Solar and Stellar Astrophysics
Unlocking HST's Stellar Treasure Trove: Stellar Activity Minima for HAT-P-11 Offer Prime Windows for Transmission Spectroscopy
Prajwal Niraula, Benjamin V. Rackham, Julien de Wit et al. (+4 more)
HAT-P-11 is a well-studied, active K
dwarf hosting an eccentric, misaligned transiting sub-Neptune. As part of the HST
Stellar Treasure Trove program (HST-AR-17551), we analyze absolutely calibrated out-of-transit \HST{} spectra from STIS and WFC3 across the G430L, G750L, G102, and G141 bandpasses to constrain the surface heterogeneity of HAT-P-11 and its impact on transmission spectroscopy. Grid-based spectral
retrievals using NewEra PHOENIX models robustly favor two-component photospheres in the WFC3 G102 and G141 data, with a ${\sim}4950$\,K photospheric component and a cooler ($\sim$3400\,K) component covering 26{–}33% of the
stellar disk. By contrast,
retrievals on the STIS optical spectra do not yield a satisfactory fit, reflecting current limitations of
stellar atmosphere models in the optical regime compared to the \HST{} observational precision. We contextualize these results using long-term photometric monitoring and chromospheric activity indices. The inferred high spot covering fractions are broadly consistent with the elevated photometric variability observed during the Kepler era ($f_{\rm spot}$$\sim$10–20%) but are in tension with the much lower rotational amplitudes observed from TESS in the mid 2020s ($f_{\rm spot}$$\sim$1–10%). This secular decline in variability is mirrored by a $\sim$20% decrease in the Ca\,ii H&K index. These results imply that HAT-P-11 undergoes comparatively quiescent phases that offer more favorable windows for atmospheric characterization, which serendipitously coincided with some of the recent JWST observations. More generally, our study demonstrates that multi-epoch, space-based
stellar spectra provides a physically grounded pathway for mitigating
stellar contamination in high-precision transmission spectra in the JWST era.
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All authors Prajwal Niraula, Benjamin V. Rackham, Julien de Wit, Daniel Apai, Mark S. Giampapa, David Berardo, Chia-Lung Lin
Cosmology and Nongalactic Astrophysics
From friction scaling to an efficient method for estimating bubble wall velocity
Tomasz Krajewski, Marek Lewicki, Marco Merchand et al. (+2 more)
We present a unified description of first-order cosmological phase transition dynamics that links the phenomenological friction model employed in hydrodynamic simulations to the microscopic treatment based on Boltzmann equations. We derive an approximate analytical expression for the chemical potential and demonstrate that the resulting friction parameter $\tilde{\eta}$ follows a simple power-law dependence on the transition strength ($\propto v_n^4/T_n^4$). Incorporating this scaling into a phenomenological framework accurately reproduces the terminal wall velocities obtained from the full microscopic analysis performed using WallGo. This approach offers an efficient method to quantify out-of-
equilibrium contributions to friction and reliably estimate bubble-wall velocities.
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All authors Tomasz Krajewski, Marek Lewicki, Marco Merchand, Ignacy Nałęcz, Mateusz Zych
Cosmology and Nongalactic Astrophysics
Dynamical Systems in Cosmology: Reviewing An Alternative Approach
Nandan Roy and L. Arturo Ureña-López
Dark energy is one of the deepest puzzles in modern cosmology, and mounting evidence suggests that it is not just a cosmological constant but a genuinely dynamical component. Although cosmology and dynamical systems theory emerged from different disciplines, dynamical systems methods have become essential tools to uncover the qualitative
evolution of the universe. The equations governing homogeneous and isotropic cosmologies can be naturally written as systems of ordinary differential equations, making them an ideal arena for dynamical system analysis. This review begins with a sharp, streamlined introduction to the standard dynamical systems toolkit widely used in cosmology. We then move on to alternative formulations based on polar and
hyperbolic variable transformations. These approaches unlock powerful new ways to probe a broad spectrum of scalar field dark energy models, to set and constrain initial conditions, and to analyze tracking behavior across wide classes of potentials. The review is self-contained, but consistently directs the reader to more specialized and in-depth treatments where needed.
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High Energy Astrophysical Phenomena
Multi-mission Investigation of X-ray Superorbital Modulation in the Supergiant High Mass X-ray Binary 4U 1538-52
H. I. Cohen, N. Islam, R. H. D. Corbet et al. (+7 more)
Superorbital modulations has been detected in the supergiant High-Mass X-ray binary 4U 1538-52 using long-term monitoring with the Neil Gehrels Swift Observatory Burst Alert
Telescope (BAT). The source also exhibits a long-term pulse period
evolution as seen with Rossi X-ray Timing Explorer (RXTE), INTEGRAL, and
Fermi Gamma-Ray Burst Monitor (GBM) that appears uncorrelated with changes in its X-ray flux. To investigate the mechanisms causing these superorbital modulations and its possible dependence on pulse period changes, we analyzed long-term monitoring with Swift-BAT and Monitor of All Sky X-ray Image Gas Slit Camera (MAXI-GSC) to construct dynamic power spectra and superorbital intensity profiles. In addition, we used pointed X-ray observations from
Nuclear Spectroscopic
Telescope Array (NuSTAR) and
Neutron Star Interior Composition Explorer mission (NICER) to investigate the pulsation and spectral properties across different superorbital and orbital phase intervals. We find the presence of superorbital modulations in the MAXI-GSC 2-20 keV lightcurves, consistent with the periodicity observed with the Swift-BAT lightcurves. However, no significant changes are detected in the pulse profiles or spectral parameters across different superorbital, orbital, or pulse-change intervals. This lack of spectral or timing variations with orbital and superorbital phases suggests that the mechanisms driving the observed superorbital modulation and pulse period changes are likely associated with large-scale
stellar wind structures, such as Co-Rotating Interaction regions, within the
stellar wind of the supergiant companion.
