Astrophysics of Galaxies
Identifying bars in galaxies using machine learning
Rajit Shrivastava
This thesis presents an innovative framework for the automated detection and characterization of
galactic bars, pivotal structures in spiral
galaxies, using the YOLO-OBB (You Only Look Once with Oriented Bounding Boxes) model. Traditional methods for identifying bars are often labor-intensive and subjective, limiting their scalability for large astronomical surveys. To address this, a synthetic
dataset of 1,000 barred spiral
galaxy images was generated, incorporating realistic components such as disks, bars, bulges, spiral arms,
stars, and observational noise, modeled through Gaussian, Ferrers, and Sersic functions. The YOLO-OBB model, trained on this
dataset for six epochs, achieved robust validation metrics, including a precision of 0.93745, recall of 0.85, and mean Average Precision (mAP50) of 0.94173. Applied to 10 real
galaxy images, the model extracted physical parameters, such as bar lengths ranging from 2.27 to 9.70 kpc and orientations from 13.41$^\circ$ to 134.11$^\circ$, with detection confidences between 0.26 and 0.68. These measurements, validated through pixel-to-kiloparsec conversions, align with established bar sizes, demonstrating the model's reliability. The methodology's scalability and interpretability enable efficient analysis of complex
galaxy morphologies, particularly for
dwarf galaxies and varied orientations. Future research aims to expand the
dataset to 5,000
galaxies and integrate the Tremaine-Weinberg method to measure bar pattern speeds, enhancing insights into
galaxy dynamics and
evolution. This work advances automated morphological analysis, offering a transformative tool for large-scale astronomical studies.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Vector-field spontaneous baryogenesis with Lorentz invariance violation
Mattia Dubbini, Orlando Luongo and Aniello Quaranta
We extend spontaneous baryogenesis by considering the spontaneous breaking of $U(1)_B$ through a complex vector field. This field interacts with
baryons and
leptons via a vector-current coupling and, by construction, acquires a nonzero
vacuum expectation value. Accordingly, the theory also exhibits a spontaneous violation of Lorentz invariance, effectively realizing a Bumblebee model. In this picture, the pseudo-Nambu-Goldstone
boson arising from spontaneous breaking of the $U(1)_B$ global
symmetry is the global phase of the Bumblebee vector and, in the broken phase, it results minimally coupled with the baryonic current, guaranteeing the violation of the
baryon number. Consequently, we assume that the pseudo-Nambu-Goldstone, arising from spontaneous breaking of $U(1)_B$, plays the role of the inflaton, leading to baryogenesis across the entire inflationary stage, up to when the inflaton decays into
baryon-antilepton and antibaryon-
lepton pairs through a CP-violating interaction that also violates the Lorentz
symmetry. Afterwards, we address the issue of
flavor oscillations among
baryon and
lepton fields, including the oscillation probability in the calculation of the
baryon asymmetry. Remarkably, our framework predicts a non-null mixing factor even for massless
fermions. This mixing acts on the spatial momenta rather than on the masses of the produced
fermions, allowing larger values of the coupling constant even guaranteeing the production of light
fermions. The net
baryon asymmetry results accordingly modified, and may also reproduce the experimental data for allowed values of the coupling constant.
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Solar and Stellar Astrophysics
The Kinematic Properties of TŻO Candidate HV 11417 with Gaia DR3
Anna J. G. O'Grady
HV 11417 is a candidate Thorne-Żytkow Object, a red supergiant with a
neutron star core, located within the Small Magellanic Cloud (SMC). Previous studies have questioned, using
Gaia DR2 data, whether HV 11417 was truly located at the distance of the SMC or was instead a foreground
star. However, the proper motion measurement uncertainties for HV 11417 in DR2 were high. In this work, we use
Gaia DR3 data to show that HV 11417 is very likely to be a true member of the SMC. We further analyze the kinematics of HV 11417 relative to its local environment, and compare it to populations of massive and evolved
stars in the SMC. We find HV 11417 has a local transverse velocity of $52\pm15$ km/s, and thus qualifies as a runaway
star (v$_\mathrm{loc}\geq$ 30 km/s). This runaway classification does not conclusively prove its nature as a TŻO, particularly given results from recent TŻO models, but does indicate that HV 11417 experienced a kinematic disruption in its
evolution.
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Astrophysics of Galaxies
Investigating the Impacts of AGN Activities on Dwarf Galaxies with FAST HI Observations
Hong-Ying Chen, Chao-Wei Tsai, Pei Zuo et al. (+9 more)
We present the results of Hi line observations towards 26 Active
Galactic Nuclei (AGN)-hosting and one
star-forming
dwarf galaxies (Mstar < 10^9.5 Msun) with the 19-beam spectral line receiver of FAST at 1.4 GHz. Our FAST observed targets are combined with other AGN-hosting
dwarf galaxies covered in the ALFALFA footprint to form a more comprehensive sample. Utilizing the information from optical surveys, we further divide them into isolated and accompanied subsamples by their vicinity of nearby massive
galaxies. We compare the Hi gas abundance and
star-forming rate (SFR) between the subsamples to assess the role of internal and external processes that may regulate the gas content in
dwarf galaxies. As a result, we find that AGN are more commonly identified in accompanied
dwarf galaxies than in their isolated counterparts. Meanwhile, AGN-hosting
dwarf galaxies have slightly but significant lower Hi mass fraction relatively to the non-AGN control sample in accompanied
dwarf galaxies. On the other hand, we find a decreasing SFR in AGN-hosting
dwarf galaxies towards denser environments, as well as an extremely low incidence of quenched isolated
dwarfs within both AGN and non-AGN subsamples. These results indicate that although these AGN could potentially regulate the gas reservoir of
dwarf galaxies, environmental effects are likely the dominant quenching mechanism in the low-mass universe.
