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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 7 May

Cosmology and Nongalactic Astrophysics

Self-interacting dark matter and core formation in field low-surface-brightness galaxies

Noriaki Kitazawa

Dark matter may play an important role in galaxy formation through its non-trivial properties. For example, self-interacting dark matter may contribute to the formation of the widely observed core structures in galaxies. However, galaxy formation is a complex process, and such core structures can also arise from baryonic effects within the cold dark matter framework. To clarify the role of dark matter self-interactions, it is necessary to study systems that evolve without significant baryonic disturbances. Low-surface-brightness galaxies in the field, which are gravitationally isolated and have evolved with minimal external influence, are suitable candidates for this purpose. Since these galaxies typically contain only a small amount of baryonic matter, strong baryonic effects are not expected in their evolutionary history. In this study, we assume that these galaxies decoupled from proto-clusters at high redshift. Based on this assumption, we set initial conditions and estimate the time required for core formation, which we compare with the time corresponding to the redshift of proto-clusters. We examine five low-surface-brightness galaxies in the field and three observed proto-clusters at redshifts z=2.45, 7.66 and 7.88. Our analyses, based on order-of-magnitude estimates without numerical simulations, excludes a self-interaction cross section of sigma/m = 1 cm^2/g, while sigma/m = 0.1 cm^2/g is favored. This result is consistent with constraints derived from the shapes of present-day cluster cores.
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Instrumentation and Methods for Astrophysics

AstroAlertBench: Evaluating the Accuracy, Reasoning, and Honesty of Multimodal LLMs in Astronomical Classification

Claire Chen, Jiabao Sean Xiao, Shuze Daniel Liu et al. (+7 more)

Modern astronomical observatories generate a massive volume of multimodal data, creating a critical bottleneck for expert human review. While multimodal large language models (LLMs) have shown promise in interpreting complex visual and textual inputs, their ability to perform specialized scientific classification while providing interpretable reasoning remains understudied. We introduce AstroAlertBench, a comprehensive multimodal benchmark designed to evaluate LLM performance in astronomical event review along a three-stage logical chain: metadata grounding, scientific reasoning, and hierarchical classification over five categories. We use a pilot sample of 1,500 real-world alerts from the Zwicky Transient Facility (ZTF), a wide-field survey that scans the northern sky to detect transient astronomical events. On this dataset, we benchmark 13 frontier closed-source and open-weight LLMs that support visual input. Our results reveal that high accuracy does not always align with model “honesty,” defined as the ability to self-evaluate its reasoning, which affects its reliability as a real-world assistant. We further initialize a human-in-the-loop evaluation protocol as a precursor to future community-scale participation. Together, AstroAlertBench provides a framework for developing calibrated and interpretable astronomical assistants.
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All authors Claire Chen, Jiabao Sean Xiao, Shuze Daniel Liu, Facundo Perez Paolino, Luke Handley, Theophile Jegou du Laz, Ricky Nilsson, Alice Zou, Matthew Graham, Ashish Mahabal

Astrophysics of Galaxies

Spin Parity of Spiral Galaxies VI – A Search for Dynamical Memory in the Spin Distribution of Galaxies in HSC WIDE Survey Regions

Masanori Iye and Masafumi Yagi

We analyzed the distribution of spin parity in spiral galaxies using the HSC DR2 data. The spiral winding parity of disk galaxies, observed as S-spiral or Z-spiral projected onto the sky plane, provides robust information on the sign of the line-of-sight component of their spin vectors, specifically whether the spin vector points toward or away from us. The distribution of 49,494 S/Z annotated spirals with spectroscopic redshift (0.05 $\le z$) was analyzed for 46,247 fiducial cubic search volumes of various sizes, 20–200 Mpc, deployed in the 3D supergalactic coordinates. We counted the number of S-spirals and Z-spirals in each cube, evaluated the binomial probability of the observed S/Z imbalance, and identified statistically anomalous cube candidates. The observed cumulative distribution functions for the 256 sets of cubes are in good agreement with the theoretical binomial distribution and with those obtained from 1000 Monte Carlo realizations assuming random S/Z spin assignments. The number of statistically anomalous cubes is also comparable to that expected from the random assignments. These results indicate that the spin-vector distribution of spiral galaxies is consistent with statistical randomness expected from the standard cosmological model of structure formation.
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High Energy Astrophysical Phenomena

How do the LIGO-Virgo-KAGRA's Heavy Black Holes Form? No evidence for core-collapse Intermediate-mass black holes in GWTC-4

Fan-Xiao-Yu Xia, Yuan-Zhu Wang and Ying Qin

We investigate the population properties of binary black holes (BBHs) from the LIGO-Virgo-KAGRA collaboration, focusing especially on those in the high-mass range, using the newly released GWTC-4 catalog. For the first time, we search for a subpopulation of low-spin intermediate-mass black holes (IMBHs) that would indicate formation via stellar core collapse. With the currently available catalog, we find no evidence for such a subpopulation, and set a 90% upper limit on the merger rate of collapse-formed IMBHs at $0.077~\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$. The mass distribution of low-spin (stellar-origin) black holes truncates at $65^{+23}_{-22}\,M_\odot$, consistent with the lower edge of the pair-instability mass gap (PIMG), although we cannot directly determine its upper boundary from current data. Informed by stellar evolution theory, we estimate the upper edge of the PIMG to be $150\pm24\,M_\odot$. We find that the observed IMBHs belong to a high-spin subpopulation, consistent with formation through successive hierarchical mergers.
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High Energy Astrophysical Phenomena

A Multiwavelength Assessment Disfavoring the X-ray Binary Origin of He III Regions in Metal-Poor Star-Forming Dwarf Galaxies

Ivan Altunin, Christopher Ellis, Richard M. Plotkin et al. (+9 more)

Recent observations of metal-poor, star-forming dwarf galaxies reveal He III regions, traced by nebular He II 4686 emission that require a strong source of extreme-ultraviolet (EUV) radiation. The origin of this hard ionizing radiation remains poorly understood, as standard stellar populations fail to account for it, posing key implications for the understanding of early galaxy formation. We present a systematic Chandra X-ray study of 21 nearby star-forming galaxies with He II emission but lacking Wolf-Rayet spectral signatures. Using 7 new and 36 archival Chandra X-ray observations combined with optical stellar population synthesis modelling, we constrain the ionizing continuum required to sustain the observed He II line, the ionizing continuum available from X-ray objects, and the properties of the host H II regions. We find that the inferred EUV output from accreting X-ray sources in our sample is systematically lower than what is required to produce the observed He II emission. Our sample is consistent with established empirical scaling relations for X-ray luminosity, indicating that this discrepancy cannot be attributed to an anomalously low number or luminosity of X-ray sources. These results indicate that accreting X-ray sources alone cannot account for the observed He II-ionizing photon budget, pointing to additional or alternative sources of hard EUV radiation in metal-poor star-forming environments. Potential alternative or additional contributors are discussed.
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All authors Ivan Altunin, Christopher Ellis, Richard M. Plotkin, Roberto Soria, Ryan Tanner, Erica Thygesen, Elena Gallo, Manfred W. Pakull, Andrea H. Prestwich, Amy Reines, Ryan Urquhart, Aarran W. Shaw

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Implications of the LISA stochastic signal from eccentric stellar mass black hole binaries in vacuum

Ran Chen, Rohit S. Chandramouli, Federico Pozzoli et al. (+2 more)

