Current date: 2026-09-14

Setting default datestamp limit: 0

Datestamp limit: 2026-09-14 (0 days ago)

Created/updated limit: 2026-09-07 (7 days ago)

Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics

Setting default set: physics

OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-09-14&until=2026-09-14&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 680

Keyword score statistics

score 9 -- 1 abstracts

score 6 -- 1 abstracts

score 5 -- 1 abstracts

score 4 -- 6 abstracts

score 3 -- 14 abstracts

score 2 -- 12 abstracts

in total -- 35 abstracts

Articles that appeared on 2026-09-14

[abstract 1 / 35] Wow! (score: 9)
arXiv:2605.01002 [pdf, ps, other]

Title: Nonuniform Particle Injection into Black Hole Jets by Radiative Magnetic Reconnection

Authors: Rin Oikawa, Kenji Toma, Shigeo S. Kimura,

Comments: 25 pages, 15 figures. Accepted for publication in ApJ

Subjects: astro-ph.HE physics.plasm-ph

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Active galactic nuclei often exhibit highly collimated RELATIVISTIC plasma outflows launched from the vicinity of their central BLACK HOLEs. One of the key theoretical challenges in understanding BLACK HOLE JET formation is the origin of the plasma that feeds the JET, which remains poorly understood, particularly in explaining the observed JET emission. In this study, we focus on electron positron pair production generated by high energy photons from non axisymmetric MAGNETic RECONNECTion near the BLACK HOLE, as suggested by recent three dimensional general RELATIVISTIC MAGNETohydrodynamics simulations. By employing general RELATIVISTIC ray tracing, we calculate the spatial distribution of the pair production rate in the JET, taking into account photon propagation and collision angles in curved spacetime. We find that our scenario can naturally supply a sufficient amount of plasma to explain the observed radio emission from the M87 JET, even when photon anisotropy is considered. Furthermore, we show that a spinning BLACK HOLE plays a crucial role in shaping the spartial dsitribution of the pairs, which in turn affects JET acceleration and very high energy emission from the JET base.

[abstract 2 / 35] Yes (score: 6)
arXiv:2609.12055 [pdf, ps, other]

Title: Time-Integrated Searches for Sub-TeV Neutrino Sources with IceCube-DeepCore

Authors: R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J. M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, L. Brusa, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. Fattorini, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, R. Neshat, L. Neste, M. Neumann, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, C. Parisel, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. Schmitt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, A. Sharma, S. Shefali, N. Shimizu, C. Silva, M. Shin, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, W. Tian, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Velazquez, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, J. Woodward, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas,

Comments:

Subjects: astro-ph.HE

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

We have developed techniques for a competitive sub-TeV time-integrated neutrino search and applied it to 11.1 years of IceCube-DeepCore data. The DeepCore subarray lowers the sensitivity of IceCube down to sub-TeV energies and is especially interesting for objects with soft spectra. Three studies were performed: a search for neutrino emission from AGN exhibiting high intrinsic X-ray flux, including NGC 1068, as identified by SWIFT/BAT; a search for neutrino emission from Galactic objects identified by FERMI-LAT as exhibiting a spectral shape consistent with neutral pion decay; and an all-sky search for neutrino point sources. Objects for this study were selected given their prospects for sub-TeV neutrino emission. No evidence for sub-TeV neutrino emission is found in any of the searches performed. Finally, for each catalog of objects, we use a statistical combination of the p-values via a binomial test to search for aggregated neutrino emission from a subset of the objects. Neither of the binomial tests yields significant results. For NGC 1068, assuming a power law spectrum with index 3.4, the 90% confidence level upper limit on per-flavor neutrino emission in the 30--400 GeV range is $Φ_{ν+\barν}|_{\mathrm{1 TeV}} < 9.5 \times 10^{-11}$ TeV$^{-1}$ cm$^{-2}$ s$^{-1}$, a factor of two higher than the extrapolation of IceCube's measurement at higher energies. We additionally provide neutrino flux upper limits for a variety of spectra.

[abstract 3 / 35] Yes (score: 5)
arXiv:2609.12215 [pdf, ps, other]

Title: Plasma Heating and Energization in Hot-Onset Flare Precursor Events

Authors: H. Da, J. F. Drake, M. Swisdak,

Comments:

Subjects: astro-ph.SR

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

Recent observations of solar flares have revealed a distinct 'hot onset' phase preceding the impulsive phase, characterized by elevated plasma temperature (>10 MK), a steady increase in emission measure, and the absence of detectable nonthermal emission. The standard flare model attributes the formation of hot flare plasma to chromospheric evaporation driven by energy deposition from nonthermal electrons, and therefore does not naturally explain why thermal heating precedes nonthermal emission. Motivated by recent observations of guide-field evolution in two-ribbon flares and by large-scale MHD simulations, we investigate hot-onset energization using simulations of MAGNETic RECONNECTion with the kinetic macroscale model kglobal initialized with a spatially non-uniform guide field. Because the efficiency of electron non-thermal energy production from FERMI acceleration decreases with guide-field strength, the evolving guide field produces two distinct energization regimes. During the initial high-guide-field phase, the bulk electron temperature rises to approximately twice its initial value, while non-thermal particle production remains weak. Upon entering the low-guide-field regime, energetic particle production is significantly enhanced, with the population of high-energy electrons growing rapidly. These findings provide a self-consistent physical explanation for the hot onset, demonstrating that the macroscopic evolution of the guide field naturally bridges the hot-onset and impulsive phases of solar flares without requiring a separate trigger mechanism.

[abstract 4 / 35] Yes (score: 4)
arXiv:2604.15798 [pdf, ps, other]

Title: Induced Scattering of Strong Waves in Pair Plasmas

Authors: Masanori Iwamoto, Kunihito Ioka,

Comments: accepted to PRD

Subjects: astro-ph.HE physics.plasm-ph

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

We study induced (stimulated) scattering of linearly polarized, strong electroMAGNETic waves in pair plasmas, which is crucial for understanding the propagation of fast radio bursts (FRBs). Magnetars are the most promising progenitors of FRBs, and FRBs propagate through the MAGNETar wind and successfully escape before being significantly scattered. We revisit the steady-state solution of linearly polarized electroMAGNETic waves in pair plasmas with arbitrary amplitude, and demonstrate that the nonlinearity is characterized by the nonlinearity parameter $a_0ω_{pe}/ω_0$ rather than the dimensionless amplitude $a_0$, where $ω_{pe}$ is the electron plasma frequency and $ω_0$ is the wave frequency. We follow the time evolution of the steady-state solution for the linear regime $a_0ω_{pe}/ω_0 \ll 1$ by performing one-dimensional particle-in-cell simulations, and show that the conventional linear analysis of induced scattering assuming $a_0 \ll 1$ is applicable even for $a_0 > 1$ when the Lorentz boost due to the plasma motion in the incident wave is considered. The saturation level is controlled by $a_0ω_0/ω_{pe}$, which corresponds to the ratio of the wave energy to the plasma energy, and the incident wave is hardly scattered for $a_0ω_0/ω_{pe} \gg 1$. We discuss the application of our results to FRBs.

