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Physics Astrophysics

astro-ph Watch Astrophysics

Sunday 23 November

Cosmology and Nongalactic Astrophysics

How Primordial Black Holes Change BBN

Tianning Wang, Evan Grohs and Laura Mersini-Houghton

Primordial Black Holes (PBHs) provide a powerful probe of the early universe physics, linking inflationary fluctuations to observable cosmological phenomena. In this work, we use a bottom-up approach to study how PBHs with masses in the range $10^{8} \leq M \leq 10^{13}\,\mathrm{g}$ modify Big Bang Nucleosynthesis (BBN) through Hawking radiation. We incorporate PBH evaporation into the BURST reaction network code to evaluate its impact on light-element abundances. Our analysis illustrates that PBH evaporation acts as an entropy injection mechanism, increasing the comoving entropy density. To reproduce the observed comoving entropy density per baryon $(s/n_{\mathrm{b}})$ from the CMB, BBN simulations must therefore begin with a smaller initial entropy than in the standard scenario without PBHs. The results also reveal a threshold near $M \approx 10^{10}\,\mathrm{g}$ that separates two distinct regimes of BBN behavior. As an example, for $M\geq10^{10}\,\mathrm{g}$, the final $^4{\mathrm{He}}$ mass fraction $Y_{\mathrm{P}}$ obtained from calculation increases monotonically with the initial PBH mass fraction $\beta_{30}$ specified at the starting temperature $T=30\,\mathrm{MeV}$. This trend is driven by the enhanced Hubble expansion caused by the PBH energy density. In contrast, for $M \leq 10^{10}\,\mathrm{g}$, $Y_{\mathrm{P}}$ exhibits non-monotonic behavior shaped by the timing of PBH evaporation and its influence on nuclear reaction rates. These findings highlight the sensitivity of BBN to PBH evaporation and establish a framework for understanding how PBH populations influence the thermal history of the early universe.
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High Energy Astrophysical Phenomena

Insights into jet-NLR energetics in PMN J0948+0022

B. Dalla Barba, L. Foschini, M. Berton et al. (+8 more)

The analysis of the optical spectra of PMN J0948+0022 showed significant variations in the spectral lines that, when combined with the Fermi $\gamma$-ray light curve and radio observations reported by other authors, were interpreted as the result of interactions between the relativistic jet and the narrow-line region (NLR). In this work, we present order-of-magnitude calculations of the energetics associated with this proposed jet-NLR interaction. We demonstrate that the observed outflows are capable of absorbing a fraction of the jet energy and converting it into kinetic energy. This mechanism provides a natural explanation for the optical spectral variability recorded with the X-shooter and Multi-Unit Spectroscopic Explorer (MUSE) instruments. Our results support the scenario in which feedback from the relativistic jet can dynamically influence the circumnuclear gas, offering new insights into the coupling between jets and the NLR in $\gamma$-ray-emitting narrow-line Seyfert 1 galaxies.
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All authors B. Dalla Barba, L. Foschini, M. Berton, A. Lähteenmäki, M. Tornikoski, E. Sani, L. Crepaldi, E. Congiu, G. Venturi, W.J. Hon, A. Vietri

Astrophysics of Galaxies

Milky Way galaxy-analogs and isolated galaxies with bars: environmental density in the Local Volume

O. V. Kompaniiets, I. B. Vavilova, O. M. Kukhar et al. (+6 more)

The environmental density of galaxies within the cosmic web constrains their 3D locations in filaments, voids, groups, and clusters. It traces the distribution of baryons and the influence of dark-matter halos on galaxy evolution, and helps diagnose external processes such as supernova and AGN feedback, tidal interactions, ram-pressure stripping, and large-scale flows. We focus on isolated barred galaxies, the parent population that includes Milky Way analogs. To measure local environmental density and verify isolation (|Delta v| <= 500 km s^-1), we built a Python pipeline that works in two redshift regimes: low (z0 < 0.02) and high (z0 >= 0.02). Densities were estimated with k-nearest neighbors and Voronoi tessellations and classified as void (Sigma < 0.05), filament (0.05 <= Sigma < 0.5), group (0.5 <= Sigma < 2.0), and cluster (Sigma >= 2.0). Our northern-sky sample contains 311 isolated barred galaxies from 2MIG plus Milky Way analog systems (z < 0.07). We find 157 void, 84 filament, 27 group, and 11 cluster galaxies; 30 have no detected neighbors. Sixty-seven lie in extremely low-density regions (Sigma_3D < 0.01 gal Mpc^-3), and 22 have the nearest companion beyond 5 Mpc, indicating residence in extended voids. The Milky Way (Sigma_5NN ~ 0.13 gal Mpc^-3, R ~ 2.1 Mpc) and its close analog NGC 3521 both lie in filamentary environments at the edge of a nearby void. For z > 0.02 we identify three additional Milky Way analog candidates from the density metrics: CGCG 208-043 (3D Voronoi) and NGC 5231 and CGCG 047-026 (5th-nearest neighbor). These results show that local environmental density is an effective, physically motivated criterion for selecting Milky Way analogs.
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All authors O. V. Kompaniiets, I. B. Vavilova, O. M. Kukhar, D. V. Dobrycheva, P. N. Fedorov, A. M. Dmytrenko, V. P. Khramtsov, O. Sergijenko, A. A. Vasylenko

Astrophysics of Galaxies

The Plane Quasar Survey: An Ionized Extension of the Magellanic Stream on the Northern Side of the Galactic Plane

Bo-Eun Choi, Jessica K. Werk, Kirill Tchernyshyov et al. (+5 more)

The Magellanic Stream (MS) is a vast gaseous structure in the Milky Way halo, containing most of its mass in ionized form and tracing the interaction between the Large and Small Magellanic Clouds and the Galaxy. Using HST/COS G160M spectra from the Plane Quasar Survey, we detect C IV absorbers likely associated with the MS, extending to the northern side of the Galactic plane, approximately 60$^\circ$ beyond its previously known ionized extent. These absorbers exhibit position and kinematic alignment and show consistent ionization trends with previously studied MS sight lines. The non-detection of low ions such as Al II and Si II, and the detection of C IV (and Si IV in some sightlines), indicates a highly ionized gas phase. The observed Si IV/C IV column density ratios suggest a gas temperature of $T \sim 10^{5.3}$~K and favor collisional ionization over photoionization. We estimate the newly detected extension increases the previous ionized gas mass of the MS, and its coherent kinematics suggest that it was stripped within the past few hundred Myr and has not yet mixed with the Milky Way halo. The existence of highly-ionized MS gas at a location above the Galactic Plane may constrain the orbital direction of the Magellanic Clouds.
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All authors Bo-Eun Choi, Jessica K. Werk, Kirill Tchernyshyov, Mary E. Putman, Yong Zheng, J. E. G. Peek, Hannah Bish, David Schiminovich

