Solar and Stellar Astrophysics
A mapping method of age estimation for binary stars: Application to the $\alpha$ Centauri system A and B
F. Thévenin, V.A.Baturin, A.V.Oreshina et al. (+4 more)
Given the wealth of data provided by
Gaia and the upcoming PLATO mission, it is essential to improve
stellar models to obtain accurate
stellar ages. Our objective is to apply a mapping technique to estimate the age of a system and the initial chemical composition. We also evaluate the influence of observational uncertainties in mass and heavy-element mixtures on results. We applied an inverse calibration method to the
evolution of a multiple
stellar system, assuming that the
stars share the same age and initial chemical composition. This approach determines age, the initial mass fractions of helium ($Y_{ini}$) and heavy elements ($Z_{ini}$), as well as the convective mixing-length parameters ($\alpha_A $ and $\alpha_B$). It uses the observed luminosities ($L_A$ and $L_B$), radii ($R_A$ and $R_B$), and surface chemical compositions ($Z/X_A$ and $Z/X_B$). We used the most recent observational data for $M$, $R$, $L$, and $[Fe/H]$ of $\alpha$ Centauri A and B as input data for our method. We compared two assumptions for the $Z/X$ ratio, following the results for the
solar composition. For an assumed high
solar $Z/X_\odot =0.0245$, we obtain an age of $7.8 \pm 0.6$ Ga, $Y_{ini} = 0.284 \pm 0.004$, and $Z_{ini} = 0.0335 \pm 0.0015$. For a low
solar $Z/X_\odot = 0.0181$, the derived age is $8.7 \pm 0.6$ Ga, $Y_{ini} = 0.267 \pm 0.008$, and $Z_{ini} = 0.025 \pm 0.002$. Observational errors in the
stellar masses of $\pm$0.002 lead to an age error of 0.6 Ga. Overshooting of $0.05-0.20H_p$ at the boundary of the convective core increases the age by $0.6-2.1$ Ga. Models with higher $Z/X$ and radiative cores, with ages of $7.2-7.8$ Ga, appear preferable and show better agreement with the observed asteroseismic frequencies.
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All authors F. Thévenin, V.A.Baturin, A.V.Oreshina, P.Morel, S.V.Ayukov, L.Bigot, A.B.Gorshkov
Astrophysics of Galaxies
The contribution of neutral gas to Faraday tomographic data at low frequencies. A first extensive comparison between real and synthetic data
Jack Berat, Marc-Antoine Miville-Deschênes, Andrea Bracco et al. (+2 more)
LOFAR observations of diffuse interstellar polarization at meter wavelengths reveal intricate polarized intensity structures with an unexpected correlation with neutral HI filaments that could not be reproduced in simulations with low cold neutral medium (CNM) abundance. We investigate whether MHD simulations of thermally bi-stable neutral interstellar medium, with a range of CNM fraction, can reproduce the properties of the 3C196 field, the high
Galactic latitude test field. Using 50 pc simulations with varying levels of
turbulence and compressibility, we generated synthetic 21 cm and synchrotron observations, including instrumental noise and beam effects, for different line-of-sight orientations relative to the
magnetic field. We developed MOOSE, a code to generate synthetic synchrotron polarization and Faraday
tomography. We also developed a metric based on the HOG
algorithm, to quantify the relative contribution of cold and warm neutral medium structures to the Faraday tomographic data. The synthetic observations show levels of polarization intensity and RM values comparable to the 3C196 field, indicating that thermal electrons associated with the neutral HI phase can account for a significant fraction of the synchrotron polarized emission at 100-200 MHz. The simulations consistently reveal a correlation between CNM and Faraday tomographic structures that depends on
turbulence level,
magnetic field orientation, and observational noise, but only weakly on CNM fraction. We found slightly weaker CNM-Synchrotron polarized emission correlation level than observed in the 3C196 field. These results suggest that low-frequency polarimetric observations provide a valuable probe of
magnetic-field morphology in the multi-phase
Solar-neighborhood ISM, while simultaneously underscoring the need for improved modeling of the turbulent, multi-phase, and partially ionized interstellar medium.
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All authors Jack Berat, Marc-Antoine Miville-Deschênes, Andrea Bracco, Patrick Hennebelle, Jeremy Scholtys
Astrophysics of Galaxies
CHIMPS2: The physical properties and star formation efficiency of molecular gas in the Central Molecular Zone
S. M. King, T. J. T. Moore, S. N. Longmore et al. (+4 more)
We present Local Thermodynamic
Equilibrium (LTE) estimates of the physical properties and
star formation efficiency (SFE) of molecular gas in the Central Molecular Zone (CMZ), using new $^{12}$CO $J=2\to1$ observations from the James Clerk Maxwell
Telescope. Combined with CHIMPS2 $^{12}$CO and $^{13}$CO $J=3\to2$, and SEDIGISM $^{13}$CO $J=2\to1$ data, we estimate a median excitation temperature of $T_{\rm ex} = 11$K for $^{13}$CO throughout the CMZ, with peaks exceeding $120$K in the Sgr B1/B2 complex. Cooler gas dominates around Sgr A and nearby clouds. We derive a median H$_{2}$ column-density of $N(\mathrm{H}2) = 2 \times 10^{22}$ cm$^{-2}$ and a total $^{13}$CO-traced gas mass of $M_{\rm gas} = 7 \times 10^6$ M$_\odot$, consistent with previous estimates when accounting for spatial coverage. The instantaneous SFE is assessed using Hi-GAL compact sources detected at 70-$\mu m$ and 160–500-$\mu m$. The 70-$\mu m$-bright SFE, tracing current
star formation, is modest overall but elevated in Sgr B1/B2, the Arches cluster, and Sgr C. In contrast, the 160–500-$\mu m$ SFE, tracing cold pre-
stellar gas, is more broadly enhanced, particularly in the
dust ridge clouds and towards negative longitudes surrounding Sgr C. The contrasting distributions suggest an evolutionary gradient in SFE, consistent with a transition from dense, cold gas to embedded protostars. Our results imply that the CMZ may be enter a more active phase of
star formation, with large reservoirs of gas primed for future activity.
