High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Neutrino mass ordering from the next Galactic supernova at DUNE, HK, and JUNO
Prantik Sarmah, Sovan Chakraborty, Abinash Medhi et al. (+2 more)
The next
Galactic core-collapse
supernova (CCSN) will offer a unique opportunity to determine the
neutrino mass ordering. We focus on two observables: the electron
neutrino ($\nu_e$) neutronization burst and the rise-time of the electron antineutrino ($\bar{\nu}_e$) flux during the
accretion phase. The neutronization burst, a sharp $\nu_e$ peak within $\sim 20$-$30$ ms, provides a clean and robust signature of mass ordering through its appearance or disappearance. During the
accretion phase, the faster rise of heavy
lepton flavor neutrinos ($\nu_x$) leads to a distinct faster rise-time behavior of the oscillated $\bar{\nu}_e$ signal, resulting in mass ordering discrimination. Using realistic CCSN simulations for multiple progenitor masses, we compute event rates and perform a statistical analysis for a
Galactic ($10$~kpc) CCSN event at DUNE, Hyper-Kamiokande (HK), and JUNO detectors. The neutronization burst remains largely independent of SN hydrodynamic simulation models, with DUNE and HK achieving $\gtrsim 6\sigma$ and $\gtrsim 4\sigma$ sensitivity for normal (NO) to inverted ordering (IO) discrimination, respectively. However, the rise-time observable is prone to progenitor degeneracies. To mitigate this cumulative and ratio-based observables constructed at characteristic timescales ($20$ ms & $100$ ms) are used. The resulting confidence levels from the rise-time analysis to discriminate IO/NO in HK and JUNO are $\sim 5\sigma$ and $\sim 3\sigma$, respectively. Our results highlight the complementarity of detectors and observables, and demonstrate that combining neutronization burst and
accretion phase information will be crucial for a definitive determination of the
neutrino mass ordering in the next
Galactic supernova.
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All authors Prantik Sarmah, Sovan Chakraborty, Abinash Medhi, Debanjan Bose, Moon Moon Devi
High Energy Astrophysical Phenomena
A Disappearing Act: Constraints From "Missing" Flares of Repeating Partial TDE Candidates
Jason T. Hinkle, Chang Liu, Adam A. Miller et al. (+6 more)
Recurrent
tidal disruption events (rTDEs) are sources that exhibit multiple TDE-like
flares; many are likely powered by the recurring partial disruption of a bound
star, in a repeating partial TDE (rpTDE). Two such sources, TDE 2022dbl (ASASSN-22ci) and TDE 2020vdq (ZTF20acaazkt), each exhibited two UV/optical
flares and, under the assumption of periodicity, both were expected to exhibit a third
flare in early 2026. Neither exhibited such a
flare, to limits of $L_{\textrm{UV/optical}} \lesssim 10^{42}$ erg s$^{-1}$, $\sim$30$\times$ fainter than the previous
flares. Here, we examine several possible explanations. Observing two independent TDEs from the same
galaxy within $\sim$2 yr has a probability of $\lesssim$0.5% for measured average TDE rates and currently expected rate enhancements, unless there is extreme intrinsic dispersion in the rates. Theoretical predictions for a double TDE of both
stars in a binary are inconsistent with the observed
flares. We therefore conclude that TDE 2022dbl and TDE 2020vdq are rpTDEs. To produce only two observable
flares with similar energetics, our semi-analytical modeling strongly favors a main-sequence
star promptly placed on a bound orbit with a deep initial
tidal encounter at pericenter. These results suggest that the majority of rTDEs with multiple
flares over a few-year baseline are likely to be rpTDEs, and that a significant fraction of systems may produce only two observable
flares. This has important implications for the use of r(p)TDEs as probes of TDE physics and dynamical processes in the
nuclei of other
galaxies, in addition to the expected yield from upcoming surveys.
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All authors Jason T. Hinkle, Chang Liu, Adam A. Miller, Ping Chen, Katie Auchettl, Benjamin J. Shappee, Christopher S. Kochanek, K. Z. Stanek, Todd A. Thompson
Solar and Stellar Astrophysics
Nonthermal line broadening at solar flare footpoints is primarily field-aligned
Andy S. H. To and Alexander J. B. Russell
Magnetic reconnection powers
solar and
stellar flares, but a full understanding of how the released energy is transported and converted within the
solar atmosphere remains elusive. One clue lies at
solar-
flare footpoints, where spectral lines are far broader than the electron temperature alone can explain. Unresolved flows, waves,
turbulence and ion heating have all been proposed, but observations have not yet conclusively distinguished between these mechanisms. Here we perform an unprecedented
geometric test for
flare footpoints, using 4,593 Hinode/EIS spectra from 407 C- to M-class
flares. Line widths decrease systematically from disk centre to limb in all coronal emission lines, showing that the dominant broadening component is
magnetic field aligned rather than isotropic or transverse. Cooler lines retain substantial broadening into the early decay phase, consistent with persistent unresolved field-aligned flows or line-of-sight velocity gradients. Hotter lines show an impulsive component that decays rapidly after the soft X-ray peak, consistent with preferential ion heating and ion temperature anisotropy. These findings resolve the long-standing question of the nature of line broadening at
flare footpoints, place direct limits on
flare energetics, and motivate a new direction in
flare physics incorporating distinct field-aligned and perpendicular ion temperatures that exceed the electron temperature.
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Earth and Planetary Astrophysics · Cross-listed from cs.LG
Gaussian Process Latent Factor Regression for Low-Data, High-Dimensional Output Problems
Edward T. Stevenson, Eric T. Wolf, Mei Ting Mak et al. (+2 more)
In the sciences, regression tasks often require predicting high-dimensional outputs from few training examples. Multi-output Gaussian processes excel in low-data regimes but typically struggle with high-dimensional outputs. Compress-then-predict pipelines such as PCA-GP (principal component analysis plus Gaussian process regression) handle high dimensionality, but rely on bases optimized for reconstruction rather than prediction. To address this gap, we propose a model that represents each output as a linear-Gaussian decoding of a low-dimensional latent state drawn from a Gaussian process prior. By analytically marginalizing the decoder weights, we couple compression and prediction in a single objective that scales to high-dimensional outputs. We refer to this model as Gaussian process latent factor regression (GPLFR). We demonstrate GPLFR by building the first spatially resolved emulator of global
climate models for rocky
exoplanets.