Astrophysics of Galaxies

From Simulations to Surveys: Domain Adaptation for Galaxy Observations

Kaley Brauer, Aditya Prasad Dash, Meet J. Vyas et al. (+2 more)

Large photometric surveys will image billions of galaxies, but we currently lack quick, reliable automated ways to infer their physical properties like morphology, stellar mass, and star formation rates. Simulations provide galaxy images with ground-truth physical labels, but domain shifts in PSF, noise, backgrounds, selection, and label priors degrade transfer to real surveys. We present a preliminary domain adaptation pipeline that trains on simulated TNG50 galaxies and evaluates on real SDSS galaxies with morphology labels (elliptical/spiral/irregular). We train three backbones (CNN, $E(2)$-steerable CNN, ResNet-18) with focal loss and effective-number class weighting, and a feature-level domain loss $L_D$ built from GeomLoss (entropic Sinkhorn OT, energy distance, Gaussian MMD, and related metrics). We show that a combination of these losses with an OT-based "top_$k$ soft matching" loss that focuses $L_D$ on the worst-matched source-target pairs can further enhance domain alignment. With Euclidean distance, scheduled alignment weights, and top-$k$ matching, target accuracy (macro F1) rises from $\sim$46% ($\sim$30%) at no adaptation to $\sim$87% ($\sim$62.6%), with a domain AUC near 0.5, indicating strong latent-space mixing.
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All authors Kaley Brauer, Aditya Prasad Dash, Meet J. Vyas, Ahmed Salim, Stiven Briand Massala

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Dynamical interplay between coupled scalar dark sectors and gravity

Mihai Marciu

We explore a novel cosmological model based on coupled fields in the framework of scalar tensor theories, considering the specific interplay between gravity and scalar fields. The model further extends a recent axion-dilaton system by introducing viable couplings with the space–time geometry encoded into the scalar curvature. After briefly introducing the action and the corresponding field equations, we employ linear stability theory to investigate the physical properties. The analysis showed the compatibility of the current theoretical model with the recent history of the Universe, obtaining viable constraints for the model's parameters in some specific cases. In the present setup, the axion–dilaton system is non–minimally coupled with gravity in an independent manner, leading to distinct physical features in the phase-space structure, possible alleviating the cosmic coincidence problem.
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High Energy Astrophysical Phenomena

r-Process nucleosynthesis from hyperaccreting neutron stars in common envelopes

Peter Anninos, Matthew Portman, Scott Carmichael et al. (+2 more)

We investigate nuclear reactions and feedback in hyperaccreting neutron star environments, considering accretion rates in the range 0.3 - $3\times10^4$ $M_\odot$ yr$^{-1}$, typical of short-period compact object binaries in common envelopes. Our mode ls account for weak reactions, neutrino energy loss, nuclear energy release, pair production, degenerate equations of state, and general relativistic hydrodynamics. Depending on accretion rates, these systems can develop both proton and neutron-rich atmospheres with strong convective instabilities linking the neutrino sphere to the outgoing accretion shock inside the radia tion trapping zone. Convection drives nucleons through multiple heating and cooling cycles, with photodisintegration dominat ing during the heating phase and heavy element synthesis during the cooling phase, ejecting material with abundances that dep end on the accretion rate and depth of the final decompression trajectory. The turbulent nature of convective currents is con ducive to creating a wide range of nuclear products through a variety of effects, including NSE freezeout and $r$, $p$ and $\ gamma$ processes. We also observe a novel multi-step process in reheated trajectories, consisting of proton-capture and photo-dissociation reactions operating on $r$-process seeds, producing overall neutron-deficient isotopes. A significant amount of infalling gas experiences high entropy and short (millisecond) freezeout timescales capable of making $r$-process elements w ith high over-abundances through a disequilibrium effect between neutrons and $\alpha$-particles that does not require an excess of neutrons.
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All authors Peter Anninos, Matthew Portman, Scott Carmichael, Robert Hoffman, Andre Sieverding

High Energy Astrophysical Phenomena

Optimizing the potential of KM3NeT in detecting core-collapse supernovae

KM3NeT Collaboration: O. Adriani, A. Albert, A. R. Alhebsi et al. (+284 more)

