High Energy Astrophysical Phenomena
Toward Black Hole Stars: supermassive black hole growth in nuclear clusters via stellar-object and gas accretion
Konstantinos Kritos and Joseph Silk
Supermassive black hole (SMBH) growth plausibly occurs via runaway astrophysical black hole mergers in
nuclear star clusters that form intermediate mass black hole seeds at high
redshifts. Such a model yields an order-of-magnitude higher rate of
tidal disruption events than that of compact-object captures. Our prediction, normalized to our proposed resolution of SMBH seeding, yields detectable
tidal disruption event rates at high
redshift. The resulting dense gas cocoons generate compact
galactic nuclei, each incorporating a central, massive, black hole
star, with comparable masses in gas,
stars, and massive black holes within a scale of around a parsec as inferred from the various Little Red Dot spectral signatures.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Hubble-Scale Tachyonic Shocks from Low-Scale Inflation – A New Gravitational-Wave Window on Inflation
Haruto Masubuchi, Yuma Narita and Wen Yin
Current bounds on the tensor-to-scalar ratio imply that the energy scale of inflation may lie below the grand-unified scale. In this paper, we show that in a broad class of single-field inflation models with sufficiently small energy scales, an extremely efficient tachyonic instability develops at the end of inflation. This instability rapidly drives the system into a nonlinear regime before coherent oscillations can be established, leading to a first-order phase-transition–like phenomenon without tunneling or barrier crossing. The resulting ultra-relativistic shock fronts surrounding the bubble interiors expand to near the Hubble scale, corresponding to the most strongly enhanced tachyonic modes, and collide with one another, producing energetic inflaton particles and gravitational waves. As a result, the post-inflationary dynamics can differ significantly from the conventional high-scale inflationary scenario. Interestingly, inflation at MeV–EeV energy scales can be probed via gravitational-wave observations, including
pulsar timing arrays, ground-based detectors, and future space-based experiments. Recent limits from the LIGO–KAGRA–Virgo collaboration already constrain EeV-scale inflation, while
pulsar timing array results may be interpreted as evidence for gravitational waves generated by GeV-scale inflation. We also briefly discuss further implications of the resulting tachyonic shocks.
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Solar and Stellar Astrophysics · Cross-listed from nucl-th
Radial oscillations of pulsating neutron stars: The UCIa equation-of-state case
G. Panotopoulos, A. Övgün, T. Iqbal et al. (+2 more)
Radial oscillations provide a clean dynamical test of the high-density stiffness of
neutron-
star equations of state. We study spherically symmetric pulsations of nonrotating relativistic
stars built from cold, charge-neutral, $\beta$-equilibrated pure nucleonic matter described within relativistic mean-field theory. As a baseline we adopt the UCIa parameter set [Astron. Astro-phys. 689, A242 (2024)], and we implement high-density stiffening via the $\sigma$-cut scheme by adding a regulator potential $U_{\rm cut}(\sigma)$ [Phys. Rev. C 92, no.5, 052801 (2015), Phys. Rev. C 106, no.5, 055806 (2022)]. For representative choices $f_s=0$ (no cutoff) and $f_s=0.58$ (stiffened), we solve the Tolman-Oppenheimer-Volkoff and
tidal perturbation equations to obtain
equilibrium sequences, mass-radius relations, and
tidal deformabilities. We then derive and solve the linear general-relativistic radial pulsation equations to compute the eigenfrequencies and eigenfunctions of the fundamental and overtone modes. The $\sigma$-cutoff suppresses the growth of the scalar field at supranuclear density, increases the pressure, and shifts the maximum mass, radii, and $\Lambda_{1.4}$ accordingly, while systematically raising the radial-mode frequencies at fixed mass. Using the sign change of $\omega_0^2$ as a stability criterion, we identify stiffened models that remain radially stable up to the observed $\sim 2M_\odot$ mass scale and are consistent with current multimessenger constraints, demonstrating how radial spectra complement static EoS tests.
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All authors G. Panotopoulos, A. Övgün, T. Iqbal, Y. Kumaran, B. K. Sharma
Cosmology and Nongalactic Astrophysics
Nearest Neighbour-Based Statistics for 21cm-Galaxy Cross-Correlations in the Epoch of Reionization
Anirban Chakraborty, Kwanit Gangopadhyay, Arka Banerjee et al. (+1 more)
21cm radiation from neutral hydrogen serves as a direct probe of the Epoch of Reionization. However, both its detection and physical interpretation are severely hindered by contamination from astrophysical foreground emission and instrumental noise that are several orders of magnitude brighter than the signal of interest. A promising way to tackle these challenges is to cross-correlate the 21cm signal with other independent tracers of large-scale structure, most notably high-
redshift galaxies. Besides validating putative 21cm detections, such joint analyses are expected to provide independent insights into the properties of ionizing sources and the evolving morphology of ionized regions during reionization. The 21cm signal, however, is intrinsically highly non-Gaussian, limiting the effectiveness of conventional two-point cross-correlation statistics, which capture information only up to the second order. In this work, we therefore investigate the utility of k-nearest-neighbour cumulative distribution functions (kNN CDF), which encode information from the joint clustering at all orders, as an alternative framework for probing 21cm-
galaxy cross-correlations. Using self-consistently simulated mock 21cm fields and a catalog of line-emitting
galaxies at z = 7, we conducted a proof-of-concept study comparing the kNN CDF formalism and the two-point cross-correlation approach. We find that the kNN CDF statistics outperform the two-point statistics in detecting 21cm-
galaxy cross-correlations, even in the presence of instrumental noise and aggressive foreground filtering. Moreover, at a fixed global ionized fraction, it is even able to differentiate between reionization models that remain indistinguishable using two-point statistics. These results demonstrate the power and unexplored potential of exploiting higher-order statistics for extracting maximal information from 21cm-
galaxy synergies.
