Current date: 2025-11-26

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Datestamp limit: 2025-11-26 (0 days ago)

Created/updated limit: 2025-11-19 (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=2025-11-26&until=2025-11-26&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 713

Keyword score statistics

score 13 -- 1 abstracts

score 12 -- 1 abstracts

score 10 -- 1 abstracts

score 9 -- 2 abstracts

score 7 -- 1 abstracts

score 6 -- 1 abstracts

score 5 -- 1 abstracts

score 4 -- 9 abstracts

score 3 -- 7 abstracts

score 2 -- 17 abstracts

in total -- 41 abstracts

Articles that appeared on 2025-11-26

[abstract 1 / 41] Wow! (score: 13)
arXiv:2510.02301 [pdf, ps, other]

Title: Relativistic Jets and Winds in Radio-Identified Supermassive Black Hole Binary Candidates

Authors: Andrew G. Sullivan, Roger D. Blandford, Anna Synani, Philipe V. de la Parra, Noémie Globus, Mitchell C. Begelman, Anthony C. S. Readhead,

Comments: 13 pages, 8 figures, Accepted to ApJ

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

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Supermassive BLACK HOLE binary systems (SMBHBs) are thought to emit the recently discovered nHz gravitational wave background; however, not a single individual nHz source has been confirmed to date. Long-term radio-monitoring at the Owens Valley Radio Observatory has revealed two potential SMBHB candidates: BLAZARs PKS 2131-021 and PKS J0805-0111. These sources show periodic flux density variations across the electroMAGNETic spectrum, signaling the presence of a good clock. To explain the emission, we propose a generalizable JET model, where a mildly RELATIVISTIC wind creates an outward-moving helical channel, along which the ultra-RELATIVISTIC JET propagates. The observed flux variation from the JET is mostly due to aberration. The emission at lower frequency arises at larger radius and its variation is consequently delayed, as observed. Our model reproduces the main observable features of both sources and can be applied to other sources as they are discovered. We make predictions for radio POLARIZATION, direct imaging, and emission line variation, which can be tested with forthcoming observations. Our results motivate future numerical simulations of JETted SMBHB systems and have implications for the fueling, structure, and evolution of BLAZAR JETs.

[abstract 2 / 41] Wow! (score: 12)
arXiv:2511.19605 [pdf, ps, other]

Title: Role of MAGNETic RECONNECTion in BLAZAR variability using numerical simulation

Authors: Chandan Kumar Das, Bhargav Vaidya, Amit Shukla, Giancarlo Mattia, Karl Mannheim,

Comments: Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

Fast $γ$-ray variability in BLAZARs remains a central puzzle in high-energy astrophysics, challenging standard shock acceleration models. Blazars, a subclass of ACTIVE GALACTIC NUCLEi (AGN) with JETs pointed close to our line of sight, offer a unique view into JET dynamics. Blazar $γ$-ray light curves exhibit rapid, high-amplitude flares that point to promising alternative dissipation mechanisms such as MAGNETic RECONNECTion. This study uses three-dimensional RELATIVISTIC MAGNETohydrodynamic (RMHD) and resistive RELATIVISTIC MAGNETohydrodynamic (ResRMHD) simulations with the PLUTO code to explore MAGNETic RECONNECTion in turbulent, MAGNETized plasma columns. Focusing on current-driven kink instabilities, we identify the formation of current sheets due to MAGNETic RECONNECTion, leading to plasmoid formation. We develop a novel technique combining hierarchical structure analysis and RECONNECTion diagnostics to identify RECONNECTing current sheets. A statistical analysis of their geometry and orientation reveals a smaller subset that aligns closely with the JET axis, consistent with the JET-in-JET model. These structures can generate RELATIVISTICally moving plasmoids with significant Doppler boosting, offering a plausible mechanism for the fast flares superimposed on slowly varying BLAZAR light curves. These findings provide new insights into the plasma dynamics of RELATIVISTIC JETs and strengthen the case for MAGNETic RECONNECTion as a key mechanism in BLAZAR $γ$-ray variability.

[abstract 3 / 41] Wow! (score: 10)
arXiv:2511.19695 [pdf, ps, other]

Title: Alignment of radio JETs in the microQUASAR V4641 Sagittarii with its high-energy structures

Authors: Josep Martí, Pedro Luis Luque-Escamilla,

Comments: 6 pages, 3 figures. Accepted for publication as a Letter in Monthly Notices of the Royal Astronomical Society

Subjects: astro-ph.HE

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

V4641 Sagittarii (V4641 Sgr) is a unique Galactic microQUASAR system featuring a stellar-mass BLACK HOLE accreting matter from a massive companion. One of its intriguing features is the presence of RELATIVISTIC radio JETs almost perpendicular to the observed extended gamma-ray emission, implying significant propagation effects or interactions with the Galactic MAGNETic field. Here we report observational evidence that the radio JET and the very high-energy (VHE) and ultra high-energy (UHE) gamma-ray emission could be aligned along a common axis, indicating a co-spatial or co-directional origin. This alignment supports a model where SYNCHROTRON radio emission, VHE and UHE gamma rays are produced within a single, highly collimated RELATIVISTIC outflow. Our findings favor scenarios of in-situ particle acceleration up to hundreds of TeV, challenge previous interpretations involving large-scale particle diffusion, and simplify the geometric modeling of the source. This case highlights the potential of V4641 Sgr as a PeVatron candidate within our Galaxy and provides a benchmark for understanding JET composition and MAGNETic structure in microQUASARs.

[abstract 4 / 41] Wow! (score: 9)
arXiv:2504.05600 [pdf, ps, other]

Title: Gravitational Wave Evidence of Spin Energy Extraction from Stellar-Mass Black Holes

Authors: Shu-Xu Yi, Tian-Yong Cao, Shuang-Nan Zhang,

Comments: 17 pages, 6 figures. 3rd version of the manuscript originally titled "A universal natal spin in stell-mass black holes"

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Relativistic JETs have been found for decades as a key phenomenon in ACTIVE GALACTIC NUCLEi (AGNs), compact binary systems, and GAMMA-RAY BURSTs (GRBs), yet their energy resources remain a mystery. Two competing ideas prevail: one attributes JET energy to accretion power of the BLACK HOLE (BH), the other, more interestingly, to MAGNETic extraction of rotational energy from the BH. A decisive observational distinction between them is still elusive. We propose that BHs remnant from their natal GRB activity can serve as a critical testbed to discriminate between these two scenarios. Via analytical approaches, we demonstrate that extraction of rotational energy to power JETs during the GRB phase drives the remnant BH to a universal equilibrium spin, independent of accretion history, initial spin, and mass. This model predicts a stellar-mass BH population with this universal spin, a hallmark of BH spin energy extraction. Testing against the 4th gravitational wave (GW) catalogue (GWTC-4.0), we find a statistically robust dominant population where secondary BH spins are narrowly centered at $\sim0.05$. These findings provide strong new evidence for BH spin energy extraction.

[abstract 5 / 41] Wow! (score: 9)
arXiv:2511.20434 [pdf, ps, other]

Title: Jet reorientation revealed by intermittent JET activity in RADIO GALAXy 0954+556

Authors: Ai-Ling Zeng, Wei Zhao, Jun Yang, Xu-Zhi Hu, Furen Deng, Yu Lei, Xiaoyu Hong, Xiang Liu, Liang Chen, Mai Liao, Xiaolong Yang, Hai-Tian Shang,

Comments: 15 pages, 10 figures

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Intermittent JET activity of AGNs is a common phenomenon, whereas significant JET reorientation during episodic JET activity in relatively young RADIO GALAXies are rarely reported. The QUASAR 0954+556 at redshift of 0.903 is an intriguing source exhibiting an unusual radio JET structure with significantly different JET directions at kpc and pc scales. At kpc scales, images from the VLA exhibit a bright core, a linear JET extending 24 kpc to the northwest, and a discrete JET component 16 kpc to the northeast. At pc scales, images from the VLBA show a two-component structure with a projected separation of 360 pc in the north-south direction. The peculiar structure of 0954+556 might result from JET reorientation. Here, our aim was to investigate the possible mechanism via multiscale and multifrequency deep radio images. We performed VLA and VLBA observations of 0954+556. Together with some existing data in the NRAO data archive, we made multiple VLA images at 1.4-22 GHz and VLBA images at 1.7-43 GHz for various image analyses of the JET structure. We identified the location of the radio core at pc scales, detected the faint counter-JETs at both pc and kpc scales for the first time, and revealed a diffuse emission region connecting pc and kpc scale forward JETs. Our spectral index distribution and spectral aging analysis indicate that 0954+556 might undergo at least two episodes of JET activity during the current AGN phase. Moreover, pc scale POLARIZATION maps display a well-resolved spine-sheath POLARIZATION structure. It seems that the JET direction of 0954+556 changed significantly during intermittent JET activity. This may explain the different JET orientations and spectral ages observed from kpc to pc scales. The research provides a strong case that AGN JET direction might change rapidly on timescales of one million years.