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All authors Edward T. Stevenson, Eric T. Wolf, Mei Ting Mak, N. J. Mayne, Miles Cranmer
Astrophysics of Galaxies
The quasi-star model for Little Red Dots: potential and challenges
Fabrizio Gentile, Mauro Giavalisco, Emanuele Daddi et al. (+25 more)
(Abridged) Little Red Dots (LRDs) are a class of sources discovered by JWST observationally defined by a "V-shaped" rest-frame UV-Optical SED, a compact or unresolved morphology, and for having, frequently, broad hydrogen emission lines. Among various models, those involving a quasi-
star interpret LRDs as an intermediate stage in the
evolution of a super-massive black hole (SMBH) seed into a classic AGN. In this paper, we employ the radiative-transfer code Cloudy to study whether this model is able to reproduce the spectral features commonly observed in LRDs. The model consists of an accreting SMBH ($M_{\rm BH}\sim10^{5-6} \ M_\odot$) surrounded by a convective layer where a black-body (BB) spectrum with $T\sim5000 \ {\rm K}$ and $L\sim10^{44.4} \ {\rm erg \ s}^{-1}$ is produced. This BB is then reprocessed by a concentric thick ($\Delta R\sim1000 \ {\rm AU}$) shell of dense ($n_{\rm H}\sim10^{11} \ {\rm cm}^{-3}$) gas partially ionised by thermal collisions. The emerging radiation is further reprocessed by a diffuse clumpy medium surrounding the quasi-
star. We fit this model to JWST/NIRSpec spectra of LRDs from the literature, deriving the main physical parameters and the SMBH masses. Once coupled with the UV emission from a host
galaxy, this model is able to reproduce the shape of the UV-to-NIR continuum, including the presence of a Balmer break, as well as the luminosity of the hydrogen emission lines. However, this quasi-
star model does not natively account for the presence of broad helium lines and for the possible presence of hot
dust, needing additional components to match these observables. Our main result is to show how some LRDs can be modeled as quasi-
stars, highlighting that a significant degeneracy exists among different LRD models. This has important consequences for our understanding of the mechanisms driving black hole growth in the early Universe.
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All authors Fabrizio Gentile, Mauro Giavalisco, Emanuele Daddi, David Elbaz, Jean-Baptiste Billand, Maximilen Franco, Benjamin Magnelli, Guillermo Barro, Yingjie Cheng, Nikko J. Cleri, Kelcey Davis, Ivan Delvecchio, Mark Dickinson, Steven L. Finkelstein, Giovanni Gandolfi, Michaela Hirschmann, Weida Hu, Dale Kocevski, Anton M. Koekemoer, Ray Lucas, Sara Mascia, Lorenzo Napolitano, Casey Papovich, Borja Pérez-Díaz, Pablo Perez-Gonzalez, Jonathan R. Trump, Xin Wang, L. Y. Aaron Yung
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
A dark-matter-sensitive orientation clock near rotating black holes
Mohsen Fathi
A coherent triaxial structure has an intrinsic orientation clock because rotation about its intermediate principal axis is unstable. I ask how this clock changes when the structure moves on a circular equatorial orbit near a rotating black hole in an effective dark matter (DM) environment. The calculation uses a comoving orthonormal tetrad, the electric part of the Riemann tensor, Euler–quaternion dynamics, and the conversion from proper time to stationary coordinate time. The clock shift separates exactly into a local proper-time response and a
geometric time-conversion response. I compute a direct grid of 600 DM models for Einasto, regularized cored Navarro–Frenk–White, and Hernquist profiles. Across the scanned domain, the total fractional frequency shift lies between about $-3\times10^{-7}$ and $-3\times10^{-4}$. For the fiducial body model, most of the shift comes from the time conversion. Synthetic timing tests show that a shift near $10^{-4}$ is recoverable only when the clock is highly coherent and its Kerr baseline is known independently. This gives a theoretical timing diagnostic and a synthetic observational forecast. I do not fit real data.
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Cosmology and Nongalactic Astrophysics
What it takes to solve the Hubble tension through Modifications of Cosmological Recombination II: in light of ACT DR6 and DESI DR2
Nanoom Lee and Tianji Zhou
We construct data-driven solutions to the Hubble tension, in light of recent data from the Atacama Cosmology
Telescope (ACT DR6) and the Dark Energy Spectroscopic Instrument (DESI DR2). We search for the minimal modification to the recombination history through a time-varying electron mass $m_e(z)$ that increases the best-fit $H_0$ inferred from CMB data toward the SH0ES value, without worsening the fit to the data. Using Planck and ACT data including
lensing, we find a perturbative modification to $m_e(z)$ that fully resolves the Hubble tension, with the solution sharing the same qualitative oscillatory structure as in previous work using Planck data alone, demonstrating its robustness to the inclusion of more precise and independent CMB data. As a byproduct, the solution also eases the $S_8$ tension. Once DESI DR2 BAO data are added, however, perturbative modifications to $m_e(z)$ cannot fully resolve the Hubble tension. This reflects the same fundamental limitation: raising $H_0$ by modifying recombination generically lowers $\Omega_m$, being inconsistent with late-time cosmological observations.
