Current date: 2025-12-22

Setting default datestamp limit: 0

Datestamp limit: 2025-12-22 (0 days ago)

Created/updated limit: 2025-12-15 (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=2025-12-22&until=2025-12-22&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 739

Keyword score statistics

score 7 -- 1 abstracts

score 6 -- 1 abstracts

score 5 -- 4 abstracts

score 4 -- 5 abstracts

score 3 -- 8 abstracts

score 2 -- 17 abstracts

in total -- 36 abstracts

Articles that appeared on 2025-12-22

[abstract 1 / 36] Wow! (score: 7)
arXiv:2512.15065 [pdf, ps, other]

Title: A Comprehensive Interpretation of FERMI-LAT Pulsars: Fundamental-Plane Death Border, Visibility Thresholds, and GeV-TeV Unification

Authors: Constantinos Kalapotharakos, Zorawar Wadiasingh, Alice K. Harding, Demosthenes Kazanas, Dimitrios Skiathas,

Comments: 30 pages, 11 figures, submitted to ApJ

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

We present a framework that links equatorial-current-sheet (ECS) physics to catalog-level, phase-averaged gamma-ray pulsar properties. Guided by analytic scalings and particle-in-cell (PIC) simulations, we show that the pulsar ``Fundamental Plane'' (relating gamma-ray luminosity, spectral cutoff energy, spin-down power $\dot{\cal{E}}$, and surface MAGNETic field) is bounded by two regimes: a radiation-reaction-limited branch and a potential-drop-limited branch. Their intersection defines a transition in $\dot{\cal{E}}$ that maps to a gamma-ray visibility threshold on the $P-\dot{P}$ diagram, above which detectability is set by distance and beaming, and below which both cutoff energy and efficiency decline rapidly. Placing ATNF pulsars and McGill MAGNETars onto these planes reproduces the observed FERMI occupancy, with millisecond pulsars (MSPs) on the observable side, young pulsars (YPs) straddling the threshold, and MAGNETars clustering at or just below it. At higher $\dot{\cal{E}}$, both MSPs and YPs depart from the maximal radiation-reaction-limited envelope at similar cutoff energies, suggesting that enhanced pair creation screens the accelerating electric field in the ECS. We interpret this behavior with a compactness-based criterion for optically thin $γγ$ pair feedback in or near the ECS and briefly note an extension to $γγ\rightarrowμ^\pm$ that could yield pulsed multi-TeV neutrinos in the most energetic systems. The framework predicts a MeV-bright, GeV-faint corridor below FERMI sensitivity, a target for next-generation MeV missions. Finally, motivated by the recent HESSII detection of pulsed multi-TeV emission from Vela, we use PIC particle distributions with a seed-photon model to reproduce a multi-TeV inverse-Compton component alongside the GeV curvature emission, supporting a unified ECS-based GeV-TeV origin.

[abstract 2 / 36] Yes (score: 6)
arXiv:2509.22843 [pdf, ps, other]

Title: Can GRB 250702B be explained as the tidal disruption of a white dwarf by an intermediate mass BLACK HOLE? Yes

Authors: Rob AJ Eyles-Ferris, Andrew King, Rhaana LC Starling, Peter G Jonker, Andrew J Levan, Antonio Martin-Carrillo, Tanmoy Laskar, Jillian C Rastinejad, Nikhil Sarin, Nial R Tanvir, Benjamin P Gompertz, Nusrin Habeeb, Paul T O'Brien, Massimiliano De Pasquale,

Comments: 8 pages, 2 figures. Second revision

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

GRB 250702B is a unique astrophysical transient characterised by its nature as a repeating gamma-ray trigger. Its properties include possible periodicity in its gamma-ray light curve, an X-ray counterpart that rose prior to the gamma-ray outbursts and faded quickly, and radio and infrared counterparts. These features are difficult to reconcile with most models of high energy transients but we show that they are compatible with a white dwarf bound to an intermediate mass BLACK HOLE that is tidally stripped over multiple pericentre passages before being fully disrupted. Accretion onto the BLACK HOLE powers a mildly RELATIVISTIC JET that produces the X-rays through internal processes and the infrared and radio counterparts through thermal emission and external shocks respectively but is unable to produce the gamma-ray emission on its own. We propose that chaotic debris streams from the multiple stripping episodes can collide with a period roughly the same as the orbital period of the star. These shocks produce hard X-ray photons that are upscattered by the JET to produce the observed MeV gamma-ray emission. Future analysis of the JET properties will allow us to place firmer constraints on our model.