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All authors Anirban Chakraborty, Kwanit Gangopadhyay, Arka Banerjee, Tirthankar Roy Choudhury
Astrophysics of Galaxies
WISDOM Project - XXVII. Giant molecular clouds of the lenticular galaxy NGC 1387: similarities with spiral galaxy clouds
Fu-Heng Liang, Martin Bureau, Lijie Liu et al. (+10 more)
Molecular gas is crucial to understanding
star formation and
galaxy evolution, but the
giant molecular clouds (GMCs) of early-type
galaxies (ETGs) have rarely been studied. Here, we present analyses of the spatially resolved GMCs of the lenticular
galaxy NGC 1387, exploiting high spatial resolution (0.15" or 14 pc) 12CO(2-1) line observations from the Atacama Large Millimeter/submillimeter Array. We identify 1285 individual GMCs and measure the fundamental properties (radius, velocity dispersion, and molecular gas mass) of each with a modified version of the CPROPStoo package. Unusually for an ETG, the GMCs of NGC 1387 follow scaling relations very similar to those of the Milky Way disc and Local Group
galaxy clouds, and most are virialised. GMCs with large masses and radii and/or small galactocentric distances have their angular momenta aligned with the large-scale
galactic rotation, while other GMCs do not. These results show that ETGs have more diversified GMC properties than previously thought. We discuss potential reasons for such diversity, and viewing-angle dependency is a plausible candidate.
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All authors Fu-Heng Liang, Martin Bureau, Lijie Liu, Pandora Dominiak, Woorak Choi, Timothy A. Davis, Jacob Elford, Jindra Gensior, Anan Lu, Ilaria Ruffa, Selcuk Topal, Thomas G. Williams, Hengyue Zhang
Solar and Stellar Astrophysics
Between Plateaus and Slopes: A Data-Driven Exploration of Spectral Diversity Across Type IIP/L Supernovae
Géza Csörnyei and Claudia P. Gutiérrez
Type II
supernovae (SNe II) have been traditionally separated into several subgroups based on their photometric and spectroscopic properties, but whether these represent distinct progenitors or a continuous distribution remains debated. Over the past decade, growing observational evidence has suggested a possible continuity between slow- (IIP) and fast-declining (IIL) SNe. We investigate the continuity of the SNe IIP/L subclasses through a data-driven statistical analysis of spectral time series, aiming to determine whether significant correlations exist between overall spectral shapes and light-curve decline rates. We introduce a novel standardization method for SN II spectra. After empirically flattening the spectra via continuum normalization, we interpolate the resulting "feature spectra" onto a fixed grid of epochs using Gaussian Process regression. The interpolated spectra are then analyzed using Principal Component Analysis to explore correlations. We find that SNe IIP and IIL form a continuum spectroscopically, though some clustering remains. The spectral diversity is characterized mainly by two components: one continuous group with well-defined P-Cygni profiles and another with "less-regular" features likely driven by enhanced circumstellar material (CSM) interaction. Our results reveal that the spectral diversity of SNe IIP/L diminishes over time. We confirm observational correlations: steeper light-curve declines correspond to weaker spectral features, indicating that SNe IIL tend to show weaker emission and, in some cases, a lack of distinct absorption lines. These trends seemingly break down by enhanced CSM interaction that affects the P-Cygni profiles. Our data-driven method reveals underlying spectral correlations and supports a continuous distribution between IIP and IIL subtypes. This method paves the way for more refined classification
algorithms.
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Instrumentation and Methods for Astrophysics
Deep Learning for Point Spread Function Modeling in Cosmology
Dayana Andrea Henao Arbeláez, Pierre-François Léget and Andrés Alejandro Plazas Malagón
We present the development of a data-driven, AI-based model of the Point Spread Function (PSF) that achieves higher accuracy than the current state-of-the-art approach, "PSF in the Full Field-of-View” (PIFF). PIFF is widely used in leading weak-
lensing surveys, including the Dark Energy Survey (DES), the Hyper Suprime-Cam (HSC) Survey, and the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). The PSF characterizes how a point source, such as a
star, is imaged after its light traverses the atmosphere and
telescope optics, effectively representing the "blurred fingerprint” of the entire imaging system. Accurate PSF modeling is essential for weak gravitational
lensing analyses, as biases in its estimation propagate directly into
cosmic shear measurements – one of the primary cosmological probes of the expansion history of the Universe and the growth of large-scale structure for dark energy studies. To address the limitations of PIFF, which constructs PSF models independently for each CCD and therefore loses spatial coherence across the focal plane, we introduce a deep-learning-based framework for PSF reconstruction. In this approach, an autoencoder is trained on
stellar images obtained with the Hyper Suprime-Cam (HSC) of the Subaru
Telescope and combined with a Gaussian process to interpolate the PSF across the
telescope's full field of view. This hybrid model captures systematic variations across the focal plane and achieves a reconstruction error of $3.4 \times 10^{-6}$ compared to PIFF's $3.7 \times 10^{-6}$, laying the foundation for integration into the LSST Science Pipelines.
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Instrumentation and Methods for Astrophysics
Slow focus sensor for the Keck I laser guide star adaptive optics system using focal plane wavefront sensing
Rafael M. Salgueiro, Carlos M. Correia, Benoit Neichel et al. (+7 more)
Laser guide
stars (LGSs) have been deployed for the last 20-30 years in ground-based astronomical
telescopes to overcome the limited sky coverage of classical adaptive optics (AO) systems. Unfortunately, slow altitude drifts of the sodium layer compromise focus measurements, generating the so-called slow focus error, and, consequently, a natural guide
star (NGS) is needed to compensate for that error. Our goal is to develop and operationalize a focal plane wavefront sensing (FPWFS) technique for slow focus tracking for the Keck I
telescope, which can significantly increase sky coverage and allow slow focus tracking at higher frequencies, reducing the lag error. We develop, characterize, and compare three different FPWFS
algorithms, namely Gerchberg-Saxton (GS), linearized focal plane technique (LiFT), and Gaussian fit (Gf). These
algorithms were studied for the specific purpose of slow focus sensing in the NIR (H and K bands) using numerical simulations and data collected at Keck in 2025 (bench and on-sky). The three
algorithms were studied and characterized against different criteria such as linearity, computational costs, and resistance to low signal-to-noise ratio and/or residuals. From the results obtained, the main candidate for an on-sky deployment was GS. On-sky tests showed promising results, with GS successfully compensating for purposely introduced focus errors, even under the presence of high
turbulence conditions. This work can also be extrapolated to other existing 8-10 m class
telescopes, or even future 30-40 m class
telescopes, where the use of FPWFS can significantly improve sky coverage and reduce the lag error.