[abstract 5 / 35] Yes (score: 4)
arXiv:2606.18341 [pdf, ps, other]

Title: Orbital evolution of asymmetric binaries within accreting environments

Authors: Albert Radulea, Marcelo E. Rubio, Konstantinos Kritos, Andrea Maselli,

Comments: 16 pages, 7 figures. Accepted in PRD, matches published version

Subjects: gr-qc astro-ph.HE

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Extreme mass-ratio inspirals embedded in accretion disks provide a natural arena for studying the interplay between RELATIVISTIC orbital dynamics and environmental effects. In this work, we develop a framework to investigate the secular evolution of compact objects repeatedly crossing an accretion disk around a supermassive BLACK HOLE. The orbital motion is modeled through Kerr geodesics, while disk interactions are encoded through effective prescriptions for mass accretion and dynamical friction. We find that disk-induced dissipation generically drives a two-stage evolution characterized by rapid alignment of the orbital plane with the disk, followed by slower eccentricity damping. By systematically comparing the dynamics with a purely Keplerian treatment, we show that cumulative RELATIVISTIC effects produce deviations even at large orbital separations, where the Keplerian approximation would naively be expected to remain accurate. These discrepancies grow through repeated disk crossings and become increasingly pronounced in more RELATIVISTIC orbital configurations. We further investigate the impact of the accretion-disk model by comparing the Sirko-Goodman and Novikov-Thorne prescriptions. Relativistic disk structures predict systematically lower densities and larger scale heights, leading to weaker orbital dissipation and slower secular evolution. By contrast, the spin of the central BLACK HOLE has only a minor effect on the overall circularization efficiency. Our results demonstrate the importance of consistently modeling both RELATIVISTIC orbital dynamics and disk structure when studying compact objects embedded in AGN disks, and provide a framework for exploring their long-term evolution, as well as a possible connection to quasi-periodic eruptions.

[abstract 6 / 35] Yes (score: 4)
arXiv:2608.21266 [pdf, ps, other]

Title: Generation of TeV Photons by PeV Neutrinos in Dense Astrophysical Environments

Authors: Jun-Chen Wang, Hanlin Song, Hao Li, Jie Zhu, Bo-Qiang Ma,

Comments: 14 pages, 7 figures, final version for journal publication

Subjects: astro-ph.HE hep-ph

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Recent observations by IceCube and KM3Net of PeV-scale ultra-high-energy (UHE) neutrinos, together with detections of TeV-PeV photons from various sources such as the Crab Nebula, the Galactic Center, and GAMMA-RAY BURST by ground-based observatories including Tibet AS$γ$, MAGIC, Carpet-3, and LHAASO, point to the existence of extreme astrophysical environments capable of accelerating particles to ultra-high energies. These findings motivate investigations of possible connections between UHE neutrinos and photons in such environments. Theoretically, dense regions surrounding compact objects can efficiently produce UHE neutrinos. In this work, we calculate the production of UHE photons from neutrino-nucleon interactions, and note that if these interactions occur in the outer, optically thin regions of dense environments, the resulting photons could potentially be observed. In our model, an incident neutrino scatters off a nucleon, generating secondary partons that hadronize into pions and subsequently decay into UHE photons. We calculate the resulting photon energy spectra and find that for incident (anti)neutrinos with energies above 1 PeV, the probability of producing photons with energies exceeding 1 TeV is greater than 13%. As a concrete application, we show that this mechanism can quantitatively account for the preburst TeV photons observed in GRB 221009A, providing a natural explanation for both their energies and lead times. These findings establish a plausible mechanism linking UHE neutrino events to gamma-ray observations, providing new insights into hadronic processes in extreme astrophysical environments and supporting multi-messenger astronomy studies.

[abstract 7 / 35] Yes (score: 4)
arXiv:2609.12699 [pdf, ps, other]

Title: Plasmoid-Trapped Condensation Associated with a Transient Thermal-Instability-Like Process in Chromospheric Magnetic Reconnection

Authors: Abdullah Zafar, Lei Ni, Samrat Sen, Yuhao Chen, Mohamed Sedik, Mehdi Yousefzadeh, Jun Lin,

Comments:

Subjects: astro-ph.SR

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

We perform high-resolution 2.5D single-fluid MAGNETohydrodynamic (MHD) simulations to explore the development of cool-dense structures within plasmoids during chromospheric MAGNETic RECONNECTion. The model incorporates temperature-dependent ionization degrees of hydrogen and helium, resulting in improved diffusivities and viscosity, as well as adequate radiative cooling. The numerical results show that plasma is significantly hot with temperatures reaching several tens of thousands of Kelvin in newly developed plasmoids in the low initial plasma-$β$ cases, $β_0$ = 0.05. Later, the localized accumulation of plasma and decreasing temperature result in an explosive much stronger radiative cooling process. Radiative cooling peaks over the temperature range 8000 K$-$20,000 K. The co-spatial density enhancement, substantial radiative cooling, shorter radiative cooling timescales, and a significant temperature decrease support the existence of thermal-instability-like condensation within the plasmoids. Similar cool-dense structures are identified in all low-$β_0$ cases at different chromospheric altitudes, suggesting that this occurrence is not limited to a single chromospheric layer. In contrast, in the high initial plasma-$β$, $β_0$ = 0.5 case, the maximum temperature inside the dense plasmoids is only about 8000 K. Therefore, the radiative cooling has never entered into the explosive increasing stage and the thermal-instability-like condensation does not happen. These findings reveal that plasmoid-trapped condensation may develop in chromospheric RECONNECTion once radiative losses become self-amplifying under low-$β_0$ conditions.

[abstract 8 / 35] Yes (score: 4)
arXiv:2609.12762 [pdf, ps, other]

Title: Gas-liquid stratified MHD flows in inclined rectangular ducts

Authors: Subham Pal, Ilya Barmak, Arseniy Parfenov, Alexander Gelfgat, Neima Brauner,

Comments:

Subjects: physics.flu-dyn

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

This study investigates fully developed stratified gas/liquid MAGNETohydrodynamic (MHD) flow of an electrically conducting liquid and a nonconducting gas in inclined rectangular ducts subjected to a vertical MAGNETic field. Analytical and numerical solutions for the velocity and induced MAGNETic fields are obtained in terms of the governing dimensionless parameters for concurrent upward, concurrent downward, and countercurrent flows. Unlike single-phase MHD flow, duct inclination strongly affects two-phase flow by altering the liquid holdup and the relative contributions of gravitational, frictional, and electroMAGNETic forces. The results reveal a complex interplay among gravity, Lorentz forces, and wall and interfacial shear stresses. These interactions govern the liquid holdup, pressure gradient, multiple steady solutions, flooding limits, local backflow, JET-like velocity structures, and pumping requirements. Wall conductivity critically affects the induced MAGNETic field and Lorentz force distribution and therefore cannot be neglected, even at very small MAGNETic Reynolds numbers. Fully insulating ducts generally exhibit the weakest electroMAGNETic effects and behavior closest to non-MHD flow. Configurations with a conducting bottom wall exhibit substantially stronger electroMAGNETic effects and greater sensitivity to side-wall conductivity, leading to pronounced changes in the velocity field, liquid holdup, pressure gradient, gas-lubrication effect, and overall pumping-power requirements.

[abstract 9 / 35] Yes (score: 4)
arXiv:2609.12998 [pdf, ps, other]

Title: An efficient approach to resistive GRMHD simulations of binary neutron star mergers

Authors: Miquel Miravet-Tenés, Ian Hawke, Rahime Matur, Alexander J. Wright,

Comments: 25 pages, 14 figures

Subjects: astro-ph.HE gr-qc

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Astrophysical plasmas are often highly conducting, but finite resistivity can nevertheless influence the evolution of strongly MAGNETised systems. Capturing these effects in general RELATIVISTIC MAGNETohydrodynamics is computationally challenging because high conductivity leads to stiff source terms in the evolution equations. Standard numerical approaches rely on implicit-explicit (IMEX) time integration to maintain stability, but this substantially increases the complexity and computational cost of the simulations. Building upon the previously developed Resistive Extension upGrade for Ideal MagnEtohydrodynamics (REGIME), we present a new fluid-frame formulation that simplifies the incorporation of leading-order resistive effects by avoiding matrix inversions required in previous approaches. The method is implemented in a general RELATIVISTIC MAGNETohydrodynamics code and validated through one-dimensional current-sheet tests and simulations of isolated MAGNETised neutron stars and binary neutron star mergers. We find that the new formulation reproduces the expected resistive behaviour with accuracy comparable to IMEX-based methods, while substantially reducing the computational cost and complexity of the simulations. In binary neutron star mergers, finite resistivity leads to measurable differences in the post-merger gravitational-wave signal and remnant structure, showing that resistive effects can produce measurable changes in the post-merger dynamics even in the high-conductivity regime.