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All authors Hong-Ying Chen, Chao-Wei Tsai, Pei Zuo, Niankun Yu, Jialai Wang, Kai Zhang, Guodong Li, Yogesh Chandola, Zheng Zheng, Jingwen Wu, Di Li, Lulu Bao
High Energy Astrophysical Phenomena
Synchrotron Self-Compton Model of TeV Afterglows in Gamma-Ray Bursts
Edilberto Aguilar-Ruiz, Ramandeep Gill, Paz Beniamini et al. (+1 more)
The detection of a very-high-energy TeV spectral component in the afterglow emission of gamma-ray bursts (GRBs) has opened a new probe into the energetics of ultra-relativistic blast waves and the nature of the circumburst environment in which they propagate. The afterglow emission is well understood as the synchrotron radiation from the shock-accelerated electrons in the medium swept up by the blast wave. The same distribution of electrons also inverse-Compton upscatters the softer synchrotron
photons to produce the synchrotron self-Compton (SSC) TeV emission. Accurate modeling of this component generally requires a computationally expensive numerical treatment, which makes it impractical when fitting to observations using Markov Chain Monte Carlo (MCMC) methods. Simpler analytical formalisms are often limited to broken power-law solutions and some predict an artificially high Compton-Y parameter. Here we present a semi-analytic framework for a spherical blast wave that accounts for adiabatic cooling and expansion,
photon escape, and equal-arrival-time-surface integration, in addition to Klein-Nishina effects. Our treatment produces the broadband afterglow spectrum and its temporal
evolution at par with results obtained from more sophisticated kinetic calculations. We fit our model to the afterglow observations of the TeV bright GRB\,190114C using MCMC, and find an energetic blast wave with kinetic energy $E_{k, \rm iso} = 9.1^{+7.41}_{-3.13} \times 10^{54} \, \rm erg$ propagating inside a radially stratified external medium with number density $n(r)\propto r^{-k}$ and $k=1.67^{+0.09}_{-0.10}$. A shallower external medium density profile ($k<2$) departs from the canonical approximation of a steady wind ($k=2$) from the progenitor
star and may indicate a non-steady wind or a transition to an interstellar medium.
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All authors Edilberto Aguilar-Ruiz, Ramandeep Gill, Paz Beniamini, Jonathan Granot
Solar and Stellar Astrophysics
CO observations in rotating circumbinary post-AGB disks
I. Gallardo Cava, J. Alcolea, H. Van Winckel et al. (+3 more)
There is a group of post-AGB
stars that are part of a binary system and that show a significant NIR excess. These systems are known to host disks with Keplerian or quasi-Keplerian dynamics and to drive
outflows of gas escaping from the rotating disk. These binary post-AGB
stars can be categorized into two subclasses depending on the predominance of specific kinematic components: disk-dominated and
outflow-dominated sources. We present the survey of such sources observed in CO using the IRAM-30m
telescope, in which we aim to identify the molecular gas in these circumbinary-disk-containing post-AGB nebulae. We aim to analyze the mass distribution of the disk objects studied in CO. We present high-sensitivity mm-wave observations of the CO line emission from ten binary post-AGB
stars. Using the derived formulation and observational data, we calculated the mass of the total gas in the CO-emitting regions of these nebulae. The logarithmic distribution of nebular masses was analyzed using a normal model that incorporates censored data, enabling a more comprehensive analysis and yielding more accurate and representative results. CO emission is detected in six post-AGB nebulae from our sample. We have significantly increased the sample of observed sources in CO lines. Some of these objects exhibit very weak molecular emission. Within the sample of disk-containing sources, the total gas mass spans a range of 1E-4 to 1E-1 Mo. The results derived from this work, along with those from a previous CO single-dish survey and interferometric data, show that this class of binary post-AGB
stars exhibits a large range of nebular masses (including both the rotating disk and the expanding component), with variations exceeding a factor of 600. The typical nebular mass of these objects, accounting for both detections and non-detections through censored data analysis, is approximately 2E-3 Mo.
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All authors I. Gallardo Cava, J. Alcolea, H. Van Winckel, V. Bujarrabal, M. Santander-García, M. Gómez-Garrido
Astrophysics of Galaxies
Joanna D. Sakowska, David Martínez-Delgado, Sarah Pearson et al. (+6 more)
While mergers between massive
galaxies and their
dwarf satellites are well studied, the properties of
dwarf -
dwarf satellite mergers are not well constrained.
Stellar streams trace satellite disruption and, in the
dwarf galaxy regime, are predicted to provide novel constraints on low-mass
galaxy evolution and dark matter. However, the mass ratios required to form these streams make them challenging to detect. We present a preview of the
Stellar Stream Legacy Survey (SSLS) in the
dwarf galaxy regime. The SSLS aims to produce a statistically large, homogeneous sample of
stellar streams for comparison with
galaxy evolution theory. We visually inspect
dwarf galaxies using the DESI Legacy Imaging Survey (DES and DECaLS footprints, r-band 29 mag arcsec^-2 within 4 - 35 Mpc. We develop a classification metric to categorise
accretion debris around
dwarf galaxies, and measure the frequency of
accretion features in the DES footprint only. We present the first release of
accretion features around
dwarf galaxies collected from the DES and DECaLS footprints, including 1 stream, 11 shells, and 8 asymmetric
stellar halos, of which 17 constitute new identifications. In the DES footprint, we inspect 730
dwarfs and find that 5.1% (37/730) show
accretion features. Although this frequency measurement is lower than the SSLS result for massive
galaxies, we discuss the observational biases behind detecting streams in the
dwarf galaxy regime. Our results highlight the difficulty of detecting streams around
dwarfs, and identify the need for improved theoretical modelling of low-mass merger morphologies. Nevertheless, they place constraints on hierarchical mass assembly in this regime.