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All authors Rafael M. Salgueiro, Carlos M. Correia, Benoit Neichel, Antonin Bouchez, Peter Wizinowich, Avinash Surendran, Max Service, Thierry Fusco, Cédric Taïssir, Pierre Jouve
Solar and Stellar Astrophysics
Impact of rotation on the amplitude of acoustic modes in solar-like stars: Insights from hydrodynamical simulations
Arthur Le Saux, Leïla Bessila and Stéphane Mathis
In
solar-like
stars, acoustic modes provide the main way of probing their internal structure and dynamics. Although these modes are expected to be ubiquitous in
stars with convective envelopes, Kepler observations reveal that a significant fraction of
solar-like
stars show no detectable acoustic modes, particularly among rapidly rotating and magnetically active
stars. Recent theoretical work has proposed that rotation tends to inhibit convective motions, thereby reducing the power available for
stochastic excitation of low degree acoustic modes. Here, we test this prediction using fully compressible hydrodynamical simulations of a
solar-like
star. We perform a series of 2.5D simulations, which consider longitudinal
symmetry, using the MUSIC code spanning rotation rates from 0 to 8 $\Omega_{\odot}$. We find a clear and systematic decline of acoustic mode amplitudes with increasing rotation rate. In the most rapidly rotating models, mode damping rates are also enhanced. The combined reduction in excitation and increase in damping with increasing rotation rate provide a physical explanation for the observed decrease in mode detectability in rapidly rotating
solar-like
stars. Our results demonstrate that rotation can significantly modify oscillation properties and must be accounted for when interpreting asteroseismic observations.
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Solar and Stellar Astrophysics
The Montreal Open Clusters and Associations (MOCA) Database: A Census of Nearby Associations, Open Clusters, and Young Substellar Objects within 500 pc of the Sun
Jonathan Gagné, Leslie Moranta, Jacqueline K. Faherty et al. (+10 more)
We present the Montreal Open Clusters and Associations database (MOCAdb), a public MySQL database with a Python interface. MOCAdb provides a census of memberships for 10259 associations and open clusters, with a comprehensive compilation of literature measurements such as spectral types, kinematics, rotation periods, activity indices, spectral indices, and photometry. All known substellar objects are cataloged in MOCAdb, along with 2943 public spectra, to enable the characterization of substellar association members. MOCAdb also features periodically updated calculations such as
Galactic UVW space velocities. We use this compilation to construct mappings between independent association definitions, and to update the BANYAN $\Sigma$ membership classification tool, which now includes 8125 associations. The BANYAN $\Sigma$ model construction is improved to account for heterogeneous and correlated errors and to capture complex association shapes using Gaussian mixture models. Combined with
Gaia DR3, this enabled us to identify 11535 yet unrecognized candidate members of young associations within 500 pc, mostly M
dwarfs. Our results corroborate a recent observation that systematics up to $\approx$4 km/s remain in
Gaia DR3 radial velocities for A-type
stars. We present an updated census of age-calibrated
exoplanets and substellar objects: 134 age-calibrated
exoplanet systems (plus 121 TESS
exoplanet candidates), 99 of which did not appear to have known memberships so far, and 455 substellar (L0 or later) candidate members of young associations, 196 of which appear newly recognized. We bring the total of candidate isolated planetary-mass objects to 101, 53 of which are newly recognized candidate members.
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All authors Jonathan Gagné, Leslie Moranta, Jacqueline K. Faherty, Jason Lee Curtis, Thomas P. Bickle, Dominic Couture, Amélie Chiasson David, Katie Christie, Samantha Lambier, Elise Leclerc, Livia Poliquin, Danika Belzile, Eric E. Mamajek
Solar and Stellar Astrophysics
Hot subdwarf stars from the Hamburg Quasar Survey
Ulrich Heber, Lennard Kufleitner, Matti Dorsch et al. (+4 more)
Hot subluminous
stars (sdO/B) are evolved low mass
stars originating from red
giants that lost their envelope almost entirely. The multitude of observed phenomena imply that several pathways may form hot subdwarfs, most involving close binary channels. The Hamburg
Quasar Survey (HQS) led to the discovery of many faint blue
stars including hot subdwarf. Many of the HQS-sdB
stars have been studied in detail, but analyses of the helium-rich sdOB and sdO
stars are lacking. The recent development of hybrid LTE/non-LTE model spectra 2nd generation Bamberg model grids enables us to improve the spectroscopic analyses of the sdB
stars as well as of the previously unstudied sdO
stars allowing precise atmospheric parameters to be derived, while consistently accounting for parameter correlations and systematic uncertainties. ... We use spectral energy distributions to identify composite-colour sdB binaries and present the result of detailed spectroscopic analyses of 122 non-composite subdwarfs from the HQS to identify potential evolutionary pathways. ...Their derived mass distribution and median mass of 0.45 Msun is consistent with the canonical EHB mass. ... The helium-rich sdOB and sdO
stars, are found near the helium main-sequence (He-MS). The derived mass distribution of the extremely He-rich subdwarfs is broader (0.48 to 1.05 Msun) and peaks at a median of 0.70 Msun, significantly larger than those of the hydrogen-rich
stars. Intermediate He-rich subdwarfs are also He-MS
stars, but of lower mass (0.55 Msun) than the extremely He-rich. This strongly supports the merger scenario for the origin of He-rich sdO
stars, in which two helium white
dwarfs merge following orbital decay driven by gravitational-wave emission, producing a He-rich sdO or sdOB
star. From comparison to the results of similar studies we speculate that older populations produce more massive He-WD mergers.(abbreviated)
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All authors Ulrich Heber, Lennard Kufleitner, Matti Dorsch, Marilyn Latour, Harry Dawson, Fabian Mattig, Stephan Geier
Cosmology and Nongalactic Astrophysics
Detecting the neutrino mass via the cross-correlation between matter tracers and the ISWRS effect?
Viviana Cuozzo, Marina Migliaccio, Matteo Calabrese et al. (+1 more)
This work explores the potential to detect the nonlinear Integrated Sachs Wolfe effect, namely the Rees-Sciama effect (ISWRS), by cross-correlating current and future
Cosmic Microwave Background (CMB) experiments – Simons Observatory, CMB-S4, CMB-HD, and PICO – with ongoing Large Scale Structure (LSS) surveys, such as Euclid and the Vera Rubin Observatory (LSST). We model the cross-correlation of the ISWRS effect with gravitational potential tracers like
galaxy clustering,
cosmic shear, and CMB-
lensing potential, to forecast results from these experiments. Our analysis also accounts for the presence of massive
neutrinos to assess the feasibility of identifying the $\nu$$\Lambda$CDM model and constraining the
neutrino mass sum, M$\nu$. Our findings indicate that the CMB-
lensing potential reconstructed by CMB-HD is expected to provide the most promising results, achieving $\gtrsim$ 5$\sigma$ detections even under conservative assumptions for detector noise and foregrounds, thereby allowing differentiation between $\nu$$\Lambda$CDM models.