[abstract 10 / 35] (score: 3)
arXiv:2604.08506 [pdf, ps, other]

Title: The Heavy Tailed Non-Gaussianity of the Supermassive Black Hole Gravitational Wave Background

Authors: Juhan Raidal, Juan Urrutia, Ville Vaskonen, Hardi Veermäe,

Comments: 20 pages, 10 figures

Subjects: astro-ph.CO astro-ph.HE gr-qc

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

We study the non-Gaussian features of the gravitational wave (GW) background generated by a population of inspiraling supermassive BLACK HOLE (SMBH) binaries. We show that the SMBH GW amplitude distribution (GWAD) features a universal heavy power-law tail $\propto A^{-4}$, while the low-amplitude tail depends on the SMBH merger rate and the energy-loss mechanisms of the binaries. The distribution of the induced timing residuals inherits this heavy tail. As a result, the ensemble averaged statistical moments of order three and higher diverge, limiting their usefulness as measures of non-Gaussianity, and the GW background from SMBH binaries exhibits the single loud source principle, according to which the strongest signals are more likely to be caused by a small number of loud sources. We confirm that the variance-averaged Gaussian approximation accurately describes the timing residual statistics. This approximation justifies a factored likelihood structure that combines standard Gaussian-process PTA posteriors with the non-Gaussian population prior, enabling consistent incorporation of non-Gaussian effects into SMBH model inference. We provide a fast and flexible Python implementation to compute the distribution of timing residuals from a given SMBH merger rate or GWAD.

[abstract 11 / 35] (score: 3)
arXiv:2606.06575 [pdf, ps, other]

Title: The quasi-star model for Little Red Dots: potential and challenges

Authors: Fabrizio Gentile, Mauro Giavalisco, Emanuele Daddi, David Elbaz, Jean-Baptiste Billand, Maximilen Franco, Benjamin Magnelli, Guillermo Barro, Yingjie Cheng, Nikko J. Cleri, Kelcey Davis, Ivan Delvecchio, Mark Dickinson, Steven L. Finkelstein, Giovanni Gandolfi, Michaela Hirschmann, Weida Hu, Dale Kocevski, Anton M. Koekemoer, Ray Lucas, Sara Mascia, Lorenzo Napolitano, Casey Papovich, Borja Pérez-Díaz, Pablo Perez-Gonzalez, Jonathan R. Trump, Xin Wang, L. Y. Aaron Yung,

Comments: Accepted for publication in A&A. The catalogue with the best-fit parameters has been submitted to the CDS. 12 pages (+ 4 in the appendix), 7 (+3) figures, 1 (+1) tables

Subjects: astro-ph.GA

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

(Abridged) Little Red Dots (LRDs) are a class of sources discovered by JWST observationally defined by a "V-shaped" rest-frame UV-Optical SED, a compact or unresolved morphology, and for having, frequently, broad hydrogen emission lines. Among various models, those involving a quasi-star interpret LRDs as an intermediate stage in the evolution of a super-massive BLACK HOLE (SMBH) seed into a classic AGN. In this paper, we employ the radiative-transfer code \texttt{Cloudy} to study whether this model is able to reproduce the spectral features commonly observed in LRDs. The model consists of an accreting SMBH ($M_{\rm BH}\sim10^{5-6} \ M_\odot$) surrounded by a convective layer where a black-body (BB) spectrum with $T\sim5000 \ {\rm K}$ and $L\sim10^{44.4} \ {\rm erg \ s}^{-1}$ is produced. This BB is then reprocessed by a concentric thick ($ΔR\sim1000 \ {\rm AU}$) shell of dense ($n_{\rm H}\sim10^{11} \ {\rm cm}^{-3}$) gas partially ionised by thermal collisions. The emerging radiation is further reprocessed by a diffuse clumpy medium surrounding the quasi-star. We fit this model to JWST/NIRSpec spectra of LRDs from the literature, deriving the main physical parameters and the SMBH masses. Once coupled with the UV emission from a host galaxy, this model is able to reproduce the shape of the UV-to-NIR continuum, including the presence of a Balmer break, as well as the luminosity of the hydrogen emission lines. However, this quasi-star model does not natively account for the presence of broad helium lines and for the possible presence of hot dust, needing additional components to match these observables. Our main result is to show how some LRDs can be modeled as quasi-stars, highlighting that a significant degeneracy exists among different LRD models. This has important consequences for our understanding of the mechanisms driving BLACK HOLE growth in the early Universe.

[abstract 12 / 35] (score: 3)
arXiv:2609.10816 [pdf, ps, other]

Title: Magnetising the quokka code with fast, second-order accurate, error-correcting schemes for MAGNETohydrodynamics on GPUs

Authors: Neco Kriel, Elizabeth Cole-Kodikara, Benjamin Wibking, Mark R. Krumholz, Chong-Chong He, Anish Sarkar, Pak Shing Li,

Comments: 29 pages, 23 figures, submitted to The Open Journal of Astrophysics

Subjects: astro-ph.IM

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

We implement a second-order accurate constrained transport (CT) MAGNETohydrodynamics (MHD) module with first-order flux correction in the open-source, adaptive mesh refinement (AMR), GPU-accelerated code quokka, supporting both ideal and resistive (constant Ohmic) regimes. For computing and averaging the electromotive forces (EMFs) at cell edges, the basis of any CT-MHD method, we experiment with a wide range of recent, state-of-the-art schemes, together with different reconstruction schemes. Alongside these, we develop a new EMF compute scheme that requires fewer reconstruction steps than existing approaches. We evaluate these scheme combinations on the basis of accuracy, stability, and GPU throughput, and demonstrate that our new scheme achieves accuracy comparable to the best-in-class existing methods, together with greater stability in RECONNECTion-dominated flows and roughly 25--60% higher GPU throughput. Using this scheme, quokka achieves excellent results across a wide range of MHD flow regimes, reaching >50 million cell updates per GPU per second, with >70% parallel efficiency out to >500 GPUs. Finally, we confirm that our CT implementation preserves divergence-free MAGNETic fields (to machine precision) under AMR.

[abstract 13 / 35] (score: 3)
arXiv:2609.12053 [pdf, ps, other]

Title: Reconsidering the role of bright and dark gravitational-wave standard sirens for cosmology

Authors: Alberto Colombo, Sonia Triscari-Benimavò, Simone Mastrogiovanni,

Comments: 20 pages, 9 figures. Comments are welcome!