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All authors Joanna D. Sakowska, David Martínez-Delgado, Sarah Pearson, Francisco J. Riquel-Castilla, Tjitske K. Starkenburg, Giuseppe Donatiello, Alis Deason, Denis Erkal, Ethan D. Taylor
Astrophysics of Galaxies
Calcium versus silicon ejecta velocities and decline rates in supernovae Ia: The role of high-velocity features
A. A. Hakobyan, M. H. Gevorgyan, A. G. Karapetyan et al. (+4 more)
Photospheric and high-velocity features (PVFs and HVFs) of Si II $\lambda$6355 and Ca II IR3 lines in
supernova Ia (SN Ia) spectra provide insights into ejecta structure, energetics, and circumstellar interaction, yet their interplay remains poorly understood. We analyse a representative sample of 145 nearby SNe Ia observed within $\pm$5 days of B-band maximum light, including normal, 91T-, and 91bg-like events with measured light-curve decline rates ($\Delta m_{15}$) and Si II and Ca II line properties from the literature. We model PVF and HVF velocity distributions using Gaussian Mixture Models, compare Si II and Ca II PVF velocity distributions, assess Ca II HVF properties, and test correlations between Si II PVF velocities and $\Delta m_{15}$, with emphasis on HVF effects. For the first time, we show that the Ca II PVF velocity distribution, measured for the same events at the same phases as Si II, is predominantly unimodal, in contrast to the well-known bimodal Si II PVF distribution that supports the high-velocity/normal-velocity division. This contrast likely reflects a subclass-dependent formation depth of the Ca II line, as supported by a positive correlation ($>3.3\sigma$) between $\Delta m_{15}$ and the velocity offset between Ca II and Si II PVFs, particularly in faster-declining SNe Ia. Importantly, HVFs do not significantly bias PVF velocity distributions. A significant negative correlation ($>3.3\sigma$) between Si II PVF velocity and $\Delta m_{15}$ is found only for HVF-weak SNe Ia, consistent with more energetic explosions yielding faster ejecta, while this trend vanishes in HVF-strong events, likely due to circumstellar interaction. These results underscore the critical role of HVFs and SN Ia subclass in interpreting ejecta kinematics in both models and observations.
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All authors A. A. Hakobyan, M. H. Gevorgyan, A. G. Karapetyan, G. A. Mamon, D. Kunth, V. Adibekyan, L. V. Barkhudaryan
Astrophysics of Galaxies
A detection of sulfur-bearing cyclic hydrocarbons in space
Mitsunori Araki, Miguel Sanz-Novo, Christian P. Endres et al. (+13 more)
Molecules harbouring sulfur are thought to have played a key role in the biological processes of life on Earth, and thus, they are of much interest when found in space. Here we report on the astronomical detection of a six-membered sulfur-bearing cyclic hydrocarbon in the interstellar medium. Observations of the
Galactic Centre molecular cloud G+0.693-0.027 reveal the presence of 2,5-cyclohexadien-1-thione, which is a structural isomer of thiophenol ($c$-C$_6$H$_6$S). For the astronomical identification, we first performed precise laboratory measurements of the thiophenol discharge products system. These measurements, conducted in the
radio band using a chirped-pulse
Fourier transform microwave spectrometer, enabled us to characterize this highly polar molecular species and provided unambiguous fingerprints needed to identify this organosulfur compound in space, which now ranks as the largest interstellar sulfur-bearing molecule. These results herald the discovery of a family of prebiotically relevant sulfur-bearing species, which potentially act as a bridge between the chemical inventory of the interstellar medium and the composition of the minor bodies of the
Solar System.
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All authors Mitsunori Araki, Miguel Sanz-Novo, Christian P. Endres, Paola Caselli, Víctor M. Rivilla, Izaskun Jiménez-Serra, Laura Colzi, Shaoshan Zeng, Andrés Megías, Álvaro López-Gallifa, Antonio Martínez-Henares, David San Andrés, Sergio Martín, Miguel A. Requena-Torres, Juan García de la Concepción, Valerio Lattanzi
Solar and Stellar Astrophysics
Properties of Core Collapse Supernovae from Binary Population Synthesis
Mark Martinez, Anna O'Grady, Katelyn Breivik et al. (+1 more)
Core collapse
supernovae (CCSNe) impact many areas of astrophysics, including compact object formation and gravitational waves, but many uncertainties remain in our understanding of the
evolution of their progenitors. We use the binary population synthesis code
COSMIC to simulate populations of CCSNe across a wide range of
metallicities and binary
evolution assumptions. Our models vary the prescriptions for mass transfer stability, common envelope ejection efficiency, natal kick strength, and remnant mass-limited explodability to assess their impact on the resulting population of CCSNe. We find that reproducing the observed Type I to Type II rate requires either low common envelope efficiency or modified prescriptions for common envelope survival, highlighting the importance of
stellar mergers in shaping the CCSN population. We further classify our synthetic CCSNe into subtypes and present their relative abundances using several different sets of classification criteria, highlighting the large uncertainties that persist in mapping progenitor properties to spectral classes. Finally, we present delay time distributions (DTDs) for our overall populations, separated into Type I and II, and into the full set of observed subtypes. Our DTDs show that models reproducing the observed Type I to Type II rate produce a larger fraction of late CCSNe than is expected under standard assumptions.