Galaxy clustering can also yield significant detections, whereas
cosmic shear can provide valuable results only if non-linearities are accurately modelled, beyond the capabilities of currently available analytical approaches. These latter LSS probes do not provide strong constraining power on M$\nu$. While our findings suggest that future CMB experiments and LSS surveys will enable the detection of the ISWRS effect, they do not imply significant prospects for imposing new constraints on
neutrino masses in the near future.
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All authors Viviana Cuozzo, Marina Migliaccio, Matteo Calabrese, Carmelita Carbone
Solar and Stellar Astrophysics
Spectroscopic analysis and RHD modeling of the first Ca II H and H-epsilon flare spectra from DKIST/ViSP
Cole Tamburri, Adam Kowalski, Gianna Cauzzi et al. (+7 more)
We analyze decay phase observations of the GOES class C6.7
flare SOL2022-08-19T20:31 by the Visible Spectropolarimeter (ViSP) on the National Science Foundation's Daniel K. Inouye
Solar Telescope (DKIST). The data include the first
flare-time DKIST observations of the chromospheric Ca II H 396.8 nm and H-epsilon 397.0 nm spectral lines. These diagnostics have rarely been studied together during the modern era of high-resolution
solar flare observations, and never at the spectral and spatial resolution of the DKIST. We directly compare DKIST spectra to state-of-the-art RADYN+RH simulations, including one heated by a nonthermal electron beam and one by in-situ thermal conduction. While certain salient properties of the spectra such as the width of H-epsilon are reproduced, the models severely underestimate the width of Ca II H in the red wing and fail to reproduce the exact relative intensity of Ca II H to H-epsilon. The models exhibit a range of condensation electron densities spanning over an order of magnitude. Unlike the modeled lower-order Balmer-series lines, we find that the width of H-epsilon is not solely related to the condensation properties; the widths and intensities are also sensitive to the deeper
flare layers. We outline possible avenues towards improvement of
flare models, such as a comprehensive evaluation of
flare heating mechanisms in the context of both impulsive and decay phase high-resolution data.
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All authors Cole Tamburri, Adam Kowalski, Gianna Cauzzi, Maria Kazachenko, Alexandra Tritschler, Rahul Yadav, Ryan French, Yuta Notsu, Kevin Reardon, Isaiah Tristan
High Energy Astrophysical Phenomena
Bayesian parameter study of the Seyfert-starburst composite galaxies NGC 1068 and NGC 7469
Björn Eichmann, Silvia Salvatore, Santiago del Palacio et al. (+4 more)
Multimessenger observation of the Seyfert-starburst composite
galaxies NGC 1068 and NGC 7469 indicate a characteristic feature in the
radio band (the so-called mm-bump) as well as indication of high-energy
neutrinos by the AGN corona. Moreover, also the starburst ring of these sources is bright in the
radio and hence, a potential source of $\gamma$-rays and
neutrinos. We aim to explain the non-thermal features of these two sources with our homogeneous steady-state Seyfert-starburst composite model, which we refined in this work. Hereby, we account for
stochastic diffuse acceleration and energy losses within the corona and $\gamma\gamma$-pair attenuation of the escaping $\gamma$-rays. Since the non-thermal features of Seyfert sources contribute only marginally to the electromagnetic spectrum, only few data points can be assigned to the starburst ring or the AGN corona. Hence, prior information on the physical parameters is incorporated within a Markov Chain Monte Carlo approach to avoid overfitting. Based on this
Bayesian parameter study we show, that the non-thermal features of NGC 1068 can be explained well. Still a more detailed treatment of the spatial inhomogeneities in the central region of the AGN could further improve the fit results. This manifests itself even more clearly in the case of NGC 7469, where the mm-bump needs to emerge from a coronal size $R_{\rm c}>100\,\mathcal{R}_{\rm s}$, whereas (TeV-PeV)-
neutrino emission requires $R_{\rm c}< 10\,\mathcal{R}_{\rm s}$. Similar to what has previously been shown in other wavebands, our analysis highlights that the spatial extension of the so-called AGN corona depends the considered energy of the messenger. Hence, it seems that there is not a unique edge of the corona and a substantial progress in the understanding of these phenomena is expected if future analysis account for these spatial inhomogeneities.
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All authors Björn Eichmann, Silvia Salvatore, Santiago del Palacio, Giacomo Sommani, Crystal Mele, Patrik M. Veres, Julia Becker Tjus
Cosmology and Nongalactic Astrophysics
Searching for Axion-like particle Dark Matter with Time-domain Polarization: Constraints from a protoplanetary disk
Kanako Narita, Tomohiro Fujita, Ryo Tazaki et al. (+1 more)
Axion-like particles (ALPs) can induce a birefringence effect that rotates the polarization angle of light, offering a probe of ultralight dark matter. We analyze archival near-infrared polarimetric data of the protoplanetary disk (PPD) around HD 163296. Whereas previous studies considered only single-epoch snapshots, we perform a consistent multi-epoch time-series analysis, extracting the polarization angle and its uncertainty from the polarized images. The resulting six-epoch time series is consistent with a constant polarization angle within the measurement uncertainties, while being sensitive to timescales of $\sim 170-400$ days. The typical polarization angle uncertainties are $1.6$–$6.4$ degrees, partly driven by multiple scattering in the optically thick disk, which broadens the intrinsic polarization angle distribution and introduces additional dispersion in the representative polarization angle. Based on these data, we derive the first upper limits on the ALP-
photon coupling from PPD polarization variability, $g_{a\gamma} \lesssim 7.5 \times 10^{-12} (m_a / 10^{-22}\,{\rm eV})\,{\rm GeV}^{-1}$. Furthermore, we forecast that achieving a polarization angle uncertainty of $\sigma \sim 0.1$ degrees would enable world-leading sensitivity to ALP-induced birefringence.