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Cosmology and Nongalactic Astrophysics
Phenomenology of Inflaton-Driven Early QCD Confinement and Solution to Axion Isocurvature Problem
Evangelos I. Sfakianakis, Barmak Shams Es Haghi and Katherine Freese
We study the phenomenology of early QCD confinement during inflation, driven by a direct coupling between the inflaton and Standard Model
gluons. This coupling dynamically raises the QCD confinement scale, making the
axion sufficiently heavy to suppress isocurvature perturbations during the CMB epoch. As inflation proceeds, the confinement scale decreases and the
axion becomes light, allowing de Sitter fluctuations during the late stages of inflation or post-inflationary thermal fluctuations to generate the observed dark matter abundance. In addition, QCD-induced corrections to the inflationary potential can shift the scalar spectral index towards smaller values, providing a further observational handle. We embed this mechanism in an $\alpha$-attractor model of inflation and explore the resulting parameter space. We show that, in the minimal scenario with reheating into
gluons, successful dark matter production requires deconfinement to occur shortly after the CMB window. Extensions involving reheating through heavy right-handed
neutrinos generally require large Yukawa couplings, which induce sizable loop corrections that spoil inflationary dynamics. We show that this tension can be resolved in the presence of supersymmetry and derive constraints on the SUSY breaking scale that allow the mechanism to remain viable within plateau models of inflation. Treating the reheat temperature as a free parameter further enlarges the viable parameter space.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Short Gravitational-Wave Transients as Probes of Cosmic Domain Walls
Tore Boybeyi, Doga Veske and David Maibach
GW190521 and GW231123 have been reported as short-duration gravitational-wave transients consistent with very massive binary black hole (BBH) coalescences whose inferred parameters, i.e., exceptionally high total masses and
spin magnitudes, challenge standard isolated binary
stellar evolution. We test a topological dark matter (TDM) interpretation invoking
cosmic domain walls by fitting a physically motivated domain wall template to the LIGO Hanford and Livingston strain data. The BBH hypothesis is individually favored, with $\log_{10}\mathcal{B}_{\rm BBH/TDM}=12.2$ and $11.3$ for GW231123 and GW190521, respectively. However, these values are lower than those typically recovered from matched maximum a posteriori BBH waveforms injected into nearby noise segments. We further perform, for the first time, a joint fit in which domain wall signals from a single underlying scalar field are constrained simultaneously by both events. Although not favored over BBH signals, we find the two events are consistent with a common scalar field, with shared TDM parameters agreeing across independent noise realizations and sky locations. We further find that injected TDM transients are systematically recovered under the BBH hypothesis with large
spin parameters, revealing a morphological degeneracy that could mask genuine domain wall signals. This analysis demonstrates that multi-event parameter consistency tests provide a new discriminant for domain wall dark matter searches in upcoming observing runs.
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High Energy Astrophysical Phenomena
Analytic insight into the physics of SASI II. Spiral instability of the prograde mode in a rotating stellar core
T. Foglizzo
During the core-collapse of a rotating massive
star, the standing
accretion shock instability (SASI) favours the development of non-axisymmetric motions which can imprint specific frequency signatures on the
neutrino and gravitational wave signals.This study establishes analytical approximations for the eigenfrequencies of the dominant SASI modes. It also explains the physical mechanism responsible for the further destabilization of prograde SASI modes by differential rotation. A perturbative analysis is used to calculate the eigenfrequencies of a stalled
accretion shock in spherical geometry, taking into account the rotation of the collapsing
stellar core. The formulation of the perturbative equations as a self-forced oscillator is extended to include differential rotation and interpret the results physically. The oscillation frequency of the dominant mode weakly depends on the detailed formulation of
neutrino emission if the shock radius exceeds ~1.5 times the radius r_nabla of maximum deceleration. Analytical expressions are obtained for the one and two-armed spiral modes with a 10% accuracy in this regime. The effect of differential rotation is explained by the role of phase mixing between the advective forcing and the acoustic structure. The radial wavelength of vorticity perturbations associated with the prograde mode is increased by differential rotation, leading to a better phase match with the large radial scale of the acoustic structure. Even when rotation is too modest to involve a corotation radius, its adverse effect on phase mixing can be significant at small radius due to the steep inward increase of the rotation frequency ~1/r^2 in the region of stationary
accretion. In the regime of faster rotation involving a corotation radius, the stationary phase approximation sheds light on the dominant advective-acoustic coupling, located between the corotation zone and the shock.
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Astrophysics of Galaxies
Dynamical evolution and dissolution timescale of young stellar clusters in the Orion star-forming complex
Sergio Sánchez-Sanjuán, Ángeles Pérez-Villegas, Jesús Hernández et al. (+1 more)
We present a comprehensive analysis of the Orion
star-forming complex (OSFC), combining structural, kinematic, and dynamical information to constrain the present-day state and future
evolution of its
stellar substructures. Using
Gaia DR3 astrometry and complementary radial velocities from high-resolution spectroscopic surveys, we derived three-dimensional velocity distributions and structural parameters for 13 young clusters. For the
stellar component, we estimated a correction of the present-day mass function for observational incompleteness and calculated the virial state, $\alpha_{\rm vir}$, finding that all clusters are supervirial. Direct $N$-body simulations initialized from the present-day global parameters and evolved for 300~Myr in a
Galactic potential suggest a separation of the OSFC clusters into two regimes: seven clusters with $\alpha_{\rm vir}\lesssim 7$ evolve in a
Galactic-potential-regulated regime that retains a bound core for $\gtrsim 170$ Myr as long-lived open clusters, whereas six clusters with $\alpha_{\rm vir}\gtrsim 7$ enter an internal-dynamics–dominated regime, dissolving before 120 Myr and rapidly populating the
Galactic stellar field. For both regimes, a control test indicates negligible cluster–cluster interactions under current OSFC conditions. Finally, long-lived clusters show low-amplitude modulations in the bound fraction correlated with the
Galactic vertical motion, consistent with disk-crossing
tidal heating and the temporary recapture of marginal members. These results highlight the OSFC as a natural laboratory where heterogeneous initial conditions give rise to persistent open clusters and dispersing groups.
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All authors Sergio Sánchez-Sanjuán, Ángeles Pérez-Villegas, Jesús Hernández, Luis Aguilar
Solar and Stellar Astrophysics
Depolarization and Polarization-Transfer Rates for Solar He I Lines due to Collisions with Neutral Hydrogen
Moncef Derouich and Saleh Qutub
Context. Neutral helium (He I) produces several spectral lines that are widely used for
solar diagnostics. The role of collisions between He I atoms and neutral hydrogen (H I) in the modeling of
solar He I lines remains insufficiently quantified. Accurate determination of collisional rates affecting atomic polarization is needed for
solar spectropolarimetry. Aims. Our aim is to provide a set of multi-level and multi-term collisional depolarization, polarization-transfer, and population-transfer rates, due to isotropic collisions with neutral hydrogen, for He I levels and terms involved in the main
solar He I diagnostic lines. Methods. The calculations are performed within the frozen-core approximation, in which the inner 1s electron is treated as a core with Lc = 0, Sc = 1/2, and Jc = 1/2, while the outer electron is treated as the active valence electron. Results. We compute both multi-level rates, describing depolarization and polarization transfer between fine-structure J-levels, and multi-term rates, which additionally account for coherences between different J-levels belonging to the same term. Conclusions. Our results provide the collisional input needed for the statistical
equilibrium equations (SEE) of the polarization of the main He I
solar lines, including the 10830 Å, D3 5876 Å, and related triplet transitions, and allow a quantitative reassessment of the role of neutral-hydrogen collisions in He I spectropolarimetry.
