Current date: 2025-12-19

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Datestamp limit: 2025-12-19 (0 days ago)

Created/updated limit: 2025-12-12 (7 days ago)

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

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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2025-12-19&until=2025-12-19&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 95

Keyword score statistics

score 6 -- 1 abstracts

score 5 -- 2 abstracts

score 4 -- 1 abstracts

score 3 -- 1 abstracts

score 2 -- 2 abstracts

in total -- 7 abstracts

Articles that appeared on 2025-12-19

[abstract 1 / 7] Yes (score: 6)
arXiv:2512.15847 [pdf, ps, other]

Title: Self-confinement of RELATIVISTIC pair beams in MAGNETized interstellar plasmas: the case of pulsar X-ray filaments

Authors: Luca Orusa, Lorenzo Sironi,

Comments: 7 pages, 6 figures. Submitted to PRL

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

Created: 2025-12-17; Updated: 2025-12-19; Datestamp: 2025-12-19

The observation of filamentary X-ray structures near bow-shock pulsar wind nebulae (PWNe) -- such as the Guitar, Lighthouse, and PSR J2030$+$4415 nebulae -- and of slow-diffusion regions around pulsars like Geminga, Monogem, and PSR J0622$+$3749, challenges the standard picture of cosmic-ray transport in the interstellar medium, implying a diffusion coefficient two orders of magnitude smaller than the Galactic average. The suppressed diffusion can be attributed to self-generated MAGNETic turbulence, driven -- via the non-resonant streaming instability -- by electron--positron pairs escaping the PWNe. This instability requires a net current, yet the beam of escaping pairs is expected to be charge-neutral. We show that a charge-neutral pair beam propagating through an electron--proton plasma can spontaneously generate a net current. Using fully kinetic two- and three-dimensional particle-in-cell simulations with realistic mass ratio, we find that beam electrons get focused into self-generated MAGNETic filaments produced by the nonlinear evolution of the Weibel instability, while beam positrons remain unconfined. The resulting net (positron) current drives the non-resonant streaming instability, further amplifying the MAGNETic field. This mechanism provides a pathway for the onset of charge asymmetries in initially charge-neutral pair beams and for the growth of MAGNETic fluctuations that efficiently scatter the beam particles, with implications for the formation of X-ray filaments and, more broadly, for particle self-confinement in TeV halos around PWNe.

[abstract 2 / 7] Yes (score: 5)
arXiv:2512.15846 [pdf, ps, other]

Title: GRHayL: a modern, infrastructure-agnostic, extensible library for GRMHD simulations

Authors: Samuel Cupp, Leonardo R. Werneck, Terrence Pierre Jacques, Samuel Tootle, Zachariah B. Etienne,

Comments: 24 pages, 16 figures, submitted to Phys. Rev. D

Subjects: gr-qc astro-ph.HE

Created: 2025-12-17; Updated: 2025-12-19; Datestamp: 2025-12-19

Interpreting multi-messenger signals from neutron stars and BLACK HOLEs requires reliable general-RELATIVISTIC MAGNETohydrodynamics (GRMHD) simulations across rapidly evolving high-performance-computing platforms, yet key algorithms are routinely rewritten within infrastructure-specific numerical-relativity codes, hindering verification and reuse. We present the General Relativistic Hydrodynamics Library (GRHayL), a modular, infrastructure-agnostic GR(M)HD library providing conservative-to-primitive recovery, reconstruction, flux/source and induction operators, equations of state, and neutrino leakage through an intuitive interface. GRHayL refactors and extends the mature IllinoisGRMHD code into reusable pointwise and stencil-wise kernels, enabling rapid development and cross-code validation in diverse frameworks, while easing adoption of new microphysics and future accelerators. We implement the same kernels in the Einstein Toolkit (Carpet and CarpetX) and BlackHoles@Home, demonstrating portability with minimal duplication. Validation combines continuous-integration unit tests with cross-infrastructure comparisons of analytic GRMHD Riemann problems, dynamical Tolman-Oppenheimer-Volkoff evolutions, and binary neutron-star mergers, showing comparable or improved behavior over legacy IllinoisGRMHD and established Einstein Toolkit codes.

[abstract 3 / 7] Yes (score: 5)
arXiv:2512.15881 [pdf, ps, other]

Title: Shedding the envelope: JWST reveals a kiloparsec-scale [OIII]-weak Balmer shell around a z=7.64 QUASAR

Authors: Julien Wolf, Eduardo Bañados, Xiaohui Fan, Antoine Dumont, James E. Davies, David S. N. Rupke, Jinyi Yang, Weizhe Liu, Silvia Belladitta, Aaron Barth, Sarah Bosman, Tiago Costa, Frederick B. Davies, Roberto Decarli, Dominika Ďurovčíková, Anna-Christina Eilers, Hyunsung D. Jun, Yichen Liu, Federica Loiacono, Alessandro Lupi, Chiara Mazzucchelli, Maria Pudoka, Sofía Rojas-Ruiz, Jan-Torge Schindler, Wei Leong Tee, Benny Trakhtenbrot, Fabian Walter, Huanian Zhang,

