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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 21 November

High Energy Astrophysical Phenomena

Magnetized particle motion and accretion process with shock cone morphology around a decoupled hairy black holes

G. Mustafa, Faisal Javed, S.K. Maurya et al. (+5 more)

Relativistic accretion onto compact objects such as black holes and neutron stars is one of the most efficient known mechanisms for converting gravitational potential energy into radiation. In the case of rapidly spinning black holes, up to $40\%$ of the rest-mass energy of accreting matter can be released, far exceeding the efficiency of nuclear fusion. In this work, we investigate magnetized particle motion and relativistic accretion processes around a decoupled hairy black hole via extended geometric deformation. The developed geometry involves two hairy parameters that preserve the horizon structure with the additional feature of the fulfillment of weak energy conditions outside the event horizon. We provide the foundation with necessary formalism for magnetized particle motion around a decoupled black hole. The effective potential and innermost stable circular orbits are then derived, which demonstrate a significant reduction of the radius of the latter quantity under the hairy parameters for the magnetized particle. Afterwards, we obtain exact analytical expressions for radial velocity profiles, mass accretion rates, and a few others which reveal improved energy efficiency and emissivity as compared to the standard black hole. Furthermore, the decoupling parameter shows strong influence on oscillations, accretion presenting fantastic agreement between analytical predictions and numerical simulations, and thus offering noticeable observational signatures for future gravitational wave and X-ray astronomy.
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All authors G. Mustafa, Faisal Javed, S.K. Maurya, A. Ditta, Orhan Donmez, Tayyab Naseer, Abdelmalek Bouzenada, Farruh Atamurotov

Astrophysics of Galaxies

RGB Tip distance to the faint gas-rich dwarf KK 153

M. Bellazzini, G. Beccari, R. Pascale et al. (+4 more)

KK 153 is a star-forming dwarf galaxy that has been recently proposed as a new member of the sparsely populated class of gas-rich ultra faint dwarfs, lying in the outskirts of the Local Group. We used the Large Binocular Telescope under sub-arcsec seeing conditions to resolve for the first time the outer regions of KK 153 into individual stars, reaching the red giant branch. The magnitude of the red giant branch tip was used to measure a distance of D=3.06 (+0.17/-0.14) Mpc, much more accurate and precise than the estimate previously available in the literature, based on the baryonic Tully-Fisher relation (D=2.0 (+1.7/-0.8) Mpc). The new distance places KK 153 clearly beyond the boundaries of the Local Group, and, together with a new measure of the integrated magnitude, implies a stellar mass of M_*=2.4 \pm 0.2 X 10^6 M_{\sun}. The dwarf populates the extreme low-mass tail of the M_* distribution of gas-rich galaxies but it is significantly more massive than the faintest local gas-rich dwarfs, Leo T and Leo P. In analogy with similar systems, the star formation history of KK 153 may have been impacted by the re-ionisation of the Universe while keeping a sufficient gas reservoir to form new stars several Gyr later.
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All authors M. Bellazzini, G. Beccari, R. Pascale, D. Paris, F. Annibali, F. Cusano, D. Pérez-Millán

Solar and Stellar Astrophysics

Dark Matter Admixed White Dwarfs: A Single-Fluid Approach

Rajasmita Sahoo, Somnath Mukhopadhyay and Mrutunjaya Bhuyan

In this study, we investigate the influence of an admixed fermionic dark matter (DM) component on the equilibrium structure of white dwarfs (WDs), with particular emphasis on the effects of varying the DM particle mass ($m_{\rm DM}$) and DM fraction ($f_{\rm DM}$). Notably, we employ a single-fluid approximation for the first time in this context, wherein the baryonic and DM contributions to the total energy density and pressure are treated within a unified framework, assuming non-interacting fermionic DM in hydrostatic equilibrium with baryons. We examine how variations in $m_{\mathrm{DM}}$ and $f_\mathrm{DM}$ modify the equation of state (EoS), the mass-radius relationship, and the internal mass and pressure distributions of WDs. Our results show that the presence of DM softens the EoS, with lighter DM particles providing stronger pressure support and leading to more extended stellar structures. Increasing the DM mass fraction leads to a more compact configuration, reducing both the radius and maximum mass of the WD. We further demonstrate that heavier DM particles enhance stellar compactness and can eventually drive the star toward gravitational instability. Moreover, the analysis of mass-radius relationships reveals that while small fractions of DM are consistent with observed WD masses, the radii predicted by our models are smaller than observations, suggesting additional influences such as rotation or magnetic fields. Our stability analysis confirms that the inclusion of dark matter does not lead to instability within the expected parameter space, indicating that white dwarfs admixed with dark matter can remain dynamically stable under certain conditions. These findings show that even a small admixture of DM can modify the structural properties and stability limits of WDs, providing a potential indirect astrophysical probe of DM particle properties.
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Astrophysics of Galaxies

RUBIX: Differentiable forward modelling of galaxy spectral data cubes for gradient-based parameter estimation

Anna Lena Schaible, Ufuk Çak{\i}r, Tobias Buck et al. (+5 more)

Although integral-field spectroscopy enables spatially resolved spectral studies of galaxies, bridging particle-based simulations to observations remains slow and non-differentiable. We present RUBIX, a JAX-based pipeline that models mock integral-field unit (IFU) cubes for galaxies end-to-end and calculates gradients with respect to particle inputs. Our implementation is purely functional, sharded, and differentiable throughout. We validate the gradients against central finite differences and demonstrate gradient-based parameter estimation on controlled setups. While current experiments are limited to basic test cases, they demonstrate the feasibility of differentiable forward modelling of IFU data. This paves the way for future work scaling up to realistic galaxy cubes and enabling machine learning workflows for IFU-based inference. The source code for the RUBIX software is publicly available under https://github.com/AstroAI-Lab/rubix.
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All authors Anna Lena Schaible, Ufuk Çak{\i}r, Tobias Buck, Harald Mack, Aura Obreja, Nihat Oguz, William H. Oliver, Horea-Alexandru Cărămizaru