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Cosmology and Nongalactic Astrophysics
The Atacama Cosmology Telescope: Probing new signatures of ultralight axions with gravitational lensing
Alex Laguë, Keir K. Rogers, Mathew S. Madhavacheril et al. (+14 more)
Ultralight
axions (ULAs) are well-motivated dark matter particle candidates that arise in many extensions of the Standard Model of particle physics. ULAs with mass $m_\mathrm{a} \lesssim 10^{-27}$ eV have been strongly constrained by
cosmic microwave background (CMB) observations in temperature and polarization. We fit recent measurements of gravitational
lensing of the CMB from Planck, the Atacama Cosmology
Telescope (ACT) and the South Pole
Telescope (SPT-3G) using a state-of-the-art simulation-calibrated nonlinear clustering model for ULAs. We derive the strongest constraints on ULAs in the mass range $10^{-26}\;\mathrm{eV}\leq m_\mathrm{a}\leq 10^{-24.5}\;\mathrm{eV}$. ULAs of this mass have been shown to alleviate tensions between inferences of the matter clustering if they compose a few percent of the total dark matter content of the Universe. We conclude that ULAs with a mass of $10^{-26}$ eV make up less than 1.5% of the dark matter and $10^{-25}$ eV
axions make less than 9% (both at 95% confidence level). We identify a slight preference for non-zero
axion density at $10^{-24.5}$ eV at $2.1\sigma$. We find that the preference for ULAs is largely driven by a few data points and that further investigation of non-linear ULA physics is needed to confirm or rule out this signal.
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All authors Alex Laguë, Keir K. Rogers, Mathew S. Madhavacheril, J. Richard Bond, Erminia Calabrese, Mark J. Devlin, Jo Dunkley, Vera Gluscevic, Renée Hložek, Hidde T. Jense, Thibaut Louis, Frank J. Qu, Bernardita Ried Guachalla, Neelima Sehgal, Blake D. Sherwin, Suzanne T. Staggs, Alexander van Engelen
High Energy Astrophysical Phenomena
A high-energy neutrino flare associated with nearby bright interacting supernova SN 2021foa
Ming-Xuan Lu, Yun-Feng Liang, Xue-Rui Ouyang et al. (+3 more)
While core-collapse
supernovae have been widely discussed as potential
neutrino sources, definitive observational evidence has remained elusive. In this work, we report evidence of high-energy
neutrino emission in the direction of
supernova SN 2021foa, which is one of the closest and brightest interacting
supernovae observed to date. Using the second data release of
muon track data from the IceCube
Neutrino Observatory, we conducted a time-dependent analysis and identified a
neutrino clustering that temporally coincides with the optical peak of SN 2021foa, occurring approximately 16 to 22 days after the discovery date, with a maximum test statistic of $\sim 28.2$. Monte Carlo simulations indicate that the probability of observing such a
neutrino excess by chance is $\sim6.7 \times 10^{-5}$, corresponding to a significance of $\sim4.0\,\sigma$. The spatial and temporal correlation strongly suggests that the
neutrinos originate from the
supernova. SN 2021foa is a unique "flip-flop"
supernova; its spectra repeatedly transitioned between hydrogen-rich (Type IIn) and helium-rich (Type Ibn) phases within 50 days post-peak, reflecting a violent and complex mass-loss history of its progenitor. The inferred
neutrino energy exceeds the optical radiative energy and ejecta kinetic energy of the
supernova by orders of magnitude, suggesting that the
neutrino emission is likely powered by a delayed central engine driving a jet that is choked within the dense circumstellar medium.
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All authors Ming-Xuan Lu, Yun-Feng Liang, Xue-Rui Ouyang, Da-Bin Lin, Xiang-Gao Wang, Yi-Zhong Fan
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
On the Possibility of a Strong First-Order Phase Transition in Neutron Stars
Zheng Cao and Lie-Wen Chen
Whether cold dense QCD matter undergoes a strong first-order phase transition remains an open question. In nature,
neutron stars provide the most direct probe of cold dense QCD matter. Theoretically,
chiral effective field theory constrains the equation of state of dense matter near
nuclear saturation density, while perturbative QCD calculations constrain it at densities well beyond stable
neutron-
star interiors. We perform
Bayesian inference with non-parametric Gaussian-process equation of state for $\beta$-equilibrated
neutron-
star matter under the assumption with and without a strong first-order phase transition, using the
tidal deformability from GW170817, the NICER mass–radius measurements of PSR~J0740$+$6620, PSR~J0030$+$0451, PSR~J0437$-$4715, PSR~J0614$-$3329,
chiral effective field theory, and perturbative QCD. Within this
Bayesian inference framework, the model comparison mildly to moderately favors a strong first-order phase transition, with its onset most likely lying above the central density of the most massive
neutron star. Such an onset reconciles the stiffness required to support massive
neutron stars with the softening favored by perturbative QCD from asymptotically high density.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Fabian Gittins, Harsh Narola, Thibeau Wouters et al. (+3 more)
As a binary
neutron star inspirals due to the emission of gravitational waves, the rising
tidal frequency resonantly excites vibrational modes. These oscillations are seismological probes of the rich
stellar interior, yet it remains to be established whether gravitational-wave interferometers can measure them. Here, we present the first fully
Bayesian study of the capability of the Einstein
Telescope to detect
tidal resonances. We simulate one year of observations and analyse the 200 loudest signals. We find that the Einstein
Telescope can identify resonant modes and is sensitive to gravitational-wave phase shifts as small as $\Delta \Phi \approx 0.03$ for favourable events. We further show that neglecting resonances can bias the inferred
tidal deformabilities. These results establish
tidal resonances as a measurable route for asteroseismology with future detectors.
