Astrophysics of Galaxies
The role of major mergers in triggering super-Eddington accretion
Riccardo Caleno, Tommaso Zana, Raffaella Schneider et al. (+6 more)
JWST observations have opened a new era in the exploration of the high-
redshift Universe, revealing black holes (BHs) with masses of several million
solar masses already at $z>8$, challenging our understanding of their growth mechanisms. In this context, super-Eddington (SE)
accretion has emerged as a promising solution and has been widely adopted in both numerical simulations and semi-analytical models. In this work, we investigate whether a major merger between two relatively low-mass
halos ($M_{\rm halo}\sim10^9\,\mathrm{M_\odot}$) at high
redshift can trigger episodes of sustained SE
accretion, with particular focus on the role of BH feedback. We employ state-of-the-art, high-resolution cosmological zoom-in simulations of a major merger at $z\sim11$. We explore different prescriptions for BH seeding and feedback, including physically motivated radiative and kinetic models (winds and jets) across the three main
accretion regimes: advection-dominated
accretion flows (ADAF), radiatively efficient sub-Eddington
accretion, and SE
accretion. For the relatively low-mass
halos studied here, our feedback prescription efficiently suppresses gas
accretion, preventing substantial BH growth. We find that, although the merger drives gas inflows towards the central regions, this is not sufficient to trigger sustained SE
accretion. Post-merger SE
accretion episodes are observed only when BH feedback is entirely switched off. Amongst the feedback channels considered, kinetic feedback is the primary mechanism regulating BH growth. Moreover, the only significant SE
accretion episodes occur immediately after BH seeding, while the merger itself does not produce a substantial enhancement of the
accretion rate.
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All authors Riccardo Caleno, Tommaso Zana, Raffaella Schneider, Alessandro Lupi, Pedro R. Capelo, Lucio Mayer, Alessandro Trinca, Rosa Valiante, Marta Volonteri
Instrumentation and Methods for Astrophysics
Relativistic Lightsail Propulsion Dynamics
Chao Shen and Jiaze Li
Lightsail technology currently stands as one of the most promising means for interstellar travel, having entered the application phase following multiple successful on-orbit validations. This paper systematically investigates the propulsion effects of incident light, specularly reflected light, and diffusely scattered light on high-speed relativistic lightsails based on radiation dynamics for the first time. The results indicate that, due to the Doppler effect, the thrust from all three components decreases as velocity increases, with incident light providing the strongest thrust, followed by specular reflection, and diffuse scattering being the weakest. Furthermore, the study reveals the existence of a critical velocity for thrust from diffuse scattering: beyond this point, it transforms into drag, although the net radiative force continues to accelerate the spacecraft. By establishing and numerically solving the equations of motion for the lightsail, it is shown that velocity increase is concentrated primarily in the initial acceleration phase, with efficiency declining as speed rises. This research provides a rigorous and in-depth theoretical foundation for lightsail dynamics
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Cosmology and Nongalactic Astrophysics
The Cosmological Hart-Tipler Conjecture
David Kipping
Self-reproducing automata, so-called von Neumann machines, have been repeatedly estimated to be capable of traversing the
Galaxy many times given its age. Our mere existence thus seems to exclude an aggressive variant of such a probe having ever been launched in the Milky Way. The Hart-Tipler
conjecture considers this to represent contra-positive evidence to the hypothesis that other extra-terrestrial technological entities have emerged in our
galaxy. Recently, several authors have extended interstellar colonization calculations to cosmological volumes, but these models are loaded with specific assumptions about behavior and emergence times. Here, we present a bare-bones model of generic artificial infections (such as but not limited to von Neumann probes) at cosmological scale in order to maximize interpretability, an approach closer to the original spirit of the Hart-Tipler calculations. Our model has just three parameters, a spontaneous spawn rate, a propagation speed (u) and a start time for the calculation. Accounting for cosmological expansion, we find that half the Universe is infected by today for u=0.1c propagation starting 4.5 Gyr after the Big Bang if the spawn rate exceeds approximately once per million
galaxies. For near-c propagation, this becomes a billion
galaxies. Over 99.9% of cosmological volumes are filled with 0.1c if even 1-in-100,000
galaxies have ever spawned an infection. The "cosmological Hart-Tipler" problem therefore offers a remarkably sharp minimal-model constraint on the prevalence of aggressive, self-propagating technological behavior. We explore its implications, such as how anthropic
reasoning implies such infections occur and its fine-tuning nature.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
A Common Antimatter Response in AMS-02 Positrons and Antiprotons
Yi Yang
I develop a common history-overlap description that gives antiparticle time orientation a physical role beyond its use in field-theory amplitudes. In this framework, opposite orientation reduces the effective overlap with a finite, matter-defined environmental history, while standard local interactions, positive physical energies, and causal detector records are retained. The common geometry connects two contrasting
cosmic-ray spectral patterns measured by AMS-02. For positrons, a
geometric exposure estimate displaces the broad maximum of an empirical energy-weighted electron reference from 8–10 GeV to the 300–400 GeV region. A number-conserving calculation combines energy redistribution and spatial dilution to interpret the relative weighted height, of order $0.1$. For antiprotons, ordinary secondary production retains the parent-
proton history. I extend the same three-direction overlap estimate to the accumulated logarithmic deformation after production. Within this approximation, an ordinary softening of a few tenths leaves a residual additional spectral index of order 0.01, yielding near preservation of the source index and a nearly flat antiproton-to-
proton ratio in the production-scaling limit. The positron comparison uses no additional dominant source, and known astrophysical contributions remain allowed. The paired AMS spectra give this time-orientation framework concrete empirical direction: a common
geometric description relates a
lepton scale displacement to hadronic index preservation and defines explicit targets for independent theoretical and experimental tests.
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High Energy Astrophysical Phenomena
Diocotron Modes in Pulsar Magnetospheres: Charge Diffusion and Implications for Radio Emission Variability
Matthew Goodbred and Anatoly Spitkovsky
The diocotron instability is a non-axisymmetric
plasma instability that should occur generically in the differentially rotating equatorial plane of
pulsar magnetospheres. We present a series of 3D particle-in-
cell (PIC) simulations of the diocotron instability in aligned and oblique
pulsars. The instability grows on timescales of the rotation period and develops a strong, stable $m=1$ mode, corresponding to a rotating, dipolar charge asymmetry in the equatorial disk.