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All authors H. I. Cohen, N. Islam, R. H. D. Corbet, A. Lange, K. Pottschmidt, E. Bozzo, P. Romano, R. Ballhausen, C. Malacaria, J. B. Coley
Cosmology and Nongalactic Astrophysics
Probing Interacting Dark Sectors with upcoming Post-Reionization and Galaxy Surveys
Rahul Shah, Antara Dey, Purba Mukherjee et al. (+1 more)
We investigate the constraining power of future post-reionization and
galaxy surveys on possible interactions between dynamical dark energy and dark matter. The analysis focuses on the interaction strength and the dark energy equation of state parameters, in addition to the six standard cosmological parameters. Using fiducial values obtained from the current observational bounds (Planck 2018 + DESI DR2 + Pantheon+), mock
datasets for upcoming 21-cm intensity mapping,
galaxy clustering and
cosmic shear observations from the SKA-mid, and for the upcoming large-scale survey from the Euclid mission, were generated. Subsequently, Markov chain Monte Carlo analyses combining current cosmological data with these mock
datasets were performed to forecast parameter constraints. The results indicate that both SKA-mid and Euclid observations can significantly improve constraints on interacting dark sector parameters. In particular, the interaction strength and dark energy equation of state parameters can be constrained considerably tighter than current combined constraints from Planck 2018, DESI DR2 and Pantheon+. Comparing different probe combinations and survey configurations, it is found that SKA2 provides the tightest projected constraints, particularly on the interaction strength, while Euclid achieves a precision broadly comparable to that of SKA1. The results highlight the potential of these upcoming surveys to probe interactions within the dark sector.
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All authors Rahul Shah, Antara Dey, Purba Mukherjee, Supratik Pal
Astrophysics of Galaxies
Massive star clusters detected by JWST as natural birth places to form intermediate-mass black holes
Dominik R.G. Schleicher, Matías Liempi, Mirek Giersz et al. (+11 more)
The James Webb Space
Telescope (JWST) has detected, through gravitational
lensing, several young massive
star clusters (YMCs), which are considered as relevant building blocks of high
redshift galaxies. In this work, we show how a significant fraction of these YMCs could act as relevant birth places for intermediate-mass black holes. We first consider the formation of massive clusters and show that the population of YMCs is consistent with a steep mass-radius relation, which includes a relevant spread of roughly an order of magnitude. We pursue a comparison of this population with young
star clusters in the local Universe and Milky Way globular clusters, including an analysis of the characteristic timescales. The YMCs show a wide spread over these properties, but include systems with both short relaxation times as well as relatively short collision timescales, implying they could go through efficient core collapse, which would lead to runaway collisions. We provide quantitative estimates of the sizes of the clusters that could efficiently form intermediate-mass black holes through a runaway collision-based channel, suggesting that these roughly correspond to the systems beyond the $1\sigma$ scatter in the mass-radius relation. This implies a fraction of ~16% of YMCs as candidates to form intermediate-mass black holes. We show that above a mass limit of ~6x10^6 M_sun, compact
star clusters are likely to retain gas even in the presence of strong
supernova feedback, altering the dynamics in the central core and providing the possibility to rapidly grow the central object both via gas dynamical friction and Bondi
accretion. Finally, we consider the possibility of a gas-dominated regime, in which strong gravitational torques may inhibit
star cluster formation and instead directly form a high-mass black holes, as suggested to have occurred in the infinity
galaxy.
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All authors Dominik R.G. Schleicher, Matías Liempi, Mirek Giersz, Marcelo C. Vergara, Francesco Flammini Dotti, Paulo Solar, Andrés Escala, Muhammad A. Latif, Bastián Reinoso, Abbas Askar, Raffaella Schneider, Roberto Capuzzo-Dolcetta, Jorge Saavedra-Bastidas, Fernando Cuevas
Earth and Planetary Astrophysics
Exoplanet Search and Characterization with the Proposed POET Canadian Space Mission
S. Metchev, J. Rowe, P. Miles-Páez et al. (+20 more)
The Photometric Observations of
Exoplanet Transits (POET) is a proposed micro-satellite mission dedicated to the characterization and discovery of transiting
exoplanets. POET has been identified as a top priority small-sat space mission in the Canadian Astronomy Long Range Plan 2020-2030. POET is being proposed as Canada's next astronomy space mission, with launch possible in late 2029. POET is an iteration on the designs of the Canadian MOST and NEOSSat space missions, which had 15 cm-sized
telescopes and observed only in the visible band pass. POET will have a larger 20 cm
telescope aperture and three band passes: near-ultraviolet (nUV; 300-400 nm), visible near-infrared (VNIR; 400-900 nm), and short-wavelength infrared (SWIR; 900-1700 nm). All mission components either already have significant space heritage or are seeing rapid adoption in commercial space missions. POET's simultaneous tri-band 300-1700 nm photometric monitoring will allow it to separate the impact of
star spots on the transmission spectrum of extended atmospheres on super-Earth or larger
exoplanets. POET's SWIR band is optimally sensitive to the emission peak of ultracool
dwarf stars and would enable a systematic search for Earth-sized
planets around them. POET aims to discover some of the nearest potentially habitable Earth-sized
exoplanets that could be scrutinized for biosignatures with JWST or future
telescopes. Herein we present the assembly of the POET Input Catalog of Ultracool
Dwarfs and simulations of the expected yield of rocky
planets with POET.
