifts northward, consistent with the long-term oscillating trend reported in other studies. An elliptical body mode of the Kelvin-Helmholtz instability can create the observed helical shape of the jet. The estimated wavelength of this instability mode suggests that its origin may be related to some processes in the
accretion disc. We present 1.7 - 4.8 GHz and 4.8 - 15.4 GHz spectral index maps showing flattening of the spectrum along the outer streamlines and along the jet spine. Simulations and analysis show that this spectral flattening is partially artificial and is a common systematic effect of the CLEAN procedure of VLBI imaging. The spectral index of the M87 jet is consistent with the optically thin emission, while its steepening can be produced by the propagation of the instability modes causing higher pressure regions near the jet boundary and in its interior.
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All authors Evgeniya V. Kravchenko, Tuomas Savolainen, Alexey S. Nikonov, Ilya N. Pashchenko, Elena E. Nokhrina, Petr A. Voitsik, Leonid I. Gurvits, Yuri Y. Kovalev, Jae-Young Kim, Mikhail M. Lisakov, Andrei P. Lobanov, Kirill V. Sokolovsky
Astrophysics of Galaxies
Galaxy-Galaxy Strong Lensing simulation with the GPU acceleration across surveys and multi-bands
Fucheng Zhong, Ruibiao Luo, Nicola R.Napolitano et al. (+3 more)
We present a GPU-accelerated, PyTorch tensor-based simulation framework designed to generate high-fidelity
galaxy-
galaxy strong
lensing images. By integrating synthetic Spectral Energy Distribution (SEDs), the pipeline accurately models the
redshift-dependent photometric properties of lens and source
galaxies, ensuring physical consistency across multi-band observations. The framework incorporates key observational parameters, including Point Spread Functions (PSF), magnitude limits, and zero points, to replicate specific survey conditions, thereby enabling robust cross-survey joint analyses. As an application, we simulate multi-band images for KiDS, LSST, and Euclid using identical lens model parameters, and employ a deep learning network to evaluate image deblending performance. In particular, the simulation leverages PyTorch to ensure full auto-differentiability and GPU acceleration, making it a highly efficient tool for advanced deep learning
algorithms that require gradient-based optimization beyond standard model training. Our framework achieves a speedup of approximately $\mathcal{O}(10^3)$ over traditional CPU-based pipelines, demonstrating the potential feasibility of joint gradient-based lens modeling across next-generation surveys.
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All authors Fucheng Zhong, Ruibiao Luo, Nicola R.Napolitano, Crescenzo Tortora, Valerio Busillo, Rui Li
Cosmology and Nongalactic Astrophysics
Constraints of Big Bang Nucleosynthesis and Cosmological Observations on varying Higgs VEV
Hongrui Feng, Yudong Luo, Toshitaka Kajino et al. (+2 more)
The
Higgs vacuum expectation value (VEV) alters both the electroweak and strong interaction rates. We study both effects on Big Bang Nucleosynthesis (BBN) and seek concordance between observed primordial abundances of light elements and cosmological constraints from
cosmic microwave background (CMB) fluctuations and anisotropies. We find a strong negative correlation between primordial 4He abundance and the
Higgs VEV. Consequently, using a 1.58% uplift of the
Higgs VEV during BBN from the current value, an agreement can be achieved among the new primordial 4He abundance, observed by the EMPRESS group, Deuterium abundance determined from absorption lines in the Lyman-alpha forest along the line-of-sight of high-
redshift quasars, and the lithium abundance on the Spite plateau. This agreement requires a baryon-to-
photon ratio different from the CMB determination, indicating the need for non-standard cosmological
evolution between BBN and recombination epochs.We also demonstrate that a 0.2% uplift in the
Higgs VEV can partially alleviate the "
cosmic Li problem", keeping consistency with the CMB with remaining discrepancy potentially accounted for by stellar depletion mechanisms.