[abstract 6 / 41] Wow! (score: 7)
arXiv:2511.20336 [pdf, ps, other]

Title: Impact of Spectral Coverage on Parameter recovery in Blazar Modeling

Authors: N. Sahakyan, D. Bégué, P. Giommi, H. Dereli-Bégué, Asaf Pe'er,

Comments: Accepted for publication in ApJ

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

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Understanding the impact of spectral coverage on parameter recovery is critical for accurate interpretation of BLAZAR spectra. In this study, we examine how the data coverage influences the reliability of parameter estimation within the one-zone SYNCHROTRON self-Compton (SSC) framework. Using OJ 287, TXS 0506+056, and Mrk 421 as representative of the low-, intermediate- and high SYNCHROTRON peak classes (LSP, ISP and HSP), respectively, we generate synthetic SEDs based on their best-fit models and perform 1,000 fits for each of the 21 observational configurations per source type. Our analysis quantifies the coverage probability for all model parameters, such has the MAGNETic field strength and the electron luminosity, and reveals that different BLAZAR subclasses exhibit distinct sensitivities to spectral gaps. For LSPs, a minimal dataset comprising optical/UV, X-ray, and GeV $γ$-ray bands is sufficient for robust parameter inference. In contrast, ISPs and HSPs require broader spectral coverage to constrain the physical parameters. For ISP, we find that reliable parameter recovery can be achieved with two different minimal band combinations: \textit{(i)} X-ray, high energy $γ$-ray, and very high energy $γ$-ray data, or \textit{(ii)} optical/UV, X-ray, and high energy $γ$-ray data. For HSPs, the minimal configuration enabling reliable parameter recovery includes the optical/UV, X-ray, and very high energy $γ$-ray bands. We discuss the role of very high energy $γ$-ray observations, showing that they significantly enhance parameter recovery for HSPs. Our results provide practical guidelines for designing optimized multi-wavelength observation campaigns and for assessing the robustness of SSC model inferences under incomplete spectral coverage.

[abstract 7 / 41] Yes (score: 6)
arXiv:2511.06393 [pdf, ps, other]

Title: Accretion Geometry of the New Galactic Black Hole Candidate AT2019wey in the Hard State

Authors: Pragati Sahu, Swadesh Chand, Gulab C. Dewangan, Andrzej A. Zdziarski, Vivek K. Agrawal, Parijat Thakur,

Comments: 17 pages, 9 figures, 4 tables, Revised version, Submitted to ApJ on July 11, 2025

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

We perform broadband spectral and timing studies of the Galactic low-mass BLACK HOLE candidate AT2019wey during its 2022 outburst, using quasi-simultaneous observations from NICER, SWIFT, and NUSTAR. The long-term MAXI light curve, along with the hardness-intensity diagram (HID) derived from NICER data, indicates that the source remained in the hard state and did not switch to the soft state. Spectral modeling using two different model combinations reveals that the broadband spectrum is best described by two distinct Comptonizing regions, associated reflection components, and thermal emission from the disk. The harder Comptonizing region dominates ($\gtrsim88\%$) the total flux and is primarily responsible for the observed reflection features from the distant part of the disk. We find that the accretion disk is truncated at a radius of $\sim16-56~r_{\rm{g}}$, while the luminosity is $\sim1.9\%$ of the Eddington limit. Our spectral results also show consistency in the estimated inner disk radius obtained through two independent methods: modeling the disk continuum and the reflection spectrum. The variability studies imply the presence of intrinsic disk variability, likely originating from an instability in the disk. We also detect hard time lags at low frequencies, possibly arising from the inward propagation of mass accretion rate fluctuations from the outer to the inner regions of the accretion disk. Moreover, an observed deviation of the lag-energy spectrum from the log-linear trend at $\lesssim 0.7$ keV is most likely attributed to thermal reverberation, arising from the reprocessing of hard coronal photons in the accretion disk.

[abstract 8 / 41] Yes (score: 5)
arXiv:2511.19660 [pdf, ps, other]

Title: Optical and cm follow-ups of the Changing-Look event in Mkn 590

Authors: Biswaraj Palit, Abhijeet Borkar, Agata Różańska, Alex Markowitz, Marzena Śniegowska, Swayamtrupta Panda, David Homan, Krystian Iłkiewicz,

Comments: 6 pages, 3 figures; Proceedings of X-ray Quasi-Periodic Eruptions and Repeating Nuclear Transients, 16-19 June 2025, ESAC, Madrid. Submitted to Astronomische Nachrichten

Subjects: astro-ph.HE

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

The Changing-Look ACTIVE GALACTIC NUCLEus Mkn 590 is currently in a rejuvenated state, exhibiting a contemporaneous flux rise across X-rays, UV, optical and cm wavelengths. In this study, we present three new optical spectra obtained with the Nordic Optical Telescope, alongside three 1.4 GHz continuum measurements from the Giant Meterwave Radio Telescope, acquired since Nov. 2024. We identified a clear increase in the broad hydrogen Balmer line emission in the most recent observational epochs. Additionally, the core radio flux densities appear to track the overall X-ray variability, suggesting a possible connection between the accretion flow and JET activity. Based on these data, we aim to explore the evolution of the circumnuclear gas in this source and potential links between accretion and ejection activity.

[abstract 9 / 41] Yes (score: 4)
arXiv:2508.06120 [pdf, ps, other]

Title: Preferential Positron Acceleration in Relativistic Magnetized Electron-Positron-Ion Shocks

Authors: Shori Arai, Yosuke Matsumoto,

Comments: 13 pages, 9 figures, accepted to ApJ

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Relativistic shocks are considered efficient accelerators of charged particles and play crucial roles in high-energy astrophysical phenomena, such as GAMMA-RAY BURSTs and pulsar winds. This study focuses on positron accelerations in MAGNETized RELATIVISTIC shocks in electron-positron-ion plasma. Employing one-dimensional ab initio particle-in-cell simulations, we found a preferential positron acceleration through an interaction with the wakefield associated with a precursor wave in the upstream region. Test particle simulations revealed that the selective acceleration occurs for sufficiently large amplitudes of the wakefield. The mechanism can be understood as the RELATIVISTIC $\boldsymbol{E}\times\boldsymbol{B}$ acceleration formulated in the upstream frame. A theoretical analysis of the positron acceleration in astrophysical contexts is presented, supporting ultra-RELATIVISTIC shocks in pulsar winds as a primary source for the high-energy positron excess.

[abstract 10 / 41] Yes (score: 4)
arXiv:2508.06232 [pdf, ps, other]

Title: A Targeted Gamma-Ray Search of Five Prominent Galaxy Merger Systems with 17 years of FERMI-LAT Data

Authors: Siddhant Manna, Shantanu Desai,

Comments: 16 pages, 16 figures. Published in the Open Journal of Astrophysics

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

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

Galaxy mergers are among the most energetic astrophysical phenomena, driving intense STAR FORMATION and potentially fueling COSMIC RAY acceleration, which can produce high energy $γ$-ray emission through hadronic processes. We present a targeted search for $γ$-ray emission from five prominent galaxy merger systems, NGC~3256, NGC~660, UGC~813/816, UGC~12914/12915, and VV~114 using 16.9 years of FERMI-LAT data in the 1--300~GeV energy range. Employing a binned maximum likelihood analysis, we model the emission with power-law spectra and derive spectral energy distributions (SEDs) to constrain $γ$-ray fluxes and spectral indices. Marginal detections are found for NGC~3256 (TS = 15.4, $\sim$3.51$σ$) and NGC~660 (TS = 8.16, $\sim$2.39$σ$), with photon fluxes of $(7.21 \pm 3.17) \times 10^{-11}$ and $(8.28 \pm 3.56) \times 10^{-11}$ ph cm$^{-2}$ s$^{-1}$, respectively, suggesting merger driven STAR FORMATION contributes to $γ$-ray emission. The remaining systems yield non-detections (TS $< 5$). This is the first targeted study of $γ$-ray emission from these aforementioned galaxy merger systems.