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All authors S. M. King, T. J. T. Moore, S. N. Longmore, D. J. Eden, J. D. Henshaw, A. J. Rigby, R. Rani
Solar and Stellar Astrophysics
New Approach to Superflare Energy Determination
Petr Heinzel, Robert Falewicz, Kamil Bicz et al. (+1 more)
We present a new method for estimating the total energy radiated by
stellar flares in broad-band continua, which assumes a constant emitting area but incorporates a time-dependent temperature
evolution. This physically motivated approach offers an alternative to the commonly used method that assumes a fixed
flare temperature about of 10 000\,K and variable area. By allowing the temperature to vary over time while keeping the emitting area constant, our method captures more realistic
flare behaviour. This time-dependent treatment of the
flare temperature is supported by numerous
solar observations, numerical simulations, and multiwavelength studies of active
stars. We demonstrate that using peak
flare temperatures estimated from a semi-empirical model grid, rather than assuming an ad-hoc
flare temperature value, improves the accuracy of total energy estimates. Although the most precise results still require a multi-band photometry/spectroscopy or independently constrained
flare temperatures, our method offers a practical and scalable solution for single-band observations. It is particularly well suited for main-sequence
stars of spectral types K4 and later with known effective temperatures. Finally we discuss how the
flare continuum behaves under varying chromospheric conditions. Our method improves
flare energy estimates by incorporating a physically relevant time-dependent temperature
evolution and empirically derived peak temperatures, rather than assuming a constant 10 000\,K value. This modification reduces systematic errors that can reach factors up to ten as compared to previous estimates. We proved this on a sample of 50,320 TESS
flares.
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All authors Petr Heinzel, Robert Falewicz, Kamil Bicz, Paweł Preś
Solar and Stellar Astrophysics
Two-Dimensional Kelvin-Helmholtz Instability with Anisotropic Pressure
Shishir Biswas, Masaru Nakanotani, Dinshaw S. Balsara et al. (+2 more)
The Kelvin-Helmholtz (KH) instability occurs in multiple heliospheric (
solar-wind stream interfaces, planetary magnetospheres, cometary tails, heliopause flanks) and interstellar (protoplanetary disks, relativistic jets,
neutron star accretion disks) environments. While the KH instability has been well-studied in the magnetohydrodynamic (MHD) limit, only limited studies were performed in the collisionless regime, which is conducive to development of anisotropic pressures. Collisionless
plasmas are often described using the Chew Goldberger and Low (CGL) equations which feature an anisotropic pressure tensor. This paper presents a comprehensive analysis of the CGL version of the KH instability using linearised and numerical techniques. We find that the largest growth rates and the greatest incidence of
magnetic effects occur in the MHD limit. In the large relaxation time CGL limit, part of the energy goes into the formation of pressure anisotropies, resulting in smaller amounts of energy being available for bending the field lines. Consequently, when we cross-compare CGL and MHD simulations that are otherwise identical, the current densities are largest in the MHD limit, and the largest
magnetic islands also form in that limit. Early and late time formation of pressure anisotropies have also been studied. We also find that the strongest trend for forming intermittencies in the flow also occurs in the MHD limit. The paper also discusses possible consequences of our results for
turbulence and reconnection in the heliosheath (the layer between the
solar wind termination shock and the heliopause).
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All authors Shishir Biswas, Masaru Nakanotani, Dinshaw S. Balsara, Vladimir Florinski, Merav Opher
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Primordial features as probes of baryogenesis from supersymmetric flat directions
Yi-Peng Wu, Xingang Chen, Nino Ephremidze et al. (+1 more)
The Affleck-Dine mechanism is a leading baryogenesis scenario in which scalar condensates form coherently during inflation along supersymmetric flat directions that are lifted by supersymmetry-breaking effects. We update the viable parameter space for baryogenesis using recent
Cosmic Microwave Background constraints on
baryon-density isocurvature perturbations, taking the
quantum fluctuations of the scalar condensate generated during inflation as initial conditions. We then show that
primordial features arising from the inflaton sector can serve as a unique probe of baryogenesis models, whose mechanisms are otherwise difficult to access directly due to their high energy scales. These
primordial features leave correlated imprints, such as sharp feature signals and clock signals, on both the
curvature and
baryon-density isocurvature perturbations, providing direct evidence for the existence of both light and heavy modes involved in the Affleck-Dine mechanism.
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All authors Yi-Peng Wu, Xingang Chen, Nino Ephremidze, Lingfeng Li
Solar and Stellar Astrophysics
A single frequency approach to nonequilibrium modeling of the chromosphere
W. Ruan, D. Przybylski, R. Cameron et al. (+1 more)
The
solar chromosphere is a region where radiation plays a critical role in energy transfer and interacts strongly with the
plasma. In this layer, strong spectral lines, such as the Lyman lines, contribute significantly to radiative energy exchange. Due to the long ionization/relaxation timescale, departures from LTE become significant in the chromosphere. Accurately modeling this layer therefore requires one to solve the non-LTE radiative transfer for the Lyman transitions. We present an updated version of the MURaM code to enable more accurate simulations of chromospheric hydrogen level populations and temperature
evolution. In the previous extension, a non-LTE equation of state, collisional transitions of hydrogen, and radiative transitions of non-Lyman lines were already implemented in the code. Building on this, we have now incorporated radiative transfer for the Lyman lines to compute radiative rate coefficients and the associated radiative losses. These were used to solve the population and temperature
evolution equations, rendering the system self-consistent. To reduce computational cost, a single-frequency approximation was applied to each line in the numerical solution of the radiative transfer problem. The extended model shows good agreement with reference solutions from the Lightweaver framework, accurately capturing the radiative processes associated with Lyman lines in the chromosphere. The extension brings the simulated hydrogen level populations in the deep chromosphere closer to detailed radiative balance, while those in the upper chromosphere remain significantly out of balance, consistent with the expected conditions in the real
solar atmosphere. The extension enables the MURaM code to accurately capture chromospheric dynamics.