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All authors Fabian Gittins, Harsh Narola, Thibeau Wouters, Peter T. H. Pang, Tanja Hinderer, Chris Van Den Broeck
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
$\tt BlackHawk$ $\tt v3.0$: Hawking Radiation from Regular Black Holes
Alexandre Arbey, Marco Calzà, Léa Malacher et al. (+2 more)
We present $\tt BlackHawk$ $\tt v3.0$, a major update of the public code designed to compute Hawking radiation spectra of black holes. Building upon previous versions, this release considerably extends the range of black hole geometries that can be studied by implementing several new spherically symmetric metrics: the Bardeen and Hayward regular black holes, the Simpson-Visser and Peltola-Kunstatter black-bounces, the D'Ambrosio-Rovelli black hole-to-white hole metric, and the Babichev-Charmousis-Lehébel black hole. For each metric, we compute the corresponding Hawking temperatures and greybody factors, enabling the determination of primary Hawking emission spectra for particles of different
spins. The greybody factors are obtained through dedicated numerical routines based on the companion code $\tt GrayHawk$. Additionally, $\tt BlackHawk$ $\tt v3.0$ introduces several technical improvements aimed at enhancing precision and efficiency, providing a highly versatile tool. The code is publicly available at https://blackhawk.hepforge.org/
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All authors Alexandre Arbey, Marco Calzà, Léa Malacher, Davide Pedrotti, Yuber F. Perez-Gonzalez
Solar and Stellar Astrophysics
Minor Ions as a Diagnostic of Solar Wind Heating: Inverted Mass-to-Charge Scaling in Imbalanced Turbulence
Michael F. Zhang, Evan L. Yerger, Matthew W. Kunz et al. (+1 more)
Alfvénic
turbulence is vital to powering the
solar wind and corona, yet eludes a comprehensive understanding of the kinetic processes by which it dissipates. Minor ions are sensitive tracers of these processes, showing extreme perpendicular temperatures and mass-weighted temperature trends that can either correlate or anticorrelate with mass-to-charge ratio, $A_i/Z_i$. We use a combination of quasilinear theory and 3D hybrid-kinetic simulations to explain these features and their correlations with properties of
turbulence in the fast
solar wind. When Alfvénic
turbulence is imbalanced, its cascade to ion-Larmor scales is throttled by the helicity barrier. This barrier ultimately leads to high-frequency
proton-cyclotron waves (PCWs), both oblique and parallel, the latter of which produce very flat electric-energy spectra ($\mathcal{E}_{E_{\perp}}\sim k_\parallel^{-\eta}$ with $\eta<2$) over the range of scales that are cyclotron resonant with minor ions. While steeper spectra lead to a positive correlation of heating with $A_i/Z_i$, the shallower spectra cause the dependence to invert, with $Q_i\propto Q_{\mathrm{p}}A_i(A_i/Z_i)^{\eta-2}$. Six simulations of balanced and imbalanced
turbulence spanning $\beta_{\rm p0}=\{1,0.3,1/16\}$ corroborate this prediction, showing minor-ion heating rates that follow $(A_i/Z_i)^a$. Minor-ion heating is strongest and most perpendicular in our lowest $\beta_{\rm p0}=1/16$ simulation of imbalanced
turbulence, reaching $T_{\perp{\rm O}^{5+}}/T_{\perp{\rm p}}\approx40$ and $T_{\perp{\rm O}^{5+}}/T_{\parallel{\rm O}^{5+}}\approx10$, consistent with low-coronal observations. Future minor-ion measurements should test whether intervals in which minor-ion thermal speeds decrease with increasing mass-to-charge ratio are associated with a history of large cross helicity, enhanced power in parallel PCWs, and a steep transition-range spectrum.
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All authors Michael F. Zhang, Evan L. Yerger, Matthew W. Kunz, Jonathan Squire
High Energy Astrophysical Phenomena
A micronova burst in the intermediate polar IGR J17014-4306
Alexandre S. Oliveira, D. C. Souza, G. J. M. Luna et al. (+1 more)
We report the detection of a short optical burst in TESS data of IGR J17014-4306, the eclipsing intermediate polar with the longest known orbital period. The burst lasts 1.56 d and shows multiple peaks, reaching $(9.3 \pm 0.2) \times 10^{33}$ erg s$^{-1}$, and releases a total energy of $(3.25 \pm 0.01) \times 10^{38}$ erg. The burst parameters are consistent with those of a micronova eruption, currently understood as a thermonuclear runaway in the magnetically-confined
accretion column. From its energy, we infer a burned column mass of $\sim 1.6 \times 10^{-11}$ M$_\odot$, which implies a recurrence time of $\sim 20$ d. Our search for similar events in long-term
Gaia, ASAS-SN, and AAVSO light curves reveals 16 possible fast brightenings over $\sim 11$ yr, suggesting that micronova events may be frequent in IGR J17014-4306. Timing analysis of the TESS data shows that the white-
dwarf spin period remains stable before and after the burst. During the burst, however, the power spectrum becomes more complex and exhibits multiple peaks. The classification of IGR J17014-4306 as a micronova brings the total number of confirmed systems to eight. Its extreme orbital period and eclipsing nature make it an ideal test-bed for further studies of magnetically confined thermonuclear burning on white
dwarfs.
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All authors Alexandre S. Oliveira, D. C. Souza, G. J. M. Luna, C. V. Rodrigues
Astrophysics of Galaxies
Ghostly DLAs in SDSS DR16
Patrick Petitjean
In Petitjean (2026, A&A 710, 340), we revisited the origin of proximate damped Lyman-alpha absorbers (PDLAs), which trace cold gas within 3000 km/s of the
quasar redshift, and interpreted their kinematics and physical properties within a unified framework. We showed that most PDLAs are associated with the environment of the AGN and/or the
quasar host
galaxy. We also provided the first census and characterization of absorption systems exhibiting strong absorption from excited levels of atomic ground states among
quasar-associated absorbers. Among these, ghostly and coronagraphic systems arise in dense, compact gas that partially covers the
quasar emission regions. Most systems are associated with
outflows reaching velocities up to -2000 km/s, while a smaller fraction of inflowing clouds extends to velocities of up to +1200 km/s. In the present work, we provide an updated classification of PDLAs, including a revised catalogue of ghostly systems that more than doubles the number of previously known detections. We investigate the properties of these systems by measuring and discussing the equivalent widths of the detected absorption lines in both stacked spectra and individual ghostly systems. In particular, we show that although most ghostly systems are bona fide DLAs, this is not always the case.