[abstract 11 / 41] Yes (score: 4)
arXiv:2510.10746 [pdf, ps, other]

Title: State-Dependent X-ray Variability in Cygnus X-1: A 12-Year NUSTAR Timing Study of Accretion Flow Geometry

Authors: Kshitij Duraphe, Kartik Mandar, Chooda Khanal, Abha Pareek, Tejaswi Kondhiya, V Sree Suswara, Deeksha Dinesh, Vidyasagar Bhat, Gopal Bhatta,

Comments: 18 pages, 8 figures, 2 tables. Updated affiliations

Subjects: astro-ph.HE

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

We present a comprehensive timing analysis of the BLACK HOLE X-ray binary Cygnus X-1 using 26 NUSTAR observations spanning 2012-2024, providing the most detailed characterization to date of its accretion flow variability across spectral states. Our analysis reveals fundamental insights into the physics governing state transitions in stellar-mass BLACK HOLEs. We discover distinct bimodal flux distributions in the 8-79 keV band with well-separated peaks, contrasting with overlapping distributions in the 3-8 keV band. This energy-dependent bimodality establishes hard X-rays as the optimal diagnostic for state classification, directly tracing the geometric transformation between corona-dominated and disk-dominated configurations. Power spectral analysis uncovers state-dependent characteristic frequencies shifting from 0.050 Hz (hard) to 0.074 Hz (intermediate), with featureless red noise in soft states. These frequencies correspond to disk truncation radii evolving from $\sim$5.5 $R_g$ to $\sim$2 $R_g$, providing direct observational evidence for the inward progression of the accretion disk during state transitions. Frequency-dependent time lags evolve systematically from $\sim$50 ms hard lags at 0.1 Hz in hard states to near-zero in soft states, quantifying the collapse of the Comptonizing corona. Linear rms-flux relations persist across all states with parameters that precisely track the relative contributions of thermal versus non-thermal emission components. Most remarkably, we identify a failed state transition (observation 30302019006) exhibiting anticorrelated band behavior, suppressed variability ($F_{var}$ < 1.38\%), and apparent sub-ISCO truncation. This discovery challenges standard transition models and suggests new pathways for accretion flow evolution in wind-fed systems.

[abstract 12 / 41] Yes (score: 4)
arXiv:2510.22211 [pdf, ps, other]

Title: Ultraviolet Spectral Evidence for Ansky as a Slowly Evolving Featureless Tidal Disruption Event with Quasiperiodic Eruptions

Authors: Jiazheng Zhu, Ning Jiang, Yibo Wang, Tinggui Wang, Luming Sun, Shiyan Zhong, Yuhan Yao, Ryan Chornock, Lixin Dai, Jianwei Lyu, Xinwen Shu, Christoffer Fremling, Erica Hammerstein, Shifeng Huang, Wenkai Li, Bei You,

Comments: 14 pages, 9 figures, Published in ApJL

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

X-ray quasi-periodic eruptions (QPEs) are rare and enigmatic phenomena that increasingly show a connection to tidal disruption events (TDEs). However, the recently discovered QPEs in ZTF19acnskyy ("Ansky") appear to be linked to an ACTIVE GALACTIC NUCLEus (AGN) rather than a TDE, as their slow decay and AGN-like variability differ markedly from that of typical TDEs. This finding may imply broader formation channels for QPEs. To further investigate Ansky's nature, we obtained a timely ultraviolet (UV) spectrum, which reveals a featureless, TDE-like spectrum devoid of broad optical or UV emission lines. Additionally, the steep UV continuum, fitted by a power law with an index of -2.6, aligns more closely with TDEs than with AGNs. Compared to other featureless TDEs, Ansky exhibits a significantly lower blackbody luminosity (10^43 erg s^-1) and much longer rise and decay timescales, suggesting a distinct TDE subclass. An offset TDE involving an intermediate-mass BLACK HOLE is unlikely, given its position consistent with the galactic center with a 3 sigma upper limit of 54 pc. Instead, we propose that Ansky may result from the tidal disruption of a post-main-sequence star by a typical supermassive BLACK HOLE. Our findings strengthen the growing evidence for TDE-QPE associations, although other formation channels for QPEs remain plausible and await future observational efforts.

[abstract 13 / 41] Yes (score: 4)
arXiv:2511.19591 [pdf, ps, other]

Title: X-ray, optical, and radio follow-up of five thermally emitting isolated neutron star candidates

Authors: J. Kurpas, A. M. Pires, A. D. Schwope, B. Li, D. Yin, F. Haberl, M. Krumpe, S. Sheth, I. Traulsen, Z. L. Zhang,

Comments: 12 pages, 5 figures, accepted for publication in A&A

Subjects: astro-ph.HE

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

We report on follow-up observations with XMM-Newton, the FORS2 instrument at the ESO-VLT, and FAST, aiming to characterise the nature of five thermally emitting isolated neutron star (INS) candidates recently discovered from searches in the footprint of the Spectrum Roentgen Gamma (SRG)/eROSITA All-sky Survey. We find that the X-ray spectra are predominantly thermal and can be described by low-absorbed blackbody models with effective temperatures ranging from 50 to 210 eV. In two sources, the spectra also show narrow absorption features at $300 - 400$ eV. Additional non-thermal emission components are not detected in any of the five candidates. The soft X-ray emission, the absence of optical counterparts in four sources, and the consequent large X-ray-to-optical flux ratios $>3000 - 5400$ confirm their INS nature. For the remaining source, eRASSU J144516.0-374428, the available data do not allow a confident exclusion of an ACTIVE GALACTIC NUCLEus nature. However, if the source is Galactic, the small inferred X-ray emitting region is reminiscent of a heated pulsar polar cap, possibly pointing to a binary pulsar nature. X-ray timing searches do not detect significant modulations in all candidates, implying pulsed fraction upper limits of 13 - 19% ($0.001-13.5$ Hz). The absence of pulsations in the FAST observations targeting eRASSU J081952.1-131930 and eRASSU J084046.2-115222 excludes periodic MAGNETospheric emission at 1 - 1.5 GHz with an $8σ$ significance down to 4.08 $μ$Jy and 2.72 $μ$Jy, respectively. The long-term X-ray emission of all sources does not imply significant variability. Additional observations are warranted to establish exact neutron star types. At the same time, the confirmation of the predominantly thermal neutron star nature in four additional sources highlights the power of SRG/eROSITA to complement the Galactic INS population.

[abstract 14 / 41] Yes (score: 4)
arXiv:2511.19799 [pdf, ps, other]

Title: Strangelet Searches from Neutron Stars, Binary Mergers, and Gamma-Ray Bursts with Current and Future Observatories

Authors: C. R. Das,

Comments: 25 pages, 4 figures, Presented in the XXVIth International Baldin Seminar on High Energy Physics Problems "Relativistic Nuclear Physics and Quantum Chromodynamics", September 15 to 20, 2025, VBLHEP, JINR, Dubna, Russia

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

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

Strange QUARK matter (SQM) is considered a possible true ground state of QCD at high densities. This idea motivates research on exotic compact objects and certain cosmic-ray phenomena. For instance, the remnant HESS J1731-347 contains a low-mass neutron star, about $0.77^{+0.20}_{-0.17}$ $M_\odot$ and $10.4^{+0.86}_{-0.78}$ km in radius, making it a strong candidate for a strange QUARK star. Other events, such as GW170817 and GRB 250702B, provide conditions that may favor the formation of strangelets. Strangelets are stable clusters of SQM, potentially created during the phase transition between the 2SC and CFL color-superconducting states. These clusters could generate monochromatic $γ$-ray lines in very-high-energy spectra through self-annihilation. This work analyzes the stability of strangelets, production cross-sections, and mass-to-charge ratios using QCD-based models. Data from H.E.S.S., FERMI-LAT, MAGIC-II, and CTA were used to set limits on spectral features and possible fluxes. Detecting narrow $γ$-ray lines will require improved instrument sensitivity. By integrating evidence from multimessenger astrophysics and dense QCD simulations, this study investigates the equations of state for compact stars and explores the potential cosmological influence of SQM.