Astrophysical formation channels of stellar-mass binary black holes (sBBHs) can induce significant orbital eccentricities in their early inspiral. We analyze the implications on the stochastic gravitational-wave background (SGWB) from unresolved sBBHs, which can be detected with the Laser Interferometer Space Antenna (LISA). We develop an improved SGWB model for the case of an idealized Dirac-delta eccentricity distribution, and extend it to the more astrophysical case of a thermal distribution. Using a fully Bayesian framework, we find that, if all binaries have a high initial eccentricity $e_0 \gtrsim 0.9$ at an orbital frequency of $f_{\rm orb} = 10^{-4}\,\mathrm{Hz}$, the resulting SGWB can be robustly distinguished from a background of quasi-circular sBBHs. For a thermal eccentricity distribution, the SGWB is consistent with a circular model when binaries form at $f_{\rm orb} = 10^{-5}\,\mathrm{Hz}$, but leads to significant systematic biases if formation occurs at $f_{\rm orb} = 10^{-4}\,\mathrm{Hz}$. We also show that, when eccentricity is properly accounted for, environmental effects such as dynamical friction can be distinguished from vacuum evolution, but only for sufficiently dense environments with gas densities $\rho \gtrsim 10^{-7}\,\mathrm{g\,cm^{-3}}$. Finally, we show that a LISA detection of the sBBH SGWB would place an upper bound on the maximum eccentricity of the sBBH population in the band of ground-based detectors, with direct implications for template modeling and data analysis. Our results highlight the importance of incorporating eccentricity in SGWB modeling to enable accurate astrophysical interpretation of LISA observations.
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All authors Ran Chen, Rohit S. Chandramouli, Federico Pozzoli, Riccardo Buscicchio, Enrico Barausse

Wednesday 6 May

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Testing General Relativity with Individual Supermassive Black Hole Binaries

Qinyuan Zheng, Bjorn Larsen, Ellis Eisenberg et al. (+1 more)

We develop a unified framework for testing gravity beyond General Relativity (GR) with continuous gravitational waves (CWs) from individual supermassive black hole binaries (SMBHBs). These long-lived, nearly monochromatic nanohertz signals offer unique strengths for precision tests of gravity, since their coherent phase evolution and inter-pulsar correlations in pulsar timing arrays (PTAs) retain detailed information about departures from GR over cosmological propagation distances. We consider three representative classes of deviations from GR: additional polarization states, modified dispersion relations, and parity-violating birefringence. For each, we derive the inter-pulsar cross correlation, the modified antenna response, and the propagation-induced pulsar-term phase delay. For non-tensorial polarizations, the CW cross correlation scales linearly in the alternative-polarization amplitude, compared to the quadratic scaling of the gravitational-wave background (GWB), provided the beyond-GR modes are sub-dominant. PTAs are also competitive for modified dispersion relations, where low frequencies enhance both the antenna-pattern modification and the pulsar-term phase delay. Birefringence, by contrast, is suppressed at nanohertz frequencies for most parity-violating theories. We validate the framework with injection-and-recovery simulations for breathing-mode and massive-graviton signals at current observational limits, recovering the injected beyond-GR parameters and distinguishing the CW signal from both correlated and uncorrelated background models. We further show that a pure-GR CW template recovers source parameters without significant bias when beyond-GR physics is present in the data, supporting a two-stage analysis strategy: identify candidates under GR, then test for deviations.
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All authors Qinyuan Zheng, Bjorn Larsen, Ellis Eisenberg, Chiara M. F. Mingarelli

Instrumentation and Methods for Astrophysics

Systematic Spectral Distortion from Digital Whitening in Radio Telescopes and Implications for 21 cm Cosmology

Ruby Byrne, Larry R. D'Addario, Daniel C. Jacobs et al. (+1 more)

We identify a systematic distortion of the gain-vs.-frequency function of radio telescopes caused by digital flattening ("whitening") of the signal's spectrum followed by re-quantization, a common pair of processes in the signal processing of modern telescopes. Wide-bandwidth telescopes often have a large variation of signal power over frequency. Flattening of the spectrum allows samples of the channelized signal to be represented in a small number of bits, allowing efficient downstream processing. However, we show that this produces subtle systematic error in the measured spectra. We explore this effect in data from the Owens Valley Radio Observatory's Long Wavelength Array (OVRO-LWA) and through detailed semi-analytic simulations. Although the effect can be small so that it has heretofore been unrecognized, we demonstrate that it produces distortion of the spectrum at a level that is problematic for some science, in particular 21 cm cosmology. Finally, we explore mitigation strategies, showing that the effect can be substantially reduced by careful choice of the gain distribution along the signal path or by incorporating dithering in the re-quantization step.
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All authors Ruby Byrne, Larry R. D'Addario, Daniel C. Jacobs, Gregg Hallinan

Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det

Hot-electron bolometric mixer with negative differential resistance

Chang Yoo, Akim A. Babenko and Boris S. Karasik

We demonstrate that the conversion gain of a superconducting hot-electron bolometer (HEB) mixer can be increased by biasing the device within the negative differential resistance (NDR) region of its current-voltage characteristic. Although NDR biasing has historically been avoided due to MHz-range resistive oscillations, we show that these oscillations arise from an LC resonance formed by the bias-T inductance and the effective thermal capacitance of the HEB. By applying stability criteria analogous to those developed for tunnel diodes, we redesigned the embedding circuit to suppress this resonance and achieve stable NDR operation. Direct measurements using two monochromatic 2.5-THz sources confirm the predicted gain enhancement. These results establish NDR biasing as a viable method for improving HEB mixer performance and motivate further studies of noise behavior and circuit optimization.
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Earth and Planetary Astrophysics

Resonant Hamiltonian Dynamics in the CR3BP: Bistability and Stochastic Resonance in Binary Planetary Systems

R. Capuzzo-Dolcetta

Context: The Circular Restricted Three-Body Problem provides a fundamental framework for understanding resonant dynamics in binary star systems. Aims: We develop a unified Hamiltonian formulation for mean-motion resonances that encompasses both circumstellar and circumbinary planetary orbits within the CR3BP. Unlike the Solar System case where the perturbing body is a planet of negligible mass, here the perturber (a stellar companion) has a non-negligible, finite mass, a crucial difference that we fully incorporate. Methods: Starting from the full Hamiltonian in each configuration, we perform canonical transformations to resonant action angle variables and derive reduced one-degree-of-freedom Hamiltonians through systematic averaging over the fast orbital motion. Leading-order scaling laws for the Fourier coefficients of the resonant perturbation are obtained, revealing their dependence on the binary mass ratio and the planet's orbital distance. Results: The resulting effective potential is shown to exhibit bistability under the well-defined condition |epsilon2/epsilon1| > 1/4, where epsilon1 and epsilon2 are the amplitudes of the first two resonant harmonics. This bistability creates the essential dynamical setting for stochastic resonance. Scaling laws for the Fourier coefficients are derived for both S-type and P-type configurations. Estimates for known binary-planet systems show that while currently observed systems lie below the bistability threshold, the theory predicts that extreme configurations (a/a_b <~ 1.5 for P-type, almost equal mass binary) could host bistable resonances accessible to future observations. Conclusions: This work provides a natural Hamiltonian framework for studying stochastic resonance in binary planetary systems, bridging analytical celestial mechanics and the nonlinear dynamics of exoplanetary systems subject to realistic perturbations.
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Solar and Stellar Astrophysics

A single power law for the TRAPPIST-1 flare distribution across four orders of magnitude in energy

Valeriy Vasilyev, Alexander I. Shapiro, Nadiia Kostogryz et al. (+10 more)