Core-collapse supernovae mark the end of life of massive stars. However, despite their importance in astrophysics, their underlying mechanisms remain unclear. Neutrinos that emerge from the dense core of the star offer a promising way to study supernova dynamics. A strategy is presented to improve the potential of the KM3NeT neutrino telescope to detect core-collapse supernovae in our Galaxy or the Large Magellanic Cloud by further exploiting the properties of its optical modules equipped with multiple photomultipliers. A supernova burst is expected to produce a sudden hit rate increase in the KM3NeT detectors. New observables have been defined for individual optical modules that exploit the geometry and time distribution of the detected hits, enabling a better discrimination between signal and background signatures. In addition, a thorough investigation of the related systematic uncertainties is presented for the first time. When implemented, this new methodology allowed KM3NeT to probe 46% more Galactic core-collapse supernova candidates than with the previous trigger strategy, reaching the dense Galactic bulge. It is now expected that, once completed, KM3NeT will achieve full Galactic sensitivity to core-collapse supernovae.
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All authors KM3NeT Collaboration: O. Adriani, A. Albert, A. R. Alhebsi, S. Alshalloudi, M. Alshamsi, S. Alves Garre, F. Ameli, M. Andre, L. Aphecetche, M. Ardid, S. Ardid, J. Aublin, F. Badaracco, L. Bailly-Salins, B. Baret, A. Bariego-Quintana, Y. Becherini, M. Bendahman, F. Benfenati Gualandi, M. Benhassi, D. M. Benoit, Z. Beňušová, E. Berbee, E. Berti, V. Bertin, P. Betti, S. Biagi, M. Boettcher, D. Bonanno, M. Bondì, S. Bottai, A. B. Bouasla, J. Boumaaza, M. Bouta, M. Bouwhuis, C. Bozza, R. M. Bozza, H.Brânzaš, F. Bretaudeau, M. Breuhaus, R. Bruijn, J. Brunner, R. Bruno, E. Buis, R. Buompane, I. Burriel, J. Busto, B. Caiffi, D. Calvo, A. Capone, F. Carenini, V. Carretero, T. Cartraud, P. Castaldi, V. Cecchini, S. Celli, L. Cerisy, M. Chabab, A. Chen, S. Cherubini, T. Chiarusi, W. Chung, M. Circella, R. Clark, R. Cocimano, J. A. B. Coelho, A. Coleiro, A. Condorelli, R. Coniglione, P. Coyle, A. Creusot, G. Cuttone, R. Dallier, A. De Benedittis, G. De Wasseige, V. Decoene, P. Deguire, I. Del Rosso, L. S. Di Mauro, I. Di Palma, A. F. Díaz, D. Diego-Tortosa, C. Distefano, A. Domi, C. Donzaud, D. Dornic, E. Drakopoulou, D. Drouhin, J.-G. Ducoin, P. Duverne, R. Dvornický, T. Eberl, E. Eckerová, A. Eddymaoui, T. van Eeden, M. Eff, D. van Eijk, I. El Bojaddaini, S. El Hedri, S. El Mentawi, V. Ellajosyula, A. Enzenhöfer, M. Farino, G. Ferrara, M. D. Filipović, F. Filippini, D. Franciotti, L. A. Fusco, T. Gal, J. García Méndez, A. Garcia Soto, C. Gatius Oliver, N. Geißelbrecht, E. Genton, H. Ghaddari, L. Gialanella, B. K. Gibson, E. Giorgio, I. Goos, P. Goswami, S. R. Gozzini, R. Gracia, B. Guillon, C. Haack, C. Hanna, H. van Haren, E. Hazelton, A. Heijboer, L. Hennig, J. J. Hernández-Rey, A. Idrissi, W. Idrissi Ibnsalih, G. Illuminati, R. Jaimes, O. Janik, D. Joly, M. de Jong, P. de Jong, B. J. Jung, P. Kalaczyński, U. F. Katz, J. Keegans, V. Kikvadze, G. Kistauri, C. Kopper, A. Kouchner, Y. Y. Kovalev, L. Krupa, V. Kueviakoe, V. Kulikovskiy, R. Kvatadze, M. Labalme, R. Lahmann, M. Lamoureux, A. Langella, G. Larosa, C. Lastoria, J. Lazar, A. Lazo, G. Lehaut, V. Lemaître, E. Leonora, N. Lessing, G. Levi, M. Lindsey Clark, F. Longhitano, S. Madarapu, F. Magnani, L. Malerba, F. Mamedov, A. Manfreda, A. Manousakis, M. Marconi, A. Margiotta, A. Marinelli, C. Markou, L. Martin, M. Mastrodicasa, S. Mastroianni, J. Mauro, K. C. K. Mehta, G. Miele, P. Migliozzi, E. Migneco, M. L. Mitsou, C. M. Mollo, L. Morales-Gallegos, N. Mori, A. Moussa, I. Mozun Mateo, R. Muller, M. R. Musone, M. Musumeci, S. Navas, A. Nayerhoda, C. A. Nicolau, B. Nkosi, B. Ó Fearraigh, V. Oliviero, A. Orlando, E. Oukacha, L. Pacini, D. Paesani, J. Palacios González, G. Papalashvili, P. Papini, V. Parisi, A. Parmar, C. Pastore, A. M. Păun, G. E. Păvălaš, S. Peña Martínez, M. Perrin-Terrin, V. Pestel, M. Petropavlova, P. Piattelli, A. Plavin, C. Poirè, V. Popa, T. Pradier, J. Prado, S. Pulvirenti, C.A. Quiroz-Rangel, N. Randazzo, A. Ratnani, S. Razzaque, I. C. Rea, D. Real, G. Riccobene, J. Robinson, A. Romanov, E. Ros, A. Šaina, F. Salesa Greus, D. F. E. Samtleben, A. Sánchez Losa, S. Sanfilippo, M. Sanguineti, D. Santonocito, P. Sapienza, M. Scaringella, M. Scarnera, J. Schnabel, J. Schumann, J. Seneca, P. A. Sevle Myhr, I. Sgura, R. Shanidze, Chengyu Shao, A. Sharma, Y. Shitov, F. Šimkovic, A. Simonelli, A. Sinopoulou, B. Spisso, M. Spurio, O. Starodubtsev, D. Stavropoulos, I. Štekl, D. Stocco, M. Taiuti, Y. Tayalati, H. Thiersen, S. Thoudam, I. Tosta e Melo, B. Trocmé, V. Tsourapis, C. Tully, E. Tzamariudaki, A. Ukleja, A. Vacheret, V. Valsecchi, V. Van Elewyck, G. Vannoye, E. Vannuccini, G. Vasileiadis, F. Vazquez de Sola, A. Veutro, S. Viola, D. Vivolo, A. van Vliet, E. de Wolf, I. Lhenry-Yvon, S. Zavatarelli, D. Zito, J. D. Zornoza, J. Zúñiga

Astrophysics of Galaxies

Revealing the magnetization of the intracluster medium of Abell 3581 using background Faraday rotation measures from the POSSUM survey

Affan Khadir, Erik Osinga, Wonki Lee et al. (+15 more)