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All authors S. Metchev, J. Rowe, P. Miles-Páez, K. Hoffman, S. Lambier, R. Cloutier, H. Ishikawa, JJ Kavelaars, M. Kunimoto, D. Lafrenière, C. Lovekin, E. Pilles, J. Ruan, J. Sabarinathan, G. Wade, P. Wiegert, F. Grandmont, A.-S. Poulin-Girard, S. Grocott, R. Zee, J. Dupuis, P. Langlois, J. Roediger
Instrumentation and Methods for Astrophysics
The VLT/ERIS grating vector Apodizing Phase Plate coronagraph
M. A. Kenworthy, F. A. Dannert, J. Hayoz et al. (+29 more)
We describe the design, laboratory manufacture, and on-sky testing of the grating vector apodizing phase plate (gvAPP) coronagraph for the Enhanced Resolution Imager and Spectrograph (ERIS) on the Very Large
Telescope. We used both laboratory measurements and on-sky observations to characterise the gvAPP in several different filters, from the K to the L band. In testing, the gvAPP reaches its design specification in the transmission of the optic with 90% in the K bands and 60% in the L band. While the gvAPP reaches its designed raw contrast performance of $1 \times 10^{-5}$, it does not reach the post-processed contrast of $5 \times 10^{-5}$ in on-sky observations. Electronic detector noise, due to the Airy core of the coronagraphic point spread function inducing cross-talk between the readout amplifiers, produces a repeated pattern within the coronagraphic regions of the gvAPP. Despite these limitations, we recommend the gvAPP as a tool for characterising substellar companions with known separations and position angles, which allow them to be placed in the coronagraphic dark holes for observations. The ERIS gvAPP's leakage term can also be used as a photometric reference for time series observations; however, we caution that the contrast performance may limit such studies to only the brightest targets. ERIS gvAPP data quality may be improved further with better modelling of detector electronic noise. This work is a pathfinder for Extremely Large
Telescope instruments including METIS, which will include gvAPP coronagraphs with improved designs based on these results.
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All authors M. A. Kenworthy, F. A. Dannert, J. Hayoz, D. Doelman, B. J. Sutlieff, P. Liu, F. Snik, M. J. Bonse, S. P. Quanz, C. U. Keller, O. Absil, G. Orban de Xivry, R. J. De Rosa, C. Ginski, X. Chen, A. Zurlo, B. A. Biller, J. L. Birkby, A. Baruffolo, Y. Dalliliar, R. Davies, M. Dolci, H. Feuchtgruber, A. Glauser, P. Grani, K. Kravchenko, M. MacIntosh, A. Puglisi, C. Rau, A. Riccardi, E. Sturm, W. Taylor
Instrumentation and Methods for Astrophysics
Short-Term Turbulence Prediction for Seeing Using Machine Learning
Mary Joe Medlej, Rahul Srinivasan, Simon Prunet et al. (+2 more)
Optical
turbulence, driven by fluctuations of the atmospheric refractive index, poses a significant challenge to ground-based optical systems, as it distorts the propagation of light. This degradation affects both astronomical observations and free-space optical communications. While adaptive optics systems correct
turbulence effects in real-time, their reactive nature limits their effectiveness under rapidly changing conditions, underscoring the need for predictive solutions. In this study, we address the problem of short-term
turbulence forecasting by leveraging machine learning models to predict the atmospheric seeing parameter up to two hours in advance. We compare statistical and deep learning approaches, with a particular focus on probabilistic models that not only produce accurate forecasts but also quantify predictive uncertainty, crucial for robust decision-making in dynamic environments. Our evaluation includes Gaussian processes (GPs) for statistical modeling, recurrent neural networks (RNNs) and long short-term
memory networks (LSTMs) as deterministic baselines, and our novel implementation of a normalizing flow for time series (FloTS) as a flexible probabilistic deep learning method. All models are trained exclusively on historical seeing data, allowing for a fair performance comparison. We show that FloTS achieves the best overall balance between predictive accuracy and well-calibrated uncertainty.
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All authors Mary Joe Medlej, Rahul Srinivasan, Simon Prunet, Aziz Ziad, Christophe Giordano
Earth and Planetary Astrophysics
Artificial precession and instability in solar system and planetary simulations: analytic and numerical results
David M. Hernandez
Wisdom–Holman (WH) methods are
algorithms used as a basis for a wide range of codes used to solve problems in
solar system and planetary dynamics. The problems range from the growth and migration of
planets to the stability of the
solar system. In many cases, these codes work with Democratic Heliocentric Coordinates (DHC) which offer some advantages. However, it has been noted these coordinates affect the dynamics of
solar system bodies in simulations, in particular Mercury's, and introduce artificial precession which affects
solar system stability. In this work, we analytically derive the two-body artificial precession induced by DHC. We show the effect is small for
solar system bodies, but the artificial effect on Jupiter is $242$ times larger than on Mercury. In a two-body Mercury-Sun system with general relativity (GR), artificial precession is negligible compared to GR precession, even with extreme timesteps that amplify the numerical effects. A simple two-
planet Mercury–Jupiter system without GR amplifies artificial precession significantly. However, large artificial precession or artificial instability is not a danger unless one uses large timesteps that break the surrogate
Hamiltonian approximation.