Comments: Revised version submitted after the first referee review

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

Created: 2025-12-17; Updated: 2025-12-19; Datestamp: 2025-12-19

Luminous QUASARs at the redshift frontier z>7 serve as stringent probes of super-massive BLACK HOLE formation and they are thought to undergo much of their growth obscured by dense gas and dust in their host galaxies. Fully characterizing the symbiotic evolution of SMBHs and hosts requires rest-frame optical observations that span spatial scales from the broad-line region to the ISM and CGM. JWST now provides the necessary spatially resolved spectroscopy to do so. But the physical conditions that regulate the interplay between SMBHs and their hosts at the highest redshifts, especially the nature of early feedback phases, remain unclear. We present JWST/NIRSpec IFU observations of J0313$-$1806 at z=7.64, the most distant luminous QUASAR known. From the restframe optical spectrum of the unresolved QUASAR, we derive a BLACK HOLE mass of $M_\mathrm{BH}=(1.63 \pm 0.10)\times10^9 M_\odot$ based on H$β$ and an Eddington rate of $λ=L/L_\mathrm{Edd}=0.80\pm 0.05$, consistent with previous MgII-based estimates. J0313-1806 exhibits no detectable [O III] emission on nuclear scales. Most remarkably, we detect an ionized gas shell extending out to $\sim 1.8$ kpc traced by H$β$ emission that also lacks any significant [O III], with a $3σ$ upper limit on the [O III]$ λ$5007 to H$β$ flux ratio of $\log_{10} \left( F(\mathrm{[OIII]})/F(\mathrm{H}β)\right)=-1.15$. Through photoionization modelling, we demonstrate that the extended emission is consistent with a thin, clumpy outflowing shell where [OIII] is collisionally de-excited by dense gas. We interpret this structure as a fossil remnant of a recent blowout phase, providing evidence for episodic feedback cycles in one of the earliest QUASARs. These findings suggest that dense ISM phases may play a crucial role in shaping the spectral properties of QUASARs accross cosmic time.

[abstract 4 / 7] Yes (score: 4)
arXiv:2512.15849 [pdf, ps, other]

Title: Cosmological Neutron Stars Produce Diffuse Axion X-Ray Signatures

Authors: Orion Ning, Kailash Raman, Benjamin R. Safdi,

Comments: 9+14 pages, 4+18 figures, video abstract at https://youtu.be/Qx-p_aU930E

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

Created: 2025-12-17; Updated: 2025-12-19; Datestamp: 2025-12-19

Axion-like particles can be abundantly produced through scattering processes in the cores of neutron stars (NSs). If they are ultralight ($m_a \lesssim 10^{-4}$ eV), then they can efficiently convert to detectable photons in the external NS MAGNETospheres, and if they are heavy ($m_a \gtrsim 1$ eV), then they can decay into photons before reaching Earth. In this work, we search for the resulting X-ray signatures from both of these channels summing over the $\textit{cosmological}$ NS population. We compare the predicted axion-induced X-ray signal to the cosmic X-ray background today as measured by a number of instruments such as NUSTAR, HEAO, SWIFT, and INTEGRAL. We model the axion-induced signal using NS cooling simulations and MAGNETic field evolution models. We find no evidence for axions and derive strong constraints for both ultralight and heavy axion scenarios, covering new parameter space for the axion-photon and axion-nucleon couplings. Our results rule out the axion-explanation of the Magnificent Seven X-ray excess from nearby isolated NSs.

[abstract 5 / 7] (score: 3)
arXiv:2512.15853 [pdf, ps, other]

Title: From "The Cliff" to "Virgil": Mapping the Spectral Diversity of Little Red Dots with JWST/NIRSpec

Authors: Guillermo Barro, Pablo G. Perez-Gonzalez, Dale Kocevski, Jonathan R. Trump, Mark Dickinson, Pablo Arrabal Haro, Madisyn Brooks, Steven L. Finkelstein, Maximilien Franco, Mauro Giavalisco, Norman A. Grogin, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Rebecca L. Larson, Gene C. K. Leung, Ray A. Lucas, Elizabeth J. McGrath, Casey Papovich, Borja Perez-Diaz, Elizabeth Taylor, Roberta Tripodi, L. Y. Aaron Yung,