Subjects: astro-ph.CO astro-ph.HE

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

Gravitational-wave (GW) standard sirens have emerged as powerful probes of cosmic expansion. They are commonly divided into two classes: bright sirens, observed in coincidence with an electroMAGNETic (EM) counterpart, and dark sirens, detected without one. Bright sirens have often been considered the main avenue for precision cosmology; however, following the latest observing run of the LIGO-Virgo-KAGRA (LVK) collaboration, the estimates of merger rates of compact objects involving neutron stars (NSs) have decreased. In this Letter, we reconsider the role that bright and dark sirens will play in precision cosmology. We demonstrate that bright sirens, although detected in small numbers, will play a crucial role in achieving the precision needed to address the Hubble tension, primarily by breaking the degeneracy between the Hubble constant ($H_0$) and the matter density parameter ($Ω_m$) inherent to dark sirens. Alternatively, we show that dark sirens alone can resolve the $H_0$ tension when supplemented with an external prior on $Ω_m$. Furthermore, we present a self-consistent statistical framework for GW cosmology with bright and dark sirens, which have traditionally been treated as independent populations although they originate from the same underlying population of BLACK HOLEs (BHs) and NSs. Finally, we find that treating bright and dark sirens as independent populations will not significantly bias GW cosmology in the next LVK observing runs, but can lead to a biased reconstruction of the low-mass end of the mass spectrum.

[abstract 14 / 35] (score: 3)
arXiv:2609.12058 [pdf, ps, other]

Title: Accretion onto a moving BLACK HOLE for stiff equations of state

Authors: Elliott Ewell, Peter K. Harris, Thomas W. Baumgarte, Stuart L. Shapiro,

Comments: 15 pages, 12 figures

Subjects: gr-qc astro-ph.HE

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

We revisit accretion of an asymptotically uniform fluid onto a moving Schwarzschild BLACK HOLE, the RELATIVISTIC analog of Bondi-Hoyle-Lyttleton accretion. Expanding on previous treatments, we focus on RELATIVISTIC accretion of stiff fluids with adiabatic indices $Γ\geq 5/3$, which is particularly relevant for the treatment of primordial BLACK HOLEs captured by neutron stars. We perform numerical simulations to systematically explore the dependence of the steady-state accretion and drag rates on the asymptotic sound speed $a_\infty$ and relative speed $v_\infty$, and identify different regimes, both subsonic and supersonic, in which these rates either increase or decrease with respect to the spherical accretion rate for $v_\infty = 0$. We propose simple analytical approximations that capture the qualitative features observed in the dependence of the accretion and drag rates on $a_\infty$ and $v_\infty$.

[abstract 15 / 35] (score: 3)
arXiv:2609.12061 [pdf, ps, other]

Title: BAQARO: Tracing Stochastic Black Hole Growth Histories and Quasar Lightcurves in a Cosmological Context

Authors: Elia Pizzati, Joseph F. Hennawi, Joop Schaye,

Comments: Submitted to MNRAS. Code available at: https://github.com/eliapizzati/baqaro. Comments welcome!

Subjects: astro-ph.GA astro-ph.CO

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

How supermassive BLACK HOLEs (BHs) assemble their mass and power the luminous QUASARs we observe across cosmic time remain central open questions in galaxy evolution. We present BAQARO, a semi-empirical framework for BH growth. Built on subhalo merger trees extracted from the FLAMINGO-10k simulation, the model links BH growth histories to those of their host subhalos through prescriptions that capture both average trends and stochastic variability. BAQARO is constrained by the bolometric QUASAR luminosity function, the clustering of UV-luminous QUASARs, and the conditional Eddington ratio distribution function. With six free parameters controlling BH seeding, the coupling between gas accretion and halo growth, and the stochasticity and temporal coherence of accretion, the model reproduces the available observational constraints over $0 \lesssim z \lesssim 7$. Using emulators, we perform Bayesian inference and quantify the constraining power of each observable. Our main findings are: (i) BH accretion is well described by the assembly of cold gas reservoirs in halos, without requiring an explicit dependence on cosmic time. (ii) BHs rapidly assemble their mass at high redshift through stochastic episodes of super-Eddington accretion. (iii) These episodes are radiatively inefficient and persist for timescales of $\sim1\,\mathrm{Myr}$, imprinting observable signatures on QUASAR lightcurves, proximity zones, and clustering measurements. (iv) The merger growth channel is always subdominant, but becomes increasingly important at $z \lesssim 1$, particularly for massive BHs. BAQARO growth histories and QUASAR lightcurves provide a flexible framework for interpreting the rapidly expanding landscape of QUASAR observations, from high-$z$ accretion probed by JWST to low-$z$ mergers constrained by pulsar timing arrays.

[abstract 16 / 35] (score: 3)
arXiv:2609.12062 [pdf, ps, other]

Title: Unified modelling of broad and narrow optical-UV emission lines from massive BLACK HOLEs: interpreting high-redshift JWST observations

Authors: Adele Plat, Michaela Hirschmann, Emma Curtis-Lake, Anna Feltre, Stephane Charlot, Steven L. Finkelstein, Lorenzo Napolitano, Fabio Pacucci, Norbert Pirzkal, Sandra Raimundo, Anthony Taylor, Alba Vidal-Garcia, L. Y. Aaron Yung,

Comments: 37 pages, 19 figures, submitted to MNRAS

Subjects: astro-ph.GA

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

JWST is uncovering a large population of ACTIVE GALACTIC NUCLEi (AGN) at high redshift, motivating the extension of models calibrated on local sources to a broader range of physical conditions. We present a consistent suite of broad- and narrow-line photoionisation models based on ionising spectra that vary with black-hole mass and Eddington ratio, spanning sub- to super-Eddington accretion. For the broad-line region (BLR), we investigate the detectability of low-mass accreting BLACK HOLEs. At z=6, broad Hα may be detectable down to $M_{BH}\approx10^{5.7} M\odot$ for a BH accreting at the Eddington limit under favourable assumptions. We derive line-to-accretion-luminosity corrections, with hydrogen and helium recombination lines providing more robust tracers than metal lines. We also explore which changes in black-hole properties and BLR conditions can contribute to the large Hα equivalent widths, elevated Balmer decrements, and weak high-ionisation lines observed in some high-redshift sources, finding that variations in BLR structure can substantially modify the emergent spectrum. For the narrow-line region (NLR), Hα and [O III] λ5007 are among the most promising tracers of low-mass accreting BLACK HOLEs, probing $M_{BH}\approx10^{5.5} M\odot$ at the Eddington limit. Many classical diagnostic diagrams miss low-metallicity AGN; we identify alternative UV and optical diagnostics that more robustly separate AGN from Pop. II and Pop. III stellar photoionisation over the conditions explored. Nevertheless, NLR line ratios are driven primarily by metallicity and ionisation parameter, with only a weak dependence on black-hole mass and Eddington ratio. Looking ahead, these models are intended for Bayesian interpretation of JWST spectra and connection to cosmological simulations through physically motivated priors.

[abstract 17 / 35] (score: 3)
arXiv:2609.12072 [pdf, ps, other]

Title: Long-term X-ray spectral analysis of Cygnus X-1 using AstroSat

Authors: H Lalthantluanga, Akash Garg, Ranjeev Misra, Vanzarmawii Chhangte, Lalthakimi Zadeng,

Comments: 13 pages, 5 figures, 3 tables. The Manuscript has been accepted for publication in Journal of High Energy Astrophysics

Subjects: astro-ph.HE

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

We performed a spectral analysis of long-term observations (2016-2019) of the BLACK HOLE binary Cygnus X-1 using AstroSat, covering its hard, intermediate, and soft states. During soft states, we found that a typical spectrum fitted with a single Comptonization, a thermal disc, and an iron line yields poor fits and unphysically small disk radii (R_in < 1 R_g). While adding a RELATIVISTIC disk component (kerrbb) improved the fit but required high color factors (f_col ~ 3.35-5.08), indicating additional Comptonization. We therefore adopted a dual-Comptonization model with hot (optically thin) and warm (optically thick) coronae. This provided consistent good fits across all soft and hard states of Cygnus X-1. The spectral evolution reveals the critical role of dual Comptonization in shaping the broadband emission of Cygnus X-1.