Stochastic fluctuations in the diocotron mode amplitude and pattern speed drive cross-field
diffusion that can rapidly transport charges through the closed zone toward the light cylinder. In the nonlinear stage, the $m=1$ mode produces electric field perturbations which can modulate the polar cap potential drop and the emission beam angle, with possible connections to
pulsar variability such as nulling, periodic amplitude modulation, and drifting subpulses.
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Instrumentation and Methods for Astrophysics
The OAD Flagship Ecosystem
Joyful E. Mdhluli
The International Astronomical Union's Office of Astronomy for Development (IAU OAD) uses astronomy as a tool to address societal challenges and contribute to sustainable development. Building on more than a decade of project funding and implementation, the OAD has developed a portfolio of flagship projects that represent tested and scalable applications of Astronomy for Development across thematic areas including socio-economic development, science diplomacy, skills development, inequality reduction, and technology transfer. To support the growth and long-term sustainability of these initiatives, the OAD has established the Flagship Ecosystem, a framework built around four interconnected pillars: Resources, Training, Community, and Implementation. This paper presents an overview of the OAD Flagship projects, the structure and components of the Flagship Ecosystem, and explores how it supports the translation of astronomy-based interventions into sustainable development outcomes. The ecosystem provides open-access resources, capacity-building opportunities, communities of practice, funding mechanisms, and evidence-generation activities that enable individuals and organizations to implement and scale astronomy-for-development initiatives. Grounded in principles of inclusivity, openness, sustainability, participation, and evidence-informed practice, the ecosystem aims to strengthen the global impact of Astronomy for Development while fostering collaboration across diverse sectors and regions.
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Astrophysics of Galaxies
Spectral Handling and Estimation of AGN Parameters (SHEAP), The first AGN fitting GPU-based code
F. Ávila-Vera, P. Sánchez-Sáez, V. Motta et al. (+1 more)
In the coming years, the number of discovered active
galactic nuclei (AGN) is expected to increase significantly due to upcoming spectroscopic surveys. This growth will challenge current analysis and modeling techniques, requiring scalable methods for large, heterogeneous
datasets with diverse signal-to-noise ratios, spectral resolutions, and host-
galaxy contamination. We present SHEAP (Spectral Handling and Estimation of AGN Parameters), a spectral-fitting framework designed to analyze large AGN samples efficiently while preserving physical interpretability, reproducibility, and robust uncertainty estimation. SHEAP uses JAX, a Python GPU-powered framework, to implement a flexible model with modular components, including continuum, host
galaxy, FeII pseudo-continuum, and multi-component emission lines, together with parameter tying and physically motivated constraints. By combining gradient-based optimization with automatic differentiation, vectorization, and just-in-time compilation, SHEAP achieves stable convergence in blended regions, such as H$\beta$, while substantially reducing runtime. We compare SHEAP measurements with literature results and public fitting pipelines across four samples covering the CIV, MgII, H$\beta$, and H$\alpha$ regions. We find good agreement for the main AGN spectral parameters, with $\sim85$–$100%$ of objects lying within the $\pm0.3$ dex band and reduced chi-square distributions close to unity. Relative to the runtime reported by \citet{2026Bernal} using pPXF, the fitting stage requires only $\sim1.7%$ of the computational time, corresponding to an improvement of approximately $100$ times. These results show that SHEAP delivers reliable AGN spectral decompositions at substantially lower computational cost, making it suitable for massive spectroscopic
datasets.
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All authors F. Ávila-Vera, P. Sánchez-Sáez, V. Motta, S. Bernal
Astrophysics of Galaxies
The VMC survey – LV. The coherent expansion of the SMC
S. Vijayasree, F. Niederhofer, M.-R. L. Cioni et al. (+8 more)
The Small Magellanic Cloud (SMC) exhibits significant kinematic disequilibrium due to interactions with the Large Magellanic Cloud (LMC). Here, we investigate the two-dimensional
stellar kinematics of the SMC to understand the dynamical effects of these interactions by exploiting the increased time baseline of 6-11 years from the VISTA Survey of the Magellanic Clouds (VMC) data release 7. We derive proper motions with a threefold improvement in precision compared to previous studies based on VMC data. We used a
geometric framework accounting for perspective effects from line of sight motion to model the systemic motion across the SMC and construct a residual proper motion map. We further introduce an anisotropic linear velocity gradient model to quantify the stretching of the
galaxy. For the first time across all
stellar populations, the residual proper motion map reveals expansion along the south-east and north-west directions, consistent with LMC-induced
tidal forces, detectable even in the central regions. The gradient-corrected residuals show predominantly radial motions towards the SMC centre with no evidence of rotation. Velocity maps for different
stellar populations, without assuming a rotating-disk model, reveal a coherent northward motion away from the centre exclusively in older red
giant branch
stars, interpreted as a kinematic signature of a past (>2 Gyr ago) interaction. This study highlights the inadequacy of simple rotating-disk models in capturing the internal kinematics of the
galaxy.
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All authors S. Vijayasree, F. Niederhofer, M.-R. L. Cioni, J. Th. van Loon, K. Bekki, R. de Grijs, S. Subramanian, N. Kacharov, A. O. Omkumar, L. R. Cullinane, V. D. Ivanov
High Energy Astrophysical Phenomena
Longitudinal Development Analysis of Extensive Air Showers Using CORSIKA Simulations
Ali A. Shihab and A. A. Al-Rubaiee
We present a comprehensive analysis of the longitudinal development of Extensive Air Showers (EAS) simulated with CORSIKA version 7.7500 for
proton, helium, and iron primaries at energies of 10^15, 10^16, and 10^17 eV across zenith angles of 0, 30, and 45 degrees. For each combination of primary type, energy, and zenith angle, 50 independent showers were simulated, resulting in a total of 450 simulated showers. The Gaisser - Hillas function was fitted to extract the depth of shower maximum (Xmax) and the number of particles at maximum (Nmax). Our results confirm the expected logarithmic increase of Xmax with energy (about 10 g/cm^2 per decade), as well as systematically shallower Xmax for heavier primaries (iron vs.
proton: Delta (Xmax) equal to about 160 g/cm^2 at 10^17 eV).The simulations also reproduce the expected sec (theta) scaling behavior. Multi-component analysis reveals distinct evolutionary patterns for electromagnetic, muonic, and hadronic components. These findings provide
benchmark-level simulations for
cosmic-ray composition studies and validate the CORSIKA framework for multi-parameter analyses of air-shower development.