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All authors W. Ruan, D. Przybylski, R. Cameron, S. K. Solanki
Astrophysics of Galaxies
An unusual pair of interstellar HI features and a related white dwarf star inside the HI cavity surrounding the Upper Sco-Cen OB2 Association
Gerrit L. Verschuur
Two mysterious unresolved HI structures at velocities of +12 and -6 km/s were discovered in high resolution 21-cm survey data in the direction of a faint white
dwarf star. Examination of the HI morphology in this area of sky shows that the
star and HI features exists in a large cavity in interstellar HI surrounding the Upper Sco-Cen OB2 Association. The cavity may have been created by an ancient
supernova. It is hypothesized that the pair of HI features and filamentary HI structure found in its immediate vicinity may be the remnants of a planetary nebula some 3 x 10^5 years old that have cooled to the point that the gas is neutral and emitting the 21-cm spectral line. This remnant has maintained the morphological characteristics of the original planetary nebula because it expanded into a volume of space relatively devoid of interstellar gas that would otherwise have absorbed any traces of the original nebula.
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Earth and Planetary Astrophysics
The Nysa family as the main source of unequilibrated LL ordinary chondrites
M. Marsset, P. Vernazza, M. Brož et al. (+16 more)
Context. The origin of the petrologic diversity observed in ordinary chondrites (OCs), the most common meteorites on Earth, remains debated. Competing models invoke either depth-dependent sampling of a single thermally stratified ("onion-shell") parent body or contributions from multiple distinct parent bodies. Aims. We aim to determine which of the two models is preferred for LL chondrites. These are unique among OCs in exhibiting a bimodal petrologic distribution, with most meteorites being LL3 or LL6. Methods. We compare the spectral and mineralogical properties of LL chondrites and corresponding LL-chondrite-like near-Earth objects (NEOs) with their possible sources in the main asteroid belt. We also model the thermal histories of the proposed parent bodies, based on revised estimates of parent-body sizes. Results. The spectral and mineralogical diversity of LL chondrites is consistent with contributions from the bright, S-type component of the Nysa family (NysaS) and the Flora family, with NysaS supplying mainly low-petrologic-type material and Flora higher-grade material. Unequilibrated, LL3 chondrites appear to originate exclusively from NysaS. Similarly, LL-chondrite-like NEOs form two distinct subpopulations consistent with origins in these same families. Conclusions. Our results favour multiple parent bodies for LL chondrites. The petrologic differences between the NysaS and Flora parent bodies can be explained by differences in their sizes, without requiring different formation times.
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All authors M. Marsset, P. Vernazza, M. Brož, C. Avdellidou, C. A. Thomas, L. McGraw, A. Madden-Watson, K. Minker, M. Monnereau, F. E. DeMeo, R. P. Binzel, M. Mahlke, B. Carry, J. Hanuš, P. N. Simon, B. Yang, P. Beck, M. Birlan, E. Jehin
Cosmology and Nongalactic Astrophysics
Synchrotron self-Compton process for constraining sub-GeV dark matter in Omega Centauri via SKA
Guan-Sen Wang, Bing-Yu Su, Yang Yu et al. (+2 more)
The search for the particle identity of dark matter (DM) continues to be a primary objective in modern physics. In this field, the sub-GeV mass range of DM detection remains a crucial yet challenging window. We investigate synchrotron self-Compton (SSC) emission from electrons and positrons produced by MeV-scale DM annihilation as a novel indirect detection channel. Focusing on the globular cluster Omega Centauri and the sensitivity of the Square Kilometre Array, we derive constraints on the annihilation cross section reaching $\langle\sigma v\rangle \sim 10^{-29}\,\rm{cm}^{3}\,\rm{s}^{-1}$ in the tens-of-MeV range. Furthermore, constraints can reach below $\langle\sigma v\rangle \sim 10^{-30}\,\rm{cm}^{3}\,\rm{s}^{-1}$ under favorable parameter choices. Although the derived limits depend on the uncertain propagation parameters, the SSC channel remains competitive with existing indirect constraints over a representative range of astrophysical assumptions, establishing SSC emission as a promising probe of sub-GeV DM.
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All authors Guan-Sen Wang, Bing-Yu Su, Yang Yu, Bo Zhang, Lei Feng
Earth and Planetary Astrophysics · Cross-listed from gr-qc
Post-Newtonian accelerations of a Mercury orbiter
Miriam Falletta, Gabriel Rodríguez-Moris and Sergei A. Klioner
We investigate the relativistic modeling of spacecraft motion in Mercury's post-Newtonian local coordinates. This investigation is motivated by the fact that Mercury's post-Newtonian gravitational field (as well as that of any other
planet) admits an expansion in terms of multipole moments, which are most appropriately defined in the local reference system. The equations of motion in the Mercury-centric local frame include relativistic local perturbations, given by the Schwarzschild term, Lense-Thirring precession, and the acceleration due to the quadrupole moment, and relativistic third-body perturbations, which are the gravito-electric and gravito-
magnetic accelerations, along with a coupling term between Mercury and other
solar system bodies. The relativistic third-body perturbations are usually neglected in all practical applications. In this study, we analyze the magnitude of the post-Newtonian terms of the equations of motion formulated in the Mercury-centric frame, evaluating them along the trajectories of the two BepiColombo spacecrafts. Based on this analysis, we provide a practical approach for constructing a high-accuracy relativistic orbital model suitable for a Mercury orbiter.
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High Energy Astrophysical Phenomena
Is plasmoid-mediated reconnection really important in accretion flows to drive flares in AGNs?