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All authors Mark Martinez, Anna O'Grady, Katelyn Breivik, Gina Chen
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Statistical analysis and correction of the pile-up effect in MAPMT single photoelectron counting with the SPACIROC-3 ASIC: application to the Mini-EUSO experiment
Enzio M'sihid, Etienne Parizot, Matteo Battisti et al. (+1 more)
We present a comprehensive study addressing pile-up effects in single photoelectron counting with R-11265 Hamamatsu multi-anode photomultiplier tubes (MAPMTs) equipped with the SPACIROC-3 ASIC. Extended dead time in the electronics causes saturation and quenching of the counting rate, an effect we counter by inverting the pile-up plot once the double pulse resolution is determined. Our work combines extensive numerical simulations with experimental validations to quantify the statistical uncertainties associated with the corrected event rates. We apply this methodology to the Mini-EUSO experiment onboard the International Space Station where machine learning techniques are employed to extract pixel-by-pixel double pulse resolutions from long-term
photon count histograms. This integrated approach enables the accurate recovery of true
photon fluxes essential for studying ELVES, meteors and other transient phenomena detected by Mini-EUSO.
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All authors Enzio M'sihid, Etienne Parizot, Matteo Battisti, Sylvie Blin
High Energy Astrophysical Phenomena
Simulating AGN feedback in galaxy clusters with pre-existing turbulence
Jia-Lun Li and H.-Y. Karen Yang
Feedback from active
galactic nuclei (AGN) is believed to play a significant role in suppressing cooling flows in cool-core (CC) clusters.
Turbulence in the intracluster medium (ICM), which may be induced by AGN activity or pre-existing motions, has been proposed as a potential heating mechanism based on analysis of Chandra X-ray surface brightness fluctuations. However, subsequent simulation results have found the subdominant role of
turbulence in heating the ICM. To investigate this discrepancy, we perform three-dimensional hydrodynamic simulations of a Perseus-like cluster including both AGN feedback and pre-existing
turbulence, which is stirred to the observationally constrained level in the Perseus cluster. Our results indicate that, although the velocity field is dominated by the pre-existing
turbulence, AGN heating through bubbles and shocks remains significant. More importantly, analysis of the velocity structure function and the energy power spectrum shows that the turbulent heating rate is smaller than the radiative cooling rate, especially in the cluster core. Our results offer insights relevant for recent XRISM observations and indicate that turbulent heating alone cannot offset radiative cooling in CC clusters.
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High Energy Astrophysical Phenomena
Multimessenger search strategy for composite dark matter with white dwarf data and gravitational wave detectors
Siyu Jiang, Aidi Yang and Fa Peng Huang
The nature of dark matter (DM) remains one of the most challenges in modern physics. Composite or macroscopic DM present a compelling alternative to conventional particle DM, yet their terrestrial search is notoriously challenging due to low number density. This Letter presents a unified, multimessenger search strategy for composite DM, dramatically improving existing constraints and proposing a new detection method. We first perform a model independent update of astrophysical constraints from compact objects, utilizing systematic calculations and additional white
dwarf data related to ignition and subsequent
supernovae. Crucially, for the first time, we explore novel signals of composite DM in future gravitational wave detectors like LISA, TianQin, and Taiji, performing detailed signal to noise ratio and Fisher
matrix analyses. We demonstrate that these detectors will possess the requisite sensitivity to probe untouched regions of the DM parameter space. Our results underscore the unique power of the multimessenger paradigm spanning
stellar astrophysics and gravitational wave astronomy to explore this distinct and challenging frontier of DM physics. Our analyses extend broadly to a wide range of macroscopic or composite DM scenarios.
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Instrumentation and Methods for Astrophysics
Tools and Advancements towards Data Standardization of the MAGIC Collaboration
C.P. Walther, C. Nigro, D. Elsässer et al. (+1 more)
Gamma-ray astronomy is able to acquire large data volumes that astronomers use to draw scientific conclusions from. Ensuring the possibility of accessing and utilizing this data also after the lifetime of currently running experiments requires the use of a standardized data format. Following the data standardization format proposed by the gamma-ray astronomy community, we present 104 h of the first production of 166 h of data from the MAGIC Imaging Air Cherenkov
Telescopes in standardized data format. Six
datasets were processed from which three are presented, all of which have been analyzed and validated through comparison using the open-source software Gammapy and the MAGIC analysis software MARS. Furthermore, looking towards a large-scale production of standardized data and a legacy of the data taken by the MAGIC experiment, we have developed and implemented the automated database-driven MAGIC data reduction tool autoMAGIC which offers a reliable and reproducible way to produce high-level
datasets. By utilizing the automatization of parameter configuration choices, the software allows for a reduction of human error as well as an acceleration in the production of standardized data. Here, we also show comparable results for data processed with manual and automatic methods.