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High Energy Astrophysical Phenomena
Suppressed diffusion and gamma-ray emission from the Cygnus bubble
Ben Li, Pasquale Blasi and Elena Amato
Recent gamma-ray observations indicate that
star clusters can be efficient particle accelerators. In particular, LHAASO has detected diffuse gamma-ray emission from Cygnus OB2 extending to $\gtrsim$ PeV energies, indicating that particles are accelerated to at least $\gtrsim$1 PeV. In this work, we study the gamma-ray emission from the Cygnus region assuming particle acceleration either at the termination shock of the cluster wind (WTS) or in an unspecified source at the bubble center, taken to be either steady or bursting. We numerically solve the transport equation for non-thermal particles in all scenarios and derive their spatial and spectral distributions throughout the bubble. We then calculate the gamma-ray emission from pp interactions, including the contribution from particles interacting with the surrounding molecular cloud, which may help explain the extended emission observed by LHAASO. We also include the penetration of
Galactic cosmic rays (GCRs) and the resulting shock reacceleration. The predicted emission is compared with
Fermi-LAT, HAWC and LHAASO observations. For three
diffusion models, we find that a spatially dependent Bohm
diffusion coefficient is required to reproduce both the spectrum and morphology in the cluster wind scenario. Penetrating GCRs can contribute significantly to the gamma-ray emission above $\sim$300 TeV. A suppressed
diffusion coefficient with respect to the
Galactic average in a region extending to at least 150 pc from the cluster center is needed to reproduce the LHAASO morphology. Our conclusion is that explaining both the spectrum and morphology of the $\sim$PeV emission with
hadrons accelerated in a non-relativistic steady source requires extreme assumptions. We also speculate on the possibility that some of the highest-energy gamma rays may originate from sources behind the Cygnus association.
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Cosmology and Nongalactic Astrophysics
Biased tracers, Hybrid Effective Field Theory and Modified Gravity
Guilherme Brando, Baojiu Li and Kazuya Koyama
The modelling of the power spectrum of biased tracers has become a central topic in the analysis of modern cosmological
galaxy surveys. Perturbative templates formulated in both Eulerian and Lagrangian frameworks have been extensively developed over the last decades, with their implementation in $\Lambda$CDM thoroughly investigated and validated. In parallel, approaches combining perturbation theory with the output of dark-matter-only simulations have emerged as powerful tools for modelling the nonlinear regime, most notably the Hybrid Effective Field Theory (HEFT) framework~\cite{Modi:2019qbt}. In this work, we discuss the perturbative biased expansion within the local Lagrangian bias scheme and its implementation in the HEFT framework for modified
gravity cosmologies. We focus on $f(R)$
gravity, a theory characterized by scale-dependent growth and chameleon screening, making it one of the most challenging scenarios for the computation of Lagrangian Perturbation Theory growth functions and for the generation of accurate numerical simulations. We present a detailed overview of the ingredients required to compute loop-corrected biased power spectra analytically and compare these predictions against fully non-perturbative simulation results. Finally, we propose a strategy to extend existing HEFT-based $\Lambda$CDM emulators, such as bacco and Aemulus, to beyond-$\Lambda$CDM cosmologies.
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Solar and Stellar Astrophysics
A Previously Underexplored Regime in TESS: Minute-Scale Eclipses Reveal Ten White Dwarf-Cool M-Dwarf Binaries
Tristan Cavalier, Julien de Wit, Mathilde Timmermans et al. (+14 more)
Short-period white-
dwarf (WD) binaries are post-common-envelope systems that constrain orbital shrinkage, envelope
evolution, and the survival of low-mass companions. We report the discovery and confirmation of ten fully eclipsing short-period WD + cool M-
dwarf binaries identified through a tailored search for minute-scale eclipses in Transiting
Exoplanet Survey Satellite (TESS) high-cadence data and validated with SPECULOOS multi-band photometry. The systems have orbital periods of a few hours and companions with effective temperatures of 2700-3400 K. These discoveries demonstrate that TESS contains a previously underexplored population of compact WD binaries whose short-duration, high-frequency, and often diluted eclipse signals are not efficiently recovered by standard transit-search pipelines. Whereas the literature contained only one eclipsing WD+M binary reported as a TESS-based discovery, our pilot search of $\sim3.7\times10^4$
Gaia-selected WDs yields ten new confirmed systems, increasing the TESS-discovered sample by an order of magnitude. SPECULOOS follow-up confirms the eclipses occur on target and uses chromatic eclipse dilution to distinguish
stellar from substellar companions. We combine multi-band eclipse photometry with
Bayesian spectral energy distribution modeling to derive self-consistent WD and companion parameters. The resulting systems expand the known population of fully eclipsing WD+M binaries and notably double the number of systems in temperature regimes corresponding to M4 and M7 companions. This work establishes a scalable framework for identifying compact WD binaries in time-domain photometric surveys. Applied to TESS archival data across the full
Gaia WD-candidate catalog ($\sim1.3\times10^6$ sources), this approach opens the prospect of assembling a population large enough to constrain post-common-envelope
evolution and the
stellar-substellar transition.