[abstract 3 / 36] Yes (score: 5)
arXiv:2205.08003 [pdf, ps, other]

Title: Revisit the periodicity of SGR J1935+2154 bursts with updated sample

Authors: Sheng-Lun Xie, Ce Cai, Shao-Lin Xiong, Yun-Wei Yu, Yan-Qiu Zhang, Lin Lin, Zhen Zhang, Wang-Chen Xue, Jia-Cong Liu, Yi Zhao, Shuo Xiao, Chao Zheng, Qi-Bin Yi, Peng Zhang, Ping Wang, Rui Qiao, Wen-Xi Peng, Yue Huang, Xiang Ma, Xiao-Yun Zhao, Xiao-Bo Li, Shi-Jie Zheng, Ming-Yu Ge, Cheng-Kui Li, Xin-Qiao Li, Xiang-Yang Wen, Fan Zhang, Li-Ming Song, Shuang-Nan Zhang, Zhi-Wei Guo, Xiao-Lu Zhang, Guo-Ying Zhao, Chao-Yang Li,

Comments: Minor corrections

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Since FRB 200428 has been found to be associated with an X-ray burst from the Galactic MAGNETar SGR J1935+2154, it is interesting to explore whether the MAGNETar bursts also follow the similar active periodic behavior as some repeating FRBs. Previous studies show that there is possible period about 230 day in SGR J1935+2154 bursts. Here, we collected an updated burst sample from SGR J1935+2154, including all bursts reported by FERMI/GBM and GECAM till 2022 January. We also developed a targeted search pipeline to reveal more bursts from SGR J1935+2154 in the FERMI/GBM data from 2008 August to 2014 December (i.e. before the first burst detected by SWIFT/BAT). With this burst sample, we re-analyzed the possible periodicity of SGR J1935+2154 bursts using the Period Folding and Lomb-Scargle Periodogram methods. Our results show that the periodicity $\sim$238 day reported in literature is probably fake and the observation effects may introduce false periods (i.e. 55 day) according to simulation tests. We find that, for the current burst sample, the most probable period is 126.88$\pm$2.05 day, which could be interpreted as the precession of the MAGNETar. However, we note that the whole burst history is very complicated and difficult to be perfectly accommodated with any period reported thus far, therefore more monitoring observations of SGR J1935+2154 are required to test any periodicity hypothesis.

[abstract 4 / 36] Yes (score: 5)
arXiv:2508.17307 [pdf, ps, other]

Title: IGR J17091-3624: Newly Formed Periodic Dips and Multiwavelength Activity During the 2025 Outburst

Authors: Zikun Lin, Yanan Wang, Shuyuan Wei, Yongkang Sun, Long Ji, Samaporn Tinyanont, Meng Sun, Song Wang, Diego Altamirano, Douglas J. K. Buisson, Wenxiong Li, Qian Chen, Jifeng Liu, Shuang-Nan Zhang, Wei Wang, Zhen Guo, Pathompong Butpan, Rungrit Anutarawiramkul,

Comments: 17 pages, 10 figures, 1 tables

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

The BLACK HOLE low-mass X-ray binary (LMXB) candidate IGR J17091-3624 experienced a hard-state-only outburst in 2025. In this paper, we show that IXPE detected a series of intermittent X-ray dips, spanning a total interval of ~1 day. Subsequent observations with NICER, EP, NUSTAR, and SWIFT reveal that these dips recur with a period of 2.83$\pm$0.07 days and are accompanied by an increase in spectral hardness. This is the first time such quasi-periodic dipping behavior has been observed in this target since discovery. Our spectral analysis shows that the dips can be explained by obscuration from an ionized absorber characterized by an ionization parameter of $logξ$ ~1-3 erg cm s$^{-1}$ and an equivalent hydrogen column density of $N^{\rm zxipcf}_{\rm H}$~(1-30)$\times10^{22}$ cm$^{-2}$. The periodic reappearance of the absorber is likely caused by obscuring material located in the outer accretion disk, modulated by the binary orbital period. If confirmed, this period would suggest that the donor star in IGR J17091-3624 has deviated from the standard main-sequence evolutionary path and is likely a (partially) stripped giant. In the optical band, no significant periodicity or correlation with the X-ray dips was detected, whereas the radio counterpart exhibited a flat to steep spectrum, in contrast to the inverted spectrum typically observed during the hard state of LMXBs.