The line-of-sight magnetic field of galaxy clusters can be probed using Faraday rotation measure (RM) data. However, our understanding of cluster magnetism is limited due to the scarcity of polarized background radio sources, with most previous studies being constrained to $\sim 10$ sources per cluster. Leveraging the increased source density of the POlarisation Sky Survey of the Universe's Magnetism (POSSUM), we probe the magnetic field properties of the galaxy cluster Abell 3581 {(A3581)} with 111 RMs. We find that the standard deviation in the RM declines monotonically with increasing radius up to 0.75 Mpc{, agreeing with a radially declining magnetic field and electron density profile modeled as Gaussian and lognormal random fields, respectively. {We compare our observations of the inner 0.75 Mpc of A3581 to various semi-analytic models of the magnetic field and electron density, and obtain several best-fit models.} For the first time, we compare the observed RMs in a cluster to full magnetohydrodynamic simulated clusters from TNG-Cluster and find that the non-monotonic trend in RM standard deviation past 0.75 Mpc in A3581 is likely caused by past or present merger activity. We identify a possible candidate for a merger to be the galaxy group [DZ2015b] 276, which would be the first group detected in RMs that is not strongly emitting in X-rays. We find a possible merger axis of A3581 with this group at a position angle of $\theta = 52\pm 4$ deg.
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All authors Affan Khadir, Erik Osinga, Wonki Lee, David McConnell, B. M. Gaensler, Chiara Stuardi, Craig Anderson, Ettore Carretti, Takuya Akahori, Shane P. O'Sullivan, Lerato Baidoo, Jennifer West, Cameron Van Eck, Lawrence Rudnick, Naomi McClure-Griffiths, Yik Ki Ma, David Alonso-López, Paris Gordon-Hall

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

From LIGO to Fiber- Compact Sagnac Interferometer for Gravitational-Wave Detection

Farhad Hakimi and Hosain Hakimi

Gravitational wave detection has transformed astrophysics, granting us direct access to black hole mergers, neutron star collisions, and the cataclysms of stellar death. Yet the great observatories of today, LIGO, Virgo, KAGRA, and the planned Einstein Telescope, rest on Michelson interferometers that, despite their triumphs, confront fundamental barriers of scale, cost, and environmental vulnerability. We envision a new path, a Sagnac-based fiber interferometer that leverages reciprocity and inherent robustness. Its meter-scale, modular design compact enough to fit within a small facility, offers dramatic gains in scalability and affordability over kilometer scale Michelson systems. Tunable to frequency bands where conventional detectors lose sensitivity, it opens the door to compact, versatile, and accessible GW observatories, empowering universities and research centers worldwide. Linked together in a global network, such facilities could transcend mere detection, they could localize cosmic sources and reconstruct them into images, much as black holes were first directly revealed, ushering in a new era of gravitational-wave astronomy and multi-messenger discovery.
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Earth and Planetary Astrophysics · Cross-listed from cs.LG

Hyperspectral Variational Autoencoders for Joint Data Compression and Component Extraction

Core Francisco Park, Manuel Perez-Carrasco, Caroline Nowlan et al. (+1 more)

Geostationary hyperspectral satellites generate terabytes of data daily, creating critical challenges for storage, transmission, and distribution to the scientific community. We present a variational autoencoder (VAE) approach that achieves x514 compression of NASA's TEMPO satellite hyperspectral observations (1028 channels, 290-490nm) with reconstruction errors 1-2 orders of magnitude below the signal across all wavelengths. This dramatic data volume reduction enables efficient archival and sharing of satellite observations while preserving spectral fidelity. Beyond compression, we investigate to what extent atmospheric information is retained in the compressed latent space by training linear and nonlinear probes to extract Level-2 products (NO2, O3, HCHO, cloud fraction). Cloud fraction and total ozone achieve strong extraction performance (R^2 = 0.93 and 0.81 respectively), though these represent relatively straightforward retrievals given their distinct spectral signatures. In contrast, tropospheric trace gases pose genuine challenges for extraction (NO2 R^2 = 0.20, HCHO R^2 = 0.51) reflecting their weaker signals and complex atmospheric interactions. Critically, we find the VAE encodes atmospheric information in a semi-linear manner - nonlinear probes substantially outperform linear ones - and that explicit latent supervision during training provides minimal improvement, revealing fundamental encoding challenges for certain products. This work demonstrates that neural compression can dramatically reduce hyperspectral data volumes while preserving key atmospheric signals, addressing a critical bottleneck for next-generation Earth observation systems. Code - https://github.com/cfpark00/Hyperspectral-VAE
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All authors Core Francisco Park, Manuel Perez-Carrasco, Caroline Nowlan, Cecilia Garraffo

Earth and Planetary Astrophysics

The Albedo Problem and Cloud Cover on Hot Jupiters

Kevin Heng, Billy Edwards and Nicolas B. Cowan

Observations of transiting hot Jupiters have revealed a mismatch between the values of the Bond versus geometric albedos. In the planetary science literature, the ratio of these quantities is known as the phase integral. It has been extensively measured for the Solar System planets and shown to generally be non-unity in value. We use existing Cassini data of Jupiter to derive bandpass-integrated geometric albedos and phase integrals in the CHEOPS, TESS and Ariel bandpasses, demonstrating that these quantities vary markedly across these different wavelength ranges. By performing a population study of geometric albedos and phase integrals, we demonstrate that atmospheres with partial cloud cover may be identified using measurements of the phase integral if its measured uncertainty is $\sim 0.1$, which corresponds to an uncertainty of $\sim 3\%$ on the optical/visible secondary eclipse depth. The upcoming Ariel space mission will conduct an unprecedented statistical survey of cloud cover on hot Jupiters via the simultaneous measurement of $\sim 100$ infrared phase curves and optical secondary eclipses. Whenever available, the shape of optical phase curves of reflected light will directly constrain the phase integral, spherical albedo, degree of cloud cover and scattering asymmetry factor.
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Instrumentation and Methods for Astrophysics

Synthesis imaging with a lunar orbit array: I. global sky map and its systematics

Furen Deng, Yidong Xu, Fengquan Wu et al. (+3 more)

Ground-based radio astronomical observation at frequencies below 30 MHz is hampered by the Ionosphere and radio frequency interference (RFI). The Discovering Sky at the Longest wavelength (DSL) mission, also known as the Hongmeng mission, employs a linear array of satellites on a circular orbit around the Moon to make interferometric observations in this band. Though vastly different from the usual ground-based arrays, the interferometric visibility data collected by such an array is linearly related to the sky map, and the reconstruction is in principle an inversion problem of linear mapping. In this paper, we investigate a number of issues in the algorithm of global map reconstruction, focusing on the impact of sub-pixel noise induced by the finite pixelization of the sky, and errors due to regularization. We find that in the reconstruction process, if one builds up the beam matrix, which relates the sky pixels to the visibilities, by naively evaluating its elements at each of the pixel centers, then the sub-pixel noise can give rise to a significant aliasing effect. However, this effect can be effectively mitigated by a simple pixel-averaging method. Based on evaluation of the image quality using the correlation coefficient between the input and reconstructed map, and the signal-to-noise ratio, we discuss the selection strategy of the regularization parameter, and show that the sky can be well reconstructed with a reasonable choice of the regularization parameter.
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All authors Furen Deng, Yidong Xu, Fengquan Wu, Yanping Cong, Bin Yue, Xuelei Chen