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Astrophysics of Galaxies
Machine Learning-Based Classification of Active Galaxies and Estimation of Supermassive Black Hole Masses
Farideh Mazoochi, Reihaneh Karimi, Mohammad Hossein Zhoolideh Haghighi et al. (+1 more)
Distinguishing active
galaxies from
star-forming
galaxies is essential for understanding
galaxy evolution. Diagnostic methods like the BPT (Baldwin, Phillips, and Terlevich) diagram use optical emission-line ratios to separate
galaxies. However, with growing availability of large surveys and high-resolution instruments, manually identifying
galaxy types has become increasingly challenging. In this study, we investigate machine learning to classify active and
star-forming
galaxies using properties like
stellar mass,
stellar velocity dispersion, colour,
redshift, and [O III] luminosity. These new approaches enable faster AGN/
star-forming
galaxy classification than the BPT diagram and provide a flexible, scalable alternative that can complement traditional diagnostics, particularly for large surveys or low-quality data. We employ four classification
algorithms – Decision Tree, Random Forest, Support Vector Classifier (SVC), and k-Nearest Neighbours (KNN) – using the
Galaxy Zoo 1
dataset derived from the SDSS sample. The
dataset contains 47,675
galaxies within the
redshift range 0.02–0.05, including 17,002 pure
star-forming and 2,254 active
galaxies, labeled using the BPT diagram. These labels train and evaluate our models through confusion
matrices, learning curves, and receiver operating characteristic (ROC) curves. Among the four
algorithms, the SVC and Random Forest models achieve the highest accuracy of approximately 93%, while KNN shows the lowest at 88%. Furthermore, we estimate supermassive black hole masses using
stellar velocity dispersion ($\sigma$) and the $M_{\rm BH}-\sigma$ relation. We apply four regression models – Random Forest Regressor, Support Vector Regressor (SVR), KNN Regressor, and
Polynomial Regression. All four models produce similar results, with $R^2$ values from 0.75 to 0.77, indicating consistent performance.
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All authors Farideh Mazoochi, Reihaneh Karimi, Mohammad Hossein Zhoolideh Haghighi, Fatemeh Tabatabaei
Earth and Planetary Astrophysics
Simulation of laser travel-time on Mercury for BELA
Jean Barron, Frédéric Schmidt, François Andrieu et al. (+3 more)
Recent
laser altimeters are able to not only measure the ranging distance between the spacecraft and the surface but also the full time-of-flight of the
photons or pulse shape. This new capabilities allows to measure the intra-footprint properties: surface slope distribution and surface microtexture. Here we simulate and discuss for the first time the effect of surface microtexture, especially for ice covered surface with longer penetration depth. Using the WARPE simulation software, two kind of microtextures are simulated: compact slab and granular.
Laser pulse shape for an ideal instrument is simulated using physical properties such as the grain size, material composition, thickness, compacity (filling factor, porosity) rather than radiative properties. The effects of these parameters on the pulse shape are discussed as well in the range that could be possibly be observed with actual BELA measurement. Finally, examples of WARPE's simulated pulse shapes are used as input in the precise simulation chain of the BELA measurement output, to further assess the capability to detect variation in surface microtexture.
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All authors Jean Barron, Frédéric Schmidt, François Andrieu, Gaku Nishiyama, Alexander Stark, Hauke Hussmann
High Energy Astrophysical Phenomena
Derivation of the injection spectrum of positrons and electrons from Geminga and Monogem
Qian Zhong
Extended $\gamma$-ray emission has been observed around several nearby
pulsars and is commonly interpreted as inverse-Compton radiation produced by relativistic electrons and positrons diffusing in the surrounding interstellar medium. In this work, a unified analysis of the
halos associated with the Geminga and Monogem
pulsars is presented, combining GeV–TeV $\gamma$-ray observations within a common physical framework. Assuming continuous injection of $e^\pm$ pairs from the
pulsar wind nebulae, the resulting $\gamma$-ray emission is modeled by accounting for particle
diffusion and radiative energy losses. I find that the observed spectra of both Geminga and Monogem can be reproduced within this framework, provided that particle transport in the vicinity of the sources is significantly suppressed with respect to the average
Galactic diffusion. The fits favor hard injection spectra and cutoff energies of order $10^5$–$10^6$~GeV, consistent with efficient
lepton acceleration in
pulsar environments. Using the best-fit injection models inferred from the $\gamma$-ray data, then I estimate the contribution of Geminga and Monogem to the local
cosmic-ray positron flux measured by AMS-02. I find that the slow-
diffusion region surrounding the sources strongly suppresses the positron flux reaching the Earth, leading to a subdominant contribution over most of the AMS-02 energy range, with a possible effect only near the upper end of the measured spectrum. The results support an interpretation in which TeV
halos trace regions of inhibited particle
diffusion around
pulsars, while at the same time implying only a limited impact on the local positron flux. This combined analysis highlights the importance of extended $\gamma$-ray observations for constraining particle transport in the vicinity of
Galactic cosmic-ray sources.
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Cosmology and Nongalactic Astrophysics
Impact of Antenna Structure and Orientation on Forward-Modelled Global 21 cm Signal Recovery
Joe H. N. Pattison, John M. Cumner, Dominic J. Anstey et al. (+4 more)
The redshifted 21 cm absorption trough from
cosmic atomic hydrogen is one of the most promising probes of the early Universe, but its detection is challenged by bright foregrounds and instrumental systematics. In this work we quantify the impact of
antenna mismodelling on signal recovery within a fully
Bayesian, forward-modelled data analysis pipeline. We show that discrepancies between simulated and modelled
antenna beams lead to frequency dependent errors in
antenna temperature that can bias parameter inference. In particular, we demonstrate that orientation mismatches at the level of 0.25 degrees can significantly bias recovered signal parameters in typical observing scenarios. However, we also show that
Bayesian evidence can be used to infer
antenna orientation within this precision by scanning over model realisations. For structural mismodelling, we find that broadband recovery of all signal parameters requires accurate beam knowledge, but that partial recovery remains possible. Signal frequency and width can be robustly recovered under restricted frequency bands even when the
antenna structure is imperfectly modelled, but signal depth is highly sensitive to beam errors. These results quantify the level of beam knowledge required for forward-modelled global 21 cm experiments and highlight the importance of observing strategy and
antenna design in mitigating beam-sky coupling systematics.