[abstract 15 / 41] Yes (score: 4)
arXiv:2511.19848 [pdf, ps, other]

Title: New constraints on axion with gamma-ray observations of the Crab Nebula

Authors: Kazunori Kohri, Haruki Takahashi,

Comments: 24 pages, 7 figures

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

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

In this paper, we derive the upper bounds on the coupling of axion-like particles (ALPs) with photon as a function of the mass by considering axion-photon conversion in the Crab Nebula. Previous studies have not considered the influence of the MAGNETic field within the Crab Nebula. The MAGNETic field plays a crucial role through the Synchrotron Self-Compton (SSC) process, in which high-energy electrons produce SYNCHROTRON radiation that is subsequently up-scattered by the same electrons via inverse Compton scattering to generate gamma rays. Therefore, neglecting the MAGNETic field in modeling leads to theoretical inconsistencies. In this work, we investigate the significance of the MAGNETic field effect and demonstrate that even differences in MAGNETic field modeling can substantially alter the conversion probability. We thus, for the first time, point out that proper consideration of the MAGNETic field is essential in ALP searches using gamma rays from the Crab Nebula. The resulting constraints reach up to a coupling of $g_{aγγ} \lesssim 1 \times 10^{-11} {\rm GeV}^{-1}$ for ALP masses in the range $10^{-10} {\rm eV} \lesssim m_a \lesssim 10^{-6} {\rm eV}$.

[abstract 16 / 41] Yes (score: 4)
arXiv:2511.20310 [pdf, ps, other]

Title: From Empirical to Physical Model: Direct Fits of Optically Thin Inverse Compton Scattering to Prompt GRB Spectra

Authors: Pragyan Pratim Bordoloi, Shubh Mittal, Shabnam Iyyani,

Comments: 10 Figures, 2 Tables, submitted

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Gamma-ray burst (GRB) prompt emission is commonly attributed to non-thermal radiation processes operating in the optically thin regions of a RELATIVISTIC outflow. Among these, optically thin inverse-Compton (IC) scattering remains an important yet under-tested mechanism. From an initial set of 41 bursts selected using empirical Band-function criteria that highlight quasi-thermal low-energy slopes ($α> -0.5$) and constrained high-energy indices ($-1.7 > β> -3.3$), only four events satisfy these conditions consistently in both time-integrated and time-resolved spectra. The IC fits yield self-consistent constraints on the seed-photon field and the electron population at the dissipation site. For bulk Lorentz factors $Γ\sim 170$-$550$, we infer seed thermal peaks of $\sim 0.05$-$0.2$ keV and electron thermal energies of $\sim 20$-$300$ keV in the co-moving frame. A fraction of only $0.1\%$-$20\%$ of electrons are accelerated into a non-thermal tail with an average index value of $δ\sim 1.8$. The derived Comptonisation parameters indicate moderate $y$ values ($\sim 1$-$3$), optical depths $τ\sim 0.2$-$0.6$, and dissipation radii just above the photosphere, consistent with mildly RELATIVISTIC ($γ_{\min} \sim 1.2$-$2.6$), photon-dominated, low-MAGNETic-field dissipation environments. Furthermore, the framework allows us to constrain even sub-dominant thermal components that lie below the detector's low-energy threshold. Taken together, our results show that optically thin IC scattering offers a physically consistent and observationally viable explanation for the prompt emission in a subset of bright GRBs, motivating the application of IC models in future GRB studies.

[abstract 17 / 41] Yes (score: 4)
arXiv:2511.20337 [pdf, ps, other]

Title: The PLUTO Code on GPUs: A First Look at Eulerian MHD Methods

Authors: Marco Rossazza, Andrea Mignone, Matteo Bugli, Stefano Truzzi, Lubomir Riha, Tomas Panoc, Ondrej Vysocky, Nitin Shukla, Alessandro Romeo, Vittoria Berta,

Comments:

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

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

We present preliminary performance results of gPLUTO, the new GPU-optimized implementation of the PLUTO code for computational plasma astrophysics. Like its predecessor, gPLUTO employs a finite-volume formulation to numerically solve the equations of MAGNETohydrodynamics (MHD) in multiple spatial dimensions. Still, this new implementation is a complete rewrite in C++ and leverages the OpenACC programming model to achieve acceleration on NVIDIA GPUs. While a more comprehensive description of the code and its several other modules will be presented in a future paper, here we focus on some preparatory results that demonstrate the code potential and performance on pre exa-scale parallel architectures.

[abstract 18 / 41] (score: 3)
arXiv:2506.23176 [pdf, ps, other]

Title: Relativistic excitation of compact stars

Authors: Zhiqiang Miao, Xuefeng Feng, Zhen Pan, Huan Yang,

Comments: 23 pages, 9 figures, updated to publishing version

Subjects: gr-qc astro-ph.HE

Created: 2025-11-23; Updated: 2025-11-26; Datestamp: 2025-11-26

In this work, we study the excitation of a compact star under the influence of external gravitational driving in the RELATIVISTIC regime. Using a model setup in which a wave with constant frequency is injected from past null infinity and scattered by the star to future null infinity, we show that the scattering coefficient encodes rich information of the star. For example, the analytical structure of the scattering coefficient implies that the decay rate of a mode generally plays the role of ``star excitation factor'', similar to the ``BLACK HOLE excitation factor'' previously defined for describing BLACK HOLE mode excitations. With this star excitation factor we derive the transient mode excitation as a binary system crosses a generic mode resonance of a companion star during the inspiral stage. This application is useful because previous description of resonant mode excitation of stars still relies on the mode and driving force decomposition based on the Newtonian formalism. In addition, we show that the scattering phase is intimately related to the total energy of spacetime and matter under the driving of a steady input wave from infinity. We also derive the relevant tidal energy of a star under steady driving and compare that with the dynamic tide formula. We estimate that the difference may lead to $\mathcal{O}(0.5)$ radian phase modulation in the late stage of the binary neutron star inspiral waveform.

[abstract 19 / 41] (score: 3)
arXiv:2511.19587 [pdf, ps, other]

Title: Estimating the masses of Narrow line Seyfert 1 galaxies using damped random walk method

Authors: Rachana, M. Vivek, Yue Shen,

Comments: v1: 13 pages, 8 figures. Comments are welcome. Accepted for publication in MNRAS

Subjects: astro-ph.GA

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

Narrow-line Seyfert 1 galaxies (NLSy1s) are a subclass of ACTIVE GALACTIC NUCLEi (AGNs), commonly associated with rapidly accreting, relatively low-mass BLACK HOLEs ($10^6$ - $10^8 M_\odot$) hosted in spiral galaxies. Although typically considered to have high Eddington ratios, recent observations, particularly of $γ$-ray-emitting NLSy1s, have raised questions about their true BLACK HOLE masses, with some estimates approaching those of Broad-line Seyfert 1 (BLSy1) systems. In this work, we present the recalibrated mass estimations for a large sample of NLSy1s galaxies with z $<0.8$. We apply the damped random walk (DRW) formalism to a comparison set of 1,141 NLSy1 and 1,143 BLSy1 galaxies, matched in redshift and bolometric luminosity using SDSS DR17 spectroscopy. Our analysis employs a multivariate calibration that incorporates both the Eddington ratio and the rest-frame wavelength to refine the mass estimates. We obtain median DRW-based BLACK HOLE masses of $\text{log}(M_{\text{BH}}^{\text{DRW}}/M_\odot) = 6.25 \pm 0.65$ for NLSy1s and $7.07 \pm 0.67$ for BLSy1s, in agreement with their respective virial mass distributions. Furthermore, we identify strong inverse trends between the variability amplitude and both optical luminosity and FeII emission strength, consistent with a scenario where higher accretion rates suppress long-term optical variability. These findings reinforce the view that NLSy1s harbor smaller BLACK HOLEs and highlight the value of variability-based approaches in tracing AGN accretion properties.