TRAPPIST-1 is an ultra-cool dwarf that flares frequently. These flares shape the surrounding planets' high-energy irradiation environments, with consequences for atmospheric chemistry and escape, and they can contaminate transmission spectroscopy of those planets. A quantitative flare-frequency distribution (FFD) spanning the full energy range is therefore essential for both interpreting JWST spectra and modeling the planets' irradiation histories. Here we present a unified FFD over four orders of magnitude in energy by jointly analyzing $\approx$87\,hr of JWST/NIRISS and JWST/NIRSpec time-series spectroscopy together with $\approx$74\,days of Kepler/K2 photometry. To enable a consistent comparison across these heterogeneous datasets, we convert all events to energies in the TESS bandpass. For the Kepler-to-TESS conversion we adopt a cooler flare continuum appropriate for ultra-cool dwarfs ($T_{\rm flare}=3500$\,K). After correcting for flare-detection sensitivities, the combined JWST+K2 cumulative FFD is consistent with a single power law, $N(\ge E_\mathrm{TESS})\propto E_\mathrm{TESS}^{-\beta}$, with $\beta=0.753$ over $E_{\rm TESS}\simeq10^{29}$-$10^{33}$\,erg. The slope of the distribution indicates that the time-averaged flare energy budget is dominated by rare, high-energy events rather than by the more numerous low-energy flares. Moreover, we found that strong flares with energies $E_\mathrm{TESS} > 10^{32}$~erg occur once every 25 days, about an order of magnitude more frequently than inferred from previous TRAPPIST-1/analog FFD estimates. This elevated rate of energetic flares has important implications for atmospheric escape, photochemistry, and habitability assessments of the TRAPPIST-1 planets.
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All authors Valeriy Vasilyev, Alexander I. Shapiro, Nadiia Kostogryz, Chia-Lung Lin, Greg Kopp, Benjamin V. Rackham, Astrid M. Veronig, Olivia Lim, Julien de Wit, Daniel Apai, Laurent Gizon, Sami K. Solanki, Sara Seager

Cosmology and Nongalactic Astrophysics

Backreaction and the Role of Spatial Curvature in the Cosmic Neighborhood

Marco Galoppo, Thomas Buchert and Pierre Mourier

We present the first direct computation of spatially averaged dynamical quantities in the local Universe, employing the Cosmicflows-4++ reconstruction and a covariant scalar averaging formalism. We extract the domain-averaged density, expansion rate, spatial curvature, and kinematical backreaction over cosmologically relevant domains around our Galaxy, extending up to a comoving radius of $300~\mathrm{Mpc}/h$. The resulting domain-averaged present-day energy budget features nontrivial variations with scale that reflect a nested structure within the cosmic neighborhood, including a large-scale void shell encompassing the local cosmic web. Remarkably, we find significant contributions to this energy budget from the average spatial curvature at the $\mathcal{O}(10\%)$ level on all probed scales. By contrast, the kinematical backreaction remains much smaller throughout the surveyed volume, reaching at most a $\mathcal{O}(1\%)$ contribution on the smallest scales considered, i.e., $30~\mathrm{Mpc}/h$. Convergence to the global $\Lambda$CDM background is not observed within this range of scales.
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Instrumentation and Methods for Astrophysics

On-Chip Resonator for Nonlinear Kinetic Inductance Characterisation and Future Spectrometry Applications

Patrick Ashworth, Peter S. Barry, Chris S. Benson et al. (+2 more)

This work focuses on the development and demonstration of tunable superconducting on-chip resonator, leveraging the intrinsic current-dependent non-linear kinetic inductance of superconducting aluminium, and investigating the effect of oxygen content. Thin films are deposited using standard metal evaporation. We present results from a comprehensive study based on a series of evaporated Al thin films. This research aims to inform and constrain optimisation strategies for the design of mm-wave on-chip spectrometers, particularly regarding yield, resolution, and efficiency. By systematically varying film stoichiometry, we use a series of DC measurements to extract fundamental film properties such as resistivity, critical current and critical temperature. Furthermore, we employ low-loss DC-coupled microwave resonators to characterise both their microwave properties and the non-linear kinetic inductance, comparing these findings to a determined non-linear kinetic model. Finally, we discuss the possibility of usage in a parametric amplifier.
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All authors Patrick Ashworth, Peter S. Barry, Chris S. Benson, Harry Gordon-Moys, Izaak Morris

Earth and Planetary Astrophysics

Finding Alien Worlds in Queensland – A Decade of MINERVA-Australis

Jonathan Horner, Robert A. Wittenmyer, Stephen R. Kane et al. (+2 more)

Three decades ago, humanity entered the Exoplanet Era, with the discovery of the first planets orbiting other stars. Today, more than 6000 exoplanets are known - a tally recently bolstered by NASA's TESS spacecraft. Whilst TESS is an exceptional planet finding machine, dedicated follow-up observations from the ground are required to confirm the existence of the planets it discovers. To achieve this, we constructed the southern hemisphere's only dedicated exoplanet detection and characterisation facility, MINERVA-Australis, at the University of Southern Queensland's Mt Kent Observatory. Funded in 2015, MINERVA-Australis saw first light in 2018, in time for the launch of TESS. MINERVA-Australis has since been scouring the skies, working to confirm and characterise the incredible harvest of planets detected by TESS. To date, the facility has contributed to the discovery of 40 new exoplanets, and continued the legacy of radial velocity data from the Anglo-Australian Planet Search program.
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All authors Jonathan Horner, Robert A. Wittenmyer, Stephen R. Kane, John Kielkopf, Duncan Wright

High Energy Astrophysical Phenomena

Searches for Binary Mergers with Sub-solar Mass Components in Data from the First Part of LIGO–Virgo–KAGRA's Fourth Observing Run

The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration: A. G. Abac et al. (+1831 more)