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All authors Tristan Cavalier, Julien de Wit, Mathilde Timmermans, Benjamin V. Rackham, Mariangel Albornoz, Artem Y. Burdanov, Khalid Barkaoui, Amaury H. M. J. Triaud, Adam J. Burgasser, Brice-Olivier Demory, Elsa Ducrot, Michael Gillon, Yilen Gómez Maqueo Chew, Matthew J. Hooton, Peter P. Pedersen, Didier Queloz, Sebastián Zúñiga-Fernández
Earth and Planetary Astrophysics
The CRIMSON survey I: super-stellar SiO in the directly imaged companion TWA 5 B from high-resolution M-band spectroscopy
Luke T. Parker, Jayne L. Birkby, Siddharth Gandhi et al. (+4 more)
Silicon is a key refractory element in
giant planet atmospheres, which governs the formation of magnesium-silicate clouds, and reflects the quantity of silicates accreted during formation. While observations of directly imaged
giant exoplanets have focused on the measurement of volatile species (e.g. CO, H$_2$O), high-resolution spectroscopy with CRIRES+ M-band provides access to gas phase silicon chemistry in sub-
stellar atmospheres, through the ro-vibrational band head of SiO at 4 $\mu$m. Here, we present the first results of the CRIMSON survey of silicon chemistry in directly imaged companions with CRIRES+ M-band. We report the strong detection of gaseous SiO (S/N = 7.5) in the directly imaged companion TWA 5 B, with an atmospheric abundance of log(SiO) = $-3.56^{+0.42}_{-0.32}$ VMR, providing access to the refractory content of the atmosphere. The high retrieved SiO abundance implies the absence of significant magnesium-silicate cloud condensation, and thus the atmospheric silicon abundance is contained almost entirely within the observed gas phase SiO. Using the detection of refractory silicon, together with strong detections of the volatile species CO (S/N = 9.1) and H$_2$O (S/N = 18.8), we measure a
stellar C/O and a marginally sub-
stellar O/Si and C/Si, but a super-
stellar Si/H ([Si/H]$_{\star}$ = $1.41^{+0.42}_{-0.32}$). Collectively, these volatile-to-refractory ratios are consistent with formation through core-
accretion beyond the CO snowline, or gravitational instability followed by substantial solid enrichment. Finally, we discuss how gas phase SiO provides a unique diagnostic of the cloud properties in hot gas-
giants, and can be used to probe the dominant cloud species forming across the directly imaged
planet and isolated brown
dwarf populations.
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All authors Luke T. Parker, Jayne L. Birkby, Siddharth Gandhi, Vivien Parmentier, Vatsal Panwar, Matteo Brogi, Sophia R. Vaughan
Cosmology and Nongalactic Astrophysics
GraphShed: A Data-derived Graph-based waterShed Group Finder
P. Ghafour, S. Ansarifard, M. H. Jalali Kanafi et al. (+1 more)
This study introduces GraphShed, a data-derived group-finder that applies top-down watershed
segmentation to Voronoi-induced graphs, identifying
galaxy systems directly from the density field via a GraphShed-derived linking length, with no density thresholds or tunable parameters. A GraphShed
galaxy group catalog compared to a Friends-of-Friends (FoF) catalog built from the IllustrisTNG100-1 simulation with a box size of $\sim 75$ Mpc/h yielding $1067$ and $987$ systems, respectively. The GraphShed-derived linking length adapts to the global clustering power of the sample, varying by $\sim 18 \%$ relative to FoF across different sample selections; thus, catalog differences originate in the watershed
segmentation. Cross-catalog comparison shows that $\sim 58 \%$ of FoF systems are identically reproduced by GraphShed, $\sim 5 \%$ are completely removed, and the remainder are partially shaved and/or split into multiple systems. While the $M_{200}$ distributions of the two catalogs are statistically consistent, other structural properties including, $R_{200}$, sphericity, compactness,
spin, and centroid shift, differ significantly in at least some richness ranges. The unweighted two-point correlation function of GraphShed systems exhibits a higher amplitude on small scales, $r \lesssim 1$ Mpc/h, and agrees with FoF for $r\gtrsim 5$ Mpc/h. A velocity-based classification reveals that GraphShed resolves more interacting pairs than FoF, demonstrating its ability to distinguish nearby overdense structures that position-only methods merge into single systems. These results demonstrate that GraphShed preserves cosmological statistics while providing a more resolved detection of
galaxy systems and their dynamical interactions.
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All authors P. Ghafour, S. Ansarifard, M. H. Jalali Kanafi, S. M. S. Movahed
High Energy Astrophysical Phenomena
Targeting black holes from metal-poor progenitors with next-generation gravitational-wave detectors
Federico Leto di Priolo, Martyna Chruślińska and Davide Gerosa
Next-generation gravitational-wave detectors such as the Einstein
Telescope and
Cosmic Explorer will be able to detect binary black-hole mergers out to the
cosmic dawn. Mergers observed in the local Universe represent a mixture of systems formed across the entire
cosmic history, spanning a wide range of astrophysical environments. Iron-group elements govern
metallicity effects on
stellar evolution, making
metallicity a key tracer that leaves a strong imprint on the black-hole population. We introduce the concept of a “target”
redshift, $z_t$, defined as the epoch at which more than $90\%$ of
stars form with
metallicity $Z < 0.1\,Z_\odot$. This provides a straightforward way to isolate mergers originating from metal-poor environments. The determination of $z_t$ relies on the reconstruction of the
cosmic star formation rate density as a function of iron abundance. This reconstruction is not unique, as it depends on the combination of different empirical scaling relations. Consequently, $z_t$ spans a broad range, from $z_t \sim 4$ to $z_t > 10$, depending on the adopted model variation. We present a statistical framework that enables rapid tests of astrophysical predictions against forecasted observations from next-generation \acrlong{gw} detectors. By quantifying variations in the binary black-hole merger-rate density between the target
redshift and the local Universe, our approach maps evolutionary trends across parameter space and estimates the detection statistics required to distinguish genuine astrophysical variations from statistical fluctuations.
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Cosmology and Nongalactic Astrophysics
The impact of source and survey modelling on the connection between [O III] emitters and Ly $\alpha$ forest transmission at z ~ 6
Luke Conaboy, James S. Bolton, Laura C. Keating et al. (+3 more)
James Webb Space
Telescope (JWST) surveys of [O III]-emitting
galaxies are offering fresh insight into the connection between
galaxies and the intergalactic medium at
redshift z ~ 6. Recent measurements of the cross-correlation between [O III]-emitting
galaxies and Ly $\alpha$ forest transmission point to excess Ly $\alpha$ transmission at a scale (r $\approx$ 30 cMpc) and amplitude (roughly twice the global mean) that is not seen in numerical models. Here we improve upon previous theoretical work by constructing an empirical model that connects
haloes with the observed population of [O III] emitters and incorporates the geometry and depth of the JWST surveys into mock
galaxy survey catalogues. We compare these mocks to recent measurements of [O III] emitter clustering, the one-dimensional
galaxy-Ly $\alpha$ transmission cross-correlation, and the relation between
galaxy surface density and Ly $\alpha$ effective optical depth. The large scatter in our mock survey measurements of the cross-correlation means there is no significant tension with the observational data, albeit the peak of the one dimensional correlation in our mocks occurs at a scale $\approx$ 10 cMpc below that observed. Though further studies of the effect of different ionising source models will be useful, the large scatter implies that, at present, current
galaxy-IGM observations may struggle to rule out a broad range of such models. We anticipate that further progress will strongly benefit from increased observational sample sizes, as well as simulations performed in box sizes > 250 cMpc that use a variety of source models.