High Energy Astrophysical Phenomena

Spectral synthesis techniques for supernovae and kilonovae

Anders Jerkstrand

Supernovae (SNe) and kilonovae (KNe) are the most violent explosions in cosmos, signalling the destruction of a massive star (core-collapse SN), a white dwarf (thermonuclear SN) and a neutron star (KN), respectively. The ejected debris in these explosions is believed to be the main cosmic source of most elements in the periodic table. However, decoding the spectra of these transients is a challenging task requiring sophisticated spectral synthesis modelling. Here, the techniques for such modelling is reviewed, with particular focus on the computational aspects. We build from a historical review of how methodologies evolved from modelling of stellar winds, to supernovae, to kilonovae, studying various approximations in use for the central physical processes. Similarities and differences in the numeric schemes employed by current codes are discussed, and the path towards improved models is laid out.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Exceptional line and pseudospectrum in black hole spectroscopy

Li-Ming Cao, Ming-Fei Ji, Liang-Bi Wu et al. (+1 more)

We investigate the exceptional points (EPs) and their pseudospectra in black hole perturbation theory. By considering a Gaussian bump modification to the Regge-Wheeler potential with variable amplitude, position, and width parameters, $(\varepsilon,d,\sigma_0)$, a continuous line of EPs (exceptional line, EL) in this three-dimensional parameter space is revealed. Notably, the EL exhibits an anisotropic spectral response: parameters migrating along the EL direction leaves the coalesced QNM spectra nearly unchanged, while moving parameters away from the EL induces the characteristic $\epsilon^{1/2}$ scaling, highlighting the directional nature of spectral instability in exceptional structures. We find that the vorticity $\nu=\pm1/2$ and the Berry phase $\gamma=\pi$ for loops encircling the EL, while $\nu=0$ and $\gamma=0$ for those do not encircle the EL. In the neighborhood of an eigenvalue, through matrix perturbation theory, we prove that the $\epsilon$-pseudospectrum contour size scales as $\epsilon^{1/q}$ at an EP , where $q$ is the order of the largest Jordan block of the Hamiltonian-like operator associated with that eigenvalue, contrasting with the linear $\epsilon$ scaling at non-EPs. Numerical implements confirm this observation, demonstrating enhanced spectral instability at EPs for non-Hermitian systems including black holes.
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All authors Li-Ming Cao, Ming-Fei Ji, Liang-Bi Wu, Yu-Sen Zhou

Instrumentation and Methods for Astrophysics

Morphological Image Similarity Search on the ALMA Science Archive Query Interface Using Deep Unsupervised Contrastive Representation Learning

Felix Stoehr, Andrea Farago, Stefan Curiban et al. (+5 more)

With the exponential growth of astronomical data over time, finding the needles in the haystack is becoming increasingly difficult. The next frontier for science archives is to enable searches not only on observational metadata, but also on the content of the observations themselves. As a step in this direction, we have implemented morphological image similarity search into the ALMA Science Archive (ASA). To achieve this we use self-supervised contrastive affine-transformation-independent representation learning of source morphologies with a deep neural network. For a given image on the ASA web interface, astronomers are presented with a summary view of the morphologically most similar images. Each time an astronomer selects an additional image from that view, the display is instantly updated to show the images most similar to the combination of the selected images. Each selection thus refines the similarity display according to the scientific needs of the astronomer. This is the first time image similarity search has been offered in an astronomical science archive.
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All authors Felix Stoehr, Andrea Farago, Stefan Curiban, Alisdair Manning, Jorge Garcia, Pei-Ying Hsieh, Andrew Lipnicky, Adele Plunkett

Astrophysics of Galaxies

Comparing galaxy merger orbits in hydrodynamical simulation and in dark-matter-only simulation

Yahan Pu, Lan Wang, Guangquan Zeng et al. (+1 more)

To investigate how the presence of baryons in simulations affects galaxy merger orbits, we compare in detail the merger timescales and orbits of the matched merger pairs in TNG100 hydrodynamical simulations and their corresponding dark-matter-only simulations, for different resolution levels. Compared with the mergers in the TNG100-1-Dark simulation without baryons, the matched mergers in the TNG100-1 simulation have similar infall time, but have statistically earlier merger times and therefore shorter merger timescales. The merger orbits for the matched pairs in the TNG100-1 and the TNG100-1-Dark simulations are similar right after infall, and both evolve to more head-on orbits at final stages, with smaller changes in the hydrodynamical simulation. In the final 2 Gyr before merger, the collision angles that represent merger orbits quantitatively are smaller in TNG100-1 than those in TNG100-1-Dark, by around 6$^\circ$ to 10$^\circ$, depending on the mass ratios and galaxy masses investigated. Our results demonstrate that the presence of baryons accelerates a bit the merger processes, and results in more spiral-in orbits for both major and minor mergers in galaxies with various stellar masses. These effects are less obvious in simulations with lower resolutions.
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All authors Yahan Pu, Lan Wang, Guangquan Zeng, Lizhi Xie

Astrophysics of Galaxies

Multiphase Astrophysics to Unveil the Virgo Environment (MAUVE)

Barbara Catinella, Luca Cortese, Jiayi Sun et al. (+26 more)