We report on a gravitational wave search for compact binary coalescences involving at least one component with mass between $0.2\,M_\odot$ to $1\,M_\odot$, and ratio of component masses between 0.1 and 1. The analysis uses data collected by the LIGO detectors between May 24 2023 15:00 UTC and January 16 2024 16:00 UTC. No statistically significant sub-solar mass candidates were identified by the participating search algorithms. We report the detection sensitivity of the current searches to the target sub-solar mass black hole population. With the absence of detections, we place upper limits on the merger rate of sub-solar mass black holes, ranging from 110 ${\rm Gpc^{-3}\,yr^{-1}}$ to 10000 ${\rm Gpc^{-3}\,yr^{-1}}$ at 90% confidence. We constrain two illustrative dark matter scenarios that can form sub-solar mass compact objects with these searches: primordial black holes, and dark black holes forming in a dissipative dark matter model. For late-forming primordial black hole binaries, our search excludes the fraction of dark matter in primordial black holes to be $\leq 1$ only for masses above $0.9\,M_\odot$. In the early-formation scenario, we limit this fraction to be $\leq 7\%$ at $1\,M_\odot$, and $\leq 40\%a$ at $0.35\,M_\odot$. For the dissipative model, the excluded region in the parameter space of dark matter fraction in dark black holes and their minimum possible mass extends down to (0.9 to 1.2) $\times 10^{-5}$ at $1\,M_\odot$ with no constraints below $0.02\,M_\odot$. For the first time, we report the detection sensitivity of our searches to binaries with sub-solar mass neutron stars, and place the 90% confidence merger rate limit at (570 to 710) ${\rm Gpc^{-3}\,yr^{-1}}$ for a population with component masses distributed uniformly down to $0.5\,M_\odot$.
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All authors The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration: A. G. Abac, I. Abouelfettouh, F. Acernese, K. Ackley, A. Adam, C. Adamcewicz, S. Adhicary, D. Adhikari, N. Adhikari, R. X. Adhikari, V. K. Adkins, S. Afroz, A. Agapito, D. Agarwal, M. Agathos, N. Aggarwal, S. Aggarwal, O. D. Aguiar, I.-L. Ahrend, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, E. Alberici, L. Albers, W. Ali, S. Al-Kershi, C. Alléné, A. Allocca, S. Al-Shammari, P. A. Altin, S. Alvarez-Lopez, W. Amar, O. Amarasinghe, A. Amato, F. Amicucci, C. Amra, C. Anand, A. Ananyeva, S. B. Anderson, W. G. Anderson, M. Andia, M. Ando, M. Andrés-Carcasona, J. L. Andrey, T. Andrić, J. Anglin, J. Anna, S. Ansoldi, J. M. Antelis, S. Antier, M. Aoumi, E. Z. Appavuravther, S. Appert, S. K. Apple, K. Arai, A. Araya, M. C. Araya, M. Arca Sedda, F. Arciprete, J. S. Areeda, N. Aritomi, F. Armato, S. Armstrong, N. Arnaud, M. Arogeti, S. M. Aronson, G. Ashton, Y. Aso, L. Asprea, M. Assiduo, S. Assis de Souza Melo, S. M. Aston, P. Astone, F. Attadio, F. Aubin, K. AultONeal, G. Avallone, E. A. Avila, S. Babak, C. Badger, S. Bae, S. Bagnasco, L. Baiotti, R. Bajpai, T. Baka, K. A. Baker, T. Baker, G. Balbi, G. Baldi, N. Baldicchi, M. Ball, G. Ballardin, S. W. Ballmer, S. Banagiri, B. Banerjee, D. Bankar, T. M. Baptiste, P. Baral, M. Baratti, J. C. Barayoga, K. Baric, B. C. Barish, D. Barker, N. Barman, P. Barneo, F. Barone, B. Barr, M. Barrios, L. Barsotti, M. Barsuglia, D. Barta, M. A. Barton, I. Bartos, A. Basalaev, R. Bassiri, A. Basti, M. Bawaj, P. Baxi, J. C. Bayley, A. C. Baylor, P. A. Baynard II, M. Bazzan, V. M. Bedakihale, F. Beirnaert, M. Bejger, D. Belardinelli, A. S. Bell, C. Bellani, L. Bellizzi, D. Beltran-Martinez, W. Benoit, I. Bentara, M. Ben Yaala, S. Bera, F. Bergamin, B. K. Berger, S. Bernuzzi, M. Beroiz, C. P. L. Berry, I. Berry, D. Bersanetti, T. Bertheas, A. Bertolini, J. Betzwieser, D. Beveridge, G. Bevilacqua, N. Bevins, R. Bhandare, R. Bhatt, A. Bhattacharjee, D. Bhattacharjee, S. Bhattacharyya, S. Bhaumik, V. Biancalana, A. Bianchi, F. Bianchi, I. A. Bilenko, G. Billingsley, A. Binetti, S. Bini, C. Binu, S. Biot, O. Birnholtz, S. Biscoveanu, A. Bisht, M. Bitossi, M.-A. Bizouard, S. Blaber, J. K. Blackburn, L. A. Blagg, C. D. Blair, D. G. Blair, N. Bode, N. Boettner, P. Bogdan, G. Boileau, M. Boldrini, G. N. Bolingbroke, A. Bolliand, L. D. Bonavena, R. Bondarescu, F. Bondu, V. A. Bonhomme, E. Bonilla, M. S. Bonilla, A. Bonino, R. Bonnand, A. Borchers, N. Borghi, V. Boschi, S. Bose, V. Bossilkov, Y. Bothra, A. Boudon, M. Boyle, A. Bozzi, C. Bradaschia, M. J. Brady, P. R. Brady, A. Branch, M. Branchesi, T. Briant, A. Brillet, M. Brinkmann, P. Brockill, E. Brockmueller, A. F. Brooks, B. C. Brown, D. D. Brown, M. L. Brozzetti, S. Brunett, G. Bruno, R. Bruntz, J. Bryant, Y. Bu, F. Bucci, J. Buchanan, O. Bulashenko, T. Bulik, H. J. Bulten, A. Buonanno, K. Burtnyk, R. Buscicchio, D. Buskulic, C. Buy, R. L. Byer, R. Cabrita, V. Cáceres-Barbosa, L. Cadonati, G. Cagnoli, C. Cahillane, A. Calafat, T. A. Callister, E. Calloni, S. R. Callos, G. Caneva Santoro, K. C. Cannon, H. Cao, L. A. Capistran, E. Capocasa, G. Capoccia, E. Capote, G. Capurri, G. Carapella, F. Carbognani, K. J. Cardona-Martínez, M. Carlassara, J. B. Carlin, T. K. Carlson, M. F. Carney, M. Carpinelli, G. Carrillo, J. J. Carter, G. Carullo, A. Casallas-Lagos, J. Casanueva Diaz, C. Casentini, S. Caudill, M. Cavaglià, R. Cavalieri, G. Cella, S. Cepic, P. Cerdá-Durán, E. Cesarini, N. Chabbra, W. Chaibi, A. Chakraborty, P. Chakraborty, S. Chakraborty, S. Chalathadka Subrahmanya, R. Chalmers, C. Chan, J. C. L. Chan, M. Chan, K. Chang, P. Charlton, E. Chassande-Mottin, C. Chatterjee, Debarati Chatterjee, Deep Chatterjee, M. Chaturvedi, S. Chaty, A. Chen, A. H.-Y. Chen, D. Chen, H. Chen, H. Y. Chen, S. Chen, Y. Chen, G. Cheng, H. P. Cheng, P. Chessa, T. Cheunchitra, H. T. Cheung, S. Y. Cheung, F. Chiadini, G. Chiarini, A. Chiba, A. Chincarini, D. Chintala, M. L. Chiofalo, A. Chiummo, C. Chou, S. Choudhary, N. Christensen, S. S. Y. Chua, G. Ciani, P. Ciecielag, M. Cieślar, M. Cifaldi, B. Cirok, F. Clara, J. A. Clark, T. A. Clarke, P. Clearwater, S. Clesse, F. Cleva, S. M. Clyne, E. Coccia, E. Codazzo, P.