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All authors C.P. Walther, C. Nigro, D. Elsässer, W. Rhode
Instrumentation and Methods for Astrophysics
SlotFlow: Amortized Trans-Dimensional Inference with Slot-Based Normalizing Flows
Niklas Houba, Giovanni Giarda and Lorenzo Speri
Inferring the number of distinct components contributing to an observation, while simultaneously estimating their parameters, remains a long-standing challenge across signal processing, astrophysics, and neuroscience. Classical trans-dimensional
Bayesian methods such as Reversible Jump Markov Chain Monte Carlo (RJMCMC) provide asymptotically exact inference but can be computationally expensive. Instead, modern deep learning provides a faster alternative to inference but typically assume fixed component counts, sidestepping the core challenge of trans-dimensionality. To address this, we introduce SlotFlow, a deep learning architecture for trans-dimensional amortized inference. The architecture processes time-series observations, which we represent jointly in the frequency and time domains through parallel encoders. A classifier produces a distribution over component counts K, and its MAP estimate specifies the number of slots instantiated. Each slot is parameterized by a shared conditional normalizing flow trained via permutation-invariant Hungarian matching. On sinusoidal decomposition with up to 10 overlapping components and Gaussian noise, SlotFlow achieves 99.85% cardinality accuracy and well-calibrated parameter posteriors, with systematic biases well below one posterior standard deviation. Direct comparison with RJMCMC shows close agreement in amplitude and phase, with Wasserstein distances $W_2 < 0.01$ and $< 0.03$, indicating that shared global context captures inter-component structure despite a factorized posterior. Frequency posteriors remain centered but exhibit 2-3x broader intervals, consistent with an encoder bottleneck in retaining long-baseline phase coherence. The method delivers a $\sim 10^6\times$ speedup over RJMCMC, suggesting applicability to time-critical workflows in gravitational-wave astronomy, neural spike sorting, and object-centric
vision.
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Cosmology and Nongalactic Astrophysics
Witten-O'Raifeartaigh potential revisited in the context of Warm Inflation
Suratna Das, Umang Kumar, Swagat S. Mishra et al. (+1 more)
Warm Inflation is a scenario in which the inflaton field dissipates its energy during inflation to maintain a subdominant constant radiation bath. Two of its remarkable features are (i) inflation can be realized even by very steep potentials and (ii) such a scenario doesn't call for a separate post-inflation reheating phase. We exploit the first feature to show that Warm Inflation can successfully take place on the very steep left wing of the Witten-O'Raifeartaigh potential while remaining in excellent agreement with current cosmological data (joint analysis of Planck, ACT and DESI). The Witten-O'Raifeartaigh potential has a flatter right wing as well, which opens up the possibility of dark energy when the field rolls along this wing. However in order to successfully realize quintessential inflation one needs to (i) normalize the two wings of the Witten-O'Raifeartaigh potential differently in order to bridge between the two extreme energy scales of inflation and dark energy, (ii) allow the quintessence field to be dissipative, which is consistent with the presence of a dissipative term in warm inflation. The dissipative dynamics of the quintessence field is needed in order to sustain slow-roll in the right wing. With these modifications, we demonstrate that the Witten-O'Raifeartaigh potential can give rise to a unified model of warm inflation (on the left wing) and transient dark energy (on the right wing).
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All authors Suratna Das, Umang Kumar, Swagat S. Mishra, Varun Sahni
Solar and Stellar Astrophysics
Predictions of gravity mode pulsations of collisional blue straggler stars in globular clusters
Lorenzo Briganti, Walter Eduard van Rossem, Andrea Miglio et al. (+2 more)
Blue straggler
stars (BSSs) are exotic objects, which, being the results of processes such as mass transfer, mergers, or collisions, are considered key objects in the study of their host clusters' dynamics. While many studies on astrometric, spectroscopic, and photometric properties of BSSs in clusters have been conducted, there are few works in the literature regarding their pulsations and internal structure, which can indeed retain traces of their origin. In this work we computed and analysed a grid of collisional BSSs at low
metallicity ($Z = 0.01\; Z_\odot$), finding that collision products present a peculiar chemical stratification that leads to periodicities in the period-spacing pattern of high-order
gravity modes. These seismic fingerprints provide a unique opportunity to constrain the formation pathways of BSSs in globular clusters.
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All authors Lorenzo Briganti, Walter Eduard van Rossem, Andrea Miglio, Angela Bragaglia, Massimiliano Matteuzzi
Cosmology and Nongalactic Astrophysics
Primordial Black Holes as Dark Matter and the Tachyonic Trap During Inflation
Yuma S. Furuta, Mindaugas Karčiauskas, Kazunori Kohri et al. (+1 more)
We show that resonant processes during multi-field inflation can generate a large
curvature perturbation on small scales. This perturbation naturally leads to the formation of
primordial black holes that may constitute dark matter, as well as to the production of
stochastic induced gravitational waves in the deci-Hz band. Such waves are within reach of future space-based interferometers such as LISA, DECIGO and BBO. In addition,
primordial black hole binaries formed at late times produce merger gravitational waves that can be probed by the resonant cavity experiments in addition to DECIGO and BBO.
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All authors Yuma S. Furuta, Mindaugas Karčiauskas, Kazunori Kohri, Alejandro Sáez
Astrophysics of Galaxies
An improved formalism for measuring the dark matter subhalos mass by its gravitational wake
M. E. Mosquera, K. J. Fushimi and M. J. de L. Domínguez Romero
We reexamined the framework used to determine the dark matter mass of a subhalo using the gravitational effects of its passage upon the
stellar halo of a host. In particular, we aim to include different density distribution functions for the perturber and a non homogeneous background due to the host's
halo gravitational potential. We have used a sample of K
giant and RRLyrae
stars based on
Gaia DR3 data and two different set of simulations, to test the new formalism. From our analysis, we found that the inclusion of a nonhomogeneous background improves substantially the estimation of the subhalo dark matter mass. The methodology is not sufficiently sensitive to discriminate between different density distribution functions for the perturber, however, in the case of the observational data, the inclussion of the cloud's circular velocity is a fundamental tool to complement the analysis. The results obtained including the host
halo potential agree with the independent previous measurements or with the reported value for the subhalo dark matter mass in the simulations. These results show that it is possible to measure the mass of smaller subhalos through their gravitational wake, even for subhalos closer to their host, with distances lower than 30 kpc.