[abstract 20 / 41] (score: 3)
arXiv:2511.19602 [pdf, ps, other]

Title: Tracing AGN-Galaxy Co-Evolution with UV Line-Selected Obscured AGN

Authors: Luigi Barchiesi, Lucia Marchetti, Mattia Vaccari, Cristian Vignali, Francesca Pozzi, Isabella Prandoni, Roberto Gilli, Marco Mignoli, Jose Afonso, Veeresh Singh, Catherine Hale, Ian Heywood, Matt Jarvis, Imogen Whittam,

Comments: Accepted for publication in MNRAS, 20 pages, 14 figures

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

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

Understanding BLACK HOLE-galaxy co-evolution and the role of AGN feedback requires complete AGN samples, including heavily obscured systems. In this work, we present the first UV line-selected ([Nev]3426 and CIV1549) sample of obscured AGN with full X-ray-to-radio coverage, assembled by combining data from the Chandra COSMOS Legacy survey, the COSMOS2020 catalogue, IR photometry from XID+, and radio observations from the VLA and MIGHTEE surveys. Using CIGALE to perform spectral energy distribution (SED) fitting, we analyse 184 obscured AGN at 0.6 < z < 1.2 and 1.5 < z < 3.1, enabling detailed measurements of AGN and host galaxy properties, and direct comparison with SIMBA hydrodynamical simulations. We find that X-ray and radio data are essential for accurate SED fits, with the radio band proving critical when X-ray detections are missing or in cases of poor IR coverage. Comparisons with matched non-active galaxies and simulations suggest that the [NeV]-selected sources are in a pre-quenching stage, while the CIV-selected ones are likely quenched by AGN activity. Our results indicate that [NeV] and CIV selections target galaxies in a transient phase of their co-evolution, characterised by intense, obscured accretion, and pave the way for future extensions with upcoming large area high-z spectroscopic surveys.

[abstract 21 / 41] (score: 3)
arXiv:2511.19609 [pdf, ps, other]

Title: Beyond the Monsters: A More Complete Census of Black Hole Activity at Cosmic Dawn

Authors: Madisyn Brooks, Jonathan R. Trump, Raymond C. Simons, Justin Cole, Anthony J. Taylor, Micaela B. Bagley, Steven L. Finkelstein, Kelcey Davis, Ricardio O. Amorín, Bren E. Backhaus, Nikko J. Cleri, Mauro Giavalisco, Norman A. Grogin, Michaela Hirschmann, Benne W. Holwerda, Marc Huertas-Company, Jeyhan S. Kartaltepe, Dale D. Kocevksi, Anton M. Koekemoer, Ray A. Lucas, Fabio Pacucci, Xin Wang,

Comments: 17 pages, 8 figures

Subjects: astro-ph.GA

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

JWST has revealed an abundance of low-luminosity ACTIVE GALACTIC NUCLEi (AGN) at high redshifts ($z > 3$), pushing the limits of BLACK HOLE (BH) science in the early Universe. Results have claimed that these BHs are significantly more massive than expected from the BH mass-host galaxy stellar mass relation derived from the local Universe. We present a comprehensive census of the BH populations in the early Universe through a detailed stacking analysis of galaxy populations, binned by luminosity and redshift, using JWST spectroscopy from the CEERS, JADES, RUBIES, and GLASS extragalactic deep field surveys. Broad H$α$ detections in $31\%$ of the stacked spectra (5/16 bins) imply median BH masses of $10^{5.21} - 10^{6.13}~ \rm{M_{\odot}}$ and the stacked SEDs of these bins indicate median stellar masses of $10^{7.84} - 10^{8.56} ~\rm{M_{\odot}}$. This suggests that the median galaxy hosts a BH that is at most a factor of 10 times over-massive compared to its host galaxy and lies closer to the locally derived $M_{BH}-M_*$ relation. We investigate the seeding properties of the inferred BHs and find that they can be well-explained by a light stellar remnant seed undergoing moderate Eddington accretion. Our results indicate that individual detections of AGN are more likely to sample the upper envelope of the $M_{BH}-M_*$ distribution, while stacking on ``normal" galaxies and searching for AGN signatures can overcome the selection bias of individual detections.

[abstract 22 / 41] (score: 3)
arXiv:2511.19611 [pdf, ps, other]

Title: Effective-one-body modelling of eccentric supermassive BLACK HOLE binaries for Pulsar Timing Array

Authors: Sara Manzini, Stanislav Babak,

Comments:

Subjects: gr-qc astro-ph.HE

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

Pulsar Timing Arrays (PTAs) observations will detect gravitational waves (GWs) from the early inspiral phase of supermassive BLACK HOLE binaries (SMBHBs) with orbital periods of weeks to years. Current PTA analyses generally assume circular binaries; however, dynamical interactions with the surrounding environment can prevent complete circularisation, allowing SMBHBs to retain appreciable eccentricities. In this work, we present a gravitational waveform model for eccentric binaries based on the Effective-One-Body (EOB) formalism, designed for continuous GW searches in PTA data. The model is accurate up to the second post-Newtonian (2PN) order for the conservative dynamics and up to post-leading order for the radiation-reaction terms. We provide both a numerically precise and a computationally efficient approximate implementation and evaluate the latter's accuracy against the full model over a broad range of eccentricities and initial orbital frequencies. Our results show that a substantial region of the parameter space exhibits pronounced orbital evolution, much stronger than in the circular case. We demonstrate the rich harmonic structure of timing residuals induced by eccentric GWs. Properly characterising eccentric binaries is an essential step toward detecting GWs in PTA data and interpreting the results, ultimately improving our understanding of the supermassive BLACK HOLE population in the local Universe.

[abstract 23 / 41] (score: 3)
arXiv:2511.20582 [pdf, ps, other]

Title: An improved time delay from VLA and ATCA monitoring of the gravitational lens system PKS 1830-211

Authors: A. D. Biggs,

Comments: 10 pages, 7 figures, published in MNRAS

Subjects: astro-ph.CO

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

We have measured a time delay of 25.3 +/- 2.0 d (1-sigma confidence) in the Einstein ring gravitational lens system PKS 1830-211 from an analysis of archival VLA and ATCA monitoring data observed between 1997 and 2004. A small portion of the ATCA data was previously used to determine a time delay and our result is consistent with the previous value, but with an uncertainty that is smaller by more than a factor of two. The long time-baseline of the monitoring reveals that the flux density ratio is smoothly varying on a time-scale of years, an effect which we attribute to millilensing by massive objects (>>1 M_sun) in the lensing galaxy. Image A is unpolarized in the VLA monitoring, but VLBI observations show that this is partly due to beam dilution by an unpolarized counter-JET that is only present in that image. Based on the identification of this feature as a counter-JET, we conclude that its unexpected prominence in image A is a consequence of lensing and that more detailed modelling is required in order to reconcile the VLBI morphology of each image.

[abstract 24 / 41] (score: 3)
arXiv:2511.20589 [pdf, ps, other]

Title: Evidence of an Energetic Magnetar Powering 1LHAASO J0500$+$4454

Authors: J. A. J. Alford, J. D. Gelfand, M. Abdelmaguid, P. Slane,

Comments: 16 pages, 6 figures, 2 tables. Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

We investigate the origin of unidentified, extended TeV source 1LHAASO J0500$+$4454, considering three possible origins: COSMIC RAYs interacting with a molecular cloud (MC), particles accelerated in a currently undetected SUPERNOVA remnant (SNR), and an energetic outflow powered by a pulsar. Upper limits on the CO and X-ray emission from the $γ$-ray emitting region disfavor the MC and SNR scenarios, respectively. If a nebula of inverse Compton scattering $e^{\pm}$ powers 1LHAASO J0500$+$4454, then SED modeling indicates that the current particle energy in the nebula is $\sim 4 \times 10^{48}$ erg. If the coincident MAGNETar SGR 0501$+$4516's rotational energy powered 1LHAASO J0500$+$4454, then a conservative energy budget calculation requires an initial MAGNETar spin period $P_{0} \lesssim 5$ ms and a spin-down timescale $τ_{\rm sd} \lesssim 30$ yr, which has implications for the origins of MAGNETars.