[abstract 18 / 35] (score: 3)
arXiv:2609.12174 [pdf, ps, other]

Title: Hidden structures in the UHE sky: unveiling potential sources via spectral signatures

Authors: Mateus Zeferino Rennó, Cainã de Oliveira,

Comments:

Subjects: astro-ph.HE

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

The search for the origin of ultrahigh-energy COSMIC RAYs (UHECRs) typically relies on identifying directional excesses in the particle flux. While this approach is well established, it cannot detect localized spectral features, which could provide constraints on the sources of UHECRs if measured. In this work, we propose a complementary metric for directional searches, based on a functional $μ_E$ of the energy spectrum in a given arrival direction. We demonstrate that $μ_E$ mathematically decouples the flux normalization of a sky region from the spectral shape, providing a distinct probe for direction-dependent spectra. To assess the statistical significance of this metric, we derive a generalization of the Li-Ma significance formula for energy-weighted metrics. Using a maximum-likelihood analysis within an exploratory Monte-Carlo model, we show that $μ_E$ can enhance discovery potential by identifying hard-spectrum regions that are not apparent in standard particle-flux maps, thereby providing a complementary probe of potential UHECR sources.

[abstract 19 / 35] (score: 3)
arXiv:2609.12333 [pdf, ps, other]

Title: Mapping the Quasar Main Sequence in the UV range: A Connection with the UV Fe III Emission

Authors: D. Martínez Collipal, M. L. Martínez-Aldama, A. Pandey, M. Cardenas, P. Marziani, S. Panda,

Comments: 5 pages, 3 figures, 1 table, oral contribution presented at ZIGUAGN Redemption: central kpc region, submitted for publication in Revista Mexicana de Astronomía y Astrofísica (RMxAA)

Subjects: astro-ph.GA

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

The QUASAR main sequence (MS) provides a consistent unification scheme for type I AGNs. This framework, constructed from the relative flux between the optical emissions $\mathrm{H}β$ and $\mathrm{Fe\,II\,(\lambda4570)}$, and the $\mathrm{FWHM(Hβ)}$, organizes QUASARs into two populations (B, A) and the subpopulation xA, which typically consists of highly accreting sources. We explored the use of the UV 1900 blend emissions ($\mathrm{Al\,III}\,\mathrmλ1860$, $\mathrm{Si\,III]}\,\mathrmλ1892$, $\mathrm{C\,III]}\,\mathrmλ1909$) and the $\mathrm{Fe\,III}$ and $\mathrm{Fe\,II}$ transitions between 1700 and 2200 Angstrom as tracers of this main sequence. We fitted these emissions for a sample of 69 low-$z$ ($z\lesssim0.8$) QUASARs observed with the Hubble Space Telescope (HST) that had available optical measurements, enabling a direct comparison with the optical QUASAR main sequence. We found a UV plane defined by $\mathrm{FWHM}(\mathrm{Al\,III})$ and the equivalent width of the combined emissions of $\mathrm{Fe\,III}$ and $\mathrm{Fe\,II}$. The plane defined by these parameters mirrors the QUASAR main sequence in the optical regime and shows a clear distinction between the different populations. The plane also enables the identification of xA sources with high completeness but a non-negligible rate of false positives. Our results suggest that the UV iron emission around the 1900 blend could be used to trace the QUASAR main sequence trend, offering an alternative way to study this scheme at high redshift.

[abstract 20 / 35] (score: 3)
arXiv:2609.12377 [pdf, ps, other]

Title: A Localized Current-Sheet Magnetic-Diffusion and Heating Prescription for Ideal-GRMHD Simulations of M87*-like Accretion Flows

Authors: Songyan Dai, Renyue Cen,

Comments: 21 pages, 13 figures, accepted for publication in the Astrophysical Journal

Subjects: astro-ph.HE astro-ph.GA

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Ideal-GRMHD calculations provide the bulk accretion flows used in black-hole emission models. A localized dissipation prescription can add a resolved map of current-sheet activity while retaining that dynamical reference. We implement such a prescription in Athena++, using a smooth threshold on the dimensionless current proxy $α_J$ to select the MAGNETic-diffusion coefficient. The constrained-transport update is coupled to a conservative energy-flux correction. Gas heating follows from primitive recovery; $q_{Ohm}=ηJ^2$ is recorded as a diagnostic, without a second energy source. Static Fourier and traveling Alfvén tests measure the evolved thermal gain, and an open-boundary Schwarzschild test closes the Killing-energy ledger. The relative total-energy residual is below $2\times10^{-15}$ in these tests. A two-resolution Harris matrix gives localized rate exponents $0.510\pm0.027$ and $0.488\pm0.028$, consistent with $1/2$ over the specified early interval. The $η=10^{-3}$ rate exceeds the same-resolution ideal control by a factor of 5.96. In matched axisymmetric M87*-like runs, localized diffusion changes the early mean MAGNETic flux, accretion rate, and normalized flux by less than $0.02\%$, with a radial-density distance of $0.005\%$. During the late active phase, a common-restart on/off comparison keeps these mean shifts below $1.6\%$, within the intrinsic temporal variability, and gives a density distance of $0.29\%$. Uniform diffusion at the tested coefficient reduces the raw flux and accretion rate by $85\%$ and $99.8\%$. These comparisons establish a spatially selective diffusion prescription with explicit energy accounting and a quantified, small bulk-flow response.

[abstract 21 / 35] (score: 3)
arXiv:2609.12390 [pdf, ps, other]

Title: A systematic study of the long-term mid-infrared color variations of Seyfert 1 galaxies

Authors: Jiahua Wu, Liming Dou, Zhining Chen, Fupeng Zhang, Luis C. Ho, Yanli Ai, Tinggui Wang, Xinwen Shu, Ning Jiang, Junfeng Wang,

Comments: Accepted for publication in ApJS

Subjects: astro-ph.GA

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

We present a comparative analysis of long-term mid-infrared (MIR) color variations (MCVs) for 1,977 narrow-line Seyfert 1 (NLSy1) and 4,113 broad-line Seyfert 1 (BLSy1) galaxies at $z < 0.3$. Using 14 years of WISE and NEOWISE data, we quantify the correlation between $W1-W2$ color and $W1$ magnitude. We categorize sources into bluer-when-brighter (BWB), redder-when-brighter (RWB), and weak/no MCV populations. Our results show that the MCV properties of BLSy1s are consistent with those of NLSy1s. This suggests that host-contaminated dust reprocessing is a universal mechanism across Seyfert 1s. Bolometric luminosity ($\Lbol$) is the primary driver of MCV behavior. However, at fixed $\Lbol$, the fraction of RWB sources decreases with increasing Eddington ratio ($\REdd$). This reveals a secondary dependence on the accretion state. Ensemble structure function analysis further shows that higher-$\REdd$ sources exhibit flatter structure functions at a given $\Lbol$, indicating smaller dust torus radii. These findings suggest that the central engine's radiation and accretion state shape the circumnuclear dust geometry. Radio-loud sources follow the same trends as radio-quiet counterparts, implying that JET emission does not significantly impact long-term MIR variability. Finally, modified blackbody modeling indicates that grains with sizes $a \gtrsim 0.1~μ$m are responsible for the observed MCVs. Our results establish a unified framework for MCVs in Seyfert~1s, where the Eddington ratio modulates both variability patterns and the physical scale of the dust torus. Furthermore, given the similarity between the MCV distributions of CLAGNs and RWB sources, we estimate that $\lesssim 6\%$ of Seyfert~1s may be CLAGN candidates, offering a potential MIR-based pre-selection.