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Astrophysics of Galaxies
Bursty star formation, chemical enrichment, and star cluster formation in numerical analogues of GN-z11
Takayuki R. Saitoh, Yutaka Hirai, Michiko S. Fujii et al. (+1 more)
The James Webb Space
Telescope reveals anomalous nitrogen enrichment (high N/O ratios) in compact,
star-forming
galaxies, such as GN-z11 at $z\sim10$. The origin of this chemical signature provides an insight into the early
star and
galaxy formation processes, yet remains unclear. We performed high-resolution cosmological zoom-in simulations of massive
galaxies at high
redshift ($z\sim10$) in rare density peaks, incorporating various chemical
evolution channels including
stellar winds, core-collapse, Type Ia
supernovae, and asymptotic
giant branch
stars. Our simulations reproduce several key features of high-
redshift galaxies: (1)
stars form with high efficiencies ($>0.1$) at the center of rare peak
halos, creating very compact
galaxies similar to GN-z11; (2) high N/O ratios emerge during the first 10-20 Myr of intense starburst, before being diluted by CCSNe; (3) multiple
star clusters form in and around the
galaxy with high efficiency ($\sim20\%$), some of which exhibit high N/O ratios and sodium-oxygen anti-correlations similar to those observed in local globular clusters. Although our simulations can reproduce the high log(N/O) values (up to -0.61, exceeding the
solar value by 0.25 dex), they remain below the observational lower limits of GN-z11, indicating room for improvement through additional chemical
evolution channels, such as supermassive
stars.
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All authors Takayuki R. Saitoh, Yutaka Hirai, Michiko S. Fujii, Yuki Isobe
Earth and Planetary Astrophysics
Large-amplitude Variability Driven by Giant Dust Storms on a Planetary-mass Companion
Xianyu Tan, Xi Zhang, Mark S. Marley et al. (+17 more)
Large-amplitude variations are commonly observed in the atmospheres of directly imaged
exoplanets and brown
dwarfs. VHS 1256B, the most variable known
planet-mass object, exhibits a near-infrared flux change of nearly 40%, with red color and silicate features revealed in recent JWST spectra, challenging current theories. Using a general circulation model, we demonstrate that VHS 1256B's atmosphere is dominated by planetary-scale
dust storms persisting for tens of days, with large patchy clouds propagating with equatorial waves. This weather pattern, distinct from the banded structures seen on
solar system
giants, simultaneously explains the observed spectra and critical features in the rotational light curves, including the large amplitude, irregular
evolution, and wavelength dependence, as well as the variability trends observed in near-infrared color-magnitude diagrams of dusty substellar atmospheres.
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All authors Xianyu Tan, Xi Zhang, Mark S. Marley, Yifan Zhou, Ben W. P. Lew, Brittany E. Miles, Natasha E. Batalha, Beth A. Biller, Gaël Chauvin, Sasha Hinkley, Kielan K. W. Hoch, Elena Manjavacas, Stanimir Metchev, Simon Petrus, Emily Rickman, Andrew Skemer, Genaro Suárez, Ben J. Sutlieff, Johanna M. Vos, Niall Whiteford
Astrophysics of Galaxies
Sulfur monoxide as a tracer of the Galactic $^{32}$S/$^{34}$S gradient
Yipeng Zou, Jiangshui Zhang, Dingyuan Wei et al. (+6 more)
To date, the
Galactic interstellar radial $^{32}$S/$^{34}$S gradient has only been studied with the CS isotopologs, which may be affected by uncertainties due to the use of a single tracer. As another abundant S-bearing molecules, SO and its isotopomer $^{34}$SO could be considered as tracers of the $^{32}$S/$^{34}$S ratio. We present the first systematic observations of SO and $^{34}$SO toward a large sample of molecular clouds with accurate distances, performed with the IRAM 30 m and the 10 m Submillimeter
Telescope (SMT). With the IRAM 30 m, SO $2_2-1_1$ was detected in 59 of 82 sources ($\sim$82%), and $^{34}$SO $2_2-1_1$ in 8 sources ($\sim$10%). With the SMT 10 m, SO $5_5-4_4$ was detected in 136 of 184 sources ($\sim$74%), and $^{34}$SO $5_5-4_4$ in 55 of 77 strong SO sources ($\sim$72%). SO/$^{34}$SO ratios were derived for 8 ($2_2-1_1$) and 55 ($5_5-4_4$) sources. No correlation was found between the SO/$^{34}$SO ratio and heliocentric distance or $T_k$, suggesting negligible distance and fractionation effects. Both LTE and non-LTE analyses consistently suggest that the optical depth effect is also insignificant. $^{32}$S/$^{34}$S ratios from the $2_2-1_1$ transitions follow the increasing radial trend proposed by previous CS species measurements, while those from the $5_5-4_4$ lines are systematically lower. The lower transitions of SO and $^{34}$SO may be suitable tracers of $^{32}$S/$^{34}$S, though the detections are rare. Comparisons between measurements and
Galactic chemical
evolution model suggest that the nucleosynthesis prescriptions need to be revised in the low-
metallicity regime, but more data for the outermost
Galactic regions are crucial for drawing strong conclusions.