[abstract 25 / 41] (score: 2)
arXiv:2501.12440 [pdf, ps, other]

Title: Pulse and Polarization Structures in Axion-Converted X-rays from Pulsars

Authors: JiJi Fan, Lingfeng Li, Chen Sun,

Comments: 5+7 pages, 8 figures, 2 tables; refs added; matching the published version

Subjects: hep-ph astro-ph.HE

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

Neutron stars (NS's) with their strong MAGNETic fields and hot dense cores could be powerful probes of axions, a classic benchmark of feebly-coupled new particles, through abundant production of axions with the axion-nucleon coupling and subsequent conversion into X-rays due to the axion-photon coupling. In this article, we point out that the pulsation structures in both the intensity and POLARIZATION of X-rays from NS's could provide us additional information about axions and their couplings. We develop new analytical formalisms of pulsation-POLARIZATION structure applicable to a wide range of NS's in the axion scenario and argue that they hold in complicated astrophysical environments. As a case study, we apply our formalism to a representative X-ray Dim Isolated Neutron Star, RX J1856.6-3754, with an unexpected hard X-ray excess which might be axion-induced. We show with an updated fit that the axion explanation is compatible with both the intensity and pulsation data available, and combining the pulsation data does not shift the posterior by more than $1\,σ$. Yet, the preferred parameter space is close to being excluded by other astrophysical constraints. With a 75% reduction of the uncertainties in the pulsation data, we could potentially draw a definite conclusion on the axion-induced X-rays at more than $3\,σ$ level.

[abstract 26 / 41] (score: 2)
arXiv:2510.01957 [pdf, ps, other]

Title: Numerical tests of formulae for volume enclosed by flux surfaces of integrable MAGNETic fields

Authors: David Martinez-del-Rio, Robert S. MacKay,

Comments: Keywords: Magnetic field, Flux surface, Volume

Subjects: math.DS physics.plasm-ph

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Numerical tests of volume formulae are presented to compute efficiently the volume enclosed between flux surfaces for integrable 3D vector fields with various degrees of symmetry. In the process, a new case is proposed and tested.

[abstract 27 / 41] (score: 2)
arXiv:2510.23470 [pdf, ps, other]

Title: A targeted radio survey of infrared-selected bow shock candidates

Authors: M. Moutzouri, J. Mackey, N. Castro, Y. Gong, P. Jiménez-Hernández, J. A. Toalá, C. Burger-Scheidlin, M. Rugel, C. Carrasco-González, R. Brose, K. M. Menten,

Comments: Accepted to A&A, abstract shortened for arxiv character limits

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

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Bow shocks around massive stars have primarily been detected in IR emission, but radio detections are becoming more frequent with the commissioning of sensitive and large field-of-view interferometers. Radio data probes both thermal and non-thermal emission, thereby constraining the RELATIVISTIC electron population. We undertook a radio survey for bow shocks based on IR catalogues of candidates, using the VLA and the 100-m Effelsberg Telescope, aiming for new detections and to better characterise the multi-wavelength emission. We used Gaia DR3 to re-calculate spatial motion of the driving stars with respect to the surrounding stellar population. We studied the radio emission from bow shocks using emission maps and spectral-index measurements, and compared our results with data from catalogues and multi-wavelength emission. Of the 24 targets observed with the VLA in the 4-12 GHz band, six were clearly detected (including two previously reported) and 5 possibly detected. A subset of these were also observed and detected with Effelsberg at 4-8 GHz. The VLA-derived spectral index maps indicate non-thermal emission for most sources, but the statistical uncertainties are large for most sources and all Effelsberg observations indicate thermal emission. Assuming thermal emission, we obtain upper limits on the electron density within the shocked layer. We obtained upper limits on radio emission from the bow shock of Zeta Oph at a similar flux level to predictions from MHD simulations. Our survey marks a significant addition to the ca. 10 previously known radio-emitting bow shocks in the literature, and demonstrates that deep, targeted radio surveys can effectively detect IR-selected bow shocks. Follow-up observations of these targets at lower and higher frequencies are encouraged to determine whether any are non-thermal emitters like the bow shocks of BD+43, BD+60 and LS2355. (abridged)

[abstract 28 / 41] (score: 2)
arXiv:2511.13642 [pdf, ps, other]

Title: Coupling between gravitational and electroMAGNETic perturbations on Kerr Spacetime

Authors: Fawzi Aly, Dejan Stojkovic,

Comments: 9 pages and 2 figures

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

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

We extend our previous Schwarzschild metric-based studies of gravitational--electroMAGNETic (GEM) coupling to rotating BLACK HOLEs by working directly in a curvature-based Newman--Penrose/Teukolsky framework on Kerr spacetime. Within a minimally coupled Einstein--Maxwell system, we derive explicit quadratic electroMAGNETic source terms for the spin-$-2$ Teukolsky equation, providing a foundation for future numerical studies of GEM interactions in the framework of black-hole spectroscopy. Moreover, we give order-of-magnitude arguments showing that GEM quadratic quasinormal modes (QQNMs) can become relevant in a range of charged and MAGNETized astrophysical scenarios. Finally, we show through a brief dilaton-theory example that the GEM QQNM spectrum is sensitive to how gravity couples to electroMAGNETism, thereby providing a model-based way to test minimal coupling and to constrain hidden $U(1)$ sectors with gravitational-wave observations.

[abstract 29 / 41] (score: 2)
arXiv:2511.19553 [pdf, ps, other]

Title: Quasinormal modes of scalar, electroMAGNETic, and gravitational perturbations in slowly rotating Kalb-Ramond BLACK HOLEs

Authors: Weike Deng, Wentao Liu, Kui Xiao, Jiliang Jing,

Comments: 17 pages, 4 figures

Subjects: gr-qc

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

We investigate quasinormal modes (QNMs) of scalar, electroMAGNETic, and axial gravitational perturbations in slowly rotating Kalb-Ramond (KR) BLACK HOLEs, where an antisymmetric tensor field induces spontaneous Lorentz symmetry breaking. Working consistently to first order in the dimensionless spin parameter, we derive the corresponding master equations and compute the QNM spectrum using both the continued-fraction and matrix methods, finding excellent agreement. Lorentz violation modifies the oscillation and damping rates in a unified manner across all perturbative sectors: the real part of the QNM frequency increases monotonically with the Lorentz-violating parameter $\ell$, while the imaginary part becomes more negative. Axial gravitational modes exhibit the strongest response, revealing an intrinsic theoretical bound $\ell< 0.5$, beyond which the spectrum approaches an extremal behavior. Our results highlight the potential of gravitational-wave spectroscopy to probe Lorentz-violating signatures in KR gravity.

[abstract 30 / 41] (score: 2)
arXiv:2511.19658 [pdf, ps, other]

Title: Mechanical Design of the PIP-II ORBUMP Pulsed Dipole Magnet

Authors: D. Karas, K. Badgley, Z. Chen, V. Chernenok, M. Davidson, D. Harding, D. Johnson, V. Kashikhin, W. Robotham, T. Strauss, B. Szabo, J. Vander Meulen,

Comments: to be published in IEEE

Subjects: physics.acc-ph

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

The Proton Improvement Plan II (PIP-II) project is a vital upgrade to the FERMIlab accelerator complex. The MAGNET pulse rate of the PIP-II Injection system requires an increase from the current rate of 15 Hz to 20 Hz as well as a roughly 30% increase in the MAGNETic field of the new Orbital Bump (ORBUMP) pulsed dipole MAGNETs in the Booster. The ORBUMP MAGNET mechanical design is presented in this paper. The ORBUMP MAGNET is secured in a vacuum box and the core is made up of 0.127 mm thick, low carbon steel laminations with a C-5 inorganic magnesium phosphate coating. The core is clamped using external tie bars welded to the core end plates. ANSYS Finite Element Analysis (FEA) was used to evaluate the clamping design to minimize the deflection of the core post welding of the tie bars. The water-cooled, single turn coil, which shapes the MAGNETic field by acting as the pole tips, is critical for the integrated field homogeneity. The coil manufacturing tolerances and fabrication techniques were evaluated to ensure the MAGNETic properties of the MAGNET could be obtained. The coil is electrically isolated from the core using virgin Polyether ether ketone (PEEK) insulating material in the gap. An investigation into the high voltage performance of the virgin PEEK insulator was conducted via partial discharge testing using a 1:1 scale sample.

[abstract 31 / 41] (score: 2)
arXiv:2511.19772 [pdf, ps, other]

Title: Analog Signal Multiplexing System for the Iota Proton Injector

Authors: Daniel R. MacLean, Dean R. Edstrom,

Comments: North American Particle Accelerator Conference (NAPAC2025)

Subjects: physics.acc-ph

Created: 2025-11-24; Updated: 2025-11-26; Datestamp: 2025-11-26

The FERMIlab Accelerator Science and Technology (FAST) Facility at FNAL is a dedicated research and development center focused on advancing particle accelerator technologies for future applications worldwide. Currently, a key objective of FAST Operations is to commission the 2.5 MeV IOTA Proton Injector (IPI) and enable proton injection into the Integrable Optics Test Accelerator (IOTA) storage ring. The low and medium-energy sections of the IPI include four frame-style dipole trims and two multi-function correctors with independently controlled coils, requiring readout of 32 analog channels for current and voltage monitoring in total. To reduce cost and optimize rack space within the PLC-based control system, a 32-to-4 analog signal multiplexing system was designed and implemented. This system enables real-time readback of excitation parameters from all MAGNETic correctors. This paper presents the design, construction, implementation, and performance of the multiplexing system.