[abstract 5 / 36] Yes (score: 5)
arXiv:2512.11488 [pdf, ps, other]

Title: The Polarized X-ray Universe: Insights and Discoveries

Authors: Arbind Pradhan, Sree Bhattacherjee, Biplob Sarkar,

Comments: 11 pages, 0 figure, The manuscript will appear as a book chapter in the forthcoming book entitled "Advances in Physical Sciences: Theories, Applications, and Innovations

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Polarization is one of the fundamental natures of electroMAGNETic radiation. The detection of POLARIZATION or polarized photons from distant X-ray radiating systems (such as X-ray binaries (XBs), ACTIVE GALACTIC NUCLEi (AGN), pulsars, and stars) complements the timing, spectral, and imagining analysis to better understand the physical mechanisms taking place in these sources. Polarization has enhanced the understanding of the internal geometry of these systems and their vicinity. Polarized X-rays can be generated either directly through non-thermal physical processes in the presence of a MAGNETic field(B) or through the scattering of unpolarized thermal radiation within plasma structures such as an accretion disk. X-ray POLARIZATION can measure the two important independent parameters, the POLARIZATION degree (PD) and POLARIZATION angle (PA) of the X-ray photons. These parameters are crucial as they reveal the characteristics of particles in such a strong MAGNETic and gravitational field. In this chapter, we have discussed (i) the basic idea of POLARIZATION, (ii) some distant sources radiating polarized X-ray photons, (iii) missions dedicated to observing polarized X-ray photons, and (iv) recent breakthroughs and upcoming missions.

[abstract 6 / 36] Yes (score: 5)
arXiv:2512.17539 [pdf, ps, other]

Title: Constraining BLACK HOLE spin in PG 1535+547 amidst complex multi-layered absorption

Authors: A. Madathil-Pottayil, D. J. Walton, Jiachen Jiang, T. Dauser, Andrew Fabian, D. Stern, Luigi C. Gallo, Mark T. Reynolds, Emanuele Nardini, Javier A. Garcia,

Comments: 14 pages, 9 figures, submitted to MNRAS; revised after referee review and resubmitted

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

We present a spectroscopic analysis of XMM-Newton and NUSTAR observations of the 'complex' NLS1 PG 1535+547 at redshift $z=0.038$. These observations span three epochs: 2002 and 2006 with XMM-Newton alone, covering the $0.3-10$ keV energy range, and a coordinated XMM-Newton and NUSTAR observation in 2016, covering the $0.3-60$ keV energy range. The X-ray spectra across all epochs exhibit both neutral and ionized absorption, along with reflection features from the accretion disc, including a prominent Compton hump in the broadband data. Notably, the spectral shape varies across epochs. Our analysis suggests this variability is attributed to changes in both line-of-sight absorption and the intrinsic emission from PG 1535+547. The source is obscured by multiple layers of partially and/or fully covering neutral and ionized absorbers, with neutral column densities ranging from undetectable levels in the least obscured phase to $\sim0.3-5\times10^{23}\mathrm{cm^{-2}}$ in the most obscured phase. A clear warm absorber is revealed during the least obscured phase. The continuum remains fairly consistent ($Γ\approx 2.2\pm0.1$) during the first two observations, followed by a substantial flux decrease (by a factor of $\sim7$ in the $2-10$ keV band) in 2016 compared to 2006. The 2016 data indicates the source is in a reflection-dominated state during this epoch, with a reflection fraction of $R>7$ and an X-ray source located at a height $\leq 1.72r_g$. Simultaneous fitting of the multi-epoch data suggests a rapidly rotating BLACK HOLE with a spin parameter, $a>0.99$. These findings imply that strong light-bending effects may account for the observed continuum flux reduction.