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All authors Luke Conaboy, James S. Bolton, Laura C. Keating, Martin G. Haehnelt, Girish Kulkarni, Ewald Puchwein
Earth and Planetary Astrophysics
KRONOS I: The $1{-}2.8\mu$m JWST Transmission Spectrum of the 23 Myr V1298 Tau c
Matthew M. Murphy, Matthew C. Nixon, Adina D. Feinstein et al. (+16 more)
While recent JWST observations of mature super-Earths and sub-Neptunes have frequently revealed featureless transmission spectra, their inflated progenitors offer a unique window into understanding their
primordial compositions. As part of the Keys to Revealing the Origin and Nature Of sub-neptune Systems (KRONOS) JWST program, we present the NIRISS/SOSS transmission spectrum of V1298 Tau c, a $\sim$23 Myr super-Earth progenitor orbiting a young
Solar analog. We detect H$_2$O in V1298 Tau c's atmosphere with a $\log_{10}$ volume mixing ratio of $-1.83^{+0.68}_{-0.77}$, but no additional molecules from these data alone. We find consistent results for the planetary atmospheric properties in both
retrievals with and without informed priors on
stellar heterogeneities based on the observed
stellar spectrum. We infer an atmospheric
metallicity [O/H] of $14.8^{+56.0}_{-12.28}\times$ the
solar value. This
metallicity is similar to literature measurements for other young
planets, including its massive outer companion V1298~Tau~b. In contrast, this measured
metallicity is systematically lower than the
metallicities of mature
planets of similar mass and temperature. Altogether, these results provide tentative but growing evidence that the
exoplanet mass–
metallicity relation evolves with planetary age.
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All authors Matthew M. Murphy, Matthew C. Nixon, Adina D. Feinstein, Luis Welbanks, Girish M. Duvvuri, Saugata Barat, Benjamin V. Rackham, Darryl Z. Seligman, Michael Radica, Ian J. M. Crossfield, Kevin France, John H. Livingston, Jonathan Lunine, Rafael Luque, Catriona Murray, Sagnick Mukherjee, Biruk Nardos, Sydney Petz, Hinna Shivkumar
Solar and Stellar Astrophysics
J0404+1112: A 3-Hour Eclipsing White Dwarf-Brown Dwarf Probing Multiple Atmospheric Regimes
J. de Wit, R. Alonso, B. V. Rackham et al. (+19 more)
White
dwarf-brown
dwarf (WD+BD) binaries are rare laboratories for probing both substellar survival through post-main-sequence
evolution and the physics of strongly irradiated atmospheres. We present time-resolved eclipse photometry and radial-velocity confirmation of J0404+1112, a compact ($P = 2.93$ hr), totally eclipsing WD+BD system initially reported in a Research Note of the AAS. New high-cadence observations resolve a total eclipse of the WD and, combined with spectroscopy, broadband photometry, and the
Gaia parallax, yield a revised system architecture. We find a hot DA WD with $T_{\rm eff} \simeq 28{,}000$ K, $\log g \simeq 8.0$, $M_{\rm WD} \simeq 0.6 \rm{M}_\odot$, and $R_{\rm WD} \simeq 0.015 \rm{R}_\odot$, orbited by a $\sim40 \rm{M}_{\rm Jup}$ BD with radius $\sim0.9 \rm{R}_{\rm Jup}$. These parameters supersede earlier SED-based estimates in which the WD temperature, radius, distance, and extinction were strongly covariant. We break this degeneracy with normalized Balmer-line profile fitting and high-cadence eclipse photometry that constraints the WD's radius geometrically. The total eclipses enable isolation of the BD flux and constrain its nightside emission. With its short orbital period and strong irradiation, J0404+1112 provides a uniquely compact, high-sensitivity JWST
benchmark for probing atmospheric heat redistribution and photochemistry in the temperature regime of the hottest ultra-hot Jupiters, spanning dayside and nightside brightness temperatures of $\sim3{,}600$ K and $\sim1{,}800$ K within a single $\sim$3 hr orbit.
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All authors J. de Wit, R. Alonso, B. V. Rackham, S. M. Lederer, A. Y. Burdanov, S. L. Casewell, Y. Zhou, J. R. French, K. Barkaoui, M. Albornoz, A. J. Burgasser, T. Cavalier, B.-O. Demory, E. Ducrot, M. Gillon, Y. Gómez Maqueo Chew, M. J. Hooton, P. P. Pedersen, D. Queloz, M. Timmermans, A. H. M. J. Triaud, S. Zúñiga-Fernández
Cosmology and Nongalactic Astrophysics
Constraining Scale-Dependent Growth in $f(R)$ Gravity with Future 21 cm Surveys
Apurba Samanta, Bhuwan Joshi, Jess Worsley et al. (+2 more)
Recent observations, particularly from DESI, have provided intriguing hints of dynamical behaviour in late-time dark energy. Modified
gravity theories offer a compelling framework for interpreting such phenomena, with $f(R)$
gravity emerging as one of the most extensively studied examples. A central challenge in these models, however, lies in determining the precise functional form of $f(R)$. Nevertheless, several viable models have been proposed that successfully reproduce the standard $\Lambda$CDM cosmology at high red shifts while generating late-time
cosmic acceleration without an explicit dark energy component. Within this framework, the
evolution of the linear matter density contrast becomes scale dependent, leading to a growth index that varies with both scale and
redshift. In this work, we explore the capability of forthcoming 21 cm observations to constrain the growth index, as well as the combined neutral hydrogen (HI) bias and growth-rate parameter. Our results indicate that future 21 cm surveys can provide meaningful, though moderate, support for these modified
gravity scenarios.