-F. Cohadon, D. E. Cohen, S. Colace, E. Colangeli, O. Cole, M. Colleoni, C. G. Collette, J. Collins, S. Colloms, A. Colombo, C. M. Compton, G. Connolly, L. Conti, T. R. Corbitt, I. Cordero-Carrión, S. Corezzi, N. J. Cornish, I. Coronado, A. Corsi, L. A. Corubolo, L. Cotnoir, R. Cottingham, M. W. Coughlin, P. Couvares, D. M. Coward, D. C. Coyne, R. Coyne, A. Cozzumbo, J. D. E. Creighton, T. D. Creighton, S. Crook, R. Crouch, J. Csizmazia, J. R. Cudell, T. J. Cullen, A. Cumming, E. Cuoco, M. Cusinato, L. V. Da Conceição, T. Dal Canton, S. Dall'Osso, S. Dal Pra, G. Dálya, O. Dan, Y. Dang, B. D'Angelo, S. Danilishin, S. D'Antonio, K. Danzmann, K. E. Darroch, L. P. Dartez, R. Das, A. Dasgupta, V. Dattilo, A. Daumas, I. Dave, A. 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Ruiz, E. Ruiz Morales, K. Ruiz-Rocha, V. Russ, S. Sachdev, T. Sadecki, P. Saffarieh, S. Safi-Harb, M. R. Sah, S. Saha, T. Sainrat, S. Sajith Menon, K. Sakai, Y. Sakai, M. Sakellariadou, S. Sakon, O. S. Salafia, F. Salces-Carcoba, L. Salconi, M. Saleem, F. Salemi, M. Sallé, S. U. Salunkhe, S. Salvador, A. Salvarese, A. Samajdar, A. Sanchez, E. J. Sanchez, N. Sanchis-Gual, J. R. Sanders, E. M. Sänger, F. Santoliquido, F. Sarandrea, T. R. Saravanan, N. Sarin, P. Sarkar, A. Sasli, P. Sassi, B. Sassolas, B. S. Sathyaprakash, R. Sato, S. Sato, Yukino Sato, Yu Sato, O. Sauter, R. L. Savage, T. Sawada, H. L. Sawant, S. Sayah, V. Scacco, D. Schaetzl, M. Scheel, A. Schiebelbein, M. G. Schiworski, P. Schmidt, S. Schmidt, R. Schnabel, M. Schneewind, R. M. S. Schofield, K. Schouteden, B. W. Schulte, M. Schulz, B. F. Schutz, E. Schwartz, M. Scialpi, J. Scott, S. M. Scott, R. M. Sedas, T. C. Seetharamu, M. Seglar-Arroyo, Y. Sekiguchi, D. Sellers, N. Sembo, A. S. Sengupta, E. G. Seo, J. W. Seo, V. Sequino, M. Serra, A. Sevrin, T. Shaffer, U. S. Shah, M. A. Shaikh, L. Shao, J. Sharkey, A. K. Sharma, Preeti Sharma, Priyanka Sharma, Ritwik Sharma, Sushant Sharma-Chaudhary, P. Shawhan, N. S. Shcheblanov, E. Sheridan, Z.-H. Shi, R. Shimomura, H. Shinkai, S. Shirke, D. H. Shoemaker, D. M. Shoemaker, R. W. Short, S. ShyamSundar, A. Sider, H. Siegel, V. Sierra, D. Sigg, L. Silenzi, L. Silvestri, M. Simmonds, L. P. Singer, Amitesh Singh, Anika Singh, D. Singh, M. K. Singh, N. Singh, S. Singh, A. M. Sintes, V. Sipala, V. Skliris, B. J. J. Slagmolen, T. J. Slaven-Blair, J. Smetana, D. A. Smith, J. R. Smith, L. Smith, R. J. E. Smith, W. J. Smith, S. Soares de Albuquerque Filho, K. Somiya, I. Song, S. Soni, V. Sordini, F. Sorrentino, H. Sotani, F. Spada, V. Spagnuolo, A. P. Spencer, P. Spinicelli, A. K. Srivastava, F. Stachurski, C. J. Stark, D. A. Steer, N. Steinle, J. Steinlechner, S. Steinlechner, N. Stergioulas, P. Stevens, M. StPierre, M. D. Strong, A. Strunk, A. L. Stuver, M. Suchenek, S. Sudhagar, Y. Sudo, N. Sueltmann, L. Suleiman, K. D. Sullivan, J. Sun, L. Sun, S. Sunil, J. Suresh, B. J. Sutton, P. J. Sutton, K. Suzuki, M. Suzuki, A. Svizzeretto, B. L. Swinkels, A. Syx, M. J. Szczepańczyk, P. Szewczyk, M. Tacca, M. Tagliazucchi, H. Tagoshi, K. Takada, H. Takahashi, R. Takahashi, A. Takamori, S. Takano, H. Takeda, K. Takeshita, I. Takimoto Schmiegelow, M. Takou-Ayaoh, C. Talbot, M. Tamaki, N. Tamanini, D. Tanabe, K. Tanaka, S. J. Tanaka, S. Tanioka, D. B. Tanner, W. Tanner, L. Tao, R. D. Tapia, E. N. Tapia San Martín, C. Taranto, A. Taruya, J. D. Tasson, J. G. Tau, A. Tejera, R. Tenorio, H. Themann, A. Theodoropoulos, M. P. Thirugnanasambandam, L. M. Thomas, M. Thomas, P. Thomas, J. E. Thompson, S. R. Thondapu, K. A. Thorne, E. Thrane, J. Tissino, A. Tiwari, Pawan Tiwari, Praveer Tiwari, S. Tiwari, V. Tiwari, M. R. Todd, E. Tofani, M. Toffano, A. M. Toivonen, K. Toland, A. E. Tolley, T. Tomaru, V. Tommasini, T. Tomura, H. Tong, C. Tong-Yu, A. Torres-Forné, C. I. Torrie, I. Tosta e Melo, E. Tournefier, M. Trad Nery, A. Trapananti, R. Travaglini, F. Travasso, G. Traylor, M. Trevor, M. C. Tringali, A. Tripathee, G. Troian, A. Trovato, L. Trozzo, R. J. Trudeau, T. Tsang, S. Tsuchida, K. Tsuji, L. Tsukada, K. Turbang, M. Turconi, C. Turski, H. Ubach, A. S. Ubhi, N. Uchikata, T. Uchiyama, R. P. Udall, T. Uehara, K. Ueno, V. Undheim, L. E. Uronen, T. Ushiba, M. Vacatello, H. Vahlbruch, G. Vajente, J. Valencia, M. Valentini, E. Vallejo-Pagès, S. A. Vallejo-Peña, S. Vallero, M. van Dael, E. Van den Bossche, J. F. J. van den Brand, C. Van Den Broeck, M. van der Kolk, M. van der Sluys, A. Van de Walle, J. van Dongen, K. Vandra, M. VanDyke, H. van Haevermaet, J. V. van Heijningen, P. Van Hove, J. Vanier, J. Vanosky, N. van Remortel, M. Vardaro, A. F. Vargas, V. Varma, A. Vecchio, G. Vedovato, J. Veitch, P. J. Veitch, S. Venikoudis, J. Venneberg, R. C. Venterea, P. Verdier, M. Vereecken, D. Verkindt, B. Verma, Y. Verma, S. M. Vermeulen, F. Vetrano, A. Veutro, A. Viceré, S. Vidyant, A. D. Viets, A. Vijaykumar, A. Vilkha, N. Villanueva Espinosa, V. Villa-Ortega, E. T. Vincent, J.-Y. Vinet, S. Viret, S. Vitale, A. Vives, L. Vizmeg, H. Vocca, D. Voigt, E. R. G. von Reis, J. S. A. von Wrangel, W. E. Vossius, L. Vujeva, S. P. Vyatchanin, J. Wack, L. E. Wade, M. Wade, K. J. Wagner, L. Wallace, E. J. Wang, H. Wang, W. H. Wang, Y. F. Wang, Z. Wang, G. Waratkar, J. Warner, M. Was, T. Washimi, N. Y. Washington, D. Watarai, B. Weaver, S. A. Webster, N. L. Weickhardt, M. Weinert, A. J. Weinstein, R. Weiss, L. Wen, K. Wette, C. Wheeler, J. T. Whelan, B. F. Whiting, E. G. Wickens, D. Wilken, B. M. Williams, D. Williams, M. J. Williams, N. S. Williams, J. L. Willis, B. Willke, M. Wils, L. Wilson, C. W. Winborn, J. Winterflood, C. C. Wipf, G. Woan, J. Woehler, N. E. Wolfe, H. T. Wong, I. C. F. Wong, K. Wong, T. Wouters, J. L. Wright, M. Wright, B. Wu, C. Wu, D. S. Wu, H. Wu, K. Wu, Q. Wu, Z. Wu, E. Wuchner, D. M. Wysocki, V. A. Xu, Y. Xu, N. Yadav, H. Yamamoto, K. Yamamoto, T. S. Yamamoto, T. Yamamoto, R. Yamazaki, T. Yan, H. Yang, K. Z. Yang, Y. Yang, Z. Yarbrough, J. Yebana, S.-W. Yeh, A. B. Yelikar, X. Yin, J. Yokoyama, T. Yokozawa, S. Yuan, H. Yuzurihara, M. Zanolin, M. Zeeshan, T. Zelenova, J.-P. Zendri, M. Zeoli, M. Zerrad, M. Zevin, H. Zhang, L. Zhang, N. Zhang, R. Zhang, T. Zhang, C. Zhao, Yue Zhao, Yuhang Zhao, Z.-C. Zhao, Y. Zheng, H. Zhong, H. Zhou, H. O. Zhu, Z.-H. Zhu, Z. Zhu, A. B. Zimmerman, L. Zimmermann, M. E. Zucker, J. Black, S. Shandera, D. Jeong