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All authors Joe H. N. Pattison, John M. Cumner, Dominic J. Anstey, Saurabh Pegwal, Wessel Croukamp, Dirk I. L. de Villiers, Eloy de Lera Acedo
Earth and Planetary Astrophysics
New Insights into Erg Chech 002 Analogues in the Main Belt from Near-Infrared Spectroscopy
M. Galinier, C. Avdellidou, M. Delbo et al. (+1 more)
Erg Chech 002 is an andesitic meteorite that formed early in the
Solar System's history, and that is thought to have been formed in the primitive crust of an early accreted and differentiated planetesimal. It shows unique spectral features, and no known asteroid spectral type was initially found to match with its compositional type. In the literature, asteroids (10537) 1991 RY16, (7472) Kumakiri and (14390) 1990 QP10 were found to show peculiar spectra, and were not classified in any known existing spectral class. These objects were hypothesised to be fragments of differentiated planetesimals. In a previous study, the
Gaia Data Release 3
dataset of visible reflectance spectra of
Solar System Objects was exploited to search for potential analogues of Erg Chech 002 in the main belt. As a result, 142 asteroids were found to potentially match this meteorite. In this work, we present NASA's IRTF near-infrared observations of 20 main belt asteroids found as potential analogues of Erg Chech 002. We classified these asteroids based on their visible-near-infrared spectra, then studied and compared their diagnostic spectral features with those of the laboratory spectra of Erg Chech 002. We classified 16 of the 20 observed asteroids as V-types, one as S-complex and one as A-type, and conclude that none of the observed objects match with Erg Chech 002. In addition, we show that asteroids (10537) 1991 RY16 and (14390) 1990 QP10 are good spectral matches to Erg Chech 002 based on the study of their diagnostic spectral features. Asteroid (7472) Kumakiri could match a more olivine-rich Erg Chech 002-like material, and cannot be completely ruled out as a match of the meteorite. This possible link between the meteorite and these asteroids is consistent with the theories regarding their formation, and these asteroids could be part of a new spectral class of andesitic bodies in the main belt.
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All authors M. Galinier, C. Avdellidou, M. Delbo, L. Galluccio
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Lyman-$\alpha$ Forest Constraint on Dark Matter from Dark Sector Decay
Si-Yuan Zhao, Yi-Cheng Dai, Wei Liao et al. (+1 more)
By exploiting small-scale structure formation probed by Lyman-$\alpha$ forest observations, we study constraints on a model of dark matter from dark sector decay. We compute the phase space distribution of the dark matter and the linear matter power spectrum. We map the non-thermal dark matter distribution in this dark matter model to an approximate thermal warm dark matter distribution, and use this approximation to obtain a constraint from the Lyman-$\alpha$ forest observation. We combine the latest Lyman-$\alpha$ forest bounds with the constraint from the Big Bang Nucleosynthesis. As these two probes offer highly complementary constraints, we impose strong limits on sub-GeV dark matter. Consequently, masses lighter than $\sim 10^{-1}$ GeV are excluded, thereby significantly limiting the allowed parameter space. More broadly, our findings demonstrate the utility of small-scale structure observations in testing non-thermal dark matter paradigms, offering valuable insights for exploring a wider class of late-time decay models.
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All authors Si-Yuan Zhao, Yi-Cheng Dai, Wei Liao, Yi-Song Lu
Earth and Planetary Astrophysics
Connecting Meteorite Spectra to Lunar Surface Composition Using Hyperspectral Imaging and Machine Learning
Fatemeh Fazel Hesar, Mojtaba Raouf, Amirmohammad Chegeni et al. (+5 more)
We present an innovative, cost-effective framework integrating laboratory Hyperspectral Imaging (HSI) of the Bechar010 Lunar meteorite with ground-based lunar HSI and supervised Machine Learning(ML) to generate high-fidelity mineralogical maps. A 3mm thin section of Bechar010 was imaged under a microscope with a 30mm focal length lens at 150mm working distance, using 6x binning to increase the signal-to-noise ratio, producing a data cube (X $\times$ Y $\times$ $\lambda$ = $791 \times 1024 \times 224$, 0.24mm $\times$ 0.2mm resolution) across 400-1000}nm (224 bands, 2.7nm spectral sampling, 5.5nm full width at half maximum spectral resolution) using a Specim FX10 camera. Ground-based lunar HSI was captured with a Celestron 8SE
telescope (3km/pixel), yielded a data cube ($371 \times 1024 \times 224$).
Solar calibration was performed using a Spectralon reference ({99}% reflectance {<2}% error) ensured accurate reflectance spectra. A Support Vector Machine (SVM) with a radial basis function kernel, trained on expert-labeled spectra, achieved {93.7}% classification accuracy(5-fold cross-validation) for olivine ({92}% precision, {90}% recall) and pyroxene ({88}% precision, {86}{%} recall) in Bechar 010. LIME analysis identified key wavelengths (e.g., 485nm, {22.4}% for M3; 715nm, {20.6}% for M6) across 10 pre-selected regions (M1 to M10), indicating olivine-rich (Highland-like) and pyroxene-rich (Mare-like) compositions. SAM analysis revealed angles from 0.26 radian to 0.66 radian, linking M3 and M9 to Highlands and M6 and M10 to Mares. K-means clustering of Lunar data identified 10 mineralogical clusters ({88}% accuracy), validated against Chandrayaan-1 Moon mineralogy Mapper ($\rm M^3$) data (140m/pixel, 10nm spectral resolution).A novel push-broom HSI approach with a
telescope achieves 0.8 arcsec resolution for lunar spectroscopy, inspiring full-sky multi-object spectral mapping.