[abstract 22 / 35] (score: 3)
arXiv:2609.12907 [pdf, ps, other]

Title: The influence of free-free absorption on the radio spectrum of Particle-Accelerating Colliding-Wind Binaries

Authors: Michaël De Becker, Agustina Belen Blanco, Mathilde Tasseroul, Anandmayee Tej, Anindya Saha, Paula Benaglia, Santiago del Palacio,

Comments: 9 pages, 3 figures, to appear in the Proceedings of the 4th BINA workshop "Moving forward with the Indo-Belgian cooperation in Astronomy", accepted for publication in the Bulletin of the Liège Royal Society of Sciences

Subjects: astro-ph.HE astro-ph.SR

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

The study of massive stars in binary and higher-multiplicity systems that participate in particle acceleration is a key topic at the crossroads of massive star physics, shock physics, and galactic COSMIC RAY astrophysics. From an observational perspective, radio measurements are our pri- mary tool for identifying these systems through their SYNCHROTRON radio emission. Out of the 54 such systems known to date, all but two have been discovered via their non-thermal radio emission. However, identifying these systems is not straightforward. The main challenge lies in free-free absorption, which can obscure the SYNCHROTRON signature and hinder detection. This paper summarizes recent developments in our understanding of these systems, with a particular focus on the strong observational bias introduced by free-free absorption. This bias significantly limits our ability to determine the true fraction of particle accelerators among colliding-wind binaries.

[abstract 23 / 35] (score: 3)
arXiv:2609.12935 [pdf, ps, other]

Title: A Variational Formulation of the MHD Induction Equation

Authors: Ahmed Farooq,

Comments:

Subjects: physics.flu-dyn physics.plasm-ph

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

We present a variational formulation of the induction equation in MAGNETohydrodynamics (MHD) based on Gauss's principle of least constraint. The central result is the Euler--Lagrange equation $\mathbf{Z}_B = -\nabla h_m$, where $h_m = \mathbf{A}\cdot\mathbf{B}$ is the MAGNETic helicity density. This reveals that the MAGNETic helicity gradient $\nabla h_m$ acts as the constraint force maintaining the solenoidality of the MAGNETic field, exactly as the pressure gradient $\nabla p$ maintains incompressibility in Taha et al.'s pressure-gradient minimization principle. The MAGNETic helicity density---which, though gauge-dependent locally, yields a gauge-invariant variational principle---naturally emerges as the Lagrange multiplier enforcing $\nabla\cdot\mathbf{B}=0$. At the solution, the field minimizes the norm of the MAGNETic helicity gradient $\|\nabla h_m\|^2$. This establishes a structural analogy: MAGNETic helicity is to the MAGNETic field as pressure is to velocity. The variational principle connects to Woltjer's theorem, Taylor relaxation, and the Hamiltonian structure of MHD.

[abstract 24 / 35] (score: 2)
arXiv:2503.15539 [pdf, ps, other]

Title: Pinched Multi Affine Geometry and Confinement: Describing the Yang-Mills Mass Gap

Authors: Shoshauna Gauvin,

Comments:

Subjects: physics.gen-ph

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

We give physical gap certificates for regulated Yang-Mills Hamiltonians and conditional continuum-transfer criteria. At fixed spatial cutoff, the physical $SU(3)$ Hamiltonian has a volume-independent gap of at least $8a/3$ for MAGNETic/electric ratio $b/a\le1/648$, with a thermodynamic ground state and a surviving finite-energy Wilson excitation. Its centered two-point autocorrelations have positive spectral representations; on the stated periodic cubes, every positive MAGNETic coupling gives the elementary plaquette at least two active energies. Quantum relative entropy identifies the physical energy form, while exact elimination retains the dynamical memory of discarded modes. We derive volume- and exterior-uniform vacuum score bounds, construct compatible finite hierarchies, and give summability and spectral-tightness criteria for limiting dynamics and surviving observables. Pinching motivates a conditional tube-energy balance; its use for an infrared gap requires uniform comparison with the complete vacuum-subtracted quantum energy after relaxation, including control of local low modes and localization errors. The remaining inputs include uniform infrared and shell estimates, local vacuum comparison rates, and RELATIVISTIC field reconstruction. The interacting four-dimensional construction, nontrivial renormalized local fields and a uniform physical mass gap remain unproved.

[abstract 25 / 35] (score: 2)
arXiv:2605.05537 [pdf, ps, other]

Title: Implications of the LISA stochastic signal from eccentric stellar mass BLACK HOLE binaries in vacuum

Authors: Ran Chen, Rohit S. Chandramouli, Federico Pozzoli, Riccardo Buscicchio, Enrico Barausse,

Comments: 19 pages, 12 figures, 3 tables

Subjects: gr-qc astro-ph.HE

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

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 $ρ\gtrsim 10^{-7}\,\mathrm{g\,cm^{-3}}$. 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.

[abstract 26 / 35] (score: 2)
arXiv:2607.05208 [pdf, ps, other]

Title: Comparing gravitational wave background predictions from cosmological simulations to pulsar timing observations

Authors: Stephanie Buttigieg, Debora Sijacki, Christopher J. Moore, Martin A. Bourne, Alberto Sesana,

Comments: MNRAS, accepted

Subjects: astro-ph.GA

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

The recent detection of a gravitational wave background (GWB) by pulsar timing arrays (PTAs) may represent the first evidence of gravitational waves from merging supermassive BLACK HOLE binaries, opening a new window on the low-frequency end of the gravitational wave spectrum. These inspiralling binaries are expected to dominate the signal, although most theoretical models seem to predict somewhat lower amplitudes than what is observed. We present the first comprehensive statistical framework to quantify the tension between PTA measurements and theoretical predictions, maximising the constraining power of current data and allowing straightforward application to future PTA datasets. We further investigate how different assumptions in the observational inference, particularly the use of a power-law model for the GWB spectrum, can bias tension estimates and potentially overstate discrepancies with theory. We apply our framework to compare predictions from the FABLE cosmological simulation with the NANOGrav 15-year dataset. For our fiducial BLACK HOLE population, we find tension values of $1σ$-$2.5σ$, indicating no statistically significant disagreement with the observations. We further explore physically motivated modifications to the merging BLACK HOLE population, guided by electroMAGNETic observations and theoretical uncertainties. In particular, scenarios with boosted BLACK HOLE masses at high redshift and more equal-mass mergers substantially increase the predicted GWB amplitude, improving agreement with PTA data. Finally, we investigate the high-mass end of the BLACK HOLE mass function and the impact of finite simulation volume. We find that the $(100 \, \mathrm{cMpc} \, h^{-1})^3$ FABLE box is sufficient to robustly predict the GWB signal at the most constraining frequency.