High Energy Astrophysical Phenomena

Multiwavelength Analysis of PSR J0437-4715 with Pulse Profile Modeling

Liqiang Qi, Juan Zhang, Weiwei Xu et al. (+6 more)

We present a multi-wavelength analysis of the nearby millisecond pulsar PSR J0437–4715, combining Hubble Space Telescope (HST) far-ultraviolet, ROSAT soft X-ray, and XMM-Newton X-ray data, to model its broadband emission and energy-resolved pulse profiles, and infer key stellar parameters via Bayesian inference. The broadband emission includes cold thermal, hot thermal, and non-thermal components: cold bulk surface emission is modeled with a non-magnetized partially-ionized hydrogen atmosphere; hot-spot emission adopts the pulse profile modeling technique with a non-magnetized fully-ionized hydrogen atmosphere model; and non-thermal emission is included as a phase-invariant power-law component. By adopting an informative prior on the hot-spot geometry informed by radio polarization position angle measurements, the joint multi-instrument analysis yields a statistically viable and radio-consistent solution with a gravitational mass of 1.38$\pm$0.03~M$_\odot$ and an equatorial circumferential radius of 13.25$_{-0.35}^{+0.34}$~km (68% confidence intervals). The hot-spot geometry consists of two spherical caps with uniform temperature distributions: the primary hot spot is situated at a colatitude of $\approx$130$^{\circ}$, and the secondary hot spot lies at a colatitude of $\approx$9$^{\circ}$, close to the north pole. It yields tighter radius constraints than HST+ROSAT fits and shifts the radius posterior distribution to larger values relative to NICER-only fits. This work demonstrates the importance of multi-wavelength data in refining neutron star mass-radius measurements and resolving geometric degeneracies.
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All authors Liqiang Qi, Juan Zhang, Weiwei Xu, Shijie Zheng, Mingyu Ge, Ang Li, Shuang-Nan Zhang, Hua Feng, Fangjun Lu

Astrophysics of Galaxies

A Dual-Band Centimetre Continuum Monitoring Survey of Young Stellar Objects in the Coronet Cluster

Johanan Ramírez-Arellano, Carlos Carrasco-González, Roberto Galván-Madrid et al. (+5 more)

We present sensitive ($\sim$9 $\mu$Jy), sub-arcsecond resolution radio continuum observations at 9.0 GHz (3.3 cm) and 14.0 GHz (2.1 cm) obtained with the Karl G. Jansky Very Large Array (VLA) toward the nearby Coronet Cluster in Corona Australis (d $\approx$ 150 pc). We monitored the region from March 2012 to February 2015 using all available VLA configurations, allowing us to construct deep X- and Ku-band maps at multiple angular resolutions. We detected 20 radio sources, including 14 previously known Young Stellar Objects (YSOs), five sources possibly associated with shock emission, and one background galaxy. We resolved IRS 5, previously known to be a binary system, and identified IRS 7A and IRS 7B as multiple systems at centimetre wavelengths. The younger Class 0 and I YSOs exhibit spectral indices $\alpha_{pk}$ ranging from -0.4 to 1.7, while the more evolved Class II YSOs show flatter values between 0 and 0.8, consistent with free-free emission, with minor contributions from non-thermal emission. The Class III source is only constrained by an upper limit. Radio variability, measured as a fraction of the mean intensity peak, is found to be ubiquitous and independent of evolutionary stage. Variability structure functions computed for nine sources indicate no preferred timescales for most of them. We also investigate spectral index variability for six sources and find significant variations in only one object. Finally, we analyse the extended radio emission toward IRS 7B, where some subcomponents exhibit negative spectral indices suggestive of non-thermal processes.
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All authors Johanan Ramírez-Arellano, Carlos Carrasco-González, Roberto Galván-Madrid, Hauyu Baobab Liu, Jan Forbrich, Arpan Ghosh, Yenifer Angarita, Carlos G Román-Zuñiga

Instrumentation and Methods for Astrophysics

Results of ten years of UCLA SETI searches with the Green Bank Telescope

Jean-Luc Margot

We have been conducting a search for narrowband radio signals with the L-band receiver (1.15-1.73 GHz) of the 100 m diameter Green Bank Telescope (Margot et al., 2023). So far, we have captured radio emissions from 70,000+ stars and planetary systems in the ~9 arcminute beam of the telescope. Our data-processing pipeline has a demonstrated 94%-99% efficiency for the detection of narrowband signals across the full range of frequency drift rates (+/-9 Hz/s). All 100 million candidate signals detected to date were either automatically (99.5%) or visually (0.5%) confirmed to be anthropogenic in nature. These results allow us to place stringent limits on transmitter prevalence: at the 95% confidence level, the fraction of stars within 20,000 ly that host a transmitter that is detectable in our search (EIRP > 5e16 W) is <6.3e-5. Our most interesting signals have been uploaded to a citizen science platform (http://arewealone.earth), where 40,000+ volunteers to date have contributed insights and classifications. We are using artificial intelligence (AI) to accelerate our search, automatically excise radio frequency interference, and improve signal detection. UCLA SETI research has involved ~200 undergraduate and ~20 graduate students so far.
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Solar and Stellar Astrophysics

The Eye of Sauron in SN 2025ngs: a Short-plateau Cousin of SN 1998S with Evidence for a Ring-like Circumstellar Medium

Conor L. Ransome, David J. Sand, K. Azalee Bostroem et al. (+35 more)

Interacting supernovae probe the twilight years of massive stars, exhibiting signatures of interaction between the supernova ejecta and surrounding material expelled from the progenitor. We present the peculiar interacting supernova, SN\,2025ngs in NGC5961 (37.8 Mpc). This transient toes the line between strongly interacting supernovae (type IIn) and type IIP supernovae. SN 2025ngs presents photometrically as a short-plateau supernova, with a plateau duration, t$_{\mathrm{PT}}^{}\approx70$ days. Interaction features subside within a week post-explosion, consistent with the growing number of flash supernovae, giving way to a short period where a typical IIP spectrum is exhibited. Towards the drop off the plateau, interaction features re-emerge, exhibiting complex H$\alpha$ profiles throughout the rest of the transient evolution. We compare with models of early spectra, finding the abundances generally consistent with a supergiant progenitor with a high mass-loss rate (10$^{-3}$ M$_\odot$ yr$^{-1}$). Early, high-resolution spectra reveal a double-horned H$\alpha$ profile, providing strong evidence for shock interaction with a proximate disk-like circumstellar medium. Spectroscopically, SN 2025ngs closely resembles the luminous SN 1998S, despite photometric differences, with SN 2025ngs having a relatively modest peak magnitude of $M_\mathrm{V}=-17.9$ mag, adding another member to the surprisingly diverse 98S-like group.
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All authors Conor L. Ransome, David J. Sand, K. Azalee Bostroem, Aravind P. Ravi, Bhagya M. Subrayan, Jennifer E. Andrews, Zachary G. Lane, Yize Dong, Anya Nugent, Stefano Valenti, Jeniveve Pearson, Manisha Shrestha, Samaporn Tinyanont, Brian Hsu, Moira Andrews, Dominik Banhidi, Imre Barna Biro, Collin Christy, Istvan Csanyi, Joseph Farah, Noah Franz, Emily T. Hoang, Griffin Hosseinzadeh, D. Andrew Howell, Daryl Janzen, Saurabh W. Jha, Lindsey A. Kwok, Chang Liu, Michael Lundquist, Aidan Martas, Curtis McCully, Darshana Mehta, Nicolas E. Meza Retamal, Nathan Smith, Tamas Szalai, Sergiy Vasylyev, V. Ashley Villar, Kathryn Wynn

Solar and Stellar Astrophysics

The Impact of Radiation Environment on the Evolution and Fragmentation of Protostellar Discs

Matt T. Cusack, Paul C. Clark, Ken Rice et al. (+5 more)