[abstract 7 / 36] Yes (score: 4)
arXiv:2404.11877 [pdf, ps, other]

Title: Finding the Particularity of the Active Episode of SGR J1935+2154 during Which FRB 20200428 Occurred: Implication from Statistics of FERMI/GBM X-Ray Bursts

Authors: Sheng-Lun Xie, Yun-Wei Yu, Shao-Lin Xiong, Lin Lin, Ping Wang, Yi Zhao, Yue Wang, Wen-Long Zhang,

Comments: Minor corrections

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

By using the FERMI/Gamma-ray Burst Monitor data of the X-ray bursts (XRBs) of SGR J1935+2154, we investigate the temporal clustering of the bursts and the cumulative distribution of the waiting time and fluence/flux. It is found that the bursts occurring in the episode hosting FRB 20200428 have obviously shorter waiting times than those in the other episodes. The general statistical properties of the XRBs further indicate they could belong to a self-organized critical (SOC) system (e.g., starquakes), making them very similar to the earthquake phenomena. Then, according to a unified scaling law between the waiting time and energy of the earthquakes as well as their aftershocks, we implement an analogy analysis on the XRBs and find that the FRB episode owns more dependent burst events than the other episodes. It is indicated that the fast radio burst (FRB) emission could be produced by the interaction between different burst events, which could correspond to a collision between different seismic/Alfven waves or different explosion outflows. Such a situation could appear when the MAGNETar enters into a global intensive activity period.

[abstract 8 / 36] Yes (score: 4)
arXiv:2512.16981 [pdf, ps, other]

Title: The accretion of QUASARs at the epoch of reionisation: $JWST$ catches the primeval monsters slowly feasting

Authors: B. Trefoloni, E. Nardini, S. Carniani, E. Lusso, A. Marconi, E. Parlanti, A. Sacchi, A. Shlentsova, M. Signorini, G. Risaliti, S. Zamora,

Comments: 19 pages, 8 figures. Submitted to A&A

Subjects: astro-ph.GA

Created: 2025-12-18; Updated: 2025-12-22; Datestamp: 2025-12-22

Quasars (QSOs) emit an enormous amount of light as a result of the accretion of gas onto supermassive BLACK HOLEs (SMBHs). Thanks to their luminosity, the most distant known QSOs allow us to trace the growth of SMBHs deep into the epoch of reionisation. In this work, we employed $JWST$/NIRSpec observations of eight luminous (log$(L_{3000\,A^{\circ}}/(erg \, s^{-1}))>$45.7) QSOs at $z\geq$5.9 to constrain their accretion properties, namely BLACK HOLE mass, accretion disc (AD) luminosity, and Eddington ratio ($M_{BH}$, $L_{AD}$, $λ_{Edd}$), by fitting the rest-frame UV and optical emission with different AD models. This method provided self-consistent measurements of both $M_{BH}$ and $L_{AD}$. The uncertainties on $M_{BH}$ and $L_{AD}$, obtained within the AD-modelling framework ($σ^{AD}_{M_{BH}}\sim$0.2 dex; $σ^{AD}_{L_{AD}}\sim$0.1 dex), are significantly smaller than the systematic uncertainties associated with single-epoch $M_{BH}$ ($\sim$0.4 dex) and $L_{AD}$ derived via bolometric corrections ($\sim$0.2 dex). Based on these results, in our sample we found an average Eddington ratio of $\langle \log(λ_{Edd}) \rangle=-0.9$, with a dispersion of $\sim$0.2 dex. Assuming that our high-z QSOs are representative of optically-selected bright blue QSOs, we derive a fraction of systems accreting above the Eddington limit of $\sim$0.2%. In conclusion, this work i) demonstrates the suitability of $JWST$ to test AD models on high-redshift ($z\gtrsim$4) QSOs, thanks to the large NIRSpec spectral coverage; ii) shows that AD modelling can yield robust $M_{\rm BH}$ and $L_{\rm AD}$ measurements, with smaller uncertainties than the typical calibrations; and iii) provides compelling evidence for sub-Eddington accretion in bright high-$z$ QSOs, challenging the widespread paradigm of near- or super-Eddington accretion occurring in these sources.