Astrophysics of Galaxies

Kinematic Mapping of Giant Arcs: A New Method to Locate Lensing Critical Curves

Ruwen Zhou, Liang Dai, Lingyuan Ji et al. (+4 more)

The vicinity of lensing critical curves features highly magnified portions of lensed galaxies. Accurate knowledge of the location and shape of the critical curve will be useful for understanding the nature of highly magnified stellar sources near critical curves and for revealing sub-galactic dark matter structures within the lens. In galaxy-cluster lenses, however, prediction of critical curves can be uncertain due to complexity in global mass modeling. We explore and validate a kinematics-based method for locating the critical curve. This method leverages the continuous line-of-sight velocity profile of the lensed galaxy mapped through integral field spectroscopy of emission lines, and combines an agnostic local lens model and a disk rotation model. Applying our method to a highly magnified region of the Dragon Arc in the Abell 370 cluster lensing field using archival VLT/MUSE IFU mapping of the H$\beta$ line, we constrain the critical curve to an uncertainty band with a half-width of 0.23" ($1\sigma$). This result reveals locations of recently detected extremely magnified stars biased toward the negative-parity side of the critical curve, as predicted for intracluster microlensing. With future JWST/NIRSpec IFU mapping of the H$\alpha$ line at SNR $\simeq$ 10 (20), uncertainty could improve to 0.12" (0.08"). A measurement of this type with sufficiently small uncertainty may reveal small-scale wiggles in the shape of the critical curve, which can arise from the lensing perturbation of sub-galactic dark matter substructure. Our approach is generally applicable to caustic-crossing giant arcs and can be incorporated into global lens modeling.
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All authors Ruwen Zhou, Liang Dai, Lingyuan Ji, Massimo Pascale, Jose M. Diego, Fengwu Sun, Yoshinobu Fudamoto

Cosmology and Nongalactic Astrophysics

Prospects for cosmological research using hundred-meter-class radio telescopes: 21-cm intensity mapping survey strategies with QTT, JRT, and HRT

Jun-Da Pan, Yichao Li, Guo-Hong Du et al. (+2 more)

Understanding dark energy requires precision measurements of the expansion history of the universe and the growth of large-scale structure. The 21 cm intensity mapping (21 cm IM) technique enables rapid large-area surveys that can deliver these measurements. China is constructing three hundred-meter-class single-dish radio telescopes, including the QiTai 110 m Radio Telescope (QTT), the 120 m Jingdong Radio Telescope (JRT), and the 120 m Huadian Radio Telescope (HRT), whose designs are well suited for 21 cm IM cosmology. We use a Fisher-to-MCMC forecasting framework to evaluate the baryon acoustic oscillations / redshift space distortions (BAO/RSD) measurement capabilities of QTT, JRT, and HRT and propagate them to dark-energy constraints in the $w_0w_a$CDM model. Our results show that achieving a redshift coverage up to $z_{\mathrm{max}} = 1$ is crucial for fully realising the potential of hundred-meter-class single-dish telescopes for 21 cm cosmology. If all three telescopes carry out 21 cm IM surveys over the same redshift range up to $z_{\mathrm{max}}=1$ and combine their BAO/RSD measurements, QTT+JRT+HRT yield $\sigma(w_0)=0.094$ and $\sigma(w_a)=0.487$, providing tighter constraints than DESI DR2 results.
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All authors Jun-Da Pan, Yichao Li, Guo-Hong Du, Tian-Nuo Li, Xin Zhang

Instrumentation and Methods for Astrophysics

A Deep Multimodal Multi–Head Neural Network for Joint Estimation of Stellar Age, Lifetime, and Evolutionary Stage

Jing Rou Puah and Sasa Arsovski

Accurate estimation of stellar parameters – stellar age, lifetime, and evolutionary stage – remains a fundamental challenge in astrophysics. We introduce a hybrid deep learning architecture combining multimodal spectroscopic and photometric data from SDSS DR17. The model comprises a Multi-Layer Perceptron for numerical features and a CNN with a Vision Transformer for spectra, with three output heads for age, lifetime, and evolutionary stage prediction. Training labels are derived from MIST v1.2 isochrones, with evolutionary stage binned into five classes (Hot, Medium, Cool, Subgiant, Red Giant). We conduct multi-phase evaluation: Phase I explores model architectures and data balancing strategies, Phase II tunes architectural complexity, and Phase III optimizes the multi-task loss composition. The final model achieves a balance between precision (Age RMSE 0.093 in $\log(\mathrm{yrs})$) and physical realism. Monte Carlo Dropout confirms well-calibrated uncertainties, enabling meaningful astrophysical interpretation and establishing a new benchmark for multimodal stellar parameter estimation.
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Astrophysics of Galaxies

A Catalog of Galactic Atomic Hydrogen Position-Position-Velocity Filaments

M.E. Putman, D.A. Kim, S.E. Clark et al. (+3 more)

We present a catalog of 3D Galactic HI filaments over 1/3 of the sky using Galactic Arecibo L-band Feed Array HI (GALFA-HI) data. The 3D filaments are defined to be linear HI features that are continuous in position-position-velocity (PPV) and are found with fil3d, an algorithm that expands on the 2D FilFinder. The catalog contains 3333 HI filaments between +/- 50 km/s at a range of Galactic positions. 1542 of the PPV filaments are identified as local at the distance of the wall of the Local Bubble, and 209 are likely at the disk-halo interface of our Galaxy. The catalog and properties of the PPV filaments are obtained after an unsharp mask (USM) is applied to the data. The widths of the filaments are consistently ~12' (0.34 pc at 100 pc), and constrained by the 4' resolution. The local filaments have median properties of N_HI = $6 \times 10^{18}$ cm$^{-2}$, M_HI = 0.17 M_sun, FWHM = 3.2 km/s, and length of 6.4 pc. The disk-halo population has similar column densities, but the median FWHM = 7.7 km/s, consistent with them being higher z-height, warmer structures. The L $\propto$ M$^{0.5}$ relationship found for the HI filaments and their bundling on the sky are consistent with a hierarchical structure, and is likely related to turbulence playing a role in their formation.
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All authors M.E. Putman, D.A. Kim, S.E. Clark, L. Li, C. Holm-Hansen, J.E.G. Peek