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All authors Yipeng Zou, Jiangshui Zhang, Dingyuan Wei, Yaoting Yan, Donatella Romano, Youxin Wang, Jialiang Chen, Hongzhi Yu, Jieyu Zhao
High Energy Astrophysical Phenomena
Blazar classification from multi-wavelength data using Deep Learning
Saqlain Afroz, Titir Mukherjee and Raj Prince
The
Fermi Large Area
Telescope (
Fermi-LAT) has detected more than 7,000 gamma-ray sources, a significant fraction of which are identified as blazars, while a comparable number remain classified as blazars of uncertain type (BCUs) or are unassociated with counterparts at other wavelengths. The absence of complete multi-wavelength spectral information presents a major obstacle to robust source classification, despite such data providing the most reliable means of understanding blazar properties. In this work, we focus on classifying BCUs into the two primary blazar subclasses, flat-spectrum
radio quasars (FSRQs) and BL Lacertae objects (BL Lacs), using a feed-forward artificial neural network (ANN) trained on multi-wavelength observational parameters. We first identify the most informative features by quantifying their information content and then use these features to train the ANN, whose performance is evaluated using a k-fold cross-validation strategy to ensure robust generalization. The trained model is subsequently applied to classify BCUs into BL Lacs and FSRQs. Our results demonstrate that machine learning-based classification using a carefully selected set of multi-wavelength parameters offers an efficient and reliable approach for resolving the nature of BCUs and improving the completeness of the gamma-ray blazar population in
Fermi-LAT catalogs.
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Solar and Stellar Astrophysics
Young M dwarfs flare activity model: Towards better exoplanetary atmospheric characterisation
E. Mamonova, A. F. Kowalski, K. Herbst et al. (+2 more)
Context.
Stellar flares can significantly influence the atmospheres and habitability of orbiting
exoplanets, especially around young and active M
dwarfs. Understanding the temporally and spectrally resolved activity of such
stars is essential for assessing their impact on planetary environments. Aims. We aim to examine in detail state-of-the-art concepts of
flare models to identify what is missing in our understanding of energy deposition during the
flare event. By comparing synthetic and observed
flare spectra, we seek to determine the modelling frameworks best suited to represent
flare energetics and spectral far-ultraviolet features while providing a foundation for investigating
flare impacts on
exoplanet atmospheres. Methods. In this work, we built the Young M
Dwarfs Flare (YMDF) model utilising the combination of radiative-hydrodynamic (RHD)
stellar atmosphere models with a high and low-energy electron beam and corresponding synthetic observables. These models are based on physical principles and were validated with
solar and
stellar observations. Results. The newly developed YMDF model reproduces the observed continuum rise in both the TESS photometric band and the FUV-A spectral range. Furthermore, the
flare distributions generated within this framework show consistency with those observed in our sample of
stars. Conclusions. We have developed the YMDF model as a tool to reproduce the time-dependent spectra of flaring young M
dwarfs, providing a physically motivated description of their spectral and temporal
evolution during
flare events.
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All authors E. Mamonova, A. F. Kowalski, K. Herbst, S. Wedemeyer, S. C. Werner
Astrophysics of Galaxies
Consequences of radially correlated rotation curves for galaxy mass models
Helena Chase, Diego Dado, Katherine E. Harborne et al. (+1 more)
Consecutive points in rotation curve measurements are correlated with each other, but this is usually ignored when constructing
galaxy mass models. We apply a recently proposed data-driven approach to include the characteristic amplitude and scale length of such correlations as `nuisance parameters'. We construct mass models for $134$
galaxies from the SPARC rotation curve compilation with Navarro-Frenk-White (NFW) and pseudo-isothermal sphere (pISO) models for the dark
halo. Allowing for correlations in the rotation curves generally improves the goodness of fit for both
halo models, often yielding a formally good fit ($\chi^2_\mathrm{r}\approx 1$) and model uncertainties that seem more representative of the constraining power of the data. For both
halo models the inference on the typical correlation amplitude and scale length are very similar and physically plausible, $\sim 20\,\mathrm{km}\,\mathrm{s}^{-1}$ and $\sim 5\,\mathrm{kpc}$, respectively. The parametric form that we use to describe the correlations is intentionally simple, and our fitting approach makes the parameters describing possible correlations prone to `absorbing' other systematic errors, so we regard these estimates as upper limits. Without allowing for correlations we find a statistical preference for the pISO over the NFW model for $88$/$134$
galaxies; this preference essentially disappears when correlations are allowed for. Accounting for correlations in rotation curves when constructing mass models fundamentally affects how they are interpreted, highlighting an important systematic uncertainty that affects evidence for cusps or cores in dark matter
haloes.
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All authors Helena Chase, Diego Dado, Katherine E. Harborne, Kyle A. Oman
Solar and Stellar Astrophysics
Predictions from $s$-process AGB models of the isotopic variations of zirconium and neodymium for comparison to bulk meteorites
Maria Lugaro, Giulia C. Cinquegrana, Balázs Szányi et al. (+6 more)
Bulk meteoritic data show isotopic variability of $slow$-
neutron-capture ($s$-process) origin in a several elements heavier than Fe. One peculiar feature is that the lighter $s$-process elements (e.g., Zr and Mo) present larger anomalies than the heavier $s$-process elements (e.g., Nd and W). To address this observation, we compared Zr and Nd data to model predictions of the s-process abundances at the surface of low-mass asymptotic
giant branch (AGB)
stars of initial
metallicity from
solar to twice
solar. We found that the relative magnitude of the isotopic variability between these two elements can be matched by models of AGB
stars of super-
solar metallicity. The match is favoured by stronger convective overshoot, leading to a deeper dredge-up of the H-rich envelope into the He-rich region, and/or a smaller (~ half than standard) mass of the region rich in the $^{13}$C
nuclei that produce free
neutrons via the $^{13}$C($\alpha$,n)$^{16}$O reaction. We conclude that nucleosynthesis in AGB
stars can match the difference in the magnitude of the bulk meteoritic variations in Zr and Nd, provided that super-
solar metallicity stars are the original site of these signatures. The AGB
stars that produced such variations could have belonged to the current population of old, super-
solar metallicity stars seen in the
galactic solar neighbourhood.