[abstract 9 / 36] Yes (score: 4)
arXiv:2512.17184 [pdf, ps, other]

Title: A VERITAS view of HESS J1857+026 within a multi-wavelength analysis

Authors: Y. Chen,

Comments: Presented at the 39th International Cosmic Ray Conference, Geneva, 2025

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

HESS J1857+026 remains a mysterious gamma-ray emitter since its discovery in 2008. Despite the disclosure of a nearby pulsar and multiple studies in the high-energy (HE, E > 100 MeV) and very-high-energy (VHE, E > 100 GeV) regimes, there have been no confirmed counterparts (e.g., an SNR shell or other extended structure) in X-ray or other wavelengths. We present the result of our study of the VHE emission of HESS~J1857+026 with VERITAS as part of a multi-wavelength investigation to uncover its emission mechanisms. Our result confirms the extended nature of the source and we characterize its spectral and morphological features in the VHE band. Using the morphology of the source revealed in our analysis, we also explore the underlying transport process of a possible electron population in a leptonic PWN scenario for the gamma-ray emission.

[abstract 10 / 36] Yes (score: 4)
arXiv:2512.17498 [pdf, ps, other]

Title: High-Resolution Measurements with the CTAO Southern Array: The Case for Pulsar Wind Nebulae

Authors: Georg Schwefer, Jim Hinton,

Comments: 17 pages, 17 figures; Submitted to A&A

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

The advent of the Cherenkov Telescope Array Observatory (CTAO) and recent advances in reconstruction of gamma-ray photons with Cherenkov telescopes are bound to push the limit of angular resolution to an unprecedented precision of less than one arcminute at tens of TeV. Naturally, such instrumental improvements open up possibilities for new and interesting scientific studies. We aim to show that the study of pulsar wind nebulae (PWNe) in particular is bound to profit from these high-resolution measurements. This is because PWNe are the dominant Galactic source population at TeV energies, exhibit hard spectra up to hundreds of TeV and from X-ray observations are known to possess plentiful structure on arcminute scales. Using HESS J1813-178 and MSH 15-52 as examples, we create simple leptonic models of the TeV morphology of these sources based on X-ray observations and existing gamma-ray measurements. Then, assuming different models for the exposure and point spread function of the observatory, we create mock observations with the future CTAO southern array. We use these to assess the ability of these observations to differentiate between models and study the physics of these sources, in particular to infer the structure of the MAGNETic field and electron distributions. We find that future observations with the CTAO southern array at multi-TeV energies - in combination with existing X-ray measurements - will likely be able to constrain the distributions of MAGNETic field and high-energy electrons in these sources. We demonstrate that the sensitivity of these measurements can be significantly enhanced with the improved angular resolution achievable with novel reconstruction algorithms. However, we also show that in the relevant multi-TeV regime, signal-photon statistics remain a limitation and trading event statistics for improved angular resolution is not necessarily advantageous.

[abstract 11 / 36] Yes (score: 4)
arXiv:2512.17880 [pdf, ps, other]

Title: On the complex nature of coronal heating

Authors: C. A. Breu, D. I. Pontin, E. Priest, I. De Moortel,

Comments: 18 pages, 18 figures

Subjects: astro-ph.SR

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

A large part of the hot corona consists of MAGNETically confined, bright plasma loops. These observed loops are in turn structured into bright strands. We investigate the relationship between MAGNETic field geometry, plasma properties and bright strands with the help of a 3D resistive MHD simulation of a coronal loop rooted in a self-consistent convection zone layer. We find that it is impossible to identify a loop as a simple coherent MAGNETic flux tube that coincides with plasma of nearly uniform temperature and density. The location of bright structures is determined by a complex interplay between heating, cooling and evaporation timescales. Current sheets form preferentially at the interfaces of MAGNETic flux from different sources. They may also form within bundles of MAGNETic field lines since motions within MAGNETic concentrations drive plasma flows on a range of timescales that provide further substructure and can locally enhance MAGNETic field gradients and thus facilitate MAGNETic RECONNECTion. The numerical experiment therefore possesses aspects of both the flux tube tectonics and flux braiding models. While modelling an observed coronal loop as a cylindrical flux tube is useful to understand the physics of specific heating mechanisms in isolation, it does not describe well the structure of a coronal loop rooted in a self-consistently evolving convection zone.