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All authors Kanako Narita, Tomohiro Fujita, Ryo Tazaki, Bunyo Hatsukade
Cosmology and Nongalactic Astrophysics
Fast computation of temperature and polarization coupling matrices
Georgia Kiddier and Steven Gratton
We present a fast and exact method for computing CMB mode-coupling
matrices based on an optimised evaluation of Wigner-3j symbols. The method exploits analytic structure in the relevant Wigner-3j symbol configurations appearing in temperature and polarization coupling
matrices, expressing all required quantities in terms of a small set of recurrence-generated values which are precomputed and stored in lookup tables. This approach reduces the computational cost of constructing the full coupling
matrices whilst maintaining numerical accuracy. We demonstrate the performance of the threej_cosmo implementation using realistic survey masks from current CMB experiments. Relative to standard recursion-based approaches used in existing pseudo-C_l pipelines, the method achieves speedups of 6-25x in practical coupling-
matrix constructions, with the largest gains occurring at high multipoles. The
algorithm admits efficient parallelisation on both CPUs and GPUs, the latter providing additional acceleration, up to a further order of 50 on modern hardware, without altering the underlying formalism. Beyond full
matrix construction, the approach is naturally suited to applications in which only a restricted set of l3 modes is required for each (l1,l2) pair, such as in the computation of band-limited coupling
matrices and analytic covariance terms. These features make threej_cosmo a practical backend for pseudo-C_l estimation and related calculations in next-generation CMB analysis pipelines.
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Astrophysics of Galaxies
Aligned and misaligned metallicity gradients in young stars and star-forming regions in the EAGLE discs
Isha Shailesh, Patricia B. Tissera and Emanuel Sillero
Disc
galaxies exhibit radial
metallicity gradients in both their
stellar and gaseous components. The
star-forming gas (SFG) in HII regions and young
stars (YSs) trace the recent evolutionary history of the
galaxy. We aim to assess the extent to which the joint analysis of
metallicity gradient
alignment in YSs and SFG can constrain the recent evolutionary history of
galaxies. Using the high-resolution run of the EAGLE project, we derived radial, azimuthally averaged oxygen abundance profiles for YSs (age < 2 Gyr) and SFG and measured their gradients as the slopes of linear fits to these profiles. We classified
galaxies into four groups based on the signs (N for negative and P for positive) of the slopes: NN, NP, PP, and PN (the first letter is for YSs and the second for SFG). We found that
galaxies with NN, NP, PP, and PN combinations of
metallicity profiles reflect different evolutionary paths over the past ~ 2 Gyr. NN
galaxies exhibit sustained inside-out growth accompanied by high
star formation efficiency, whereas NP and PP systems show evidence of recent or ongoing feedback-driven disruption, with PP
galaxies likely being predominantly shaped by
supernova feedback. PN
galaxies, by contrast, show evidence of past violent events followed by gradient recovery, highlighting the interplay between inflows, feedback, and gas cooling in shaping
metallicity distributions. The degree of
alignment between the
stellar and gas
metallicity gradients provides a way to time the occurrence of significant events in the evolutionary history of
galaxies, which contribute through a combination of gas inflows,
star formation triggering, and metal mixing. They could also serve as probes of sub-grid physics when observations provide suitable comparison
datasets. [Abridged]
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Solar and Stellar Astrophysics
Morphological variations of solar granules in the presence of magnetic fields
J. I. Campos Rozo, J. Jurčák, S. M. Díaz Castillo et al. (+1 more)
Solar granulation consists of dynamic convective
plasma cells that rise from the
solar interior to the surface. The interaction between these
plasma cells and the Sun's
magnetic field provides valuable insights into
plasma dynamics near the
solar surface and how they evolve in the presence of
magnetic fields. This study analyses the morphological characteristics of
solar convective
cells, investigating the relationship between
magnetic field properties and granule dynamics - specifically how granule area, shape, and brightness vary under different
magnetic field conditions. Observations of the active region NOAA 11768 were taken with the Swedish 1-m
Solar Telescope (SST). A
segmentation algorithm was applied to continuum intensity images to identify individual granules and determine their sizes, shapes, and mean brightness. The
magnetic field vector and line-of-sight velocity were derived from CRISP spectropolarimetric data to investigate their role in shaping granule properties. We find that granular area decreases systematically with increasing
magnetic field strength, with the largest granules occurring in non-
magnetic regions and a mean granule area of approximately 1.58 arcsec$^2$ (effective diameter of 1.42 arcseconds). Both mean continuum intensity and granule size decrease with stronger fields, confirming the suppression of convective energy transport in magnetised regions. No correlation was found between mean granule brightness and mean up-flow velocity. Highly elongated granules appear in both
magnetic and non-
magnetic regions, while near-circular granules are exclusive to non-
magnetic areas. An
alignment between granule major axes and
magnetic field azimuth is observed where the horizontal field component is strong, confirming that granules are highly sensitive to
magnetic fields, which inhibit the lateral expansion of convective
cells.
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All authors J. I. Campos Rozo, J. Jurčák, S. M. Díaz Castillo, M. van Noort
Earth and Planetary Astrophysics
Dust measurements with the Mars Dust Counter on board Nozomi (PLANET-B)
Harald Krüger, Masanori Kobayashi, Hiroshi Kimura et al. (+3 more)
Nozomi was Japan's first space mission to Mars, launched on 3 July 1998 UT. It was equipped with the Mars
Dust Counter (MDC) which was an impact ionisation
dust detector. MDC detected 96
dust particle impacts when the spacecraft was in Earth orbit and later in interplanetary space, before its operation ended in April 2002 due to a technical failure on board. We compare the Nozomi
dust measurements with the
dust measurements obtained with the
dust detector on board the Ulysses spacecraft. Impact speeds and masses of
dust particles measured by Nozomi MDC are overall consistent with the measurements obtained by Ulysses in the same region of interplanetary space. Based on the impact speeds measured while Nozomi was in Earth orbit, MDC detected neither
dust particles of natural origin that were bound to the Earth nor space debris. The
dust impact rate measured in interplanetary space varied by approximately a factor of 2, consistent with theoretical predictions by the Interplanetary Meteoroid Engineering Model. The particle impact direction was concentrated towards the ecliptic plane, in agreement with an interplanetary origin of the majority of the measured
dust particles. No impacts of cometary trail particles could positively be identified during known cometary trail crossings of Nozomi. The Nozomi
dust data may become a valuable reference for the
dust measurements to be obtained in the same region of interplanetary space with future space missions like, for example, MMX and DESTINY$^+$.