The Multiphase Astrophysics to Unveil the Virgo Environment (MAUVE) project is a multi-facility programme exploring how dense environments transform galaxies. Combining a VLT/MUSE P110 Large Programme and ALMA observations of 40 late-type Virgo Cluster galaxies, MAUVE resolves star formation, kinematics, and chemical enrichment within their molecular gas discs. A key goal is to track the evolution of cold gas that survives in the inner regions of satellites after entering the cluster, and how it evolves across different infall stages. With its high spatial resolution – probing down to the physical scales of giant molecular cloud complexes – and multiphase synergy, MAUVE aims to offer a time-resolved view of environmental quenching and set a new benchmark for cluster galaxy studies.
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All authors Barbara Catinella, Luca Cortese, Jiayi Sun, Toby Brown, Eric Emsellem, Amelia Fraser-McKelvie, Adam B. Watts, Amy Attwater, Andrew Battisti, Alessandro Boselli, Woorak Choi, Aeree Chung, Elisabete da Cunha, Timothy A. Davis, Sara Ellison, Pavel Jáchym, Maria J. Jimenez-Donaire, Tutku Kolcu, Bumhyun Lee, James McGregor, Ian Roberts, Eva Schinnerer, Kristine Spekkens, Sabine Thater, David Thilker, Jesse van de Sande, Vicente Villanueva, Thomas G. Williams, Nikki Zabel

Astrophysics of Galaxies

TRAO Survey of the Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO-FUNS). IV. Filaments and Dense Cores in the W40 and Serpens South Regions of Aquila

Satyajeet Moharana, Chang Won Lee, Shinyoung Kim et al. (+9 more)

We present the results of molecular line observations toward the W40 and Serpens South regions of the Aquila molecular cloud complex, conducted as part of the TRAO-FUNS project to investigate the role of filamentary structures in the formation of dense cores and stars in molecular clouds. We performed a Gaussian decomposition of the C$^{18}$O spectra to disentangle multiple velocity components along the line-of-sight and a `Friends-of-Friends' algorithm on these decomposed components to identify 24 velocity-coherent filaments in the observed region. The `FellWalker' algorithm is applied on the N$_{2}$H$^{+}$ integrated intensity map to identify the dense cores embedded within the filaments. Many of the filaments previously identified from the Herschel survey are found to contain multiple velocity-coherent filaments. Virial analysis indicated that all of our identified filaments are thermally supercritical and gravitationally bound. Velocity gradients are observed along the filaments in the vicinity of embedded dense cores, indicating the presence of longitudinal flows that contribute to core formation. The median mass flow rate across the observed region is estimated to be $\sim$35 M$_{\odot}$ Myr$^{-1}$, with Serpens South showing a rate $\sim$40% higher than W40. The analysis of non-thermal motions revealed that the dense cores mainly show subsonic to transonic motions, while their host filaments are mostly supersonic, suggesting that the turbulent motions in filaments may dissipate on smaller scales, allowing core formation. These findings highlight the essential role of the filaments' criticality, mass flow, and turbulent dissipation in the formation of dense cores within the filaments.
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All authors Satyajeet Moharana, Chang Won Lee, Shinyoung Kim, Eun Jung Chung, Spandan Choudhury, Mario Tafalla, Jongsoo Kim, Archana Soam, Donghyeok Koh, Shivani Gupta, Maheswar Gopinathan, Woojin Kwon

Cosmology and Nongalactic Astrophysics

Probing Dark Matter Substructure with Image Number Anomaly in Strong Lensing Systems

Wenlin Hou, Jianxiang Liu and Kai Liao

Gravitational lensing observables, including anomalies in image positions, flux ratios, and time delays, serve as usual probes of dark matter (DM) substructure. When dark matter substructure possesses sufficient perturbations, it may lead to the formation of extra images in otherwise canonical doubly or quadruply imaged systems. With the advent of increasingly precise observational instruments, previously undetectable images may become measurable and image number anomalies therefore could be an increasingly viable method. In this paper, we utilize the gravitational lensing phenomenon of image number anomaly to derive constraints on dark matter substructure. We present the extra images induced by distinct forms of DM substructure, specifically primordial black holes (PBHs) and fuzzy dark matter (FDM) and show that higher angular resolution observations increase the probability of detecting additional lensed images. Based on a null detection of image number anomalies in a sample of 3500 lens systems generated from the Strong Lensing Halo model-based mock catalogs (SL-Hammocks), we derive upper limits on the abundance of PBHs. At the 95% confidence level, the PBH abundance is constrained to $\lesssim 0.125\%$, $0.08\%$, and $0.04\%$ for PBH masses in the range $\sim 10^{7}$–$10^{9}~M_{\odot}$, corresponding to angular resolutions of $0.1''$, $0.05''$, and $0.01''$, respectively. Similarly, we exclude particle masses below $0.4$, $0.6$, and $3.5 \times 10^{-22} \ \mathrm{eV}$ for FDM at the same confidence level for the respective resolutions. Furthermore, the abundance of PBHs $\lesssim 0.9\%$ could be constrained at an angular resolution of $0.5''$ for the Legacy Survey of Space and Time (LSST) Observations. Finally, we discuss methodologies for identifying image number anomalies in special cases and demonstrate feasibility using a fitting procedure.
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Instrumentation and Methods for Astrophysics

A novel double-rim forebaffle design for centimeter to sub-millimeter astrophysical observations

Jacques Delabrouille, Oliver Jeong, Michel Piat et al. (+1 more)

Stray radiation of various origin is a major source of degradation of centimeter to sub-millimeter astronomical observations. This is particularly problematic for the detection of signals such as faint cosmic microwave background polarization B modes, or for mapping large-scale extragalactic or Galactic diffuse emission. In this paper, we propose a double-rim forebaffle design to reduce the impact of such stray radiation contamination. Using qualitative arguments and numerical simulations, we show that such a design has the potential to substantially improve the quality of future observations.
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All authors Jacques Delabrouille, Oliver Jeong, Michel Piat, Alexander Steier