Giovani H. Vicentin, Elisabete M. de Gouveia Dal Pino, George N. Wong et al. (+4 more)
Based on very high-resolution resistive 2D and 3D magnetohydrodynamical (MHD) simulations of current sheets, our findings suggest that the answer to this question is likely no. In contrast,
turbulence-mediated reconnection yields significantly faster reconnection rates - about an order of magnitude higher than the so-called universal rate for plasmoid-mediated reconnection in MHD flows ($V_\text{rec}/V_A \sim 0.01$). We conclude that
turbulence-driven reconnection is the dominant mechanism responsible for fast reconnection and
flares in systems such as
accretion flows and relativistic jets in Active
Galactic Nuclei (AGNs). In these environments,
turbulence is driven by instabilities such as the magneto-rotational instability (MRI), Parker-Rayleigh-Taylor instability (PRTI), and current-driven kink instability (CDKI). Finally, we present 3D General Relativistic MHD simulations of
accretion flows that confirm the crucial role of
turbulence-mediated reconnection in AGN systems. These findings have important implications for understanding the origin of
flares, particle acceleration, and the production of polarized radiation in these extreme environments.
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All authors Giovani H. Vicentin, Elisabete M. de Gouveia Dal Pino, George N. Wong, Lia Medeiros, Grzegorz Kowal, James M. Stone, Alex Lazarian
High Energy Astrophysical Phenomena
IceCube's Sensitivity Prospects to MeV-Scale Axion-Like Particles from Core-Collapse Supernovae
Nora Valtonen-Mattila, Shlok Shah and Segev BenZvi
We present a novel framework to estimate the sensitivity and discovery potential of IceCube to
axion-like particles (ALPs) produced in core-collapse
supernovae (CCSNe), covering ALP masses from 1 MeV to several hundred MeV. A key feature of this work is the explicit handling of the final-state
leptons produced in ALP interactions with $^{16}$O
nuclei and
protons, which can generate Cherenkov light detectable in IceCube. These processes are being fully integrated into a detector-level simulation chain, enabling realistic detector signal modeling beyond existing estimates. The framework enables sensitivity forecasts for both direct detection and constraints based on time delays relative to the
neutrino burst, across a range of ALP emission models. This approach may also extend to other MeV-scale dark sector particles. Preliminary sensitivity estimates are in progress and will be presented.
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Astrophysics of Galaxies
Modeling Tidal Disruption Events and Compact Object Plunges in Nuclear Star Clusters
Philip Cho, Kai Wu, Francesco Flammini Dotti et al. (+2 more)
We study
tidal disruption events (TDEs) and compact object inspirals in
nuclear star clusters (NSCs) hosting a central supermassive black hole (SMBH), focusing on their role in SMBH growth. Using the STARDISK version of the direct N-body code NBODY6++GPU, we perform pilot simulations with two improved models: one for mass fallback from TDEs and another for compact object plunges based on orbital decay timescales. Our results show that mass
accretion via TDEs peaks within the first 2 Myr and decreases more rapidly for higher initial SMBH masses, with roughly half the disrupted
stellar debris being accreted. Compact object
accretion is confined mostly to orbits with pericenters between 4 and 27 Schwarzschild radii and is suppressed by an order of magnitude when inspiral criteria are applied.
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All authors Philip Cho, Kai Wu, Francesco Flammini Dotti, Taras Panamarev, Rainer Spurzem
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Thermal Vacuum Cosmology Explains Hubble Tension
Robert Alicki
It is argued that the previously proposed modification of the standard (flat) inflationary $\Lambda CDM$ model in which cosmological constant is replaced by thermal energy of expanding vacum, characterized by the Gibbons-Hawking temperature, explains the origin of notorious “Hubble tension”.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Can UV meet IR in the Swiss cheese?
Madina Abilmazhinova, Diana Kulubayeva, Hrishikesh Chakrabarty et al. (+1 more)
We consider the
embedding of regular black holes in an expanding universe and study how the ultraviolet modifications to the Schwarzschild geometry that regularize the black hole singularity affect the exterior universe's expansion rate. We consider several proposals for the regular black hole geometry and obtain the corresponding Friedmann equations for a universe filled only with
dust and black holes. We show that different proposals have different implications which may be distinguished. We then test the hypothesis that the UV corrections to the black hole geometry may be responsible for the current phase of accelerated expansion. To this aim we constrain the value of the regular black hole UV cutoff parameter from observations. Interestingly we find that the best fit is obtained by values of the parameter corresponding to regular horizonless compact objects.
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All authors Madina Abilmazhinova, Diana Kulubayeva, Hrishikesh Chakrabarty, Daniele Malafarina
Astrophysics of Galaxies
GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended (GLEAM-X) III: Galactic Plane
S. Mantovanini, N. Hurley-Walker, K. Ross et al. (+3 more)
We present the third data release for the
Galactic and Extragalactic All-Sky Murchison Widefield Array eXtended (GLEAM-X) survey, covering = 3800 deg2 of the southern
Galactic Plane (GP) with \ang{233} < l < \ang{44} and |b| < \ang{11} across a frequency range of 72 - 231 MHz divided into 20 sub-bands. GLEAM-X observations were taken using the "extended" Phase-II configuration of the Murchison Widefield Array (MWA), which features baselines ranging from approximately 12 m to 5 km. This configuration limits sensitivity to the diffuse structure of the GP, with an angular resolution range of about 45” to 2'. To achieve lower noise levels while being sensitive to a wide range of spatial scales (45”- \ang{15}), we combined these observations with the previous
Galactic and Extragalactic All-Sky Murchison Widefield Array (GLEAM) survey. For the area covered, we provide images spanning the whole frequency range. A wide-band image over 170 - 231 MHz, with RMS noise of = 3 - 6 mJy/beam and source position accuracy within 1 arcseconds, is then used to perform source-finding, which yields 98,207 elements measured across 20 x 7.68 MHz frequency bands. The catalogue is 90% complete at 50 mJy within \ang{233} < l < \ang{324} and at 125 mJy in \ang{290} < l < \ang{44}, while it is 99.3% reliable overall. All the images and the catalogue are available online for download.