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All authors Harald Krüger, Masanori Kobayashi, Hiroshi Kimura, Tomoko Arai, Hakan Svedhem, Sho Sasaki
Solar and Stellar Astrophysics
Inference of horizontal velocity fields from the induction equation in the solar atmosphere. I. Analytical and numerical solutions in 2D
H. Vila Crespo, J.M. Borrero, I. Milić et al. (+2 more)
Spectroscopic and spectropolarimetric observations, which rely on the Doppler effect, only provide access to the line-of-sight component of the
solar plasma velocity (vz). However, many dynamic processes in the
solar atmosphere involve strong horizontal motions (in the plane perpendicular to the line-of-sight: vx, vy). Existing methods for estimating horizontal velocities are generally insensitive to variations in height (the z-coordinate), providing them only on a single plane perpendicular to the line-of-sight: vx(x,y), vy(x,y). Motivated by the fact that modern analysis techniques allow us to retrieve the height dependence of vz and B, our goal is to infer also this height dependence for the horizontal velocity field in the
solar atmosphere. As a first step, we present, and test a method for the two-dimensional case on the (y,z) plane so as to show that the z dependence can be successfully retrieved. The components of the two-dimensional
magnetic induction equation are discretized via finite differences, leading to an overdetermined system whose solution provides vy. The method assumes that B, its time variation, as well as vz are known. This is currently possible through modern Stokes inversion techniques applied to spatially and temporally resolved spectropolarimetric observations. Using analytically prescribed values and two-dimensional magneto-hydrodynamic simulations of the
solar surface, we demonstrate that, in these idealized cases, the horizontal velocity component in a two-dimensional domain, can be successfully recovered with a mean error of about 1 %. The proposed method successfully retrieves the horizontal velocity field in the (y,z) plane, thereby establishing the foundation for future extensions to three-dimensional reconstructions of the horizontal velocity field.
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All authors H. Vila Crespo, J.M. Borrero, I. Milić, G. Vigeesh, A. Asensio Ramos
Astrophysics of Galaxies
Bridging Scales in Black Hole Accretion and Feedback: Subgrid Prescription from First Principles
Hyerin Cho, Ben S. Prather, Ramesh Narayan et al. (+4 more)
Understanding how supermassive black holes (BHs) couple to their host
galaxies across a vast spatial and temporal dynamic range remains a central challenge in
galaxy evolution. Using the multizone framework – designed to capture bidirectional inflow–
outflow from the event horizon to the Bondi scale – we present a suite of long-duration GRMHD simulations spanning BH
spins $|a_\ast|=0$–0.9 and Bondi radii $R_B/r_g=4\times10^2$–$2\times10^6$. From these simulations we derive
spin-dependent subgrid prescriptions from first principles, applicable to hot
accretion flows with low-Eddington ratios ($f_{\rm Edd}\lesssim10^{-3}$), for adoption in cosmological simulations and semi-analytic models. We provide compact analytic fits for the time-averaged
accretion rate $\dot M(R_B,a_\ast)$ and feedback power $\dot E_{\rm fb}(R_B,a_\ast)$ with respect to the Bondi rate $\dot{M}_B$, which are largely insensitive to the initial gas configuration and
magnetic field strength. To capture intrinsic time-variability, we also quantify the full distributions of $\dot M$ and feedback efficiency $\eta$, both well described by lognormal statistics, with widths that increase toward larger $R_B$. We further measure self-consistent
spin evolution in the hot
accretion mode, finding that the
spin-up parameter varies as $s(a_\ast)\simeq -3.7\,a_\ast$, which implies a very long spindown timescale $t_s\simeq 12(10^{-3}/f_{\rm Edd})\,{\rm Gyr}$. Thus, BH
spins are effectively frozen during phases of quiescent
accretion. Compared to conventional small-domain GRMHD calculations, our simulations, which reach dynamical
equilibrium across horizon-to-
galaxy scales, yield systematically different long-term
accretion, feedback, and
spin properties, cautioning against direct extrapolation from small-scale GRMHD simulations when constructing
galactic-scale subgrid models.
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All authors Hyerin Cho, Ben S. Prather, Ramesh Narayan, Kung-Yi Su, Angelo Ricarte, Priyamvada Natarajan, Antonio J. Porras-Valverde
Cosmology and Nongalactic Astrophysics
An observational test of the plasma lensing effect using QSOs with and without MgII absorption
Xinzhong Er, Yiping Shu and Chenxu Liu
Radio wave propagation can be perturbed by compact ionized gas clumps through
plasma lensing, which induces frequency dependent magnification and may distort the observed number counts of background sources. The
quasar (QSO) number densities are a powerful probe for understanding the effects of intervening material. Absorption lines in QSO spectra reveal the presence of interstellar and intergalactic gas, which can change observed fluxes through
dust extinction and
plasma lensing. By combining observations from
radio (VLASS), infrared (WISE), and optical bands (DESI), we assembled a sample of QSOs: ~4000 sources with MgII absorbers, and ~12, 000 non-absorbers. In the
radio band, the MgII sample shows a moderate excess at the bright end of the flux distribution, which is broadly consistent with
plasma lensing predications. In the optical, the MgII sample turns over at higher g-band fluxes and exhibits a steeper decline at the faint end than the non-MgII sample. Control samples were constructed by matching in
redshift, infrared (W1), and optical (g) luminosities. In these comparisons, the
radio excess becomes less prominent, suggesting that the apparent magnification may not be robust evidence for
plasma lensing. Nevertheless, a weak contribution cannot be ruled out, especially given residual excess observed at the bright end relative to the non-MgII sample.