Instrumentation and Methods for Astrophysics

Fast far-sidelobe modeling for centimeter to sub-millimeter astrophysical observations

Oliver Jeong, Jacques Delabrouille and Michel Piat

Next-generation centimeter to sub-millimeter telescopes require exquisite control over instrumental far-sidelobe response to accurately measure faint signals like the Cosmic Microwave Background B modes. Because existing electromagnetic modeling methods are computationally expensive, we developed a novel, diffraction-based beam modeling method for rapid and low-cost calculations. We applied this methodology to model the BICEP3 far-sidelobes and found good qualitative agreement with in situ beam measurements. Using this validated simulated beam, we calculated the sidelobe temperature pickup for a specific observation scenario: scanning near the slopes of Cerro Toco in the Atacama Desert. This rapid, predictive framework is most valuable as a tool for optimizing instrument baffling and identifying efficient scan strategies during the conceptual design phase.
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Solar and Stellar Astrophysics

Fully self-consistent nova explosion models reproducing light curves of KT Eri, V339 Del, V597 Pup, and SMC NOVA 2016-10a

Mariko Kato, Izumi Hachisu and Hideyuki Saio

The rising phase toward the optical maximum of a classical nova is one of the last frontiers of nova study. Constructing free-free emission model light curves based on our fully self-consistent nova explosion models, we present several theoretical light curves of classical novae and compare them with the four novae having the observed rising phase toward the optical maximum. Our 1.25 $M_\odot$ white dwarf (WD) models show excellent agreements with the light curves of KT Eri, V339 Del, and V597 Pup while our 1.35 $M_\odot$ WD models are consistent with the light curves of SMC NOVA 2016-10a. These agreements indicate that the light curves toward the optical maximum of these novae are dominated by free-free emission, rather than by photospheric emission. Our results justify the previously obtained WD masses and distance moduli for these novae, and shows that the post-maximum evolution can be well approximated with the evolution sequences of steady-state envelope solutions.
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Cosmology and Nongalactic Astrophysics

Exploring the Cosmological Model Degeneracy with a new evaluate factor G

Yuan-bo Xie, Yun-dong Wu, Wei Hong et al. (+1 more)

In the context of fitting cosmological models, parameter degeneracy remains a central issue. This paper critically examines traditional methods for constraining parameters and focuses on the G factor as a tool for evaluating the quality of observational data. To ensure analytical independence, two datasets–Cosmic Chronometers (CC) and Baryon Acoustic Oscillations (BAO)–were utilized as samples for parameter fitting, supplemented by Markov Chain Monte Carlo (MCMC) simulations. The Figure of Merit (FoM) matrix served as the final criterion for assessing fitting performance. The results show that the G factor of the CC dataset increases linearly with redshift z, whereas the G factor of the BAO dataset follows a cubic relationship. Further analysis indicates that the FoM value for datasets with high G factors is significantly higher than that for datasets with low G factors, thereby validating the G factor's effectiveness as a tool for assessing observational data quality and reducing parameter degeneracy. This suggests that the G factor may serve as a diagnostic tool and selection criterion for optimizing observational datasets in future research.
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All authors Yuan-bo Xie, Yun-dong Wu, Wei Hong, Tong-jie Zhang

Astrophysics of Galaxies

A deep ALMA Band 3 survey of HDFS/MUSE3D: Survey description and initial results

Hugo Messias, Laura Gomez, Harold Francke et al. (+7 more)

(abridged) After more than 10yr of ALMA operations, the community interest in conducting deep, extra-galactic, millimetre surveys resulted in varying strategic compromises between areal size and map depth to survey the sky. The current bias leans towards a galaxy population found in the field or towards rich star-bursty proto-cluster groups, both tendentiously surveyed at coarse spatial resolutions. Here, we describe a deep 3mm ALMA survey in long-baselines on a 1x1arcmin2 region in the Hubble Deep Field South, also covered by the Multi Unit Spectroscopic Explorer (MUSE) in order to assess resolved molecular gas properties in galaxies in group environments at z>1. ALMA observations comprising a 4-pointing mosaic with a single Band3 (3mm) spectral tuning were conducted to cover CO transitions from different groups identified by MUSE. This work consists in a total effective time on source of 61h in configurations with up to 15km baselines. The final data-set yields an angular resolution of 0.15"-0.2" (imaging weights dependent) and maximum recoverable scales of 1"-2". The final continuum map reaches a sensitivity of rms~2uJy/beam, allowing the detection of three sources at 3mm (only one showing multi-wavelength counterparts). Moreover, we detect six line emitters associated with CO J=2-1 at zspec=1.284, one of them previously undetected by MUSE and none detected in 3mm continuum. The inter-stellar medium gas masses range from ~2E9 to ~9E10 Msun (adopting alphaCO=4Msun/(K.km/s.pc2), including Helium). Overall, this galaxy group is quite diverse with no two galaxies alike, some showing clear physical offsets with respect to Hubble imaging tracing rest-frame ultra-violet emission. We also derive cosmic molecular gas mass densities using this sample as a reference for group environments, and we find that these yield comparable densities as the galaxy population found in field environments.
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All authors Hugo Messias, Laura Gomez, Harold Francke, Bill Dent, Belén Alcalde Pampliega, Ruediger Kneissl, Yiqing Song, Dirk Petry, Paulo Cortés, Sergio Martín

Astrophysics of Galaxies

CO Multi-line Imaging of Nearby Galaxies (COMING). XI. Azimuthally averaged star formation rate and stellar mass relation with molecular gas amount