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All authors Hongrui Feng, Yudong Luo, Toshitaka Kajino, Bao-Hua Sun, Tatsushi Shima
Astrophysics of Galaxies
A Detailed GASKAP-HI View of Shells and Loops in the Magellanic Bridge
Shin-Jeong Kim, Antoine Marchal, N. M. McClure-Griffiths et al. (+19 more)
We present 8 pc-scale GASKAP-HI observations of an HI shell (diameter \sim130 pc) associated with the H\alpha shell DEM171 in the Magellanic Bridge. The Bridge's diffuse, HI-dominated environment, with minimal galactic shearing and fewer overlapping
star-forming regions, provides an ideal environment to study cold gas formation driven by stellar feedback. To investigate the HI multi-phase structure and kinematics of the shell, we perform Gaussian decomposition of HI line profiles. We identify cold HI components with velocity dispersions \sigma < 2.5 km/s located within the shell. Complementary Herschel far-infrared (FIR) 250\micron and H\alpha maps show that while the central cavity is ionized, the shell walls contain cold HI, molecular gas, and dust, suggesting that stellar feedback has promoted cold gas formation or swept pre-existing cold gas into the shell walls. We also identify cold HI clumps outside the shell tracing a larger-scale structure, MB-Loop I. To investigate the large-scale context, we apply a
Fourier transform method to HI emission-line profiles to map the lower limit of cold-gas column densities across a section of the Bridge, revealing structures from large loops to smaller shells. The association between MB-Loop I and the HI shell suggests that cold HI gas may pre-exist before shell expansion. Finally, the shell exhibits asymmetric expansion, with a preferred orientation roughly perpendicular to the arc along MB-Loop I. Our results show that cold HI gas exists across a wide range of spatial scales in the Magellanic Bridge, highlighting the dynamic interplay that shapes the surrounding interstellar medium.
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All authors Shin-Jeong Kim, Antoine Marchal, N. M. McClure-Griffiths, J. R. Dawson, James Dempsey, Helga Dénes, John M. Dickey, Steven J. Gibson, Katie Jameson, Ian Kemp, Bumhyun Lee, Min-Young Lee, Adam K. Leroy, Callum Lynn, Yik Ki Ma, Marc-Antoine Miville-Deschênes, Eric G. M. Muller, Claire Murray, Hiep Nguyen, Nickolas Pingel, Hye-Jin Park, Jacco Th. van Loon
Instrumentation and Methods for Astrophysics
Transitioning from ADS to SciX to Serve 21st Century Astronomy
Jennifer Lynn Bartlett, Suze Kundu, Alberto Accomazzi et al. (+1 more)
For decades, the NASA Astrophysics Data System (ADS) has been the foundational digital library for astronomy. As ADS becomes the Science Explorer (SciX), the team prioritizes preserving this trusted experience while increasing their support for space and Earth sciences broadly, without diluting its commitment to astrophysics.
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All authors Jennifer Lynn Bartlett, Suze Kundu, Alberto Accomazzi, Michael J. Kurtz
High Energy Astrophysical Phenomena
FRB 20250607A: Weirder Than Fiction
J. C. F. Balzan, A. Bera, C. W. James et al. (+4 more)
We present a detailed analysis of FRB 20250607A, a two-component FRB detected by the CRAFT survey which exhibits several unusual component-dependent properties, including apparent differential DM, circular polarisation, and time-resolved RM, together with a polarisation-angle (PA) swing that persists through the scattering tail. The scattering timescale and scintillation bandwidth are inconsistent with a single thin-screen origin, placing the dominant scattering screen within $\lesssim61$ kpc of the FRB source. The lack of PA flattening in the scattering tail is a behaviour not previously reported in an FRB or
pulsar and difficult to reconcile with a simple propagation origin. We find no statistically significant differential DM between the two components despite an apparent, and visually obvious, difference in their dispersion, indicating that current uncertainties may be overly conservative. If this apparent differential DM is true, it implies a substantial difference in electron column density between the component sightlines. Two further CRAFT FRBs, FRB 20190611B and FRB 20210407E, show similarly large component-dependent electron-column differences, corresponding to electron-density contrasts consistent with
plasma local to a
neutron-
star magnetosphere. We find no evidence for generalised Faraday rotation, and FRB 20210407E shows component-dependent PA structure. Taken together, these results suggest that the observed DM, circular polarisation, and PA behaviour may arise from differing sightlines through an inhomogeneous or evolving magnetosphere rather than from independent phenomena. Multi-component FRBs therefore provide a sensitive probe of
plasma structure local to their progenitors.
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All authors J. C. F. Balzan, A. Bera, C. W. James, B. W. Meyers, A. T. Deller, R. M. Shannon, Z. Wang