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All authors Apurba Samanta, Bhuwan Joshi, Jess Worsley, Peter Dunsby, Saikat Chakraborty
High Energy Astrophysical Phenomena
Neutron Star Observations Challenge a Large Colour-Superconducting Gap in Dense Quark Matter
Shao-Peng Tang, Yong-Jia Huang and Yi-Zhong Fan
At asymptotically high density,
quantum chromodynamics (QCD) predicts that
quark matter becomes a colour
superconductor in the colour-flavour-locked (CFL) phase, yet, away from the asymptotic regime, the magnitude of the pairing gap is uncertain. Here we combine multi-messenger
neutron star observations with perturbative QCD and
chiral effective field theory inputs in a
Bayesian inference built on a flexible Gaussian-process–neural-network representation of the equation of state (EOS). By matching the EOS at a
baryon chemical potential of 2.6 GeV to the perturbative QCD prediction supplemented by the next-to-leading-order CFL contribution, we infer a gap of $\Delta^{*}_{\rm CFL}=34^{+32}_{-28}$ MeV and a 95% credible upper limit of about 66 MeV, which is a factor of two tighter than previous bounds and at the lower edge of most microscopic model predictions. We further place the first data-driven constraint on the unknown high-order constant of the perturbative QCD pressure, i.e., $c_0=-21^{+9}_{-8}$. Our results indicate that colour-superconducting pairing makes only a subdominant contribution to dense matter pressure, tightening the connection between
neutron star data and the QCD phase diagram.
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Earth and Planetary Astrophysics · Cross-listed from physics.plasm-ph
Velocity space origins of pressure-strain interaction in multi-population distributions and its application to magnetic reconnection
M. Hasan Barbhuiya, Paul A.Cassak, Sarah Conley et al. (+7 more)
A forefront research question is how energy evolves in weakly collisional
plasmas for which departures from local thermodynamic
equilibrium (LTE) are significant. The standard approach is studying the terms in the non-LTE energy
evolution equation derived by taking the second moment of the Boltzmann equation, but the resultant fluid metrics do not retain information about which particles at which velocities drive energy
evolution. A widely studied channel for internal energy density
evolution is the pressure-strain interaction. Here we employ the kinetic pressure-strain [S. A. Conley et al., ${\it Phys. Plasmas,} {\bf 31}$, 122117 (2024)], a phase space diagnostic whose velocity-space integral recovers the pressure-strain interaction to disambiguate the contributions to pressure-strain interaction from disparate particle populations in composite phase-space densities. We develop phase-space analogs of the pressure-strain interaction decompositions to provide the phase-space origins of normal vs. sheared flow. We introduce the "kinetic strain-rate" tensor, the phase-space analog of strain-rate tensor, which we argue is needed to interpret phase-space origins of pressure-strain interaction. To demonstrate the utility of these quantities, we investigate them for composite electron distributions near the electron
diffusion region in two-dimensional particle-in-
cell simulations of antiparallel symmetric
magnetic reconnection. We find that the phase space-based diagnostics isolate the roles of distinct populations. These results contribute to a growing body of work providing new methods for quantifying phase space energy
evolution for a broad array of processes, from
magnetic reconnection to collisionless shocks and
turbulence, opening new pathways for answering longstanding problems of particle energization in weakly collisional
plasmas.
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All authors M. Hasan Barbhuiya, Paul A.Cassak, Sarah Conley, Julia E. Stawarz, Emily Lichko, Jason TenBarge, James Juno, Jason R. Shuster, Gregory G. Howes, Subash Adhikari
Astrophysics of Galaxies
Constraining AGN accretion physics with black hole mass-luminosity scaling relations
F. Fiore, M. Gaspari, S. Puccetti et al. (+3 more)
We test how supermassive black holes are fed by combining new black hole mass-luminosity relations with physically motivated feeding models. We build a uniform sample of 1729 unobscured blue
quasars at z>2 by cross-matching SDSS DRE16 with eROSITA, and augment it with hyperluminous
quasars (WISSH, HYPERION) plus 49 JWST broad-line AGN at z>3.5. We find for the SDSS-eROSITA sample of blue
quasars a near-linear scaling of bolometric luminosity with mass (slope 0.91+/-0.01) and a shallower hard-X-ray trend (slope 0.73+/-0.01). Classical hot-mode (Bondi)
accretion underpredicts the observed luminosities by about 2 dex at the high-mass end and is inconsistent with the measured slopes. In contrast, Chaotic Cold
Accretion (CCA) - in which multiphase gas condenses, collides, and rains onto the
nucleus - consistently reproduces both the normalization and the near-linear slope expected from
halo thermodynamics. The shallower X-ray relation points to a decreasing coronal power fraction with black hole mass. JWST broad-line AGN frequently appear X-ray weak or Halpha enhanced. The latter case can be due to contributions from collisional ionization and photoionization from
star-formation to the broad Halpha emission, leading to overestimate AGN luminosities and black hole masses. In the former case, the X-ray weakness is consistent with coronal shielding or anisotropy at high
accretion rates. Overall, the data favor CCA-driven, self-regulated feeding over local spherical capture across the BH mass range 1E7-1E10
solar masses, and motivate extending these tests to lower masses and higher
redshifts.
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All authors F. Fiore, M. Gaspari, S. Puccetti, M. Bischetti, C. Feruglio, E. Piconcelli
Astrophysics of Galaxies
Systematically Measuring Ultra-Diffuse Galaxies. IX. A Gyr in the Life of Nearby Low Surface Brightness Galaxies
Dennis Zaritsky, Richard Donnerstein, Loraine Sandoval Ascencio et al. (+3 more)
We augment the published optical photometry of ultra-diffuse
galaxy candidates in the SMUDGes catalog with UV and IR measurements to investigate the recent ($<1$ Gyr)
star formation history of 966
galaxies. We find that 1) we classify
star forming, post-starforming, and quenched
galaxies with a precision that is comparable to that of spectroscopic studies, 2) the
star forming systems are sub-normally efficient and would not have formed their current
stellar mass at their current
star formation rate over a Hubble time, 3) the sample is biased against more strongly
star forming systems by the central surface brightness criterion of ultra-diffuse
galaxies, 4) for
galaxies that are not quenched, the timescale of
star formation episodes in this sample is typically $\lesssim$ 1 Gyr, 5) post-starburst
galaxies in the sample tend to be of lower
stellar mass and
star forming
galaxies of higher
stellar mass, suggesting that the
star forming behavior of these
galaxies does depend on mass, and 6) there is a marginal indication, with caveats, that
star formation episodes increase
galaxy size, as measured by the half-light radius, by about 8%. In addition to providing a statistically-sized sample with which to explore the
star formation behavior of these
galaxies, this study also provides a way to select
galaxies with specific recent
star formation histories for spectroscopic follow-up.