[abstract 32 / 41] (score: 2)
arXiv:2511.19975 [pdf, ps, other]

Title: Data-constrained MAGNETohydrodynamic simulation of global solar corona including solar wind effects within 2.5 $R_\odot$

Authors: Yihua Li, Guoyin Chen, Jinhan Guo, Yang Guo, Hao Wu, Yuhao Huang, Xin Cheng, Mingde Ding, Rony Keppens,

Comments: 29 pages, 11 figures, accepted for publication in ApJ

Subjects: astro-ph.SR

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Total solar eclipses (TSEs) provide a unique opportunity to observe the large-scale solar corona. The solar wind plays an important role in forming the large-scale coronal structure and MAGNETohydrodynamic (MHD) simulations are used to reproduce it for further studying coronal mass ejections (CMEs). We conduct a data-constrained MHD simulation of the global solar corona including solar wind effects of the 2024 April 8 TSE with observed MAGNETograms using the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC) within 2.5 $R_\odot$. This TSE happened within the solar maximum, hence the global corona was highly structured. Our MHD simulation includes the energy equation with a reduced polytropic index $γ=1.05$. We compare the global MAGNETic field for multiple MAGNETograms and use synchronic frames from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager to initialize the MAGNETic field configuration from a MAGNETo-frictionally equilibrium solution, called the Outflow field. We detail the initial and boundary conditions employed to time-advance the full set of ideal MHD equations such that the global corona is relaxed to a steady state. The MAGNETic field, the velocity field, and distributions of the density and thermal pressure are successfully reproduced. We demonstrate direct comparisons with TSE images in white-light and Fe XIV emission augmented with quasi-separatrix layers, the integrated current density, and the synthetic white-light radiation, and find a good agreement between simulations and observations. This provides a fundamental background for future simulations to study the triggering and acceleration mechanisms of CMEs under solar wind effects.

[abstract 33 / 41] (score: 2)
arXiv:2511.20042 [pdf, ps, other]

Title: Search for higgsinos in compressed mass spectra using low-momentum tracks in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Authors: ATLAS Collaboration,

Comments: 65 pages in total, author list starting page 48, 15 figures, 15 tables, submitted to JHEP. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HMBS-2024-65

Subjects: hep-ex

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

This paper presents two searches for the electroweak production of higgsinos with compressed mass spectra using 140 fb$^{-1}$ of $\sqrt{s}=13$ TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider. Events are required to feature an energetic JET, large missing transverse momentum, and at least one low-momentum charged particle that serves as a candidate higgsino decay product. In the first search, targeting higgsino mass splittings in the range of 0.3-1 GeV, the higgsinos are expected to predominantly decay into pions that are identified as low-momentum charged particles with large transverse impact parameters due to the long higgsino lifetime ($cτ\approx\mathcal{O}$(0.1-1 mm)). The second search targets larger mass splittings in the range of 1-3 GeV, where the higgsinos are expected to decay promptly into low-momentum leptons, one of which is identified by dedicated low-momentum electron or muon taggers based on neural networks utilising tracking and calorimeter information. No significant excess above the Standard Model prediction is observed in either search and the results are used to set lower limits on the masses of the higgsino-like charginos and neutralinos within a simplified model. Together, these searches exclude chargino masses below 126 GeV at 95% confidence level for mass splittings between the chargino and lightest neutralino in the range of 0.3-2 GeV, representing the first ATLAS constraints in this parameter space and surpassing the limits previously set by the LEP experiments.

[abstract 34 / 41] (score: 2)
arXiv:2511.20083 [pdf, ps, other]

Title: The covariant equations of motion of massive spinning particles in a background Yang-Mills field

Authors: Jie Zhou, Ying Shan Zhao, Yifeng Sun,

Comments: 14 pages

Subjects: nucl-th hep-th

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

A strong classical color field, known as the glasma, is generated in the earliest stage of RELATIVISTIC heavy-ion collisions and can significantly influence the momentum and spin dynamics of hard probes such as QUARKs and JETs. Most existing studies based on the classical equations of motion in a background Yang-Mills field, such as Wong equations, may not capture the full range of effects, for example, they neglect the Stern-Gerlach force experienced by spinning particles in non-uniform glasma fields. Although several extensions of Wong equations have been proposed to include spin degrees of freedom, they generally fail to satisfy all the required conditions simultaneously, such as Lorentz covariance, allowance for an arbitrary chromoMAGNETic moment, and respect for the necessary physical constraints. In this work, we extend the framework of a RELATIVISTIC classical spinning particle in an electroMAGNETic field to describe spin one-half QUARKs propagating in a background non-Abelian Yang-Mills field. By systematically applying the Dirac-Bergmann algorithm, we derive self-consistent equations of motion for the particle's coordinates, momenta, spin, and color charge that satisfy all these requirements. This formalism provides a more complete and physically relevant description for studying momentum diffusion and spin POLARIZATION phenomena of hard probes in the glasma.

[abstract 35 / 41] (score: 2)
arXiv:2511.20184 [pdf, ps, other]

Title: Search for the potential electroMAGNETic counterparts of neutrino events in SDSS galaxies at z<0.1

Authors: O. Sergijenko., I. B. Vavilova, I. O. Izviekova, D. R. Karakuts,

Comments: 12 pp., 1 Figure, 4 Tables

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

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Identification of electroMAGNETic emission in coincidence with high-energy neutrinos is fundamentally important for multimessenger astronomy. Such observations are essential for constraining source localization, determining the source type, and understanding emission mechanisms. Typically, they require following up a neutrino alert (IceCube issues two alert streams: Gold, with at least 50 percent probability of astrophysical origin, and Bronze, with at least 30 percent probability) with an electroMAGNETic facility, primarily in X-ray and gamma-ray bands. Another approach involves electroMAGNETic monitoring of hot spots in the IceCube skymap, i.e., positions exceeding the instrument sensitivity. An alternative method consists in performing correlation analysis across available neutrino events and source catalogs. We searched for spatial coincidence between galaxies from SDSS and high-energy neutrino events. The analysis includes IceCube Gold alerts and neutrino-electroMAGNETic coincidence events from AMON (Astrophysical Multimessenger Observatory Network), identified through the end of September 2025. We examined galaxies from the morphological catalog at redshifts 0.02 to 0.1, which contains 315,776 SDSS DR9 objects with absolute stellar magnitudes in the range from -24 to -13 in the r band. Among 59 IceCube Gold alerts, we found three with only one galaxy (SDSS J231231.52+033415.1) within the 50 percent containment radius. Among 24 neutrino-electroMAGNETic coincidence events, three more contain only one galaxy (SDSS J220711.14+122535.9) within the same radius. These six galaxies represent the most promising candidates for potential host galaxies of neutrino sources. We summarize their available multiwavelength data and the ZTF light curves obtained from 2018 to 2025.

[abstract 36 / 41] (score: 2)
arXiv:2511.20199 [pdf, ps, other]

Title: Rotation of flux ropes in the low corona

Authors: Brigitte Schmieder, Anwesha Maharana, Jin Han Guo, Luis Linan, Stefaan Poedts,

Comments: 7 pages, 3 figures

Subjects: astro-ph.SR

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Eruptions of filaments are defined by different parameters, specially, sigmoid handedness and direction of the eruption, which are important parameters for forecasting the geoeffectiveness of consequent interplanetary coronal mass ejection (ICME) or MAGNETic cloud. Solar filaments often exhibit rotation and deflection during eruptions, which would significantly affect the geoeffectiveness of the coronal mass ejections (CMEs). Therefore, understanding the mechanisms that lead to such lateral displacement of filaments is a great concern to space weather forecasting. Two case studies are discussed. Firstly, the events of September 8 and September 10 2014, were analyzed from the Sun to the Earth. The numerical heliospheric simulation EUHFORIA shows that the handedness of the EUV sigmoid deduced from coronagraph observations was different from the tilt of the ICME at 1~au, suggesting a rotation of the CME in the low corona. A potential undetected low coronal rotation led to erroneous space weather prediction. The second event concerns a filament observed on August 20 2021, which underwent a rotation of 73 degrees during its eruption, implying a significant lateral drifting of the filament material. A data-constrained MAGNETohydrodynamic (MHD) simulation confirms such a rotation. These two studies reinforce the idea that CMEs are subjected to more significant rotation and deflection in the low corona than during their journey in the heliosphere.