Ayumi Kajikawa, Kazuo Sorai, Kana Morokuma-Matsui et al. (+13 more)

This study investigated the relation between the surface density of star formation rate (SFR) ($\Sigma_{\mathrm{SFR}}$), stellar mass ($\Sigma_{M_{\ast}}$), and molecular gas mass ($\Sigma_{M_\mathrm{mol}}$) on nearly 1 kpc scales averaged over concentric tilted rings using the $^{12}$CO $J=1-0$ mapping data of 92 nearby galaxies obtained in the CO Multi-line Imaging of Nearby Galaxies (COMING) project. We categorized these galaxies into three groups based on the deviation of each global SFR from the star-forming main sequence (MS), $\Delta$MS: upper MS (UMS), MS, and lower MS (LMS). UMS galaxies tend to be less massive or barred spiral galaxies, exhibiting molecular gas fraction ($f_{\mathrm{gas}}$) comparable to those of MS galaxies but higher star formation efficiency (SFE). In contrast, the LMS galaxies tend to be massive or active galaxies hosting an active galactic nucleus (AGN). Their $f_{\mathrm{gas}}$ values are lower than those of MS galaxies, and their SFEs are slightly lower or comparable to those of MS galaxies in the inner region. These trends indicate that enhanced SFE contributes to higher $\Delta$MS values, whereas reduced $f_{\mathrm{gas}}$ results in lower $\Delta$MS values. The less prominent bulge or the presence of a bar structure in UMS galaxies induces disk-wide star formation, consequently increasing the SFE. In LMS galaxies, the molecular gas is exhausted, and their star formation activity is low. Environmental effects, such as tidal gas stripping, may also reduce gas supply from the outer regions. Furthermore, our sample galaxies show that both the specific star formation rate (sSFR) and $f_{\mathrm{gas}}$ decrease in the central region in LMS galaxies but did not change in the same region in UMS galaxies. These results seem to support the inside-out quenching of star formation although the dominant cause of depletion remains uncertain.
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All authors Ayumi Kajikawa, Kazuo Sorai, Kana Morokuma-Matsui, Tsutomu T. Takeuchi, Dragan Salak, Nario Kuno, Kazuyuki Muraoka, Yusuke Miyamoto, Hiroyuki Kaneko, Yoshiyuki Yajima, Atsushi Yasuda, Takahiro Tanaka, Kiyoaki Christopher Omori, Kazuki Shimizu, Suphakorn Suphapolthaworn, Kyoko Hama

High Energy Astrophysical Phenomena

Exploring Emission Line Variability and Jet-Broad Line Region Interaction in the Blazar TON 599

Jonhatan U. Guerrero-González, Vahram Chavushyan and Víctor M. Patiño-Álvarez

Blazars, a highly variable Active Galactic Nuclei (AGNs) subclass, provide a unique opportunity to explore the physical processes within their relativistic jets and emission regions. In this study, we investigate the multiwavelength variability of the blazar TON 599, a Flat Spectrum Radio Quasar (FSRQ), with a particular emphasis on its emission line behavior. We focus on the Mg II $\lambda$2798 Å emission line, a key tracer of the ionized gas in the broad-line region (BLR), and its role in jet-induced variability. In addition to optical emission lines, we analyze gamma-rays (0.1-300 GeV), X-rays (0.2-10 keV), optical continuum ($\lambda$3000 Å), optical polarization, and millimeter-wavelength light curves. Three cross-correlation methods are employed to investigate temporal relationships between the emission line and continuum across various wavelengths. Using the Non-Thermal Dominance (NTD) parameter, our analysis confirms that synchrotron emission dominates the continuum during active states, highlighting the jet's primary role in the observed variability. The Mg II emission line exhibits quasi-simultaneous variability with the optical continuum, suggesting photoionization driven by the jet's non-thermal radiation. Additionally, the minimal time lag between gamma-ray and optical/near-ultraviolet emissions supports a synchrotron self-Compton origin for the most variable component of the gamma-ray emission. These findings highlight the importance of emission line variability and multiwavelength observations in constraining the interaction between jets and the BLR in blazars. The results contribute to a deeper understanding of AGN emission mechanisms and the complex interplay between jets and their surrounding environments.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Accelerating parameter estimation for parameterized tests of general relativity with gravitational-wave observations

Dhruv Kumar, Ish Gupta and Bangalore Sathyaprakash

Tests of general relativity (GR) with gravitational waves (GWs) introduce additional deviation parameters in the waveform model. The enlarged parameter space makes inference computationally costly, which has so far limited systematic, large-scale studies that are essential to quantify parameter degeneracies, check the effect of waveform systematics, and assess robustness across non-stationary and non-Gaussian noise effects. The need is even sharper for next-generation observatories where signals are longer, signal-to-noise ratios (SNRs) are higher, and likelihood evaluations increase substantially. We address this by applying relative binning to the TIGER framework for parameterized tests of GR. Relative binning replaces dense frequency waveform evaluations with evaluations on adaptively chosen frequency bins, reducing the cost per likelihood call while preserving posterior accuracy. Using simulated binary black hole signals, we demonstrate unbiased recovery for GR-consistent cases and targeted non-GR deviations, and we map how bin resolution controls accuracy, with finer binning primarily required for the $-1$ post-Newtonian term. A high-SNR simulated signal at next-generation sensitivity further shows accurate recovery with tight posteriors. Applied to GW150914 and GW250114, both single and multi-parameter TIGER analyses finish within a day, yielding bounds consistent with GR at 90% credibility and in agreement with previous results. Across analyses, the method reduces wall time by factors of $\mathcal{O}(10)$ to $\mathcal{O}(100)$, depending on frequency range and binning scheme, without degrading parameter estimation accuracy.
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High Energy Astrophysical Phenomena