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All authors Dennis Zaritsky, Richard Donnerstein, Loraine Sandoval Ascencio, M.C. Cooper, Donghyeon J. Khim, Kristine Spekkens
Cosmology and Nongalactic Astrophysics
Model-independent H0 from GWTC-4 standard sirens and TDCOSMO 2025 strong lensing time delays
En-Yu Xiong, Ji-Yu Song, Jing-Fei Zhang et al. (+1 more)
The significant discrepancy between early- and late-Universe measurements of the Hubble constant, known as the Hubble tension, remains one of the most pressing open questions in cosmology. Since both sides of the tension rely on model-dependent assumptions or multi-rung calibration chains, a cosmological-model-independent measurement of $H_0$ is essential to arbitrate this discrepancy. In this work, we combine 142 gravitational-wave standard siren events from the Fourth Gravitational-Wave Transient Catalog with the latest TDCOSMO2025 time-delay strong
lensing data to constrain $H_0$ in a cosmological-model-independent framework based on the distance sum rule. Under the FullPop-4.0 population model with the TDCOSMO2025-only
lensing configuration, we obtain $H_0 = 83.78^{+12.53}_{-10.23}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, with a relative precision of $13.58\%$. We find that the $H_0$ precision is governed primarily by the mass-sheet transformation treatment on the strong-
lensing side: replacing the conservative TDCOSMO2025 hierarchical framework with the H0LiCOW method tightens the constraint to $H_0 = 75.42^{+3.74}_{-4.66}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, with a relative precision of $5.57\%$. At the current precision, all results are consistent with both the Planck and SH0ES values, and future improvements from more high-
redshift dark siren events and more time-delay lens systems are expected to strengthen this model-independent approach.
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All authors En-Yu Xiong, Ji-Yu Song, Jing-Fei Zhang, Xin Zhang
Astrophysics of Galaxies
Probing the Variation of the Inner Surface-Brightness Profile of Nuclear Star Clusters on the Intermediate-Mass Black Hole Mass Measurements Using Mock Observations of ELT/MICADO and HARMONI
Tinh Q. T. Le, Dieu D. Nguyen, Hai N. Ngo et al. (+3 more)
Simulations of intermediate-mass black holes (IMBH) in
dwarf galaxies within 10 Mpc that host bright
nuclear star clusters (NSCs),
prime candidates for IMBH formation, using the High Angular Resolution Monolithic Optical and Near-infrared Integral (HARMONI) field spectrograph on the Extremely Large
Telescope, probe black hole formation in the early Universe. Our approach combines observed surface brightness profiles from the Hubble Space
Telescope (HST), synthetic
stellar population spectra, and Jeans Anisotropic Modeling (JAM) for
stellar dynamics. Mock HARMONI observations were generated with the HSIM simulator and analyzed in a
Bayesian framework to infer IMBH masses down to 0.5% of the NSC mass. In this work, we extend these simulations by constructing improved
stellar-mass models using SimCADO to simulate imaging with the Multi-AO Imaging Camera for Deep Observations (MICADO). The MICADO data are jointly analyzed with HARMONI kinematics via JAM to reassess IMBH masses and uncertainties. This combined framework enables us to examine how variations in the NSC inner surface-brightness slope influence IMBH mass estimates, providing tighter constraints on low-mass black holes and advancing models for IMBH detection in NSCs.
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All authors Tinh Q. T. Le, Dieu D. Nguyen, Hai N. Ngo, Tien H. T. Ho, Tuan N. Le, Long Q. T. Nguyen
High Energy Astrophysical Phenomena
Multimodal Transformer Based Generic Mixture Density Network for Scattering Timescale Estimation of Fast Radio Bursts
Bikash Kharel, Emmanuel Fonseca, Srinjoy Das et al. (+5 more)
The discovery rate of fast
radio bursts (FRBs) continues to increase with the advent of new
radio facilities and yet extracting their astrophysical parameters such as scattering timescale ($\tau$) remains a significant bottleneck. Current $\tau$ measurement approaches like fitting analytic template models and scattering aware de-convolution are accurate but slow, sensitive to initialization, limited by low signal to noise and often require manual supervision. These limitations inspired us to explore fast, robust and scalable machine learning methods to estimate the astrophysical parameter value. We present a deep learning approach named
Multimodal Transformer Based Generic Mixture Density Network (MT-GMDN) which ingests FRB dynamic spectrum and its corresponding timeseries profile through parallel
transformer encoders, fuses their latent representations and predicts the distribution of $\tau$ with probabilistic output derived from generic mixture-density formulation. This formulation not only estimates the value of $\tau$ but also captures the (zero inflated) nature of FRB populations where a significant fraction of bursts exhibit unresolvable scattering. We trained MT-GMDN on $\sim3500$ FRBs from CHIME/FRB \cattwo while holding out some fraction of FRBs for validation during training and for testing after the training completes. The model achieves a coefficient of determination ($R^2$) value of $94\%$ on the expected value of $\tau$ for the events with measurable scattering with an excellent recall value of $90\%$ on the test data set. The model was also able to incorporate heteroskedastic errors enabling us the construction of a confidence interval for the predictions.