Comments: 24 pages, 11 figures, submitted to ApJ

Subjects: astro-ph.GA

Created: 2025-12-17; Updated: 2025-12-19; Datestamp: 2025-12-19

One of JWST's most unexpected discoveries is the emergence of "Little Red Dots'' (LRDs): compact sources at $z \gtrsim 3$ with blue rest-frame UV continua, red optical slopes, and broad Balmer emission lines that challenge standard models and suggest a population of early, unusual ACTIVE GALACTIC NUCLEi (AGNs). Using a comprehensive photometric selection and public NIRSpec/PRISM spectroscopy across six JWST deep fields, we identify a large sample of 118 LRDs with high-S/N spectra, enabling a population-wide analysis of their UV--optical continuum and emission lines. We find clear correlations between rest-frame color ([0.3-0.9\,$μ$m]) and slopes: bluer LRDs have blue UV slopes ($β_{ν,\mathrm{UV}} \sim 0.3$) and red optical slopes, while redder LRDs exhibit redder UV slopes ($β_{ν,\mathrm{UV}} \sim 1.1$). The continuum shape shows a similar trend: redder LRDs display prominent Balmer breaks and curvature, while bluer LRDs follow power-law-like optical SEDs. From literature compilations, $\sim$60% of known broad-line AGNs satisfy our LRD criteria, and up to 90% of LRDs show broad Balmer lines. Emission-line diagnostics reveal a shift from high H$_α$/H$_β$ and low [OIII]$\lambda5007$/H$_β$ in redder LRDs to the opposite in bluer ones, along with stronger narrow-line equivalent widths, suggesting a transition from AGN- to host-dominated emission. We fit the spectra with a two-component model combining a gas-enshrouded BLACK HOLE (BH) and a galaxy host. Redder LRDs require higher-luminosity, unreddened BHs and modestly reddened hosts; bluer LRDs require lower-luminosity, reddened BHs and dust-free galaxies. This framework reproduces the diversity in colors and spectral shape by varying BH luminosity, obscuration, and host-to-BH luminosity ratio.

[abstract 6 / 7] (score: 2)
arXiv:2512.15873 [pdf, ps, other]

Title: In-plane Black-hole Spin Measurements Suggest Most Gravitational-wave Mergers Form in Triples

Authors: Jakob Stegmann, Fabio Antonini, Aleksandra Olejak, Sylvia Biscoveanu, Vivien Raymond, Stefano Rinaldi, Beth Flanagan,

Comments: 14 pages, 8 figures, 1 table; comments welcome

Subjects: astro-ph.HE gr-qc

Created: 2025-12-17; Updated: 2025-12-19; Datestamp: 2025-12-19

The spin-orbit tilt angles $θ_{1(2)}$ of merging stellar-mass BLACK HOLEs provide key insights into their astrophysical origin. The LIGO, Virgo, and KAGRA Collaborations (2025a, arXiv:2508.18083) report that the spin-orbit tilt distribution of mergers in the latest Gravitational-Wave Transient Catalog 4.0 exhibits a global peak at near-perpendicular directions $\cosθ_{1(2)}\approx0$. Here, we recover this feature using hierarchical Bayesian inference with parametric models that are tailored to enhance the diagnostic power about astrophysical formation channels. We find that the spin distribution of the low-mass bulk of the binary BLACK HOLE merger population $(m_1\lesssim 44.3^{+8.7}_{-4.6}\,\rm M_\odot)$ can be well-modelled by a dominant Gaussian component that peaks at $\cosθ_{1(2)}\approx0$, possibly mixed with a subdominant isotropic component. Models that include a component with spins preferentially aligned with the orbit are disfavoured by current data (with Bayes factors $|Δ\ln\mathcal{B}|\approx1$ to $3$) and constrain its contribution to be small ($ξ\sim\mathcal{O}(1)\,\%$). If these findings are reinforced by more detections, they would challenge any major contribution from the traditional isolated-binary formation scenario yielding closely aligned spins. Instead, the dominant component with near-perpendicular spins qualitatively matches expectations from the evolution of isolated massive stellar triples in the galactic field, where the Lidov-Kozai effect naturally produces a unique overabundance of mergers with $\cosθ_{1(2)}\approx0$.

[abstract 7 / 7] (score: 2)
arXiv:2512.15911 [pdf, ps, other]

Title: The Era of Binary Supermassive Black Holes: Coordination of Nanohertz-Frequency Gravitational-Wave Follow-up

Authors: Sarah Burke-Spolaor, Tamara Bogdanović, Daniel J. D'Orazio, Michael Eracleous, Suvi Gezari, Matthew J. Graham, Kayhan Gültekin, Jeffrey Hazboun, Chiara M. F. Mingarelli, Gautham Narayan, Polina Petrov, Nicolo Veronesi,

Comments: To appear in BAAS, expanded summary of the conference "The Era of Binary Supermassive Black Holes: Coordination of Nanohertz-Frequency Gravitational-Wave Follow-up," held at the Aspen Center for Physics from February 2-7, 2025

Subjects: astro-ph.GA gr-qc

Created: 2025-12-17; Updated: 2025-12-19; Datestamp: 2025-12-19

Here we summarize discussions and conclusions from the conference ``The Era of Binary Supermassive Black Holes: Coordination of Nanohertz-Frequency Gravitational-Wave Follow-up,'' held at the Aspen Center for Physics from February 2-7, 2025. The meeting facilitated a crucial knowledge exchange between electroMAGNETic and gravitational-wave theorists, observers, and cyber-infrastructure experts. The central goal was to guide the development of multi-messenger follow-up strategies for binary supermassive BLACK HOLE detections by pulsar timing arrays. To build a common basis of understanding for the broader scientific community, this summary outlines the main considerations and recommendations from the meeting, summarizes the knowledge gaps identified, and ends with a potential roadmap to catalyze discussion about the search for electroMAGNETic counterparts to massive BLACK HOLE binaries detected by pulsar timing arrays.