[abstract 27 / 35] (score: 2)
arXiv:2607.24517 [pdf, ps, other]

Title: Time-Domain Dust Astrophysics. I. Polarization Flares, Polarization-Angle Reverberation, and Fossil Imprints in Supernova-Illuminated Clouds

Authors: Thiem Hoang,

Comments: 12 pages, 6 figures; minor revisions

Subjects: astro-ph.GA astro-ph.HE

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Cosmic transients can enhance the local radiation field on timescales of days to months. Using the time-domain \TransRAT\ framework, which self-consistently follows grain heating, alignment, rotational disruption, and switching of the alignment axis between the MAGNETic field ({\bf B}) and the radiation direction ({\bf k}), we predict the time-dependent dust POLARIZATION of a dense cloud, represented by a homogeneous one-zone model, illuminated by a Type~IIP SUPERNOVA over a range of source--cloud distances. We identify four key signatures. First, for $D\lesssim1$~pc, a \emph{POLARIZATION flare} develops within days to weeks, marked by sharp increases in both thermal dust POLARIZATION and extinction-POLARIZATION efficiency; this is followed by a \emph{POLARIZATION dip} as radiative torque disruption (RAT-D) destroys the large aligned grains. Second, the peak wavelength of extinction POLARIZATION, $λ_{\rm max}$, shifts blueward as the minimum aligned-grain size decreases. Third, the transition from B-RAT to k-RAT produces an abrupt \emph{POLARIZATION-angle rotation} of up to $45^{\circ}$ in our fiducial geometry. Fourth, as the transient fades, the return to B-RAT generates a \emph{POLARIZATION-angle reverberation} governed by Larmor precession. At $D>1$~pc, SN-induced POLARIZATION properties can persist long after the radiation has faded. These {\it fossil imprints} offer the most practical near-term observational test: clouds near SUPERNOVA remnants younger than the relaxation timescale of $\sim10\,t_{\rm gas}$ with $t_{\rm gas}$ gas damping time, should exhibit elevated POLARIZATION and blueshifted $λ_{\max}$ today. Time-dependent dust POLARIZATION can therefore probe dust physics, dust properties, and pristine pre-shock MAGNETic fields in real time, while fossil imprints preserve a record of past explosions.

[abstract 28 / 35] (score: 2)
arXiv:2608.29649 [pdf, ps, other]

Title: Origin of small-scale evaporation flows deep in the chromosphere during a solar flare

Authors: L. P. Chitta, H. N. Smitha, F. A. Iglesias, T. L. Riethmüller, A. Feller, W. Chen, A. Lagg, A. Gandorfer, J. Hölken, S. K. Solanki, J. C. del Toro Iniesta, Y. Katsukawa, P. Bernasconi, T. Berkefeld, A. Álvarez-Herrero, M. Kubo, D. Orozco Suárez, B. Grauf, M. Carpenter, A. Bell, Valentín Martínez Pillet, F. J. Bailén, J. Blanco Rodríguez, J. Sebastián Castellanos Durán, E. Harnes, R. T. Ishikawa, Y. Kawabata, T. Matsumoto, T. Oba, A. L. Siu-Tapia, H. Strecker, D. Vukadinović,

Comments: Published in the Astrophysical Journal Letters (Issue: Sunrise III Early Science)

Subjects: astro-ph.SR physics.plasm-ph physics.space-ph

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Flares are caused by an abrupt release of MAGNETic energy in the solar atmosphere. Plasma heated to well over 10 MK filling the post-flare corona originates from a rapid heating and ablation of the cooler chromospheric material. This chromospheric evaporation is thought to be facilitated primarily by nonthermal electrons impinging on to the lower atmosphere. Questions on when and where in the chromosphere these upflows originate, however, are not fully resolved. Here we report on unprecedented high-resolution observations of an M-class flare recorded by the Sunrise Ultraviolet Spectropolarimeter and Imager on board the balloon-borne SUNRISE observatory, that reveal highly structured upflows on spatial scales of ~100 km originating deep in the chromosphere. The flows even precede the onset of nonthermal electrons by about 10 minutes and last through the impulsive phase of the flare. Our observations shed new light on the lower atmospheric heating and mass circulation in flares that are challenging to reconcile with the standard solar flare model.

[abstract 29 / 35] (score: 2)
arXiv:2609.12051 [pdf, ps, other]

Title: Muon decay across scales: from LEFT to SMEFT

Authors: Jakob Moritz, Tyler Corbett,

Comments: 31 pages plus appendices, 3 figures, 4 tables

Subjects: hep-ph

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

We revisit precision muon decay in the framework of the LEFT by considering how the LEFT perturbs the total rate as well as the standard and POLARIZATION-dependent Michel parameters. We derive the dependence of these observables on the dimension-five and -six LEFT operators, including lepton number violating operators, allowing for arbitrary neutrino flavor assignments. We consider fits of the LEFT to the muon decay data, in particular an approach to neutrino flavor general fits that does not respect the LEFT power counting and assuming new physics couples to all flavors equally and therefore allows for a consistent fit. We then consider how new physics imprints on the SMEFT and subsequently the LEFT in order to constrain specific scenarios of single-field extensions as well as two motivated two-field extensions. While we infer associated mass scales for these scenarios in the hundreds of GeV to multi-TeV range we also find that for the specific cases of lepton number violation, neutrino mass constraints from operator mixing are more restrictive than muon decay.

[abstract 30 / 35] (score: 2)
arXiv:2609.12194 [pdf, ps, other]

Title: Distinguishing Dymnikova and Schwarzschild Black Holes through Gravitational Lensing with EFT-Corrected Photon Propagation

Authors: Takamasa Kanai,

Comments: 25 pages, 6 figures

Subjects: gr-qc

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

We investigate whether a Dymnikova regular BLACK HOLE can be observationally distinguished from a Schwarzschild BLACK HOLE through strong gravitational lensing, taking into account effective field theory (EFT) corrections to photon propagation. We derive the modified photon propagation law induced by non-minimal couplings between the electroMAGNETic field and spacetime curvature and analyze the resulting photon trajectories in the Dymnikova spacetime. Within the strong deflection limit, we derive the EFT corrections to the photon sphere and the strong-deflection coefficients characterizing the logarithmically divergent behavior of the deflection angle. Although the EFT corrections are parametrically small, their effects can become relevant in the strong-deflection regime, where the deflection angle is highly sensitive to photon propagation near the critical orbit. We evaluate the strong-deflection observables for representative values of the Dymnikova parameter $\ell$ and compare them with the corresponding Schwarzschild results. We find that EFT corrections to photon propagation leave characteristic imprints on the strong-lensing observables. Furthermore, the contribution of the EFT corrections becomes more pronounced as the Dymnikova parameter $\ell$ approaches its critical value, indicating that the near-critical regime provides a particularly sensitive setting in which curvature-dependent corrections to photon propagation may affect gravitational lensing. These results suggest that strong gravitational lensing, together with EFT-induced modifications of photon propagation, may provide a means of distinguishing Dymnikova regular BLACK HOLEs from Schwarzschild BLACK HOLEs.

[abstract 31 / 35] (score: 2)
arXiv:2609.12279 [pdf, ps, other]

Title: Dynamics for Spin-$1/2$ Particles in Einstein-Gauss-Bonnet Gravity II: Non-Relativistic Case

Authors: E. Maciel,

Comments: 48 page, 9 figures, 1 table

Subjects: gr-qc

Created: 2026-09-10; Updated: 2026-09-14; Datestamp: 2026-09-14

In this work, I investigate the non-RELATIVISTIC quantum dynamics of spin-1/2 particles in Einstein-Gauss-Bonnet (EGB) gravity and establish a direct connection between higher-curvature corrections, fermionic dynamics, and the phenomenology of compact objects. Starting from the Dirac Hamiltonian in a static, spherically symmetric EGB spacetime, we perform a Fold-Wouthuysen transformation and derive the effective Hamiltonian, including RELATIVISTIC kinetic, gravitational, spin-orbit, and higher-curvature contributions. Heisenberg equations are then used to obtain the dynamics of velocity, force, and spin, revealing explicit EGB corrections for both translational motion and spin transport. In particular, the spin-orbit sector induces a modified precession frequency whose fractional deviation from general relativity scales as $δ_Ω=-4(ξ/M^{2})(M/ρ)^{3}$, providing a clear dimensionless signature of the Gauss-Bonnet coupling. Through Ehrenfest's theorem, we also establish the correspondence between the dynamics of quantum operators and their semiclassical gravitational limit. As an astrophysical application, we consider the stellar-mass BLACK HOLE A0620-00 and show that prospective relative sensitivities in spin precession on the order of $10^{-3}$ to $10^{-4}$ can probe Gauss-Bonnet couplings in the range of approximately $10^{6}$ to $10^{8}\,{\rm m}^{2}$, depending on the orbital radius. This result identifies fermionic spin precession as a complementary channel for testing gravity with higher-curvature corrections and provides a quantum-mechanical framework connecting modified gravitational dynamics to precision phenomenology in strong-gravity regimes.