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All authors Fatemeh Fazel Hesar, Mojtaba Raouf, Amirmohammad Chegeni, Peyman Soltani, Bernard Foing, Elias Chatzitheodoridis, Michiel J. A. de Dood, Fons J. Verbeek
Solar and Stellar Astrophysics
Stellar Variability and Distance Indicators in the Near-infrared in Nearby Galaxies. II. Pulsating Stars in the Carina Dwarf Spheroidal
Chow-Choong Ngeow, Anupam Bhardwaj, Prashant Nishad et al. (+1 more)
We present homogeneous, near-infrared ($JHK_s$ bands) time-series observations of the classical Carina
dwarf Spheroidal (dSph)
galaxy to determine accurate and precise distances using the pulsating
stars as standard candles. These observations cover two Carina dSph fields ($\sim10.8'\times10.8'$) obtained with the FourStar infrared camera mounted on the 6.5-m Magellan
Telescope. We collected precise photometric measurements of 43 RR Lyrae, 11 anomalous Cepheids (ACep), and 102
dwarf Cepheids (DCep) in Carina dSph. Using RR Lyrae, we obtained a distance modulus of $20.079\pm0.028\mathrm{(statistical)}\pm0.045\mathrm{(systematic)}$~mag, or a distance to Carina of $103.7\pm1.3\mathrm{(statistical)}\pm2.2\mathrm{(systematic)}$~kpc. The literature calibrations based on SX Phoenicis or delta-Scuti
stars were used to anchor the $JHK_s$ period-luminosity relations for DCep. This resulted in a distance modulus that is in excellent agreement with RR Lyrae based determination. Finally, the distance
moduli estimates using the ACep were found to be systematically smaller than the RR Lyrae-based distance modulus, suggesting a
metallicity dependence on the ACep period-luminosity relation.
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All authors Chow-Choong Ngeow, Anupam Bhardwaj, Prashant Nishad, Das Susmita
High Energy Astrophysical Phenomena
Core-Collapse Supernovae and their Gravitational Wave Signals: The Status of Theory and Modeling
Bernhard Müller
The detection of gravitational waves from a core-collapse
supernova in the Milky Way or its vicinity represents a unique opportunity to probe the inner workings of these explosions. In this review, I briefly summarize our current understanding of the
supernova explosion mechanism and then outline the physical processes that shape the
supernova gravitational wave signal. The review highlights how the various components of the signal have the potential to constrain the progenitor rotation, the proto-
neutron star structure, the
nuclear equation of state, the nature of hydrodynamic instabilities, and the violence of turbulent motions in the
supernova core. I also highlight some open questions and uncertainties in the theory of
supernova gravitational wave astronomy as well as challenges for further progress. Specifically, there is a need to develop large model databases, systematic uncertainty quantification and methods for evidence assessment to prepare for multi-messenger observations from a
Galactic supernova.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Direct cosmographic reconstruction of the quintessence potential
Saikat Chakraborty, Peter K.S. Dunsby and Robert J. Scherrer
We derive expressions for the first and second derivatives of the quintessence potential $V(\phi)$, in terms of $\lambda = -V^{\prime}/V$ and $\Gamma = (V^{\prime \prime}/V)/(V^\prime/V)^2$, as functions of the quintessence density fraction $\Omega_\phi$ and the cosmographic parameters $q$, $j$, and $s$. Our mapping is not explicitly a function of the equation of state parameter $w$. We use these results, along with recent observational data, to derive expansions of $V(\phi)$ about the present-day value of the scalar field, $\phi_0$.
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Earth and Planetary Astrophysics
Gas dynamics around dust asymmetries in turbulent disks
Lizxandra Flores-Rivera, Natascha Manger, Michiel Lambrechts et al. (+4 more)
High-resolution ALMA observations have revealed asymmetric
dust crescents in several protoplanetary disks, suggesting efficient
dust trapping mechanisms potentially linked to gas
vortices. While such features have been associated with
vortices–whether induced by massive
planets,
turbulence , or other disk processes–their origin remains unclear. In this study, we investigate the viability of
dust trapping by
vortices that are self-sustained in disks dominated by Vertical Shear Instability (VSI)
turbulence. We perform 3D hydrodynamic simulations using the PLUTO code with Lagrangian particles of three sizes (1 mm, 500~$\mu$m, 100~$\mu$m) to analyze the gas-
dust dynamics around
vortices. Our simulations reveal the formation of multiple
vortices, including two characteristic large-scale, long-lived
vortices that are able to capture the
dust particles. We also find that
dust vertical
diffusion is reduced within
vortices, suggesting that these structures preferentially enhance radial and azimuthal motions. Finally we generate synthetic
dust continuum images at different wavelength bands and velocity residuals to compare the observable properties with ALMA observations. No clear spiral features are observed in either the synthetic
dust images or the velocity residuals, unlike in
vortices triggered by
planets. Projection effects at high disk inclinations can obscure
dust asymmetries, implying that more disks may host
dust crescents than currently reported.
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All authors Lizxandra Flores-Rivera, Natascha Manger, Michiel Lambrechts, Mario Flock, Sebastian Lorek, Anders Johansen, Hubert Klahr
Solar and Stellar Astrophysics
SS Cygni: An analysis of quasi-periodic oscillations in the range of 0.25h to 8h
Ian D Sharp
Presented here is an analysis of over 66,000 magnitude measurements, made by the author, of the cataclysmic variable SS Cygni in two photometric filters (Cousins R and Johnson V). This large number of measurements, along with their cadence, is sufficient to analyse the light curve for quasi-periodic oscillations (QPOs) ranging from a few minutes to a few hours with the most frequently found QPOs having periods of 30 minutes (48 cycles/day). These QPOs occur predominantly during quiescent phases rather than outbursts, representing a previously understudied aspect of SS Cygni's variability.