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Astrophysics of Galaxies
Bar-induced deflection of open cluster tidal tails
Hanna Parul, Laia Casamiquela, Paola Di Matteo et al. (+1 more)
We present a systematic study of how the
Galactic bar affects the orientation of
tidal tails of open clusters and assess the power of tail morphology to constrain the bar's pattern speed. Using test-particle simulations, we follow the
evolution of $\sim 1450$ observed open clusters from the Hunt & Reffert (2024) catalogue in an axisymmetric reference potential and in eight barred potentials with pattern speeds ranging from $\Omega_b = 20$ km/s/kpc to $\Omega_b = 55$ km/s/kpc. We quantify the bar effect through the deflection angle – the rotation of the tail orientation in the barred model relative to the axisymmetric case. The deflection angle varies systematically with bar pattern speed and cluster guiding radius. The largest deflections occur for clusters near the outer Lindblad resonance (OLR), with the sign of the angle set by the orientation of the orbit's pericentre relative to the bar's major axis. For each cluster we measure the distance from the centre beyond which different bar models produce distinguishable tail orientations, and classify each cluster as bar-sensitive or bar-insensitive based on its maximum absolute deflection across the bar models. Comparing with observed
tidal tails from the literature, we find that the extended tails of NGC 2632 and the Hyades disfavour moderate pattern speeds. We provide a catalogue of deflection angles, minimal tail extents, and bar-sensitivity flags to guide future observational searches and the re-assessment of existing
tidal tail catalogues.
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All authors Hanna Parul, Laia Casamiquela, Paola Di Matteo, Salvatore Ferrone
Instrumentation and Methods for Astrophysics
Sensitivity Limits and Operational Threshold Calibration for DINOv2-based Gravitational-Wave Glitch Characterization: A Strain-Domain Mock Data Challenge on LIGO O4a
Luca Cirfeta
We present a Mock Data Challenge (MDC) to characterize the sensitivity limits of the gravi-signal-ml pipeline (Cirfeta 2026) for unsupervised gravitational-wave glitch detection. Strain-domain synthetic injections of eight morphological families into public LIGO O4a L1 data reveal two threshold-dependent sensitivity regimes. With a session-adaptive dynamic threshold (tau_dyn = mu_bg - 2.5 * sigma_bg), the pipeline recovers visually anisotropic morphologies (Butterfly, ZSweep) at matched-filter SNR >= 70, reaching Recall = 1.0, though the False Positive Rate (FPR) remains uncontrolled across sessions. Characterization of the full O4a
embedding distribution (N = 188,142 segments) reveals extreme non-Gaussianity (skewness = -4.12, excess kurtosis = 15.38, Shapiro-Wilk p-value near 0), with the left tail best modeled by a Generalized Extreme Value (GEV) distribution. Under a statistically rigorous operational threshold (tau_op = 0.874) calibrated at the empirical 5x10^-5
quantile (FPR < 0.01%), the MDC yields Recall = 0 for all eight morphologies at all tested SNR levels, including narrowband structures (HarmonicComb, NarrowChirp) and impulsive transients (AsymBlip) at SNR up to 430. We trace this insensitivity to the global average pooling of the DINOv2 [CLS]
token, which dilutes signals occupying a small fraction (<5%) of the spectrogram's 37x37 patch grid. The null result of Cirfeta (2026) is conditionally reinterpreted: it confirms the absence of novel macro-structures but cannot exclude localized micro-structures. These findings provide a quantitative roadmap for next-generation ViT-based pipelines using patch-level scoring and multi-scale windowing.
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Solar and Stellar Astrophysics
gr8stars II : judgement day for spectroscopic parameter model systematics
Alix Violet Freckelton, Annelies Mortier, Megan Bedell et al. (+18 more)
Many areas of astrophysics, including exoplanetary studies, rely on precise and accurate
stellar parameters. This demands that uncertainties on these parameters truly reflect all biases and systematics. Within this second work of the gr8
stars collaboration, we take a set of 585 bright FGK
dwarfs with high resolution, high signal-to-noise ratio spectra from the SOPHIE spectrograph. We determine
stellar effective temperature, surface
gravity, and
metallicity using five different spectroscopic methods for each
star, with an additional method used for comparisons. We find a typical scatter of 76 K in \teff, 0.14 dex in \logg, and 0.07 dex in \feh. These deviations are significantly larger than the average precision error on these parameters. We furthermore use isochrone fitting to determine mass, radius, and age for all 585
stars, using input from all results. We use the radii determined by SED fitting in the first gr8
stars paper as a comparison to our isochronal radii from this work, in addition to comparing the isochronal \logg to spectroscopic \logg. The scatter in mass and radius from the use of different spectroscopic methods is investigated and propagated to exoplanetary parameters. The induced fractional uncertainties in planetary radius ($\lesssim$ 3 %) and mass ($\lesssim$ 5%) are found to be below those typically found in the literature. We estimate a lower limit on planetary
equilibrium temperature fractional uncertainty of $\approx$ 4%, a noise floor that is currently not sufficiently represented in the literature.
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All authors Alix Violet Freckelton, Annelies Mortier, Megan Bedell, Michael Cretignier, Jared R. Kolecki, Andreas J. Korn, Sérgio G. Sousa, Maria Tsantaki, John M. Brewer, Lars A. Buchhave, Guy R. Davies, J. I. González Hernández, Sam Morrell, Martin B. Nielsen, Vera Maria Passegger, Andreas Quirrenbach, Arpita Roy, Nuno C. Santos, A. Suárez Mascareño, Christopher Allan Watson, Lily L. Zhao
Earth and Planetary Astrophysics
Peas and USPs: Can Stellar Spindown and Peas in a Pod Replicate Ultra-Short-Period Planet Characteristics?