[abstract 37 / 41] (score: 2)
arXiv:2511.20219 [pdf, ps, other]

Title: Evaluating a Transition-jump System for the FERMIlab Main Injector Using Xsuite

Authors: A. P. Schreckenberger, R. Ainsworth, M. Xiao,

Comments: North American Particle Accelerator Conference (NAPAC2025)

Subjects: physics.acc-ph

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

We describe an Xsuite simulation framework for the FERMIlab Main Injector (MI) along with an evaluation of transition-crossing behaviors in the accelerator. In particular, we studied the introduction of quadrupole MAGNETs into the lattice as part of a transition-jump system that will be implemented through the $2^{nd}$ Proton Improvement Plan (PIP-II). Simulated beam losses spurred by transition-induced instabilities were assessed under several systematic effects, including MI quad errors, MAGNET-to-MAGNET variability in the jump MAGNETs, power-supply errors, and timing jitter.

[abstract 38 / 41] (score: 2)
arXiv:2511.20259 [pdf, ps, other]

Title: Stood-up drop to measure receding contact angles

Authors: Diego Díaz, Aman Bhargava, Franziska Walz, Azadeh Sharifi, Sajjad Sumally, Rüdiger Berger, Michael Kappl, Hans-Jürgen Butt, Detlef Lohse, Thomas Willers, Vatsal Sanjay, Doris Vollmer,

Comments: 11 pages, 6 figures, currently under review for publication in RSC journal Soft Matter

Subjects: physics.flu-dyn

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

The wetting behavior of drops on natural and industrial surfaces is determined by the advancing and receding contact angles. They are commonly measured by the sessile drop technique, also called goniometry, which doses liquid through a solid needle. Consequently, this method requires substantial drop volumes, long contact times, tends to be user-dependent, and is difficult to automate. Here, we propose the stood-up drop (SUD) technique as an alternative to measure receding contact angles. The method consists of depositing a liquid drop on a surface by a short liquid JET, at which it spreads radially forming a pancake-shaped film. Then the liquid retracts, forming a spherical cap drop shape (stood-up drop). At this quasi-equilibrium state, the contact angle ($θ_\text{SUD}$) closely resembles the receding contact angle measured by goniometry. Our method is suitable for a wide variety of surfaces from hydrophilic to hydrophobic, overcoming typical complications of goniometry such as needle-induced distortion of the drop shape, and it reduces user dependence. We delineate when the receding contact angle can be obtained by the stood-up method using Volume-of-Fluid (VoF) simulations that systematically vary viscosity, contact angle, and deposited drop volume. Finally, we provide simple scaling criteria to predict when the stood-up drop technique works.

[abstract 39 / 41] (score: 2)
arXiv:2511.20445 [pdf, ps, other]

Title: Diffusion for Fusion: Designing Stellarators with Generative AI

Authors: Misha Padidar, Teresa Huang, Andrew Giuliani, Marina Spivak,

Comments:

Subjects: cs.LG physics.plasm-ph

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Stellarators are a prospective class of fusion-based power plants that confine a hot plasma with three-dimensional MAGNETic fields. Typically framed as a PDE-constrained optimization problem, stellarator design is a time-consuming process that can take hours to solve on a computing cluster. Developing fast methods for designing stellarators is crucial for advancing fusion research. Given the recent development of large datasets of optimized stellarators, machine learning approaches have emerged as a potential candidate. Motivated by this, we present an open inverse problem to the machine learning community: to rapidly generate high-quality stellarator designs which have a set of desirable characteristics. As a case study in the problem space, we train a conditional diffusion model on data from the QUASR database to generate quasisymmetric stellarator designs with desirable characteristics (aspect ratio and mean rotational transform). The diffusion model is applied to design stellarators with characteristics not seen during training. We provide evaluation protocols and show that many of the generated stellarators exhibit solid performance: less than 5% deviation from quasisymmetry and the target characteristics. The modest deviation from quasisymmetry highlights an opportunity to reach the sub 1% target. Beyond the case study, we share multiple promising avenues for generative modeling to advance stellarator design.

[abstract 40 / 41] (score: 2)
arXiv:2511.20449 [pdf, ps, other]

Title: A meshless data-tailored approach to compute statistics from scattered data with adaptive radial basis functions

Authors: Damien Rigutto, Manuel Ratz, Miguel A. Mendez,

Comments: Submitted to Experiments in Fluids

Subjects: physics.flu-dyn

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Constrained radial basis function (RBF) regression has recently emerged as a powerful meshless tool for reconstructing continuous velocity fields from scattered flow measurements, particularly in image-based velocimetry. However, existing formulations based on isotropic kernels often suffer from spurious oscillations in regions with sharp gradients or strong flow anisotropy. This work introduces an anisotropic, gradient-informed, and adaptively sampled extension of the constrained RBF framework for regression of scattered data. Gradient information is estimated via local polynomial regression at collocation points, smoothed, and used to (1) re-sample data, maximizing sampling density near steep gradients while downsampling in smooth regions, and (2) construct a local anisotropic metric that shapes each basis function according to the flow directionality. In addition, a gradient-informed regularization is introduced by embedding observed gradients into the least-squares system as weighted soft constraints. The resulting formulation is fully meshless, linear, and computationally efficient, while significantly improving reconstruction quality in challenging regions. The method is evaluated on both synthetic and experimental datasets, including direct numerical simulation (DNS) data of a turbulent channel and time-resolved particle tracking velocimetry of a turbulent JET. Results show that the proposed approach outperforms isotropic and gradient-free RBF formulations in accuracy, smoothness, and physical consistency -- particularly near shear layers and boundaries -- while reducing the number of bases by an order of magnitude. To support the application, we have created a repository (https://github.com/mendezVKI/SPICY_VKI) that provides access to the investigated datasets.

[abstract 41 / 41] (score: 2)
arXiv:2511.20452 [pdf, ps, other]

Title: A Self-Consistent Model of the Ultra High-Energy Gamma-Ray Emission of Pulsar Wind Nebulae: Insights from LHAASO and ATNF Catalogs

Authors: Samy Kaci, Gwenael Giacinti, Dmitri Semikoz,

Comments: 15 pages, 5 figures

Subjects: astro-ph.HE

Created: 2025-11-25; Updated: 2025-11-26; Datestamp: 2025-11-26

Pulsar wind nebulae (PWNe) are the dominant Ultra-high-energy (UHE) gamma-ray sources in the LHAASO catalog suggesting that they are the dominant leptonic PeVatrons in our Galaxy. Despite this, still very little is known about their UHE gamma-ray emission, their number in the Galaxy, or their contribution to the gamma-ray emission of our Galaxy. In this work, we propose a self-consistent data-driven model of the UHE gamma-ray emission of PWNe based on the ATNF and LHAASO catalogs. More specifically, we build a model of the UHE gamma-ray emission of PWNe that preserves the statistical relationships in the ATNF catalog and reproduces the number of PWNe detected in the LHAASO catalog. To cope with the limited data available in the LHAASO catalog when performing fits on gamma-ray data, we introduce the concept of censored regression that allows to also use the information provided by unresolved sources. Using our model, we find that reproducing the number of PWNe detected by LHAASO requires either fractions of misaligned pulsars smaller ($\lesssim60\%$) than usually found in the literature, or that some of the associations of PWNe to ATNF pulsars made by LHAASO may not be true. In both cases, we find that in order to reach self-consistency between radio and gamma-ray data, it is necessary that the majority of the unidentified sources in the LHAASO catalog are PWNe associated to an unseen pulsar. Moreover, using our model we also find that the contribution of unresolved PWNe to the total (diffuse) gamma-ray background measured by LHAASO in the $1-1000\,\rm{TeV}$ range is always smaller than $\lesssim10\%$ ($\lesssim30\%$). We conclude that PWNe mostly contribute to the source component of the UHE gamma-ray sky, while having almost no imprint on its diffuse component.