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All authors S. Mantovanini, N. Hurley-Walker, K. Ross, S. W. Duchesne, G. Anderson, T. J. Galvin
High Energy Astrophysical Phenomena
Identifying Host Galaxies of Binary Black Hole Mergers with Next-Generation Gravitational Wave Detector Networks
Sumedha Biswas, Andrew Levan, Peter G. Jonker et al. (+3 more)
Identifying the host
galaxy of a binary black hole (BBH) merger detected via gravitational waves (GWs) remains a challenge due to the absence of electromagnetic counterparts and the large localization volumes produced by current-generation detectors. A confident host association would provide
stellar population properties to constrain BBH formation channels and enable measurements of cosmological parameters such as the Hubble constant, H0. We simulate BBH mergers in nearby (z<0.25) host
galaxies to evaluate the feasibility of host identification with future GW detector networks, including configurations with the planned LIGO-India detector and third-generation detectors such as the Einstein
Telescope (ET) and
Cosmic Explorer (CE). We construct two injection grids to explore variations in BBH mass, distance, and directional sensitivity, and infer localization volumes using the Fisher Information
Matrix (FIM)-based parameter estimation implemented through BILBY. To assess the prospects for unique host identification, we introduce a set of diagnostics: theoretical comoving volume thresholds for
galaxies of a given
stellar mass, derived from
galaxy stellar mass functions, a
metallicity-based volume threshold motivated by progenitor environment models,
stellar mass fractions to quantify candidate host prominence, and the probability of chance
alignment (p_c). These metrics provide ways to evaluate host associations and constrain BBH formation channels. We find that future networks that include ET and CE localize BBH mergers to volumes smaller than those theoretical thresholds, implying potentially unique host identification, out to ~1000 Mpc at a rate of ~100 yr^{-1}. While associations for individual events may remain uncertain, our framework is well-suited to population-level analyses, enabling constraints on BBH formation scenarios in the era of next-generation GW detector networks.
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All authors Sumedha Biswas, Andrew Levan, Peter G. Jonker, Kendall Ackley, Gregory Ashton, Nikhil Sarin
Astrophysics of Galaxies
Stratification of the AGN-Driven multi-phase outflows in the dwarf Seyfert galaxy NGC 4395
Payel Nandi, Luis Colina, Rogemar A. Riffel et al. (+5 more)
We present a multi-wavelength study of
nuclear outflows in the nearby
dwarf Seyfert
galaxy NGC~4395, which hosts an intermediate-mass black hole. Using JWST/NIRSpec and MIRI IFU spectroscopy (1.66–28.6~$\mu$m), together with ALMA and Gemini/GMOS data, we probe the ionised and molecular gas on parsec scales. The JWST
nuclear spectra reveal 134 emission lines, including H\,i, He, numerous fine-structure lines, H$_2$ rotational/ro-vibrational transitions, and several PAH bands. Modelling of the H$_2$ rotational lines reveals three warm/hot molecular components ($T\!\approx\!580$, 1480, and 2900~K), along with a cold ($<50$~K) phase traced by ALMA CO(2–1).
Outflow signatures are detected in cold and warm/hot molecular gas, in H\,i, and in 36 fine-structure lines spanning ionisation potentials of 7.6–300~eV. Ionised
outflow velocities range from 127 to 716~km\,s$^{-1}$, with blueshifted and redshifted components consistent with a stratified biconical geometry. The cold molecular gas shows a mass
outflow rate nearly 1–2 orders of magnitude larger than that of the warm/hot molecular and ionised phases. The kinetic coupling efficiency is 0.003–0.12% for the coronal-line gas and 0.4–1.4% for the H\,i
outflow, indicating that only the low-ionisation gas significantly impacts the surrounding ISM.
Outflow velocity and the fraction of flux in the outflowing component increase with ionisation potential, implying that the most highly ionised gas originates closest to the AGN and is most efficiently accelerated.
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All authors Payel Nandi, Luis Colina, Rogemar A. Riffel, Miguel Pereira Santaella, C. S. Stalin, D. J. Saikia, Javier Alvarez-Marquez, Markus Kissler-Patig
Solar and Stellar Astrophysics
Dynamics of Y Dwarf Atmospheres
C. Ak{\i}n, E. K. H. Lee, L. Gkouvelis et al. (+1 more)
The global circulation regime of the coolest brown
dwarfs, the Y
dwarfs, remains largely unexplored. We investigate the interplay between convection, rotation, and cloud thermal feedback using a selected sample of Y
dwarf atmospheric models. We explore effective temperatures $400~\mathrm{K} \leq T_{\mathrm{eff}} \leq 600~\mathrm{K}$ and rotation periods $P_{\mathrm{rot}} = 2.5 \text{--} 20\ \mathrm{h}$, where salt and sulfide condensates are expected. We include $\mathrm{KCl,~Na_{2}S}$, and $\mathrm{MnS}$ clouds to assess their atmospheric impact and identify circulation regimes across parameter space. We run twelve general circulation models (GCMs) spanning this grid and develop additional physics modules for the THOR GCM to model brown
dwarf atmospheres. The dynamical core is coupled to interior thermal perturbations near the radiative-convective boundary, a mixing-length convection scheme, gray two-stream radiative transfer with Rosseland-mean opacities, and simple cloud tracers including thermal feedback and scattering. All simulations exhibit a radiative-forcing-dominated regime with weak winds, minimal horizontal temperature contrasts, and no persistent jets. Convection controls vertical mixing and sets the extent of salt and sulfide cloud layers below the photosphere. Thermal structures equilibrate quickly and cloud radiative feedback remains insignificant, with limited variability. Within the gray radiative transfer framework adopted here, Y
dwarf atmospheres in this parameter space are controlled by interior thermal radiation. Rotation sets modest variability, while clouds play a secondary role. Because our single-band approach does not capture spectral windows that could probe deeper cloud layers, our constraints on cloud radiative feedback are likely conservative, and we outline pathways toward more active regimes.