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Cosmology and Nongalactic Astrophysics
Perturbative and numerical study of nonlinear relativistic effects in weak lensing
Matteo Magi, Francesca Lepori and Julian Adamek
The standard weak
lensing formalism assumes that the
lensing map relating the observed image of a source to its intrinsic shape depends only on the deflection angle. We show that this description is incomplete beyond linear perturbation theory, even when only scalar perturbations are present at first order. Using the Jacobi map formalism, we derive expressions for the rotation field, shear B-modes, and their angular power spectra at second order in relativistic perturbation theory. In the standard formalism, rotation and shear B-modes share the same spectrum, however, this degeneracy is broken once the parallel transport of the Sachs basis is consistently taken into account. We quantify this correction numerically, finding a difference of about $5\%$ on large angular scales $\ell \sim 5$ for sources at
redshift $z_\mathrm{s} = 0.5$. We also investigate frame-dragging effects, which are usually neglected in weak
lensing. We present the first analytical derivation of the corresponding impact on the angular power spectrum of shear B-modes and show that it becomes the dominant contribution on scales $\ell \lesssim 10$. While both Sachs-basis rotation and frame dragging significantly affect shear B-modes on large scales, their contribution to the observed ellipticity B-mode angular power spectrum is at the percent level relative to the total ellipticity B-mode signal, making these nonlinear relativistic corrections challenging to detect in practice. Our results are supported by relativistic simulations of weak
lensing observables, including the first numerical study of frame dragging in the power spectra of the
lensing convergence and
cosmic shear.
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Instrumentation and Methods for Astrophysics
Refractive multi-conjugate adaptive optics for wide-field atmospheric turbulence correction
Tommaso Furieri and Stefano Bonora
Multi-Conjugate Adaptive Optics (MCAO) is essential for increasing the corrected Field-of-View (FoV) in astronomical imaging and potentially for free-space optical communications, particularly for small-aperture, transportable systems. We demonstrate the viability and performance of a Refractive-MCAO system utilizing a novel multi-actuator Deformable Lens (DL) as the wavefront correction element. Unlike conventional Deformable Mirrors (DMs), the transmissive nature of the DL simplifies the optical train, making it ideal for compact setups. Using a Shack-Hartmann Wavefront Sensor (SH-WFS) in conjunction with two DLs conjugated to different atmospheric layers, we achieved an extension of the isoplanatic patch up to three times the uncorrected atmospheric isoplanatic angle under moderate
turbulence D/r0 = 2. We tested the MCAO system in a setup that emulates a free space optical communication for compact transportable system. In a double-channel, single-mode fiber coupling experiment we demonstrated the efficiency of this method.
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Solar and Stellar Astrophysics
ZIMPOL detects scattering polarization in He I D$_3$ during a solar flare
Francesco Vitali, Andrea Francesco Battaglia, Luca Belluzzi et al. (+5 more)
Spectropolarimetric observations of
solar flares in the He I D$_3$ line at 5876 Å are extremely rare, and their diagnostic potential remains largely unexplored. We report the first unambiguous detection of linear polarization in He I D$_3$ during a
solar flare. Using the high-precision ZIMPOL polarimeter at the IRSOL observatory in Locarno (Switzerland), we tracked the temporal
evolution of the He I D$_3$ Stokes profiles throughout the M7 GOES-class
flare that occurred on 3 May 2023 at 10:45 UT. We analyzed the time
evolution of the maximum in linear polarization and the absorption depth of the intensity profile. Both the fractional linear polarization, which peaks at $6\times10^{-4}$, and the absorption depth increase rapidly before gradually decaying, with their maxima occurring approximately 5 minutes after the peaks in GOES X-ray flux and SDO/AIA 304 Å emission. From the evolving He I D$_3$ core position, we also derived the temporal
evolution of the
plasma bulk velocities. The intensity profiles exhibiting strong absorption seems to originate from the
flare ribbons. The time
evolution of all Stokes parameters in the 3 May 2023 event was driven by changes in ortho-helium density prompted by the different phases of the
flare. Our analysis suggests that the observed He I D$_3$ linear polarization is likely not dominated by the theorized impact polarization, as it exhibits neither spatial correspondence with electron precipitation sites nor temporal synchronization with the impulsive phase. Instead, the signals are consistent with scattering polarization produced by anisotropic radiation pumping. We conclude that scattering polarization signal on the order of $0.01\%$ can be produced in the He I D$_3$ line during
solar flares. This can provide constraints for
flare models.
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All authors Francesco Vitali, Andrea Francesco Battaglia, Luca Belluzzi, Svetlana Berdyugina, Renzo Ramelli, Jiří Štěpán, Gioele Janett, Fabio Riva
High Energy Astrophysical Phenomena
Simultaneous Multi-band Optical Follow-up Observations of a Gamma-Ray Flare in BL Lacertae
X. Chang, D. R. Xiong, Chenxu Liu et al. (+17 more)
On $2024$ October $5$, BL Lacertae ($2200+420$) experienced one of its brightest gamma-ray
flares. We conducted simultaneous follow-up observations in the $u$, $v$, $g$, $r$, $i$, and $z$ bands from $2024$ October $17$ to November $21$ using the Mephisto
telescope and its two $50$ cm twin auxiliary photometric
telescopes of Yunnan University. Intraday variability (IDV) was detected in the $g$, $r$, $i$, and $z$ bands. The IDV duty cycle increased with observing frequency across these bands. The shortest variability time-scale, derived from auto-correlation analysis, constrains the upper limit of the black hole mass to be $M_{\bullet} \lesssim 10^{8.29} M_{\odot}$ assuming a Kerr black hole, and $M_{\bullet} \lesssim 10^{8.77} M_{\odot}$ assuming a Schwarzschild black hole. The emission region responsible for the observed variability has a size of $R \le 3.51 \times 10^{14}$ cm and is located at a distance of $R_H \le 2.83 \times 10^{15}$ cm from the central supermassive black hole. This distance is approximately three orders of magnitude smaller than the typical radius of the broad-line region, indicating that the emission region lies well within it. A general bluer-when-brighter (BWB) trend was detected on intraday time-scales, suggesting that shock-accelerated relativistic electrons enhance the high-energy particle population, leading to spectral hardening. A potential quasi-periodic oscillation (QPO) with a period of $\sim 100.77$ minutes was detected with $>99.99$ per cent confidence, consistent with predictions from the
magnetic reconnection model. These observed optical intraday variabilities and colour variations of BL Lacertae can be well explained by the turbulent jet model.