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All authors Maria Lugaro, Giulia C. Cinquegrana, Balázs Szányi, James M. Ball, Borbála Cseh, Mattias Ek, Amanda I. Karakas, Maria Schönbächler, John C. Lattanzio
Solar and Stellar Astrophysics
$\delta$ Circini: A massive hierarchical triple system with an eclipsing binary
J. Švrčková, P. Harmanec, R. Klement et al. (+6 more)
$\delta$ Circini is known to be a massive multiple system containing a 3.9 d inner eclipsing binary in a slightly elliptical orbit exhibiting slow apsidal motion and a distant tertiary with a probable period of 1644 d. All three components of the system are O- or B-type
stars. We carried out a comprehensive study of the system, based on light curves from TESS and other instruments, a new series of echelle spectra, older spectra from the ESO archive, and several VLTI interferometric observations. Due to the large amount of different types of data covering both orbits in the system, we obtained a more precise value of the long orbital period ($1603.24\pm0.19$ d) and fully determined all other orbital parameters. Although both orbits are eccentric, their period ratio is large enough for the system to be dynamically stable. The inner and outer orbits are in the same plane, which means that no Kozai-Lidov mechanism is acting in the system. Assuming
solar metallicity in our MESA models, we found ages of $(4.4\pm 0.1)$, $(4.7\pm 0.2)$, and $(3.8\pm1.3)$ Myr for the primary, the secondary, and the tertiary, respectively. Our evolutionary scenario predicts that the inner eclipsing binary will merge within approximately 1.7 Myr and eventually evolve into a black hole. The distance to the system, estimated from the angular size of the outer orbit is $(809.9 \pm 1.8)$ pc, which implies that $\delta$ Cir might be located close to the centre of a
stellar population ASCC 79, a subgroup of the young Circinus complex. With a total mass of $(53.04\pm0.29)$ M$_{\odot}$, $\delta$ Cir can contribute a significant fraction of the total mass of the population.
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All authors J. Švrčková, P. Harmanec, R. Klement, Th. Rivinius, B. N. Barlow, J. Juryšek, M. Mašek, K. Hoňková, A. Oplištilová
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Scalar field effective potentials in de Sitter spacetime
Lucas Vicente García-Consuegra and Arttu Rajantie
We investigate two different definitions of a scalar field effective potential in
quantum field theory in de Sitter spacetime: the standard textbook definition, and the constraint effective potential proposed by O'Raifeartaigh et al. in 1986. While these definitions are equivalent in Minkowski spacetime, they differ significantly in de Sitter. We demonstrate this by computing them both explicitly at one-loop order in perturbation theory. It is well known that the perturbative expansion of the standard effective potential fails converge for light fields. In contrast, the constraint effective potential does not suffer from this infrared problem, and it can therefore be computed using perturbation theory. We discuss the physical interpretation of the two effective potentials. In particular, we provide evidence supporting an earlier
conjecture that the constraint effective potential is the correct one to use in the
stochastic Starobinsky-Yokoyama theory.
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Cosmology and Nongalactic Astrophysics
Constraining dark matter halo profiles with symbolic regression
Alicia Martín, Tariq Yasin, Deaglan J. Bartlett et al. (+2 more)
Dark matter
haloes are typically characterised by radial density profiles with fixed forms motivated by simulations (e.g. NFW). However, simulation predictions depend on uncertain dark matter physics and baryonic modelling. Here, we present a method to constrain
halo density profiles directly from observations using Exhaustive Symbolic Regression (ESR), a technique that searches the space of analytic expressions for the function that best balances accuracy and simplicity for a given
dataset. We test the approach on mock weak
lensing excess surface density (ESD) data of synthetic clusters with NFW profiles. Motivated by real data, we assign each ESD data point a constant fractional uncertainty and vary this uncertainty and the number of clusters to probe how data precision and sample size affect model selection. For fractional errors around 5%, ESR recovers the NFW profile even from samples as small as 20 clusters. At higher uncertainties representative of current surveys, simpler functions are favoured over NFW, though it remains competitive. This preference arises because weak
lensing errors are smallest in the outskirts, causing the fits to be dominated by the outer profile. ESR therefore provides a robust, simulation-independent framework both for testing mass models and determining which features of a
halo's density profile are genuinely constrained by the data.
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All authors Alicia Martín, Tariq Yasin, Deaglan J. Bartlett, Harry Desmond, Pedro G. Ferreira
Instrumentation and Methods for Astrophysics
The observation of Ground Level Enhancement GLE 77 by the neutron detectors of the Experimental Complex NEVOD
Evgenii Volkov, Kseniia Chelidze, Dmitrii Gromushkin et al. (+4 more)
A Ground Level Enhancement event was observed by
neutron detectors designed for the registration of extensive air showers at the Experimental Complex NEVOD. The potential for that was unlocked by a recent modernization of the experimental setup that included implementation of additional channels for measuring
neutron flux variation. At 10:15 UT on November 11, 2025, a sudden and significant increase in the
neutron flux was detected by two installations: PRISMA-36 and URAN arrays. For the first time, a GLE has been recorded using a set of
neutron detectors oriented at the extensive air shower studies. We present the measured EC NEVOD data and the results of the preliminary analysis of the observed GLE.
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All authors Evgenii Volkov, Kseniia Chelidze, Dmitrii Gromushkin, Semen Khokhlov, Evgenii Khomchuk, Anatoly Petrukhin, Ivan Shulzhenko