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All authors C. Ak{\i}n, E. K. H. Lee, L. Gkouvelis, K. Heng
Earth and Planetary Astrophysics
NovaMoon: A Strategic Lunar Reference Station for Positioning, Timing, and Largely Enhanced Science in the Earth-Moon System
Serena Molli, Agnès Fienga, Pascale Defraigne et al. (+82 more)
The renewed interest in lunar exploration and the development of future lunar communication and
navigation services highlight the need for a precise, stable, and interoperable geodetic and timing infrastructure on the Moon. NovaMoon, proposed as a scientific and
navigation payload for ESA's Argonaut lander, is designed as a lunar-based local differential, geodetic, and timing station supporting both operational needs in the Moon's south polar region and a broad range of scientific investigations. The payload integrates a lunar
laser retroreflector, a Very Long Baseline Interferometry transmitter, a receiver for
navigation signals compatible with LunaNet standards, high-stability atomic clocks, and direct-to-Earth
radio links – making it the first lunar station to co-locate multiple ranging, tracking, and timing techniques. NovaMoon will enable sub-metre to decimetre positioning, provide local differential corrections for lunar users, and ensure an accurate and stable realisation of position and time. Preliminary simulation studies show that this multi-technique
dataset improves the lunar reference frame, orientation and ephemerides, and estimates of interior parameters like
tidal response and core properties. NovaMoon will also provide the first long-duration physical realisation of a lunar time reference. Beyond its primary goals, it supports improved cartography, precise surface geolocation, and higher-resolution topography, contributing to safer landings and operations. It also enables new tests of fundamental physics, including constraints on relativity and possible deviations from classical
gravity.
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All authors Serena Molli, Agnès Fienga, Pascale Defraigne, Krzysztof Sośnica, Luigi Cacciapuoti, Luca Porcelli, Lotfi Massarweh, Sara Bruni, Riccardo Pozzobon, Albert Roura, Francesco Vespe, Diego Blas, Ozgur Karatekin, Yoann Audet, Floor Melman, Richard Swinden, Javier Ventura-Traveset, Olivier Alibart, Marie-Christine Angonin, Daniel Arnold, Ruth Bamford, Emmanuele Battista, Marco Belloni, J.C. Berton, Orfeu Bertolami, Mathis Bloßfeld, Adrien Bourgoin, Giada Bargiacchi, Salvatore Buoninfante, Nicolò Burzillà, Roberto Campagnola, Paolo Cappuccio, Salvatore Capozziello, Giuseppe Cimò, Clément Courde, Rolf Dach, Mario Siciliani de Cumis, Simone Dell'Agnello, Fabrizio De Marchi, Valentina Galluzzi, Francesco Gini, Philipp Glaeser, Klaus Gwinner, Alex Guinard, Rüdiger Haas, Aurélien Hees, Hauke Hussmann, Luciano Iess, Alexander C. Jenkins, Siddarth K. Joshi, Maria Karbon, Sergei Klioner, Kaisa Laiho, Christophe Le Poncin-Lafitte, Marco Lucente, David Lucchesi, Riccardo March, Lucia McCallum, Jürgen Müller, Weijie Nie, Jillian Oduber, Roberto Peron, Francesco Picciariello, Théo Pichavant, Michael Plumaris, Eleonora Polini, Ana-Catalina Plesa, Dimitrios Psychas, Bernardino Quaranta, Nicolas Rambaux, Marc Rovira-Navarro, Francesco Santoli, Matthias Schartner, Florian Seitz, Ilaria Sesia, Yan Seyffert, Stefano Speretta, Tim Springer, Giuseppe Vallone, Paolo Villoresi, Sebastien Vincent-Bonnieu, Ben Wadsworth, Pierre Waller, Radosław Zajdel, Erik Schoenemann
Cosmology and Nongalactic Astrophysics
Kosmulator: A Python framework for cosmological inference with MCMC
Renier T. Hough, Robert Rugg, Shambel Sahlu et al. (+1 more)
We present Kosmulator, a modular and vectorised Python framework designed to accelerate the statistical testing of cosmological models. As the theoretical landscape expands beyond standard $\Lambda$CDM, implementing new expansion histories into traditional Einstein–Boltzmann solvers becomes a significant computational bottleneck. Kosmulator addresses this by leveraging array-native execution and efficient ensemble slice sampling (via Zeus) to perform rapid
Bayesian inference. We validate the framework against the industry-standard Cobaya code using a combination of Type Ia
Supernovae,
Cosmic Chronometers, and
Baryon Acoustic Oscillation (BAO) data. Our results demonstrate that Kosmulator reproduces Cobaya's posterior constraints to within $\leq0.3\sigma$ statistical agreement on $H_{0}$ and $\Omega_{m}$ and $<0.6\%$ precision on $\chi^{2}$, while achieving a $\sim 4.5\times$ reduction in wall-clock time on a single CPU core compared to a standard MPI-parallelised baseline. Furthermore, we showcase the framework's utility by constraining the implicit power-law $f(Q)$ "$f_1$CDM" model and demonstrating its automated model selection capabilities (AIC/BIC). Kosmulator is introduced as a "scientific sieve" for rapid hypothesis testing, allowing researchers to efficiently filter theoretical candidates before deploying high-precision resources.