Adam Distler and Juliette Becker
Peas-in-a-Pod (PIAP) systems have been shown to be common across
exoplanet systems, with regular
planet spacings and similar
planet sizes. In contrast, ultra-short-period
planets have displayed distinct differences from PIAP systems, including higher mutual inclinations, ages, and
planet sizes. Using Laplace-Lagrange secular theory, we investigate the ability of
stellar spindown to decouple PIAP systems. We find that strictly PIAP systems with regular spacings cannot undergo secular resonance crossings for the expected
stellar $J_2$
evolution, and that we instead require the inner
planet to migrate inward to undergo this resonance crossing. As a result, there is no inner edge to PIAP systems where systems will always cross a secular resonance and decouple the inner
planet. Using expected $J_2$
evolution tracks from
stellar evolution models, we find a diversity of expected resonance crossing times, highlighting the ability to test migration pathways and initial
stellar obliquities using this framework.
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Astrophysics of Galaxies
A New Member of the Fast and Furious Family: A Relativistic and Time-Variable UV Outflow in a Luminous Quasar
Lucas M. Seaton, Patrick B. Hall, Liliana Flores et al. (+20 more)
We report the fastest
quasar outflow first detected in the ultraviolet, via variable C IV and Si IV absorption at
outflow velocities $-77,000$ km s$^{-1}$ to at least $-90,000$ km s$^{-1}$, in the
radio-quiet
quasar SDSS J231854.31+243954.2 (J2318). J2318 is a weak-lined
quasar in the rest-frame ultraviolet, but Gemini GNIRS spectroscopy reveals an H$\alpha$
redshift of $z=2.6781\pm0.0004$. A twenty-year photometric time series shows peak-to-peak variability of 0.5 mag in the $g$ band. The C IV
outflow strengthened monotonically over three epochs spanning $\sim$2.2 rest-frame years. The existence of such a high-velocity
outflow implies that models of
quasar outflows must be able to either accelerate gas to $0.3c$ while still preserving C IV and Si IV ions, or enable the formation of C IV and Si IV ions in gas which has been accelerated to $0.3c$. Virial estimates reveal a black-hole mass of $1.65\times10^9~M_\odot$, which leads to an Eddington luminosity and Eddington ratio of $2.4\times10^{47}$ erg s$^{-1}$ and $0.45$, respectively. Using very conservative assumptions, the UV-absorbing
outflow alone has an estimated mass loss of $>0.82~M_\odot~{\rm yr}^{-1}$ and a kinetic luminosity ratio $L_{kin}/L_{bol}\geq0.75$%. The lower limit is just above the threshold usually cited for significant feedback on the host
galaxy. Comparison to PDS 456, the only other known
quasar with a UV-absorbing
outflow at $0.3c$, suggests that the true $\dot{M}$ and $L_{kin}/L_{bol}$ could be up to two orders of magnitude larger.
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All authors Lucas M. Seaton, Patrick B. Hall, Liliana Flores, Paola Rodríguez Hidalgo, Marianna Veltri, Zezhou Zhu, Javier Serna, W. Niel Brandt, Scott Anderson, Roberto J. Assef, Eduardo Bañados, Catherine J. Grier, Yasaman Homayouni, Sean Morrison, C. Alenka Negrete, Amy L. Rankine, Jessie Runnoe, Donald P. Schneider, Yue Shen, Matthew Temple, Benny Trakhtenbrot, Jonathan R. Trump, Erik Weiss
High Energy Astrophysical Phenomena
Probing a new subclass of llGRB-SN transients: Insights from EP250304a and its associated supernova
L. Cotter, A. Martin-Carrillo, R. A. J. Eyles-Ferris et al. (+62 more)
With the advent of the Einstein Probe (EP) mission, we are entering a new era in the study of gamma-ray bursts (GRBs), enabling the detection of faint, low-luminosity transients that would previously have gone undetected. EP250304a was an event discovered by EP associated with the broad-lined type Ic
supernova (SN) SN 2025fhm located at z = 0.2. Despite no gamma-ray emission being detected at the time of the EP trigger, we identify evidence for a relativistic
outflow consistent with a GRB-like jet across multiple wavelengths. We present a detailed spectral and photometric analysis of EP250304a/SN 2025fhm, including multi-band light curve modelling performed with the Redback Python package. We find that this event closely resembles low-luminosity GRB-SNe (llGRB-SNe) such as GRB 060218/SN 2006aj, GRB 100316D/SN 2010bh, and GRB 171205A/SN 2017iuk, all of which exhibit early-time emission consistent with a thermal shocked cocoon. These similarities suggest that EP250304A/SN 2025fhm may belong to an emerging subclass of shocked cocoon-dominated llGRB-SNe, representing the low-luminosity end of a broader continuum of engine-driven GRB-SN explosions.
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All authors L. Cotter, A. Martin-Carrillo, R. A. J. Eyles-Ferris, L. Izzo, D. B. Malesani, Y. Julakanti, G. Corcoran, A. Saccardi, P. G. Jonker, A. J. Levan, F. Carotenuto, P. T. O'Brien, J. H. Gillanders, J. N. D. van Dalen, M. E. Ravasio, S. Schulze, N. Sarin, F. E. Bauer, M. Fraser, J. Quirola-Vasquez, A. P. C. van Hoof, S. J. Smartt, C. Gall, A. Rest, C. T. Murphey, N. Tanvir, T.-W. Chen, Q. Wu, Y. Yin, S. Campana, C. Ashall, J. P. Anderson, J. A. Chacon, F. J. Cowie, V. D'Elia, L. Galbany, C. P. Gutierrez, D. H. Hartmann, P. Jakobsson, S. Kobayashi, A. H. Kong, P. Mazalli, T. E. Muller-Bravo, M. De Pasquale, L. Rhodes, A. Rossi, J. Sanchez-Sierras, J. Sollerman, A. Andersson, A. Aryan, T. de Boer, J. S. Bright, K. C. Chambers, M. Gromadzki, M. E. Huber, C. Inserra, T. Lowe, P. Minguez, G. S. Narayan, M. Nicholl, G. S. H. Paek, A. Sedgewick, K. W. Smith, J. W. Tweddle, S. Yang
Cosmology and Nongalactic Astrophysics · Cross-listed from cs.NE
Hub-Aware Hybrid Search: Accelerating the Locally Aligned Ant Technique
Simone Vilardi, Reynier Peletier, Felipe Contreras et al. (+1 more)
Finding
manifold structures in noisy and high-dimensional point clouds is a challenging but important problem. In astronomical observation survey and simulation data the detection of filaments, streams (1D), walls (2D) and clusters (3D) gives rise to deeper understanding of the
evolution of our universe. The Locally Aligned Ant Technique (LAAT) uses biologically inspired
agents to efficiently recover faint and multidimensional structures. However, very dense hubs (e.g. nodes or globular clusters) dominate the ants' activity, creating unnecessary computational overheads. In this paper we propose a two-stage solution. First a fast preprocessing step locates the hubs and replaces them with a tailored likelihood model. Subsequently, a mixed likelihood-pheromone strategy guides the ants to efficiently bridge the dense regions. We demonstrate improvements in detection efficiency and robustness of LAAT with synthetic and a large-scale astronomical N-body simulation of the
cosmic web.