High Energy Astrophysical Phenomena

Approximate analytic model of the boundary layer around a low magnetic field neutron star at the disk accretion

G. S. Bisnovatyi-Kogan

An approximate analytic one-dimensional model is constructed, for the accretion disk boundary layer surrounding a neutron star whose low magnetic field does not affect the process of accretion. A high luminosity model is considered, with radiation pressure dominant in the interior part of the disk.
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Solar and Stellar Astrophysics

Resolution and calibration effects in high contrast polarimetric imaging of circumstellar scattering regions

H.M. Schmid and J. Ma

Many circumstellar dust scattering regions have been detected and investigated with polarimetric imaging. However, the quantitative determination of the intrinsic polarization and of dust properties is difficult because of complex observational effects. This work investigates instrumental convolution and polarimetric calibration effect for high contrast imaging polarimetry with the aim to define procedures for accurate measurements of the circumstellar polarization. For this we simulate the instrumental convolution and polarimetric cancellation effects for a Gaussian PSF and an extended PSF_{AO} typical for a modern adaptive optics system. Further, polarimetric zero-point corrections (zp-corrections) are simulated for different cases like coronagraphic observations or systems with barely resolved circumstellar scattering regions. We find that the PSF convolution reduces the integrated azimuthal polarization Q_phi for the scattering region while the net Stokes signals Q and U are not changed. For non-axisymmetric systems a spurious U_phi-signal is introduced. These effects are strong for compact systems but scattering regions can still be detected down to small separations while unresolved scattering regions can be constrained by the central Stokes Q,U signal. The smearing by PSF_{AO} produces an extended, low surface brightness polarization signal changing the angular distribution of the polarization, but the initial signal can be recovered partly from the Stokes Q and U quadrant pattern. A polarimetric zp-correction applied for the removal of offsets from instrumental or interstellar polarization depends on the selected reference region and can also introduce strong bias effects for the azimuthal distribution of the polarization signal. Strategies for the zp-correction are described for coronagraphic data or observations of partly unresolved systems.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Constraint on massive vector field with extreme-mass-ratio inspirals around a slowly rotating black hole

Tieguang Zi, Peng-Cheng Li, Bao-Min Gu et al. (+1 more)

We study the influence of a massive vector (Proca) field on the energy fluxes from extreme-mass-ratio inspirals (EMRIs) around a slowly rotating Kerr black hole. The secondary compact object, carrying a Proca hair, emits additional dipolar radiation that alters total energy flux relative to general relativity (GR). These modifications induce a secular drift in the orbital evolution of circular geodesic orbits, leading to measurable dephasing in the resulting EMRIs waveforms. By evaluating waveform mismatches between the Einstein-Proca framework and its GR counterpart, we show that the Laser Interferometer Space Antenna (LISA) can distinguish the signatures of a light Proca field when black hole rotation is included. Furthermore, using a Fisher information matrix analysis, we forecast LISA's capability to place stringent constraints on the Proca mass with EMRIs signal from slowly rotating Kerr black holes. For representative EMRIs configurations, we find that LISA can detect or constrain Proca masses down to $\mu_v\sim 10^{-20}$eV, with typical fractional uncertainties at the level of tens percent, depending on the black-hole spin.
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All authors Tieguang Zi, Peng-Cheng Li, Bao-Min Gu, Fu-Wen Shu

Cosmology and Nongalactic Astrophysics

On the bin sensitivity of the transverse BAO

Paula S. Ferreira and Carlos A. P. Bengaly

We investigate the transverse BAO projection effect caused by redshift binning uncertainty ($z_c$). For SKA HI and DESI LRG surveys, we compare Gaussian, top-hat, and semi-Gaussian bins over widths $0.01<\sigma_z<0.1$, and propose a statistical correction using adjacent redshifts. The semi-Gaussian bin best recovers the BAO signal for $\sigma_z<0.04$, despite higher shot noise. Constraints are survey-dependent: Gaussian binning is weakest for SKA, while for DESI semi-Gaussian is tightest for $\sigma_z<0.04$ (otherwise comparable). The semi-Gaussian scheme offers the optimal balance between cosmological parameter constraints and BAO fidelity, making it robust for multi-probe analyses.
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High Energy Astrophysical Phenomena

Black Hole Spin Estimation with Time-variable Image of M87 During the Flaring State

Mikiya M. Takahashi, Tomohisa Kawashima and Ken Ohsuga

By investigating the time-variable 230 GHz images using ray-tracing general relativistic radiative transfer calculation, we propose a novel method for estimating the spin parameter of the supermassive black hole at the M87 center by utilizing the sudden and short-term increase in emissivity in the innermost region of the accretion disk. It is found that the flux of the photon ring increases simultaneously as the flux of the direct ring, which brightens first, decreases, and then gradually diminishes, when the increase in emissivity persists for $15 t_{\rm g}$ with $t_{\rm g}$ being the light crossing time of the gravitational radius. The direct ring is formed by photons emitted from the vicinity of the innermost region of the disk and traveling directly to the observer without orbiting around the black hole, while the photon ring is formed by photons passing near the spherical photon orbit. The time-averaged width of the dark region between the direct ring and the photon ring (dark crescent) becomes thinner when the spin parameter is higher and the increase in the emissivity of the accretion disk is greater. The time variation of two rings also causes the intensity-weighted center to oscillate both in the direction of the black hole's angular momentum vector projected onto the screen ($Y$-direction) and in the perpendicular direction ($X$-direction). The amplitude of oscillatory time variation in the $X$-direction becomes large when the spin parameter is higher, and that in the $Y$-direction becomes large when the increase in the emissivity of the disk is large. The spin parameter can be estimated by combining the time-averaged dark crescent width and the ratio of the amplitudes in the $X$- and $Y$-directions. This method is applicable when the duration of the increase in emissivity of the accretion disk ranges at least from approximately 10-20 $t_{\rm g}$.
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High Energy Astrophysical Phenomena