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All authors Renier T. Hough, Robert Rugg, Shambel Sahlu, Amare Abebe
Instrumentation and Methods for Astrophysics
Towards FAIR Astrophysical Simulations
Susanne Pfalzner, Stephan Hachinger, Jolanta Zjupa et al. (+4 more)
Reproducibility is a cornerstone of science. FAIR (findable, accessible, interoperable, and reusable) data is often a vital step towards testing the reproducibility of results. The implementation of FAIR principles in the astrophysical simulation community is still varied. We approach the discussion of this topic mainly from a high-performance computing (HPC) point of view. We identify the main obstacles to FAIR astrophysics simulations: First, the vast
datasets created in simulations on HPC facilities complicate FAIR data management. Second, missing incentives to fully share codes, results, and diagnostic data. Third, a lack of workflows that include data publication and technical support. Therefore, particularly smaller research groups struggle due to the unavailability of dedicated personnel and time in their efforts towards FAIR and open simulations. We propose actionable steps towards achieving “FAIRer” data and open source publication standards in numerical astrophysics. Our suggestions include low-threshold methods to fulfil the basic FAIR requirements as well as basic tools for FAIR (meta-)data generation and data/code publication. This work is a high-level overview intended to initiate discussions within the community, offering initial solutions to these challenges.
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All authors Susanne Pfalzner, Stephan Hachinger, Jolanta Zjupa, Salvatore Cielo, Frank W. Wagner, Marcus Brüggen, Annika Hagemeier
High Energy Astrophysical Phenomena
High-resolution X-ray spectroscopy of Cen X-3 with XMM-Newton
J. J. Rodes-Roca, J. M. Torrejón, G. Sanjurjo-Ferrín et al. (+1 more)
The spectral analysis of two XMM-Newton observations of the high-mass X-ray binary system Cen X-3 is presented. In particular, it is focused on the eclipse and out-of-eclipse spectra in order to compare the properties of the environment around the compact object. The high-resolution spectra obtained from the reflection grating spectrometer on board XMM-Newton was analysed focusing on studying eclipse and out-of-eclipse spectra separately. Several continuum models were explored in SPEX for which we studied the properties of emitting and absorbing matter depending on the emission and absorption lines identified in the spectra. It was found that the X-ray continuum is heavily absorbed by a neutral gas and photoionised matter. Emission lines from Si v, Mg xii, Mg xi, and Ne x were detected in the eclipse spectrum. In particular, H-like lines of Mg and Ne with a significance greater than 5 sigma in the eclipse spectrum and 3 sigma in the out-of-eclipse spectrum. But in the out-of-eclipse spectrum any absorption lines, if any, were detected with a significance less than 2 sigma. RGS light curve showed dips in the out-of-eclipse spectrum which are not due to an increase in the column absorption but may be produced by instabilities in the
accretion stream. On the other hand, the level of counts above 20 was compatible with the X-ray background. A simple local continuum model was used to describe the He-like triplet of Ne and the derived values of R and G ratio parameters pointed out that the UV photospheric field should be important at the line production site and an electron density greater than 10(12) cm-3. As a consequence, a hybrid
plasma may be present in the binary system.
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All authors J. J. Rodes-Roca, J. M. Torrejón, G. Sanjurjo-Ferrín, J. Planelles Villalva
Astrophysics of Galaxies
CFHT MegaCam Two Deep Fields Imaging Survey (2DFIS) II: Decoding the Lensing Profile of a "Rotating" Cluster with Deep CFHT Imaging
Yicheng Li, Liping Fu, Wentao Luo et al. (+15 more)
We present a multi-wavelength analysis of the
galaxy cluster RXCJ0110.0+1358 ($z=0.058$), a rotating cluster candidate, combining deep CFHT imaging, SDSS photometry, spectroscopic
redshifts, and XMM-Newton X-ray observations. We find a notable discrepancy between the optical and X-ray views: while optical data reveal a pronounced bimodal
galaxy distribution with significant kinematic substructure signatures, the X-ray emission exhibits a single, smoothly extended component centered on the BCG. Our weak
lensing analysis resolves this discrepancy by revealing that the mass is predominantly concentrated in the southeast ($\log M_{200}/M_\odot = 14.04_{-0.40}^{+0.24}$), while the northwestern substructure has a negligible mass ($\sim 10^{13} M_\odot$). This immense mass disparity rules out the dynamical possibility of a rotating system. We demonstrate that the apparent optical bimodality arises from the projection of a filament, which led optical group-finding
algorithms to misclassify these
galaxies as cluster members. This contamination creates a spurious substructure that mimics a rotation signal and leads to an overestimation of the luminosity-based
halo mass, resolving the observed inconsistencies.
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All authors Yicheng Li, Liping Fu, Wentao Luo, Binyang Liu, Wei Du, Martin Kilbinger, Calum Murray, Christopher J. Miller, Ray Wang, David Turner, Lance Miller, Dezi Liu, Mario Radovich, Jean-Paul Kneib, Huanyuan Shan, Kaiwen Mai, Zicheng Wang, Haoran Zhao
Cosmology and Nongalactic Astrophysics
Dark Matter from Eternity
G. Franciolini, M. Peloso and A. Riotto
We propose that the totality of dark matter in the universe might ascribe its origin to one of the key properties of cosmological inflation, that it may be eternal: regions that at the end of the
primordial accelerated expansion of the universe never reheated, but keep eternally inflating, manifest themselves as
primordial black holes in our observable universe. This mechanism can provide a
primordial black hole abundance which is larger than the standard one due to the gravitational collapse of sizeable overdensities in the radiation phase. It also predicts a broad spectrum for the
curvature perturbation and a flat
stochastic gravitational wave background at a level of $\Omega_\text{GW} h^2 \simeq 10^{-10}$ up to the mHz.