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All authors Simone Vilardi, Reynier Peletier, Felipe Contreras, Kerstin Bunte
Cosmology and Nongalactic Astrophysics
AKRA 3.0: A matrix-free Inversion Framework for Weak Lensing Mass Mapping and Its Application to DES Y3 Data
Yuan Shi, Pengjie Zhang, Li Cui et al. (+2 more)
Weak gravitational
lensing mass mapping offers a direct probe of the matter distribution. Accurate reconstruction of mass maps from masked shear catalogs remains challenging due to survey boundaries and spatially varying noise. In AKRA 2.0, we addressed the mask problem on the curved sky by constructing and inverting the normal-equation
matrix $\bf{H} \equiv \mathbf{A}^\mathrm{T}\mathbf{N}^{-1} \mathbf{A}$ explicitly, necessitating a split-scale strategy that reconstructed different angular scales independently to reach high resolution. Here we present AKRA 3.0, in which $\mathbf{H}$ is treated as a linear operator and the normal equations are solved by the conjugate gradient (CG) method. This reformulation reduces the
memory requirement from $O(N^2)$ to $O(N)$ and the inversion cost from $O(N^3)$ to $O(N_{\rm iter}N^{3/2}), N \sim \ell_{\rm{max}}^2$ for full-sky (SHT-based) operations. Such optimizations render high-resolution full-sky reconstruction tractable for Stage~III and Stage~IV surveys. Applying AKRA 3.0 to the DES Y3 METACALIBRATION catalog, we produce the highest-resolution convergence map of this
dataset to date at HEALPix $N_{\rm{nside}}= 2048$ without imposing any prior assumptions. We extract the convergence power spectrum directly from the reconstructed map and demonstrate that unbiased two-point measurements can be obtained directly from the reconstructed map. The reconstructed E-mode convergence map will be publicly released as data products to enable future studies of non-Gaussian statistics, higher-order moments, and cross-correlations with external
datasets.
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All authors Yuan Shi, Pengjie Zhang, Li Cui, Jian Qin, Ji Yao
Solar and Stellar Astrophysics
Mass-Orbital Period Distribution of Massive White Dwarfs Formed Through Stable Mass Transfer
Rizhong Zheng, Hongwei Ge, Christopher A Tout et al. (+10 more)
White
dwarfs (WDs) in binaries can form through either the stable mass-transfer process or common envelope
evolution (CEE). Compared to CEE, the stable mass-transfer process can lead to a distinct mass$-$orbital period ($M_{ \mathrm{WD}}$-$P_{ \mathrm{orb}}$) relation. Thus, this relation of WDs contains the information about the
evolution channels. We can study the relation in WD binary systems to determine whether their progenitors undergo a CEE. We use the
stellar evolution code MESA as our primary computational tool and adopt the quasi-adiabatic criterion to ensure that our models satisfy the conditions for stable mass transfer. Our study considers different mass-transfer schemes, varying
metallicities, and the relation for both low-mass and intermediate-mass progenitors. Previous studies have focused on the relation for low-mass progenitors, which cannot explain some long-period, high-mass WD binaries. Our results show that the $M_{ \mathrm{WD}}$-$P_{ \mathrm{orb}}$ distribution for intermediate-mass progenitors whose cores remain nondegenerate prior to central helium burning can account for the formation channels of long-period and massive WD binaries.
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All authors Rizhong Zheng, Hongwei Ge, Christopher A Tout, Hailiang Chen, Zhenwei Li, Dengkai Jiang, Chengyuan Li, Zhijia Tian, Bo Ma, Lifu Zhang, Jian Mou, Xuefei Chen, Zhanwen Han
High Energy Astrophysical Phenomena
Detectability of secondary images from flares near Sgr A* with mock GRAVITY data
Fengting Xie, Qing-Hua Zhu and Xin Li
The orbital motion of near-infrared
flares reported by the
GRAVITY collaboration encodes information about both the dynamics of
accretion matter and the underlying spacetime geometry. The centroid track of these
flares, which corresponds to the flux-weighted center of light, incorporates contributions from primary, secondary and higher-order images. Thus, it potentially indicates distinctive signatures of the spacetime geometry, even when these individual multiple images remain unresolved. In this study, we explore the detectability of the secondary images from
flares orbiting Sgr A* through mock data simulating future
GRAVITY observations. Specifically, we compare the model in which the centroid coincides with the track of the primary images with another model in which the centroid incorporates flux-weighted contributions from both the primary and secondary images. Fitting these models to the mock data based on
Bayesian framework, we quantify the conditions under which the signature of secondary images can be statistically distinguishable. We demonstrate that increasing the sample size by an order of magnitude alone could not yield strong evidence for distinguishing the secondary image. Robust detectability ($|\Delta\text{BIC}| >7.9$) is achieved when both with the improved sample size and astrometric uncertainties reduced to 40% of current uncertainties of
GRAVITY astrometric data. Unlike the primary image, which is dominated by
accretion flow physics, the secondary images originate from gravitational
lensing in the strong-field regime. Their detection is an essential first step toward probing higher-order images and the
photon rings.
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