Dust extinction along the line-of-sight remains a plausible alternative. Regardless of the dominant mechanism, the multi-wavelength differences offer a valuable probe of the physical state of the intervening medium.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Some phenomenological aspects of a quantum-corrected Reissner-Nordström black hole: quasi-periodic oscillations, scalar perturbations and thermal fluctuations
Faizuddin Ahmed, Ahmad Al-Badawi and Mohsen Fathi
In this work, we investigate several phenomenological aspects of a covariant
quantum-corrected Reissner-Nordström black hole characterized by the mass $M$, electric charge $Q$, and the
quantum correction parameter $\zeta$. We first study the motion of neutral test particles and derive the fundamental orbital and epicyclic frequencies, which are then employed to analyze different quasi-periodic oscillation (QPO) models. Using observational QPO data from
stellar-mass, intermediate-mass, and supermassive black hole candidates, we perform a
Bayesian parameter estimation through a Markov Chain Monte Carlo (MCMC) analysis and obtain constraints on the black hole parameters. The results show that the presence of the
quantum correction significantly affects the location of the QPO radii and the separation between the QPO orbit and the ISCO. We then examine the scalar perturbations by deriving the Schrödinger-like radial equation and the corresponding effective potential. The influence of the parameters $Q$ and $\zeta$ on the perturbation potential and stability of the spacetime is discussed. Furthermore, we compute the greybody factor and the energy emission rate in the high-frequency (
geometric-optics) regime, showing how the
quantum correction modifies the absorption probability and radiation spectrum. Finally, we study the effect of thermal fluctuations on the black hole
entropy and obtain the logarithmic corrections to the Bekenstein-Hawking area law. We show that these corrections become important for small black holes, while for large horizon radius the standard thermodynamic behavior is recovered. Our analysis demonstrates that the
quantum correction parameter leaves observable imprints on both dynamical and thermodynamical properties of the spacetime and can be constrained through QPO observations.
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Solar and Stellar Astrophysics
A homogeneous view of asymptotic giant branch carbon stars as seen by Gaia
Alessio Liberatori, Despina Hatzidimitriou, Konstantinos Antoniadis et al. (+12 more)
Carbon
stars on the asymptotic
giant branch are major contributors to
galactic dust enrichment, with gas mass-loss rates up to 1e-4 Msun/yr. We present a homogeneous spectral energy distribution analysis of the
Gaia DR3 Golden Sample of carbon
stars in the Milky Way and Magellanic Clouds. Our
dataset includes 14,747 sources with multi-band photometry from
Gaia, 2MASS, and WISE, combined with recent distance and extinction estimates. For a subsample of 2,494 Mira variables, we model multi-band light curves to derive accurate mean magnitudes.
Stellar and circumstellar parameters are obtained by fitting observations with a large grid of synthetic spectra computed with the DUSTY radiative transfer code using COMARCS atmospheres. We derive effective temperature, optical depth, and gas mass-loss rate for each source. The distributions peak around Teff = 3150 K, with mass-loss rates spanning 1e-11 to 1e-4 Msun/yr and inner
dust temperatures near 1000 K. We find a correlation between variability amplitude and mass-loss rate. This framework provides a statistically robust view of carbon
stars across environments with different
metallicities. Apparent environmental dependencies are influenced by luminosity distributions and selection effects rather than purely intrinsic
metallicity differences. The combined
Gaia and WISE selection limits the detection of both highly obscured and faint Magellanic Cloud sources, but the observed trends remain significant within the sampled populations.
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All authors Alessio Liberatori, Despina Hatzidimitriou, Konstantinos Antoniadis, Giada Pastorelli, Michele Trabucchi, M.A.T. Groenewegen, Diego Bossini, Leo Girardi, Paola Marigo, Alessandro Bressan, Ioannis N. Kallimanis, Guglielmo Costa, Vasileios Katsis, Georgios Vasilopoulos, Stamatis Chatzipetros
Cosmology and Nongalactic Astrophysics
Cosmic topology. Part IIc. Detectability with non-standard primordial power spectrum
Joline Noltmann, Andrius Tamosiunas, Deyan P. Mihaylov et al. (+13 more)
Non-trivial spatial
topology of the Universe can imprint potentially observable signatures on the
cosmic microwave background (CMB). In this study, we investigate how deviations from the standard nearly-scale-free
primordial power spectrum impact observables for the fully compact, orientable Euclidean
topologies ($E_1$–$E_6$). We examine how such deviations modify the detectability of the underlying
topology, depending on whether they are an intrinsic consequence of non-trivial
topology or independent of it. We compute CMB temperature correlation
matrices across a range of
topologies, fundamental domain sizes, and observer locations for both standard and modified
primordial power spectra. The impact of these modifications on the detectability of
topology is quantified using the Kullback-Leibler divergence, providing an estimate of the distinguishability of non-trivial and simply-connected
topologies based solely on CMB temperature observations. In addition, we employ the CatBoost machine learning
algorithm to classify harmonic-space realizations of CMB temperature maps and thereby assess the observational prospects for
topology detection. Signatures of non-trivial
topology are encoded in the off-diagonal structure of the CMB temperature correlation
matrices and are most prominent on the largest angular scales. Deviations from the simple power-law
primordial spectrum at these scales can substantially alter the detectability of
topology, either enhancing its characteristic CMB imprints or suppressing them below observational sensitivity. Our results demonstrate that uncertainties in the
primordial power spectrum must be carefully accounted for in robust searches for
cosmic topology using the CMB.
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All authors Joline Noltmann, Andrius Tamosiunas, Deyan P. Mihaylov, Yashar Akrami, Javier Carrón Duque, Thiago S. Pereira, Glenn D. Starkman, George Alestas, Stefano Anselmi, Craig J. Copi, Fernando Cornet-Gomez, Andrew H. Jaffe, Arthur Kosowsky, Mikel Martin Barandiaran, Anna Negro, Amirhossein Samandar
Earth and Planetary Astrophysics
Upper atmosphere dynamics and drivers of volatiles loss from terrestrial-type (exo)planets
Daria Kubyshkina, Michael J. Way, Iannis Dandouras et al. (+7 more)
Volatile loss from exoplanetary atmospheres and its possible implications for the longevity of habitable surface conditions is a topic of vigorous debate currently. The vast majority of the habitable zone terrestrial-like
exoplanets known to date orbit low-mass M- and K-
dwarf stars and are subject to the conditions drastically different to those of terrestrial
planets in the
Solar System. In particular, they orbit far closer to their host
stars than similar
planets around G-
dwarfs similar to the Sun. Therefore they receive higher X-ray and UV fluxes, even though luminosities of M- and K-
dwarfs are lower than those of heavier
stars. Furthermore, due to their slower
evolution, M-
dwarfs retain high activity on the gigayear timescales. The combination of these two effects has led to claims that most terrestrial
planets orbiting M-
dwarfs may have their atmospheres stripped from the higher X-ray and UV fluxes of their host
stars. Opposing this are researchers who point out that volatile inventories for terrestrial
exoplanets are ill-constrained, and hence, they may be able to "weather the storm" of these higher X-ray and UV fluxes. In this chapter, we focus on exploring volatile loss in the upper atmospheres of terrestrial
planets in our
solar system and applications to those in exoplanetary systems around
stars of different types.