GRB 240715A: Revealing Novel Intrinsic Mechanism by Different Individual Pulse

Wen-Jun Tan, Chen-Wei Wang, Shao-Lin Xiong et al. (+37 more)

The Space-based multiband astronomical Variable Objects Monitor (SVOM), detected its first short gamma-ray burst, GRB 240715A, in-flight, which was jointly observed by Fermi. Based on observational data of SVOM/GRM and Fermi/GBM, we perform a comprehensive temporal and spectral analysis for individual pulse in the prompt emission of this burst, and novel characteristics are revealed. Firstly, opposite evolutions of spectral lag are found in the first and third pulse of this burst. Second, the large negative lag of the first pulse is an outlier in short GRB sample, especially when the pulse duration is considered. Spectral analysis shows that the negative lag of the first pulse is caused by the evolution of spectrum index, and is irrelevant to Epeak, which is inconsistent with the previous study. The intrinsic mechanism is probably attributed to electron cooling in the decaying magnetic field, which leads to the continuous hardening of the spectrum index and results in negative lag. Furthermore, spectral analysis also shows that the third pulse is more likely to be described by a quasi-thermal spectrum, indicating the existence of photospheric emission. It is difficult to explain how the synchrotron radiation appears before photospheric emission in a single GRB and some assumptions are discussed.
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All authors Wen-Jun Tan, Chen-Wei Wang, Shao-Lin Xiong, Shi-Jie Zheng, Jiang He, Xiao-Yun Zhao, Yue Huang, Shu-Xu Yi, Bing Li, He Gao, Bo-bing Wu, Bing Zhang, Frederic Daigne, Maria-Grazia Bernardini, Bin-Bin Zhang, Stephane Basa, Bertrand Cordier, Jin-Song Deng, Yong-Wei Dong, Damien Dornic, Olivier Godet, Xu-Hui Han, Mao-Hai Huang, Cyril Lachaud, Hua-Li Li, Pierre Maggi, Frederic Piron, Yu-Lei Qiu, Stephane Schanne, Li-Ming Song, Damien Turpin, Susanna Vergani, Jing Wang, Ping Wang, Jian-Yan Wei, Chao Wu, Li-Ping Xin, Yang Xu, Li Zhang, Shuang-Nan Zhang

High Energy Astrophysical Phenomena

Beyond the Simple Power Law: A Bayesian Analysis of 897 Pulsar Spectra

Qingzheng Gao, Xiao-Jin Liu, Zhi-Qiang You et al. (+2 more)

We present a comprehensive re-evaluation of pulsar radio spectra using the largest curated dataset of calibrated flux densities to date, comprising 897 pulsars, and employing a robust Bayesian framework for model comparison alongside frequentist methods. Contrary to the established consensus that pulsar spectra are predominantly simple power laws, our analysis reveals that complex spectral shapes with curvature or breaks are in fact the norm. The broken power law emerges as the most common spectral shape, accounting for 60% of pulsars, while the simple power law describes only 13.5%, with 68.8% of pulsars decisively favoring curved or broken models. We further identify 74 confident gigahertz-peaked spectrum pulsars, and demonstrate that millisecond pulsars frequently exhibit spectral curvature. A key finding is that the previously reported dominance of the simple power law was largely a statistical artifact of the frequentist method used in earlier work. These findings substantially revise the prevailing view of pulsar spectra and establish a critical, model-classified foundation for future theoretical work.
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All authors Qingzheng Gao, Xiao-Jin Liu, Zhi-Qiang You, Zheng Li, Xingjiang Zhu

Cosmology and Nongalactic Astrophysics

Curvature Perturbations from Higgs Modulated Reheating

Weiyi Deng, Chengcheng Han, Zhanhong Lei et al. (+1 more)

In this work we investigate curvature perturbations and non-Gaussianity arising from Higgs modulated reheating in the early Universe. We employ three different methods – the period-averaging (PA) method, the exact method, and the non-perturbative $\delta N$ formalism – to compute the power spectrum and bispectrum of curvature perturbations. Our results show that the non-perturbative $\delta N$ method provides a reliable estimate across a wide range of reheating time and Higgs field values, including regimes where the Higgs field oscillates significantly after inflation. We find that a smaller Higgs self-coupling ($\lambda$) leads to a larger curvature perturbation, with the non-Gaussianity predominantly taking a local shape. This highlights the importance of considering non-perturbative effects in calculating the curvature perturbation during Higgs modulated reheating, especially for smaller values of $\lambda$. Our findings offer valuable insights into the dynamics of reheating and the generation of primordial perturbations in the early Universe.
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All authors Weiyi Deng, Chengcheng Han, Zhanhong Lei, Jin Min Yang

Astrophysics of Galaxies

Deep X-ray observation of NGC 3221: everything everywhere all at once

Sanskriti Das, Smita Mathur, Bret D. Lehmer et al. (+3 more)

We present a comprehensive analysis of 475 ks (438 ks unpublished & 37 ks archival) XMM-Newton/EPIC-pn observation of a nearby, highly inclined, star-forming, luminous infrared galaxy NGC 3221 through spatial, temporal, and spectral information. We confirm the presence of a low-luminosity (presumably Compton-thick) AGN. The 0.4$-$12 keV luminosity and the hardness ratio of the six ultra-luminous X-ray sources (ULX) previously identified in Chandra data exhibit diverse variability on day-scale. The collective emission from unresolved sources exhibits a different day-scale variability. We have also discovered two new predominantly soft ($<1$ keV) sources. One of these has an enigmatic spectral shape featuring a soft component, which we interpret as a superbubble in NGC 3221, and a variable hard component from a compact object, which is unresolved from the superbubble. We do not confidently detect any X-ray emission from SN 1961L. The hot gas in the ISM (out to $\pm$6 kpc from the disk plane) and the extraplanar region (6$-$12 kpc) both require two thermal phases at $\sim 0.15$ keV and $\sim 0.55$ keV. The $\sim 0.55$ keV component is fainter in the ISM than the $\sim 0.15$ keV component, but the emission from the latter falls off more steeply with disk height than the former. This makes the extraplanar region hotter and less dense than the ISM. The proximity of NGC 3221 and the occurrence of the underluminous AGN offer a unique observing opportunity to study the hot diffuse medium in conjunction with nuclear and disk-wide point sources.
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All authors Sanskriti Das, Smita Mathur, Bret D. Lehmer, Steven W. Allen, Yair Krongold, Anjali Gupta