Self-bound quark stars with a first-order two-to-three flavor phase transition

G. Teruya, G. Lugones and A. G. Grunfeld

We investigate self-bound quark stars in a flavor-dependent quark-mass density-dependent model with an excluded-volume correction. We chart the parameter space at zero pressure to identify self-bound regimes, including parametrizations in which self-bound two-flavor matter undergoes a genuine first-order $ud \to uds$ transition at finite pressure. We construct cold, $\beta$-equilibrated stellar sequences and compute the corresponding global properties (mass-radius relation, tidal deformability, and moment of inertia). For a wide region of the model parameter space, we find that the onset of a $uds$ core occurs before the maximum-mass configuration is reached, yielding self-bound hybrid stars that follow the typical strange-quark-star sequence morphology but develop a characteristic kink at $p_c=p_{\rm tr}$ along the stellar curves. The excluded-volume parameter $\kappa$ controls the stiffness of the equation of state and thus masses, radii, tidal deformabilities, and moments of inertia; intermediate repulsion typically reconciles $M_{\max}\!\gtrsim\!2\,M_\odot$ with current astrophysical constraints. We further identify two equation-of-state-insensitive trends: dimensionless moment of inertia versus compactness and gravitational versus baryonic compactness. These results provide model-guided priors and tools for discriminating between hadronic and self-bound equations of state with multimessenger data.
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High Energy Astrophysical Phenomena

Which active galaxies might be neutrino emitters?

Shuying Zhou, Mouyuan Sun, Guobin Mou et al. (+4 more)

The IceCube Neutrino Observatory has identified several individual neutrino emitters associated with supermassive black hole accretion phenomena, including blazars, tidal disruption events, and, unexpectedly, Seyfert galaxies. A key open question is which types of active galactic nuclei (AGNs) are most likely to be neutrino emitters. Here we show that high-confidence extragalactic neutrino emitters tend not only to have higher hard X-ray fluxes but also to be more variable in mid-infrared (MIR) than other AGNs in the Swift BAT AGN Spectroscopic Survey. MIR variations effectively trace long-term fluctuations in AGN accretion disks and/or jets. In addition to the role of X-ray flux emphasized in previous studies, we speculate that long-term central engine fluctuations may also be critical for neutrino production. This hypothesis may inform IceCube neutrino-electromagnetic counterpart association studies and provide new insights into cosmic ray acceleration sites. First, the observed neutrinos are unlikely to originate from AGN host galaxies or from interactions between large-scale (dozens of parsecs) winds/outflows and the surrounding interstellar medium. Second, if neutrinos are produced in the X-ray corona, the corona should exhibit strong magnetic turbulence dissipation or magnetic reconnection whose rate changes substantially on timescales of years. Third, the relativistic jets of blazar neutrino emitters may be intrinsically unstable over years. Finally, if neutrinos are related to interactions between small-scale winds/outflows and torus clouds, such winds/outflows must be highly episodic.
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All authors Shuying Zhou, Mouyuan Sun, Guobin Mou, Da-bin Lin, Tong Liu, Ming-Xuan Lu, Yongquan Xue

Instrumentation and Methods for Astrophysics

GSpyNetTreeS: a machine learning solution for glitch localization in time and frequency

Man Leong Chan, Jess McIver, Yannick Lecoeuche et al. (+6 more)

Data from ground-based gravitational wave detectors are often contaminated by non-Gaussian instrumental artifacts or detector noise transients. Unbiased source property estimation relies on the ability to correctly identify and characterize these artifacts and remove them if necessary. To this end, the LIGO-Virgo-KAGRA Collaboration has implemented candidate vetting for all significant candidates to identify the presence of artifacts and assess the need for mitigation. The current candidate vetting process requires human experts to identify the frequency ranges and the time windows associated with any data quality issues present. Differences in judgment between human experts may cause inconsistency, making results difficult to reproduce across gravitational wave events. We present GSpyNetTreeS, an extension to GSpyNetTree based on the You Only Look Once algorithm, for the automatic detection, classification, and time-frequency localization of detector noise transients. As a proof of concept, we tested GSpyNetTreeS's performance on the data collected by the LIGO detectors during the third observing run for gravitational waves as well as common detector glitch classes included in GSpyNetTree: Blip, Low frequency blip, Low frequency line and Scratchy. We also demonstrated that GSpyNetTreeS is capable of accurately identifying common glitch classes and capturing the frequency and time information associated with detected detector noise transients, establishing its potential as an automatic event validation tool for LIGO-Virgo-KAGRA's observing runs.
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All authors Man Leong Chan, Jess McIver, Yannick Lecoeuche, Dhatri Raghunathan, Sofía Álvarez-López, Julian Ding, Annudesh Liyanage, Raymond Ng, Heather Fong