We present high-resolution zoom-in simulations of molecular clouds exposed to an interstellar radiation field and cosmic ray ionisation rate up to 1000 times stronger than that of the solar neighbourhood. We detail the evolution of the accretion discs that form around the first protostar in each simulation, for a total of 7 discs, for up to 100 kyr. The use of a zoom-in procedure allows for the au-scale discs to be well resolved (with resolution < 0.25 au) whilst retaining the structure of the wider parsec-scale molecular cloud. We find that discs exposed to a stronger radiation field tend to be more massive, hotter and denser. Similarly, their host stars grow to become more massive as a result of accreting more rapidly from their surroundings. All the discs show evidence of recurrent instability during the simulations, but only some of them fragment. We investigate whether stability metrics, such as the Toomre $Q$, $\alpha$ viscosity, and $\beta$ cooling parameter, can predict fragmentation by calculating them just before the discs fragment. We find that the metrics are generally unable to do so, as the discs appear stable even up to a few hundred years before fragmenting. In solar-like environments fragments are typically of planetary mass and often migrate to the centre of the disc, whereas fragments in a high-radiation environment are massive ($\rm > 0.1 \, M_\odot$) and fully disrupt/accrete from the progenitor disc. We conclude that the evolution and properties of circumstellar discs depend on both their radiation and physical environment.
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All authors Matt T. Cusack, Paul C. Clark, Ken Rice, Simon C. O. Glover, Ralf S. Klessen, Anthony P. Whitworth, Felix D. Priestley, Ana Duarte-Cabral

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Small Vacuum Energy and Tunneling in a Modified Bousso-Polchinski Model

James Halverson, Justin Khoury and Cody Long

We propose a simplified model for the cosmological constant in string theory flux vacua motivated by type IIB and F-theory compactifications. Relative to the Bousso-Polchinski model, small vacuum energy spacing occurs in thin wafers rather than thin shells. The model is applied to the entire Schöller-Skarke database of Calabi-Yau fourfolds, which exhibit $532,600,483$ distinct sets of Hodge numbers. The overwhelming majority of those ($99.95\%$ percent for some choices of parameters) exhibit a vacuum energy spacing of~$10^{-120}$ in Planck units or smaller. Brown-Teitelboim membrane nucleation transitions can populate this landscape of flux vacua. In the thin-wall approximation, and ignoring gravitational corrections, we find that the bubble transitions are always dominated by giant leaps in flux space. The age of the universe places a bound on Calabi-Yau topology that is satisfied for the entire Schöller-Skarke database.
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Solar and Stellar Astrophysics

Ag I model atom and the 3D non-LTE solar silver abundance

Sema Caliskan, Anish M. Amarsi, Per Jönsson et al. (+2 more)

Silver is an important light neutron-capture element whose stellar abundances help constrain the origin of the weak r-process. The Sun is an important reference point for such studies; moreover, being a moderately volatile element in CI chondrites, the solar silver abundance is interesting as a diagnostic for the debated Sun-CI abundance vs. condensation temperature trend. These studies require accurate silver abundances that go beyond the commonly used assumptions of 1D atmospheres and local thermodynamic equilibrium (LTE); however, no consistent 3D non-LTE analysis of silver has been available to date. We present a new Ag I model atom built from carefully curated radiative and collisional data, including newly computed oscillator strengths using an ab initio multi-configurational Hartree-Fock method and inelastic hydrogen collision rates based on a combined asymptotic and free-electron model approach. We assess modelling uncertainties via targeted sensitivity tests, finding the results most sensitive to hydrogen collision data. Applying the model to the solar Ag I 328 and 338 nm resonance lines, we find severe positive abundance corrections from coupled 3D and non-LTE effects. Using revised equivalent width measurements, we derive a recommended solar 3D non-LTE silver abundance of 1.15 +/- 0.08. This is an increase of 0.19 dex relative to the current reference value. Our ab initio model significantly reduces the discrepancy with the meteoritic value from 0.25 to 0.06 dex; moreover, this residual offset is consistent with recent results for other moderately volatile elements. The Sun provides the benchmark test for the first Ag I non-LTE model atom presented here. In subsequent work, this model will be applied to determine 3D non-LTE silver abundances in metal-poor dwarfs and giants, enabling improved constraints on Galactic chemical evolution and weak r-process nucleosynthesis.
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All authors Sema Caliskan, Anish M. Amarsi, Per Jönsson, Nicolas Grevesse, Bijaya K. Sahoo

High Energy Astrophysical Phenomena

Astrophysical X-Ray Polarization

Philip Kaaret and Brian D. Ramsey

X-ray polarimetry is now providing a new way to look at the high energy sky. The addition of two observables, polarization fraction and angle, reveals crucial new information on the structure of accretion flows and magnetic fields in astrophysical systems. Here, we review the basic physical processes that produce polarized X-rays in astrophysical contexts. Then, we briefly describe the physical processes used to measure X-ray polarization and the detectors that have been flown or are under construction.
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Astrophysics of Galaxies · Cross-listed from gr-qc

Perturbations in the parametrized wormhole spacetime and their related quasinormal modes

Shauvik Biswas and Sayan Chakrabarti

We study electromagnetic perturbations and the associated quasinormal modes (QNMs) of parametrized static, spherically symmetric wormhole spacetimes, focusing on Damour-Solodukhin and braneworld geometries as well as their galactic extensions. Using the Bronnikov-Konoplya-Pappas (BKP) parametrization, we express the metric functions in terms of a compactified radial coordinate and characterize the spacetime through far-field and near-throat parameters. The far-field coefficients govern the asymptotic structure and post-Newtonian behaviour, while the near-throat continued-fraction expansion captures the strong-field geometry near the throat. We first apply the parametrization to isolated wormholes and identify its range of validity, showing that the non-analytic metric functions can limit the applicability of the BKP scheme. Moreover we have shown that such issues can indeed hamper the primary ringdown waveform. We then extend the framework to a galactic Damour-Solodukhin wormhole embedded in a Hernquist dark matter halo. Imposing observational bounds from the shadow of Sgr A$^*$, we constrain the galactic compactness and deformation parameters and obtain an observationally viable parametrized metric. Within the allowed parameter space, we compute the fundamental QNM frequencies using the transfer matrix method and analyze the corresponding time-domain ringdown signals. We find that the damping rate is more sensitive to galactic compactness, whereas the oscillation frequency remains comparatively stable. Although the spectral shifts are small within the shadow-allowed region, the framework provides a systematic link between geometric parametrization, shadow constraints, and dynamical response. Our results establish an observationally consistent parametrized description of wormhole perturbations for strong-field tests of horizonless compact objects.
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Instrumentation and Methods for Astrophysics

Computer Vision Methods for Frequency Analysis of RFI in Radio Astronomy Data

Natalia A. Schmid, Sasanka Katreddi and Yechan Kweon

Radio Frequency Interference (RFI) increasingly contaminates the radio astronomy spectrum, often exceeding astronomical signal amplitudes by 50-70 dB. Reliable detection and mitigation are therefore essential for studies of faint transient phenomena such as pulsars and fast radio bursts (FRBs). Existing practical methods (including Spectral Kurtosis (SK), Median Absolute Deviation (MAD), and SumThreshold) perform well in many settings but depend on assumptions about the RFI environment and data statistics, limiting their effectiveness for weak, broadband, or non stationary interference. We develop a transform based RFI detection method that requires no prior knowledge of RFI origin or type. Using Green Bank Telescope (GBT) data containing PSR J1713+0747, with 4096 channels spanning 1.1-1.9 GHz and 5.12 micro second sampling, we apply a Short Time Fourier Transform (STFT) to each channel and use an image segmentation algorithm on the STFT magnitude to generate a binary RFI mask. The masked data are inverse transformed and reassembled into a cleaned time series. Performance is assessed using the Signal to Noise Ratio (S/N) of a single pulse of PSR J1713+0747, with SK serving as the baseline. The cleaned spectrogram is dedispersed, integrated across frequency, and evaluated through the resulting S/N. Experimental results show that refining each channel's frequency content via STFT, followed by segmentation in the STFT domain, yields measurable improvements in RFI suppression.
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Astrophysics of Galaxies