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All authors Daria Kubyshkina, Michael J. Way, Iannis Dandouras, Helmut Lammer, Antonino Francesco Lanza, Manasvi Lingam, Rumi Nakamura, Moa Persson, Manuel Scherf, Kanako Seki
Earth and Planetary Astrophysics
Precise measurement of WASP-31 b's Rossiter-McLaughlin effect and characterization of the planet transmission spectra
M. Steiner, V. Bourrier, D. Ehrenreich et al. (+23 more)
Context. Hot Jupiters are ideal natural laboratories to investigate atmospheric composition and dynamics. However, high-resolution transmission spectroscopy is currently limited by our capability of removing
planet-occulted line-distortion (POLD) contamination from the signal. Aims. In this paper, we aim to characterize the transmission spectrum of WASP-31 b from two and a half transits observed with the ESPRESSO spectrograph at the VLT. Methods. The Rossiter-McLaughlin (RM) signature was analyzed using the RM "revolutions" method. Before extracting the transmission spectrum of the
planet, we corrected the
dataset for telluric lines using molecfit and further modeled the POLD deformations using EvE. Results. We confirm the
planet low sky-projected
spin-orbit angle from previous studies and further refine its value to $\lambda = -0.09^{+0.31}_{-0.32}$ deg. We do not detect any species (including previously detected species such as K or CrH) in the planetary atmosphere. In most cases the non-detections are due to the strong POLDs contamination or lack of observable lines in the ESPRESSO wavelength range, and so previous detections cannot be ruled out. Conclusions.
Planet-occulted line-distortion contamination continues to be the main limitation of high-resolution transmission spectroscopy for species present in both the
star and the
planet, hindering atmospheric detections even with state-of-the-art models, in particular for
planets with a low sky-projected
spin-orbit angle. Developing advanced techniques to isolate planetary signatures is of utmost importance in the advent of ELT-like observations.
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All authors M. Steiner, V. Bourrier, D. Ehrenreich, W. Dethier, H. Chakraborty, S. Pelletier, M. Lendl, B. Akinsanmi, R. Allart, J. M. Almenara, S. Cristiani, J. I. González Hernández, P. D. Marcantonio, C. J. A. P. Martins, L. Mishra, D. Mounzer, M. R. Zapatero Osorio, E. Palle, F. Pepe, A. Psaridi, N. C. Santos, J. V. Seidel, A. Sozzetti, V. Vaulato, G. Viviani, J. Yu
Cosmology and Nongalactic Astrophysics
Scaling solutions in three-form cosmology
Vitor da Fonseca, Bruno J. Barros, Tiago Barreiro et al. (+1 more)
A hybrid three-form model of dark energy is developed in order to identify scaling solutions, a long-sought feature in three-form cosmology. Exploiting Hodge dualities, the theory is formulated in terms of two scalar functions that are associated with the conjugate momentum, and the three-form dual vector in an isotropic background. The resulting Lagrangian yields a stable scaling attractor where the three-form energy density tracks the dominant background fluid. A dynamical mechanism is also identified that naturally drives the system out of this regime toward a late-time accelerated phase distinguishable from a cosmological constant. This constitutes the first realization of scaling behavior within a three-form dark energy framework.
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All authors Vitor da Fonseca, Bruno J. Barros, Tiago Barreiro, Nelson J. Nunes
Solar and Stellar Astrophysics
Coronal Non-Thermal and Doppler Plasma Flows Driven by Photospheric Flux in 28 Active Regions
James McKevitt, Sarah Matthews, Deborah Baker et al. (+5 more)
Magnetohydrodynamic (MHD) waves and/or the braiding of
magnetic field lines are largely thought to be responsible for heating the
solar corona, both being mechanisms which are driven by the Sun's photospheric
magnetic field. Recent modelling work leads us to expect that such heating mechanisms would be seen in the excess broadening (non-thermal velocity) of coronal spectral emission lines and that larger magnitudes of photospheric
magnetic flux would generate more heating, but a direct connection between
magnetic flux and spectral line broadening has been difficult to establish. We combine measurements of the photospheric
magnetic field from SDO/HMI and non-thermal velocity in log T~6.2 coronal
plasma from Hinode/EIS for 28 active regions and find a moderate correlation between the two exists in quiescent active regions, consistent with the photospheric field injecting upward Poynting flux into the
solar corona and causing coronal heating. We find that no strong correlation with coronal composition makes it difficult to distinguish between MHD wave heating and
magnetic field braiding heating using these diagnostics with current instrumentation.
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All authors James McKevitt, Sarah Matthews, Deborah Baker, Hamish A. S. Reid, David H. Brooks, Ignacio Ugarte-Urra, Peter R. Young, Teodora Mihailescu
Cosmology and Nongalactic Astrophysics
A Quantum Genetic Algorithm with application to Cosmological Parameters Estimation
Giuseppe Sarracino, Vincenzo Fabrizio Cardone, Roberto Scaramella et al. (+14 more)
An Amplitude-Encoded
Quantum Genetic
Algorithm (AEQGA) has been developed to minimize $\chi^2$ functions of different cosmological probes (
Supernovae Type Ia,
Baryon Acoustic Oscillations,
Cosmic Microwave Background Radiation), to find the best-fit value for two cosmological parameters, namely the Hubble Constant and the density matter content of the Universe today. Our main aim is to pave the way to testing the adoption of
quantum optimization in the inference of the cosmological parameters that describe the universe
evolution. AEQGA computes the merit function classically, and then uses a
quantum circuit to entangle the population and perform crossover and mutation operations. The results show consistency with the isocontours of the objective functions. We then tested the general behavior of AEQGA as a function of its hyperparameters and compared it with a second
quantum genetic
algorithm found in the literature as well as with classical
algorithms, finding consistent results.
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All authors Giuseppe Sarracino, Vincenzo Fabrizio Cardone, Roberto Scaramella, Giuseppe Riccio, Andrea Bulgarelli, Carlo Burigana, Luca Cappelli, Stefano Cavuoti, Farida Farsian, Irene Graziotti, Massimo Meneghetti, Giuseppe Murante, Niccolò Parmiggiani, Alessandro Rizzo, Francesco Schillirò, Vincenzo Testa, Tiziana Trombetti