Thursday 20 November

Cosmology and Nongalactic Astrophysics

Spatial Phonons: A Phenomenological Viscous Dark Energy Model for DESI

Muhammad Ghulam Khuwajah Khan

We explore a phenomenological model of dark energy in which space is treated as an elastic brane with uniform tension $T_s$ and supports a longitudinal phonon sector described by three scalar fields $\phi^I$. At the background level the construction reproduces a perfect fluid whose enthalpy and bulk modulus are controlled by two dimensionless parameters $\varepsilon$ and $\kappa$, which encode the elastic and viscous response and determine both the effective equation of state $w_{\rm eff}(z)$ and the physical sound speed thriugh $c_s^2 = \kappa/\varepsilon$. Motivated by the consistency requirements of a phonon effective description, we focus on the stable regime $0 < \kappa < \varepsilon < 1$, which prevents tachyonic behavior and is natural given that $\varepsilon$ and $\kappa$ are defined as fractional response coefficients. To connect the model predictions to current observational summaries, we map $w_{\rm eff}(z)$ onto the Chevallier–Polarski–Linder form $w(z) = w_0 + w_a z/(1+z)$ over the redshift range relevant to DESI. We then use the public DESI DR1 compressed Gaussian likelihood in $(w_0,w_a)$ for BAO combined with Pantheon+ Type I a supernovae and Planck 2018, and scan the model parameter space to identify viable regions. We find that the model can reproduce the DESI compressed constraints at the background level, with representative best match values $(w_0,w_a) \simeq (-0.83,-0.74)$ and therefore, a near luminal sound speed $c_s^2 \simeq 0.9618$ as an output of the fit rather than a built in restriction. The covariance weighted distance is found to satisfy $\chi^2 \ll 1$ in the $(w_0,w_a)$ plane. The associated phonon mass scale $m_\phi = H_\star/(2\pi)$ is ultralight, corresponding to a Compton wavelength of order the cosmological horizon, consistent with interpreting the relevant excitations as infrared collective modes of the brane.
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Earth and Planetary Astrophysics

Constructing Earth Formation History Using Deep Mantle Noble Gas Reservoirs

Vincent Savignac and Eve J. Lee

Noble gases are powerful probes of the Earth's early history, as they are chemically inert. Neon isotopic ratios in deep mantle plumes suggest that nebular gases were incorporated into the Earth's interior. This evidence implies the Earth's formation began when there was still gas around, with Earth embryos accreting primordial gas and a fraction of that gas dissolved into molten magma. In this work, we examine these implications, simulating the growth of primordial envelopes using modern gas accretion schemes, and computing the dissolution of nebular Ne into magma oceans following chemical equilibrium. We find that the embryo mass that reproduces the deep mantle concentration of primordial Ne is tightly constrained to $\sim 0.3 M_\oplus$, within a solar nebula depleted by $\geq 100 \times$ in gas density. Embryos of smaller masses cannot accrete enough gas to allow the mantle to reach the melting temperature of basalt. Embryos of larger masses accrete way too much gas, producing excessive Ne concentrations in the deep mantle. Based on our calculations, we suggest that the Earth's formation began with the assembly of $\sim 0.3 M_\oplus$ embryos during the dispersal of the solar nebula. Light noble gases (He, Ne) in the deep mantle reflect the primordial gas accretion history of the Earth, while heavy noble gases (Ar, Kr, Xe) probe early solid accretion processes. Our results are consistent with the final assembly of the Earth through at least two giant impacts after the dispersal of the nebula.
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Cosmology and Nongalactic Astrophysics

Quantifying the impact of selection effects on FRB DM-$z$ relation cosmological inference

Kritti Sharma, Vikram Ravi, Liam Connor et al. (+3 more)

Fast Radio Bursts (FRBs) have emerged as powerful probes of baryonic matter in the Universe, offering constraints on cosmological and feedback parameters through their extragalactic dispersion measure-redshift (DM$_\mathrm{exgal}$-$z$) relation. However, the observed FRB population is shaped by complex selection effects arising from instrument sensitivity, DM-dependent search efficiency, and FRB source population redshift-evolution. In this work, we quantify the impact of such observational and population selection effects on cosmological inference derived from the conditional distribution $p(\mathrm{DM}_{\mathrm{exgal}}|z)$. Using forward-modeled FRB population simulations, we explore progressively realistic survey scenarios incorporating redshift evolution, luminosity function, and instrument DM selection function. To enable rapid likelihood evaluations, we build a neural-network emulator for the variance in cosmic DM, $\sigma^2[\mathrm{DM}_{\mathrm{cosmic}}(z)]$, trained on $5\times10^4$ baryonification halo-model simulations, achieving $\leq4\%$ accuracy up to $z=4$. We demonstrate that while redshift and DM-dependent selection effects substantially alter the joint distribution $p(\mathrm{DM},z)$, they have a negligible impact on the conditional distribution $p(\mathrm{DM}_{\mathrm{exgal}}|z)$ for current sample sizes. The parameter biases are $\lesssim0.8\sigma$ for $10^2$ FRBs, indicating that conditional analyses are robust for present surveys. However, depending on the survey DM-dependent search efficiency, these biases may exceed $3\sigma$ for $10^4$ FRBs, thus implying that explicit modeling of selection effects will be essential for next-generation samples.
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All authors Kritti Sharma, Vikram Ravi, Liam Connor, Elisabeth Krause, Pranjal R. S., Dhayaa Anbajagane

Solar and Stellar Astrophysics

Gray Spectral Variability in Three Brown Dwarfs Observed by HST/WFC3 Time-Series Observations

Madalyn F. Chapleski and Yifan Zhou

The L/T transition is a critical evolutionary stage for brown dwarfs and self-luminous giant planets. L/T transition brown dwarfs are more likely to be spectroscopically variable, and their high-amplitude variability probes distributions in their clouds and chemical makeup. This paper presents Hubble Space Telescope Wide Field Camera 3 spectral time series data for three variable L/T transition brown dwarfs and compares the findings to the highly variable benchmark object 2MASS J2139. All four targets reveal significant brightness variability between 1.1 to 1.65 micron but show a difference in wavelength dependence of the variability amplitude. Three of our targets do not show significant decrease in variability amplitude in the 1.4 $\mu$m water absorption band commonly found in previous studies of L/T transition brown dwarfs. Additionally, at least two brown dwarfs have irregular-shaped, non-sinusoidal light curves. We create heterogeneous atmospheric models by linearly combining SONORA Diamondback model spectra, comparing them with the observations, and identifying the optimal effective temperature, cloud opacity, and cloud coverage for each object. Comparisons between the observed and model color-magnitude variations that trace both spectral windows and molecular features reveal that the early- T dwarfs likely possess heterogeneous clouds. The three T dwarfs show different trends in the same color-magnitude space which suggests secondary mechanisms driving their spectral variability. This work broadens the sample of L/T transition brown dwarfs that have detailed spectral time series analysis and offers new insights that can guide future atmospheric modeling efforts for both brown dwarfs and exoplanets.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Numerical tiling-based simulations of decoherence in multifield models of inflation