Shape of the direct-method mass-metallicity relation with JWST: Fast-Track Nitrogen and Helium Enrichment

A.Giménez-Alcázar, R.Amorín and J.M.Vilchez

We investigate the mass-metallicity relation (MZR) from z=1 to z=9 using electron-temperature-based gas-phase metallicities and examine how auroral-line selection, star-formation history, and secondary abundances affect its interpretation in the early Universe. We compile a homogeneous sample of 286 star-forming galaxies observed with JWST/NIRSpec medium resolution spectroscopy, selected through detections of the [O\,III]\,$\lambda$4363 auroral line from the public DAWN JWST Archive (DJA). We derive electron densities, temperatures, and oxygen abundances using the direct $T_e$ method, along with relative N/O and He/H abundances. Stellar masses are obtained via SED fitting and star-formation rates from reddening-corrected Balmer emission lines. To quantify auroral-line selection biases, we additionally stack galaxy spectra with and without auroral-line detections, extending the MZR into regimes inaccessible to individual measurements. The auroral-line-detected sample spans log(M*/Msun)=6.77-10.5 and 12+log(O/H)=6.9-8.4. A linear fit gives an MZR slope of $\gamma$=0.38 $\pm$ 0.09. Stacked galaxies without individual $\lambda$4363 detections define a relation with a similar slope but metallicities higher by ~0.2-0.3 dex at fixed stellar mass. Auroral-line detections also show higher SFRs, larger equivalent widths, and larger offsets from the fundamental metallicity relation, whereas non-detections appear more chemically evolved and closer to it. Several stacked bins also show enhanced N/O and He/H ratios. These results indicate that the low-mass high-redshift MZR traced by JWST is shaped by both recent star-formation history and auroral-line selection effects. Auroral lines preferentially identify high-EW, high-sSFR galaxies in the low-metallicity envelope, whereas non-detections reveal a more enriched sequence closer to the metallicity expected from the FMR.
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Instrumentation and Methods for Astrophysics

A useful representation of TESS light curves

Dovi Poznanski

We present a simple and interpretable representation of TESS light curves designed for large-scale exploratory analysis. Our goal is not to optimize classification performance, but to construct a computationally efficient mapping in which proximity reflects meaningful similarity, without using labels or explicit period information as inputs. We represent each light curve using either quantile graphs or scattering transforms, reduce dimensionality with principal component analysis, and project the resulting features onto a self-organizing map (SOM). We evaluate ~1500 model configurations using a combination of standard embedding diagnostics and a light-curve-shape-based cohesion metric, and select a compact quantile-graph-based model that balances interpretability, stability, and performance. Applying the model to ~1.5 million TESS 2-minute cadence light curves, we find that the map organizes sources primarily by variability amplitude, signal-to-noise ratio, characteristic timescale, and light-curve shape. Repeat observations of the same stars show that most sources occupy stable and contiguous regions of the map, indicating that the representation captures persistent properties rather than noise and systematics. We provide an interactive web interface at http://tess-l8.space that enables inspection of nodes, nearest neighbors, and individual sources across sectors. The resulting representation serves as a practical tool for exploration, anomaly detection, and dataset characterization, and illustrates how simple, deterministic encodings can yield useful structure in large astronomical time-series datasets.
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Cosmology and Nongalactic Astrophysics

Primordial Magnetic Fields at Cosmic Dawn: 21-cm Forecasts with HERA and SKA

Keduse Worku, Hector Afonso G. Cruz and Marc Kamionkowski

Primordial magnetic fields (PMFs) can enhance the abundance of low-mass halos during Cosmic Dawn by sourcing additional small-scale matter fluctuations. This enhanced small-scale power can accelerate early galaxy formation, shifting the timing of Lyman-$\alpha$ coupling, X-ray heating, and reionization toward earlier times and imprinting correlated signatures on the global and fluctuating 21-cm signals. We extend the fast analytic framework {\tt\string zeus21} to include a physically motivated PMF contribution to the linear matter power spectrum, including radiative damping before recombination and magnetic-pressure suppression below the magnetic Jeans scale. The implementation preserves the speed and modularity of {\tt\string zeus21}, enabling efficient exploration of PMF parameter space. For $n_B=-2.9$, we quantify the impact of PMFs on early structure formation and 21-cm observables across a range of fiducial magnetic amplitudes, and forecast detectability with HERA and SKA. Combining 21-cm forecasts with external CMB priors, we find that upcoming experiments can probe PMFs through their impact on small-scale structure, providing constraints complementary to existing cosmological probes.
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High Energy Astrophysical Phenomena

Moving-mesh simulations of spreading dynamics and local electron cooling in structured gamma-ray burst afterglow jets

Sayan Kundu and Hendrik van Eerten

We present the results for the dynamics and emission profiles of axi-symmetric numerical simulations of structured gamma-ray burst afterglow jets, computed using the relativistic moving-mesh hydrodynamics code GAMMA. We find that the spreading of jets of average opening angle is moderately impacted by the initial steepness of the angular structure, although the effect disappears once the working surface of the jet substantially exceeds its initial width, and that the travel time of a sound wave across the front surface remains the best indicator of the onset of spreading also for structured jets. When computing the afterglow spectrum using a local cooling approach that traces the electron population following shock-acceleration, we observe a significant impact on the synchrotron cooling break. Similar to earlier results for top-hat jets, the cooling break is found to shift upward in frequency by well over a factor of ten relative to approaches that assume a global cooling timescale across the jet. The cooling break transition in the spectrum also becomes substantially smoother. For both local and global cooling, jet breaks become sharper with increasing frequency. Local cooling is found to initially lead to a steeper slope post jet-break. The local-cooling emission is shown to originate from a narrow frequency-dependent sized region behind the shock front, as expected, but in strong contrast to a global cooling approach.
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Instrumentation and Methods for Astrophysics

HOLISMOKES XXI: Detecting strongly lensed type Ia supernovae from time series of multi-band LSST-like imaging data – Part II

Satadru Bag, Raoul Canameras, Sherry H. Suyu et al. (+5 more)

Strong gravitationally lensed supernovae (LSNe) are rare but extremely valuable probes of cosmology and astrophysics. Prompt identification within the alert streams of time-domain surveys such as the Rubin Legacy Survey of Space and Time (LSST) is essential for timely follow-up observations. In our previous study, Bag et al. (2026), we introduced a deep-learning framework for detecting LSNe Ia directly from multi-band, multi-epoch image cutouts. The model employs a convolutional LSTM architecture to capture spatiotemporal correlations in time-series imaging data, enabling classification updates as new observations arrive. In this work, we extend that framework by incorporating greater realism into the simulations. In particular, we present a method to construct realistic image time series from single-epoch observations by introducing epoch-to-epoch point spread function variations with corresponding variance-map corrections. The dataset is based on HSC PDR3 observations and includes simulated lensed host-galaxy arcs, SN light-curve variations, and Poisson noise. We also introduce an additional negative class consisting of SN Ia occurring in the foreground lens galaxy, representing a challenging source of false positives. Despite these additional complexities, the model retains strong performance. The receiver operating characteristic improves rapidly during the first few observations, reaching a true-positive rate of $\sim60\%$ at a false-positive rate of $\mathcal{O}(10^{-4})$ by the seventh observation and $\sim80\%$ by the tenth. We also investigate potential confusion with sibling SNe occurring in LRGs and identify the configurations that best mimic lensed systems. These results demonstrate that the image-time-series approach remains robust under more realistic observing conditions, and is well suited for real-time LSN searches in LSST and other time-domain surveys.
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All authors Satadru Bag, Raoul Canameras, Sherry H. Suyu, Stefan Schuldt, Stefan Taubenberger, Irham Taufik Andika, Alejandra Melo, Ming Kei Chan