[abstract 32 / 35] (score: 2)
arXiv:2609.12467 [pdf, ps, other]

Title: Magnetic Fields and Asymmetric Accretion in the Class 0 Protostellar System L1527 IRS

Authors: Hanju Nam, Woojin Kwon, Youngwoo Choi, Ian W. Stephens, Leslie W. Looney,

Comments: 18 pages, 13 Figures, 1 table, Accepted for publication in ApJ

Subjects: astro-ph.SR astro-ph.GA

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Magnetic fields play a crucial role in regulating the collapse of dense molecular clouds, shaping the early stages of protostellar evolution. We present POLARIZATION observations in submillimeter wavelengths with the SCUBA-2/POL-2 instrument on James Clerk Maxwell Telescope toward the Class 0 protostellar system L1527 IRS (IRAS 04368+2557). The MAGNETic field morphology varies across the core of L1527 IRS. Magnetic fields in the eastern region are perpendicular to the outflow axis, while those in the western region show a pinched morphology, overall aligned with the outflow cavity. These distinct bipolar outflow regions also have a clear color difference in near infrared observed by James Webb Space Telescope. In addition, the spectral index derived from 450 μm and 850 μm observations reveals that the northwestern region of the protostellar system is colder and denser compared to the southeastern region. Furthermore, in the large-scale structures and MAGNETic fields revealed by Herschel and Planck, we find a ~0.1 pc scale filamentary structure parallel to the large-scale MAGNETic fields in the eastern region and a relatively isotropic mass distribution in the western region. Based on these results, we propose an accretion scenario of the protostellar system in which an asymmetric mass distribution causes the distinct features observed in near-infrared and submillimeter wavelengths.

[abstract 33 / 35] (score: 2)
arXiv:2609.12539 [pdf, ps, other]

Title: Spin-POLARIZATION of the neutron ocean in MAGNETar crusts

Authors: Juliette Servais, Nicolas Chamel,

Comments: 7 pages, 3 figures

Subjects: astro-ph.HE nucl-th

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Magnetars, neutron stars harboring the strongest MAGNETic fields known in the Universe, are associated with a broad range of observational phenomena, from giant flares to fast radio bursts, and have also been proposed as potential sites of heavy-element nucleosynthesis. These phenomena are thought to be closely linked to the structure and composition of MAGNETar crusts. The outer crust consists of fully ionized nuclei embedded in a degenerate electron gas, while the inner crust additionally contains free neutrons. We investigate how strong MAGNETic fields modify MAGNETar crusts, accounting for the spin POLARIZATION of free neutrons. Arising from the coupling between the MAGNETic field and the neutron MAGNETic moment, neutron spin POLARIZATION lowers both the pressure and matter density marking the boundary between the outer and inner crusts for MAGNETic field strengths $B \gtrsim 10^{17}~\mathrm{G}$. As a consequence, the outer crust becomes thinner, the formation of the superheavy nuclei predicted in previous studies is suppressed, and the neutron ocean permeating the inner crust becomes spin-polarized. These effects may have important implications for the diverse manifestations of MAGNETars and for $r$-process nucleosynthesis in the ejecta of MAGNETar giant flares.

[abstract 34 / 35] (score: 2)
arXiv:2609.12561 [pdf, ps, other]

Title: Shadows and Polarimetric Signatures of Rotating Simpson-Visser Black Holes with Thick Disk Illumination

Authors: Bing-Bing Chen, Deyou Chen, Yu-Kang Wang, Muhammad Israr Aslam, Rabia Saleem, Nazek Alessa,

Comments: 21 pages, 9 figures

Subjects: gr-qc

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

In this manuscript, we investigate the shadow and POLARIZATION images of a Simpson-Visser rotating BLACK HOLE surrounded by a ballistic approximation accretion flow model. Solving the numerically geodesic and radiative transfer equations, we discuss the influence of the regularization parameter $g$, spin parameter $a$, and observer inclination angle $θ_o$ on the resulting images at $230\,\mathrm{GHz}$ with an infalling motion. The results interpret that, a bright circular ring corresponding to higher-order images is observed, accompanied by an inner region of decreased intensity. Both $g$ and $a$ has little influence on the size of the higher-order images, but significantly changes their shape and intensity distribution. Whereas, variation in $θ_o$ modify the image morphology, producing a crescent-shaped bright region on the left side. Finally, the POLARIZATION patterns trace the brightness distribution and vary with both $g$ and $a$, reflecting the spacetime structure. These results demonstrates that the intensity and POLARIZATION in thick disk models provide probes of Simpson-Visser rotating BLACK HOLEs and near-horizon accretion physics.

[abstract 35 / 35] (score: 2)
arXiv:2609.12619 [pdf, ps, other]

Title: Heavy Seed Black Hole Growth in Metal-Enriched Halos through Disk-Induced Stellar Disruptions: A Semi-Analytical Modelling

Authors: Zijian Wang, Zhili Wang, Yiqiu Ma, Boyuan Liu, Zheng Cai, Mengye Wang, Qingwen Wu,

Comments: 20 pages, 12 figures

Subjects: astro-ph.GA astro-ph.HE gr-qc

Created: 2026-09-11; Updated: 2026-09-14; Datestamp: 2026-09-14

Recent simulations suggest that heavy seed BLACK HOLEs may form in weakly metal-enriched atomic cooling halos, where the supermassive-star progenitor and small-scale stellar fragments emerge nearly coevally. In this picture, the newly born heavy seed is naturally embedded in a metal-enriched Pop~I/II nuclear star cluster rather than in an isolated pristine environment. We investigate whether disk-induced tidal disruption events (TDEs) from these Pop~I/II stars can provide an efficient and sustained growth channel for heavy seed BLACK HOLEs. We construct a semi-analytical model for stellar orbital damping, disk capture, migration, and tidal disruption around a heavy seed BLACK HOLE, and incorporate the resulting disk-induced TDE contribution into cosmological merger trees with baryonic and metallicity evolution. Heavy seed host halos are selected from atomic cooling halos with $Z\lesssim10^{-3}Z_\odot$ that satisfy either a rapid gas-inflow criterion or a strong Lyman--Werner radiation criterion. We find that disk-induced Pop~I/II TDEs can dominate the early growth of heavy seeds: the median BLACK HOLE mass grows from $\sim10^4\,M_\odot$ to $\sim10^5\,M_\odot$ within the first $\sim0.1$ Gyr after seed formation, and reaches several $10^5\,M_\odot$ by $\sim0.2$ Gyr. The cumulative mass supplied by TDEs initially exceeds that from gas accretion and remains comparable over the first $\sim200$ Myr. Including disk-induced TDEs shifts the BLACK HOLE population toward higher masses, increases the abundance of massive BLACK HOLEs at $z\sim9$--10, and produces larger BLACK HOLE-to-stellar mass ratios. This channel helps alleviate, but does not fully remove, the tension between heavy-seed models and the most extreme high-redshift BLACK HOLE candidates, suggesting that additional growth mechanisms may still be required.