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All authors X. Chang, D. R. Xiong, Chenxu Liu, J. R. Xu, G. Bhatta, T. F. Yi, J. Zhang, Y. Pan, X. Z. Zou, X. L. Chen, Y. P. Yang, J. H. Zhang, X. K. Liu, Y. Fang, G. W. Du, T. Wang, X. F. Zhu, Y. L. Gong, Z. X. Wang, X. W. Liu
Instrumentation and Methods for Astrophysics
Ising noise filter: physics-informed filtering for particle detectors
I. Kharuk
We present the Ising noise filter, a highly portable, graph-based pre-filtering
algorithm for early-stage background suppression in particle accelerators and astrophysical detectors. Standard noise rejection methods relying on track fitting suffer from severe combinatorial explosion. Our method bypasses this by mapping individual detector hits to a network of binary
spins and minimizing an energy functional. The interaction kernels are physics-informed, tailored to the underlying physics and geometry of the experiment. We demonstrate the efficacy of this approach in two distinct experimental regimes. Applied to the Baikal-GVD
neutrino telescope the filter yields fast, standard-quality noise rejection with 96.8% recall for astrophysical
neutrinos. For the SPD detector at the NICA
collider the filter attains recall of 97% on a toy Monte Carlo sample. Furthermore, when combined with a Peterson–Hopfield network for track finding, our physics-informed coupling improves the TrackML score from 0.5 to 0.95.
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High Energy Astrophysical Phenomena
Unifying the X-ray coronae and ultra-fast outflows: a PBI-enhanced outflow-based corona model for the inner accretion disc
Haichao Xu
The fact that luminous X-ray coronae and Ultra-Fast
Outflows (UFOs) are both inferred to originate from the innermost regions of active
galactic nuclei (AGNs) suggests a deep physical connection between them. However, standard
magnetic buoyancy models struggle to transport sufficient energy through the radiation-pressure-dominated inner disc to sustain both the phenomena, creating a theoretical energy deficit. In this work, we propose an
outflow-based model with energy transport enhanced by the
Photon Bubble Instability (PBI) in the inner region. By coupling this enhanced energy supply with the MHD
turbulence-driven mass-loading mechanism appropriate for weakly magnetized standard discs, we solve the dynamical and thermodynamic structure of the corona. We find that the model can successfully launch high speed winds matching observed UFO kinematics provided the mechanical acceleration efficiency is high ($f_{\rm acc}\gtrsim 0.5$). Furthermore, the model naturally reproduces the observed spectral
evolution found in AGN coronae: as the
accretion rate increases, the corona becomes optically thicker and cooler and produces a softer spectrum. Our results support an extended slab-like coronal geometry and suggest that UFOs and X-ray coronae in the inner discs are manifestations of the same
magnetic activity.
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High Energy Astrophysical Phenomena
The annular gap model under a rotating dipole field approximation: simulating gamma-ray light curve
Jie Tian, Xin Xu, Qijun Zhi et al. (+5 more)
A more realistic description of the magnetosphere is crucial for understanding the radiation emitted by
pulsars. In this paper, we revisit the annular gap model by employing a rotating dipole field, which is more realistic than the static dipole field, as an approximation of the
magnetic structure of the
pulsar magnetosphere. Compared with the static dipole field approximation, the open field-line region, including both the core and annular gaps, is significantly enlarged, and the two regions become asymmetric with respect to the fiducial plane. We apply this model to three young gamma-ray
pulsars with distinct light-curve morphologies, PSRs J0631$+$1036 (single peak), J1709$-$4429 (double peaks), and J1048$-$5832 (three peaks). Using viewing geometries constrained by
radio polarization measurements, the annular gap model within the rotating dipole field successfully reproduces the main morphological features of their gamma-ray light curves above 0.1 GeV. Our model provides a framework for interpreting
pulsar high-energy emission, which can be used to analyze the emission properties of high-energy
pulsars.
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All authors Jie Tian, Xin Xu, Qijun Zhi, Jiguang Lu, Shijun Dang, Ke Yang, Xiao Wei, Guojun Qiao
Solar and Stellar Astrophysics
A Catalog of 1,408 Carbon-Enhanced Metal-Poor Stars from LAMOST DR11
Xianqi Liu, Xiangru Li and Ziyu Fang
Metal-poor (MP)
stars are important targets for investigating the chemical
evolution of the early universe. Among them, Carbon-Enhanced Metal-Poor (CEMP)
stars have attracted extensive
attention due to their rarity and astrophysical significance. Owing to their low occurrence rate, the identification of MP
stars and CEMP
stars remains a task of considerable scientific value. In this study, we investigate the search for CEMP
stars based on the low-resolution
stellar spectra from LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic
Telescope) DR11 and propose a deep-learning-based approach for this purpose. By analyzing the LAMOST DR11 spectral library, we identify 1,408 CEMP
star candidates. For ease of reference and further use, we provide the estimated
stellar parameters for these objects, including $T_\texttt{eff}$, $\log~g$, [Fe/H], and [C/H].
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