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High Energy Astrophysical Phenomena
Neutrino Emission from Gamma-ray Burst Jet inside the Cavity within Active Galactic Nucleus Accretion Disks
Hao-Yu Yuan, Wen-Long Xu, Kai Wang et al. (+1 more)
Active
galactic nucleus (AGN)
accretion disks are promising sites for compact binary mergers. Short gamma-ray burst (SGRB) jets from binary
neutron star coalescence can propagate within low-density cavities carved by circumbinary
outflows. We investigate the high-energy
neutrino emission and detectability of such SGRB jets, adopting three seed
photon components:
prompt GRB emission, AGN disk thermal radiation, and external inverse Compton (EIC) scattered
photons. Our results show that
neutrino emission is dominated by
proton-
photon ($p\gamma$) interactions, with
prompt GRB
photons and AGN disk
photons serving as the dominant target components. The inclusion of AGN disk
photons significantly reshapes the
neutrino spectrum, shifting the emission peak to lower energies. This effect becomes more pronounced as the mass of the central supermassive black hole decreases and the burst location approaches the black hole. For a fiducial model with a $10^6~ M_\odot$ central black hole and the burst at 10 Schwarzschild radii, IceCube and IceCube-Gen2 achieve maximum luminosity distances of $\sim$180 Mpc and $\sim$400 Mpc, respectively. Next-generation high-sensitivity
neutrino observatories, combined with multi-messenger observations, hold promise for identifying such GRBs in AGN environments.
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All authors Hao-Yu Yuan, Wen-Long Xu, Kai Wang, Wei-Hua Lei
Astrophysics of Galaxies
CFHT MegaCam Two Deep Fields Imaging Survey (2DFIS) I: Overview
Binyang Liu, Wentao Luo, Martin Kilbinger et al. (+14 more)
We present the Two Deep Fields Imaging Survey (2DFIS), a wide-field imaging program conducted with the Canada-France-Hawaii
Telescope (CFHT) targeting two astrophysically distinct regions: one containing a repeating fast
radio burst (FRB) source and another hosting a candidate of a rotating
galaxy cluster. Achieving a depth of r~26mag, the survey enables a search for faint optical counterparts and environmental signatures associated with the FRB, while high-quality photometric and
galaxy shape measurements in the cluster field support a weak-
lensing analysis of its mass distribution. This paper describes the observing strategy and data processing methodology adopted for 2DFIS, including the use of the LSST Science Pipelines with survey-specific adaptations for CFHT/MegaCam data. We outline a complete workflow for transforming raw CFHT exposures into science-ready data products, including calibrated single-epoch images, multi-band coadded mosaics, and extensive source catalogs. These data products provide the foundation for ongoing and future studies of FRB host environments, cluster mass reconstruction, and related cosmological applications.
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All authors Binyang Liu, Wentao Luo, Martin Kilbinger, Shenming Fu, Ian Dell'Antonio, Liping Fu, Xian Zhong Zheng, Yi-fu Cai, Cheng Jia, Ning Jiang, Qinxun Li, Yicheng Li, Shurui Lin, Christopher J. Miller, Surhud S. More, Huiyuan Wang, Yibo Wang
Astrophysics of Galaxies
K-DRIFT Science Theme: Galaxies in the Faint Universe
Woowon Byun, Yongmin Yoon, Jongwan Ko et al. (+17 more)
Low-surface-brightness (LSB) structures serve as evidence of the intricate mass assembly of
galaxies, and dedicatedly studying them promises to give us profound insights into the evolutionary history of
galaxies. Furthermore, delving into the properties of
star formation (SF) in the LSB regime can broaden our understanding of SF activity in regions characterized by low surface gas density, thereby shedding light on fundamental
cosmic processes. However, systematic uncertainties may hamper the exploration of the LSB universe by limiting detectable SB levels. Indeed, despite dedicated advancements in
telescope and observing techniques over decades, achieving ultra-deep photometric depths in optical wavelengths remains a formidable challenge. To overcome this challenge and explore the LSB universe that we have yet to see, we have been developing a novel
telescope called K-DRIFT. This paper outlines the
telescope's specification and describes various LSB features we aim for, explicitly focusing on nearby individual
galaxies. To further advance the capabilities of the K-DRIFT survey, focused on LSB detection, we present several feasible research topics that utilize other survey data together and discuss the role of LSB observation in understanding the
evolution of
galaxies.
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All authors Woowon Byun, Yongmin Yoon, Jongwan Ko, Yun Hee Lee, Gain Lee, Ho Seong Hwang, Cristiano G. Sabiu, Kwang-il Seon, Kyungwon Chun, Jihye Shin, Jinsu Rhee, Jae-Woo Kim, Jaewon Yoo, Jaehyun Lee, Sang-Hyun Chun, Hong Soo Park, Soung-Chul Yang, Sungryong Hong, Jeehye Shin, Hyowon Kim
High Energy Astrophysical Phenomena
A Minimal Interpretation of the Galactic Cosmic-Ray Proton and Helium Spectra from GeV to PeV Energies
Felix Aharonian and Bing Theodore Zhang
High-precision measurements of the
cosmic-ray (CR)
proton and helium spectra have revealed significant deviations from a simple power law, characterized by multiple spectral features, including a hardening above $\sim$100~GeV, a broad excess in the multi-TeV range, and a pronounced structure at PeV energies. We propose a minimal phenomenological two-
cosmic-ray-population framework that consistently accounts for the observed spectra of
protons and helium across six decades in energy, with agreement at the level of $\sim 10 \%$ or better over most of the explored energy range. In this scenario, the spectral complexity arises from a transition between two
Galactic CR populations in the 10~TeV-1~PeV energy range. The low-energy
proton population exhibits a sharp cutoff at tens of TeV, while a second, higher-energy population emerges and dominates above 100~TeV, terminating with a smooth exponential cutoff at $\sim$6.5~PeV. The same two-component model applied to CR helium, with a slightly harder first component extending effectively to several hundred TeV and a second component that scales with the
proton spectrum in
magnetic rigidity, provides a consistent description of both the helium spectrum and the p/He ratio. This framework reproduces the main observed spectral features of CR
protons and helium without invoking contributions from nearby sources or non-standard assumptions about CR acceleration or propagation. Recent gamma-ray observations of
supernova remnants,
star-forming regions, and microquasars offer plausible astrophysical sites for these two CR components.
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