Johor D. Peñalba Quispitupa, Guillermo F. Quispe Peña and Jose T. Galvez Ghersi

In previous work, we developed a method for computing two-point correlators by decomposing the mode degrees of freedom into fast and slow components. Building on this framework, we present a numerical implementation to study the evolution of primordial scalar perturbations under controlled state deformations induced by the simplest environment corrections from the Lindblad equation. The primary contribution of this work is the development of a numerically stable and flexible framework for implementing open-system effects in inflationary perturbations, rather than the extraction of concrete predictions for the primordial spectrum. Our approach generalizes to an arbitrary number of degrees of freedom and does not rely on the slow-roll approximation. The computational routine is numerically efficient and allows users to configure arbitrary sequences of decoherence events, with full control over their duration, shape, amplitude and effective wavelength range. The resulting outputs are compatible with nonlinear numerical codes, enabling studies of how decoherence effects propagate during reheating.
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High Energy Astrophysical Phenomena

In-depth analysis of the clustering of dark matter particles around primordial black holes. Part II. Analytical prescriptions for spikes

Julien Lavalle and Pierre Salati

Primordial black holes (PBHs) are very appealing dark matter (DM) candidates. It is highly plausible though, should they exist, that they would not make up all of the DM. Several studies showed that if the rest of DM is made of thermal particles, then these should accumulate around such PBHs, leading to the formation of very dense spikes in the radiation era. We contributed a detailed analytical study about this phenomenon, providing clear explanations as for the origin of scaling relations in the form of power-law density profiles with up to 3 different spectral indices, i.e. $3/4$, $3/2$, and $9/4$, and 4 asymptotic regimes. Here, we further derive an approximate analytical solution that enables fast numerical predictions for the density profiles of these spikes. We also address the specific case of self-annihilating DM species and derive new approximate analytical formulae. Our approximate density yields the correct annihilation rate within $\pm 15\%$ precision. We then focus on indirect detection in the cosmic microwave background and in extragalactic gamma-rays. We shed new and subtle light on how mutually exclusive PBHs and self-annihilating DM species can really be. In particular, the discovery of a population of sub-solar PBHs would set stringent constraints on the $s$-wave annihilation cross-section of these particles, a point so far missed in the literature.
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Solar and Stellar Astrophysics

Solar Cycle 25 Dynamics from Observational and Statistical Parameters: Characterization of the Maximum Phase and Rotational Behaviour

Homer Dávila Gutiérrez

We present a comprehensive analysis of Solar Cycle 25 aimed at precisely constraining the interval of its activity maximum using multiple observational parameters: sunspot number (SSN), Wolf number, the 10.7 cm solar radio flux (F10.7), the occurrence rate and speed of coronal mass ejections (CMEs), the statistics of X-ray flares, and the reversal of the global magnetic field. A percentile-based classification of the adjusted F10.7 flux (EPH scale) is introduced, which allows us to identify the maximum-activity interval as August 2024 to January 2025. This period coincides with the reversal of the solar polar fields and is characterized by enhanced eruptive activity, including more than 190 M-class and 19 X-class flares (including an X6.3 flare on 10 December 2024) and multiple CMEs with speeds exceeding 2000 km/s. In the second part of the study we investigate solar rotation during this cycle using an independent observing campaign conducted in April 2025 in San Jose, Costa Rica, with privately owned telescopes in white light and in the H alpha line. Photometric techniques and active-region tracking yield mean synodic angular velocities of 12.8 +/- 2.8 deg/day in the northern hemisphere and 13.38 +/- 0.54 deg/day in the southern hemisphere, corresponding to sidereal periods of 22.78 and 21.77 days, respectively. Complementary SWPC-NOAA sunspot-region data provide synodic periods between 21.19 and 25.74 days, consistent with classical differential-rotation measurements. Linear velocities derived from SDO images span from about 872 km/h to more than 7400 km/h, depending on latitude and date.
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Instrumentation and Methods for Astrophysics

Lord of the (sub-)Rings : Mapping the surface reflectance and spin-axis of Ajisai

Robert J.S Airey, Paul Chote, James A. Blake et al. (+4 more)

Active debris removal techniques are posed to become an important tool in maintaining the safety of the near-Earth space environment. These techniques rely on a clear understanding of the rotational motion of the debris targets, which is challenging to constrain from unresolved imaging. The Ajisai satellite provides an ideal test case for developing and demonstrating these techniques due to its simple geometry and well constrained spin behaviour. We present four observations of the Ajisai satellite taken with SuperWASP in August of 2019, where high cadence photometry was extracted from streaked images as a part of a larger survey of Low Earth Orbit. We develop an MCMC-driven method to determine the spin-state of Ajisai by comparing the alignment between a map of modelled mirror positions and a novel derived map of surface reflectivity. We generally find good agreement within the expectation and uncertainties set by empirical models and our determined spin-state solutions align the surface reflectivity map and modelled mirror location well. Our results show that streak photometry can be used to recover the spin-axis and rotation period of fast-spinning objects such as Ajisai using modest ground-based instrumentation, making it readily scalable to a wider range of targets and observatories.
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All authors Robert J.S Airey, Paul Chote, James A. Blake, James McCormac, Billy Shrive, Don Pollacco, Benjamin F. Cooke