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

Detection prospects for the Cosmic Neutrino Background using matter interferometers

Chrisna Setyo Nugroho and Martin Spinrath

In this paper we discuss how the Cosmic Neutrino Background can affect the measured phase difference in a matter interferometer. This phase is proportional to a difference in potential energies along the two interferometer paths. The relevant potentials here are the well-known neutrino matter potential and a potential related to the Stodolsky effect. We show how they can be rewritten in terms of scalar potentials, pseudo magnetic fields and spin-spin interactions. Unfortunately, current technology is unlikely to detect this effect and we discuss prospects for the future. We also briefly comment on fermionic Dark Matter which can give rise to very similar effects which can easily be larger than the neutrino case.
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Astrophysics of Galaxies

Tracing Quenching in Nearby Galaxies Through Inner Surface Mass Density and Cold Gas Content

Evangela E. Shread, Trevor J. Weiss, Jerome J. Fang et al. (+1 more)

The inner stellar mass surface density within 1 kpc, Sigma1, has emerged as a suitable proxy for bulge growth and galaxy quenching. However, the dependence of cold gas content on Sigma1 has not been thoroughly explored. In this paper, we examine the relationship between Sigma1, as well as the mass-relative parameter delSigma1, and the atomic (fHI) and molecular (fH2) cold gas fractions in massive, nearby galaxies. We utilize a sample of 341 galaxies with HI data and 201 galaxies with H2 data from the xGASS and xCOLDGASS surveys, spanning 0.02 <= z <= 0.05 and a stellar mass range of 10^10 <= M_*/M_odot <= 10^11.5. While we observe that a decline in both fHI and fH2 is associated with increasing Sigma1, we find that fH2 shows a sharper decline above a threshold value of delSigma1 = 0. In addition, the fraction of galaxies with AGN activity (Seyferts and LINERs) increases with delSigma1, with the greatest increase occurring between 0 <= delSigma1 <= 0.2 dex. We propose an evolutionary track in the plane of fH2-delSigma1, whereby molecular gas depletion at fixed mass coincides with a rise in AGN activity. Our results suggest that central bulge growth is more tightly coupled to the depletion of molecular gas rather than atomic gas, with AGN feedback possibly contributing to this process. Our work highlights the utility of Sigma1 and delSigma1 as tracers of quenching in massive galaxies.
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All authors Evangela E. Shread, Trevor J. Weiss, Jerome J. Fang, Cameron Law

Saturday 22 November

Earth and Planetary Astrophysics

JWST COMPASS: Insights into the Systematic Noise Properties of NIRSpec/G395H From a Uniform Reanalysis of Seven Transmission Spectra

Tyler A. Gordon, Natalie M. Batalha, Natasha E. Batalha et al. (+9 more)

JWST has already observed near-infrared transmission spectra of over a dozen super-Earths and sub-Neptunes. While some observations have allowed astronomers to characterize sub-Neptunes in unprecedented detail, small feature amplitudes and poorly-understood systematics have led to ambiguous results for others. Using the first seven targets from the COMPASS program, which is currently surveying 12 small planet atmospheres using NIRSpec/G395H, we investigate these timeseries systematics. We implement a model that uses the principle components of the normalized pixel fluxes to account for variations in the shape and position of the spectral trace. We find that observations with a smaller number of groups-per-integration benefit most profoundly from the use of this model, and that systematics are particularly strong between 2.8 and 3.5 $\mu$m. Despite these systematics, pandexo is a relatively accurate predictor of the precision of the spectra, with real error bars on average 5% larger in NRS1 and 12% larger in NRS2 than predicted. We compute new limits on metallicity and opaque pressure level for each target and compare these to previous results from the COMPASS program. Next, we co-add spectra from multiple targets to reduce the effective noise in the combined spectra in hopes of detecting transmission features in common between the targets, but this exercise does not yield compelling evidence any signals. We find that a handful of additional transits are sufficient to break the degeneracy between metallicity and aerosols for the majority of our targets, pointing towards the possibility of unraveling the mysteries of these worlds with future allocations of JWST time.
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All authors Tyler A. Gordon, Natalie M. Batalha, Natasha E. Batalha, Artyom Aguichine, Anna Gagnebin, James Kirk, Mercedes Lopez-Morales, Annabella Meech, Nicholas Scarsdale, Johanna Teske, Nicole L. Wallack, Nicholas Wogan

High Energy Astrophysical Phenomena

Cosmogenic Origin of KM3-230213A: Delayed Gamma-Ray Emission from A Cosmic-Ray Transient

Sovan Boxi, Saikat Das and Nayantara Gupta

The highest-energy cosmic neutrino detected by the ARCA detector of KM3NeT has reignited the quest to pinpoint the sources of ultrahigh-energy cosmic rays (UHECRs; $E\gtrsim 0.1$ EeV). By uncovering the associated multimessenger signals, we investigate the origin of the 220 PeV $\nu_\mu$ event KM3-230213A from an unknown transient that accelerated cosmic rays to $\sim 10$ EeV. Unlike an astrophysical origin, where the $\nu_\mu$ is produced inside the source, here we consider UHECR protons that escape the source interact with the cosmic background radiation, producing a PeV-EeV cosmogenic neutrino spectrum. The secondary $e^\pm$ and $\gamma$-rays initiate an electromagnetic cascade, resulting in a cosmogenic $\gamma$-ray spectrum. The latter peaks at a delayed time of $\gtrsim 10^4$ years compared to the light travel time from the transient to observer, due to deflection of charged particles in the extragalactic magnetic field (EGMF). Our results shed light on the nature of the UHECR source for the $\nu_\mu$ event and provide crucial insights into the detection of multi-TeV $\gamma$-rays of cosmogenic origin from similar past cosmological transients. Using the $\gamma$-ray sensitivity of currently operating and next-generation imaging atmospheric Cherenkov telescopes, the flux and time-delay distribution can constrain the source distance. We further show that the detection of such a $\gamma$-ray signal above the background depends on the EGMF strength. Together with the non-detection of coincident spatial or temporal photon counterparts at the current epoch, this detection is the first compelling candidate for a sub-EeV cosmogenic neutrino.
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