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All authors Bikash Kharel, Emmanuel Fonseca, Srinjoy Das, Mason Ng, Paul Scholz, Mawson W. Simmons, Lordrick Kahinga, Afrokk Khan
Astrophysics of Galaxies
Varstrometry for Off-nucleus and Dual sub-Kpc AGN (VODKA): Radio Classification of High-Redshift Dual AGN Candidates with the Very Large Array
Sude Baltaci, Arran C. Gross, Xin Liu et al. (+3 more)
Dual active
galactic nuclei (dual AGNs) are pairs of simultaneously accreting supermassive black holes in merging
galaxies. We investigate dual AGNs to understand whether merger-induced
accretion is a significant growth mechanism for supermassive black holes. Searching for such systems is favorable at close separations and high
redshift (
Cosmic Noon, $z \sim 2$) due to the expected combination of high
galaxy merger rate and peak AGN activity which characterize this era of the Universe. The sample of nine dual AGN candidates is selected based on resolved optical dual detections with
Gaia, whose angular separations are less than 1$' '$ and
redshifts range between 1.5 and 2.8. Each pair is spatially coincident with a Sloan Digital Sky Survey
quasar primary target. We aim to classify the secondary targets and other components in the
radio regime using 2-band Very Large Array imaging (C and Ku-bands) to test for dual AGN presence. We identify two dual AGNs and three quadruply imaged gravitational lens AGNs, two out of which show evidence of
radio flux anomaly. The two new dual AGNs add to the limited census of confirmed kpc-scale pairs at
Cosmic Noon, while the
radio flux anomalies in J0911+0550 and J1118+0745 provide independent evidence for substructure in their
lensing potentials, consistent with microlensing on compact AGN emission regions. Besides one confirmed AGN-
star pair, three candidates remain unclassified due to lack of
radio detection for one or two components.
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All authors Sude Baltaci, Arran C. Gross, Xin Liu, Nadia Zakamska, Yue Shen, Mingrui Liu
Astrophysics of Galaxies
An analysis of the Type Ia SN 2024gy and a comparison of different host extinction estimation techniques
Jacco H. Terwel, Kate Maguire, Cillian O'Donnell et al. (+38 more)
Type Ia
supernovae (SNe Ia) are well-known standardisable candles, and are one of the main ways to measure the distance to their host
galaxies. However, extinction due to interstellar
dust causes objects to appear fainter and redder. Correcting for this requires estimating the amount of intervening material and how the extinction changes as a function of wavelength. We present and analyse optical and near-infrared data of the well-observed SN 2024gy and use these to compare different extinction estimation techniques, making use of photometric, spectroscopic, and polarimetric data. SN 2024gy is a normal SN Ia with high velocity (HV) components in Si II $\lambda6355$ (phase $<-10$ days) and a particularly strong HV feature in the Ca II near-infrared triplet (up to peak). Modelling SN 2024gy with TARDIS shows better matches with a double-detonation scenario compared to a delayed-detonation scenario due to a better match to the Ca II HV component. A measurement of the stable Ni/Fe ratio however favours a delayed-detonation scenario. Host extinction estimates range from $E(B-V)_{host}=0.12\pm0.02$ mag (narrow interstellar absorption lines) to $E(B-V)_{host}=0.24\pm0.06$ mag (Lira law) with a mean of $E(B-V)_{host}=0.22\pm0.04$ mag, assuming $R_V=3.1$. The spread between different methods highlights the challenge of accurately estimating the amount of extinction light suffers before being observed.
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All authors Jacco H. Terwel, Kate Maguire, Cillian O'Donnell, Miika Pursiainen, Alba Casasbuenas, Julie Thiim Gadeberg, Ben Godson, Luke Harvey, Benjamin Nobre Hauptmann, Niilo Koivisto, Chang Liu, Shravya Shenoy, Samuel Grund Sørensen, María Alejandra Díaz Teodori, Astrid Guldberg Theil, Mikael Turkki, Alaa Alburai, Joe Anderson, Thomas de Boer, Tomás Müller Bravo, Umut Burgaz, Kenneth C. Chambers, Ting-Wan Chen, João Duarte, Lluis Galbany, Mariusz Gromadzki, Cosimo Inserra, Joel Johansson, Young-Lo Kim, Thomas Lowe, Eugene Magnier, Rita P. Santos, Jesper Sollerman, Richard Wainscoat, David R. Young, Tracy X. Chen, Matthew J. Graham, Mansi M. Kasliwal, Frank J. Masci, Josiah N. Purdum, Ines Belkhodja
Astrophysics of Galaxies
Acenaphthene Derivatives as Signatures of C$_{11}$H$_9^+$ Reactivity with Methylated Naphthalenes
Ana I. Lozano, Anthony Bonnamy, Aude Simon et al. (+1 more)
C$_{11}$H$_9^+$ ion is the dominant fragment cation formed from methyl-naphthalene (MeNp) and dimethyl-naphthalene (diMeNp). Using the multiplex capabilities of PIRENEA, a setup dedicated to laboratory astrophysics, we studied the reactivity of the benzylium-like isomers of C$_{11}$H$_9^+$ with diMeNp under isolated conditions relevant to radiative association. Two reaction products are observed, C$_{12}$H$_{11}^+$ – also formed in the reaction with MeNp – and C$_{13}$H$_{13}^+$, with branching ratios that depend on the specific diMeNp isomer. The reaction products were subsequently exposed to UV-visible irradiation to gain insight into their structures. The acenaphthylene radical cation, C$_{12}$H$_{8}^{\bullet +}$, was identified as the most stable photofragment. We show that this experimental approach, supported by density functional theory calculations and molecular dynamics simulations, provides new constraints on the chemistry of benzylium-type species. We highlight the role that long-lived ion-molecule complexes can have in promoting C-C coupling and the formation of a pentagonal cycle. Moreover, the chemistry uncovered here highlights new pathways for the formation of pentagonal rings during PAH growth under low-pressure and cold conditions. In particular, it can lead to efficient formation of acenaphthylene-like species, recently detected in the TMC-1 cold cloud.
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All authors Ana I. Lozano, Anthony Bonnamy, Aude Simon, Christine Joblin
High Energy Astrophysical Phenomena
Taxonomy of High Mass X-ray binaries from a historical perspective
Pablo Reig
High-mass X-ray binaries serve as important laboratories for studying a broad range of fundamental astrophysical questions. These systems host two distinct types of astrophysical objects at different stages of
stellar evolution: a massive donor
star and a compact object. I will explore how our understanding of these systems has evolved over the past 50 years, from the dawn of the X-ray astronomy era to the present day. Along this historical journey, I will introduce the various classes and sub-classes of high-mass X-ray binaries and highlight their key observational characteristics.
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