[abstract 12 / 36] (score: 3)
arXiv:2307.01010 [pdf, ps, other]

Title: GECAM Observations of the Galactic Magnetar SGR J1935+2154 during the 2021 and 2022 Burst Active Episodes. I. Burst Catalog

Authors: Sheng-Lun Xie, Ce Cai, Yun-Wei Yu, Shao-Lin Xiong, Lin Lin, Yi Zhao, Shuang-Nan Zhang, Li-Ming Song, Ping Wang, Xiao-Bo Li, Wang-Chen Xue, Peng Zhang, Chao Zheng, Yan-Qiu Zhang, Jia-Cong Liu, Chen-Wei Wang, Wen-Jun Tan, Yue Wang, Zheng-Hang Yu, Pei-Yi Feng, Jin-Peng Zhang, Shuo Xiao, Hai-Sheng Zhao, Wen-Long Zhang, Yan-Ting Zhang, Yue Huang, Xiao-Yun Zhao, Xiang Ma, Shi-Jie Zheng, Xin-Qiao Li, Xiang-Yang Wen, Ke Gong, Zheng-Hua An, Da-Li Zhang, Sheng Yang, Xiao-Jing Liu, Fan Zhang,

Comments: Minor corrections

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Magnetar is a neutron star with an ultrahigh MAGNETic field ($\sim 10^{14}-10^{15}$ G). The MAGNETar SGR J1935+2154 is not only one of the most active MAGNETars detected so far, but also the unique confirmed source of fast radio bursts (FRBs). Gravitational wave high-energy ElectroMAGNETic Counterpart All-sky Monitor (GECAM) is dedicated to monitor gamma-ray transients all over the sky, including MAGNETar short bursts. Here we report the GECAM observations of the burst activity of SGR J1935+2154 from January 2021 to December 2022, which results in a unique and valuable data set for this important MAGNETar. With a targeted search of GECAM data, 159 bursts from SGR J1935+2154 are detected by GECAM-B while 97 bursts by GECAM-C, including the X-ray burst associated with a bright radio burst. We find that both the burst duration and the waiting time between two successive bursts follow lognormal distributions. The period of burst activity is $134\pm20$ days, thus the burst activity could be generally divided into four active episodes over these two years. Interestingly, the hardness ratio of X-ray bursts tends to be softer during these two years, especially during the active episode with radio bursts detected.

[abstract 13 / 36] (score: 3)
arXiv:2504.12906 [pdf, ps, other]

Title: Water activation using Ar-H$_2$ atmospheric pressure plasma JETs

Authors: Fellype do Nascimento, Ananias Alves Barbosa, Konstantin Georgiev Kostov,

Comments: 28 pages, 15 figures

Subjects: physics.plasm-ph

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Whether for materials processing or medical applications, the use of atmospheric pressure plasma JETs (APPJs) has emerged as a relevant alternative to conventional methods. Within the APPJs research field, the search for innovation aims not only to solve existing problems but also to explore novel options for generating plasma JETs and find new possible applications. In this work, the properties of Ar-H$_2$ APPJs generated using two plasma sources that differ in the frequency, amplitude, and waveform of the generated voltage signal were studied through electrical, thermal, and optical characterization. The discharge parameters were analyzed as a function of the H$_2$ content in the gas mixture, with this parameter varying from 0\% to 3.5\%. Optical emission spectroscopy revealed that the same reactive species were produced for both plasma sources, except nitric oxide (NO), which was observed only for the source operated at a higher frequency (PS #1). Applications for water activation were performed without H$_2$ and with 3.5% H$_2$ in the gas mixture. The results of water treatment revealed that ammonia is also produced when H$_2$ is added to the working gas. This finding suggests that the water treated by a Ar-H$_2$ plasma JET can be an attractive option for use in agriculture.

[abstract 14 / 36] (score: 3)
arXiv:2512.17337 [pdf, ps, other]

Title: Influence of plasma shaping on the parity of core-localized toroidal Alfvén eigenmode in an advanced tokamak configuration

Authors: Shiwei Xue, Ping Zhu, Haolong Li,

Comments:

Subjects: physics.plasm-ph

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Toroidal Alfvén eigenmodes (TAEs) and energetic particle modes (EPMs) can both be excited by energetic particles from auxiliary heating and fusion-born alpha particles in a tokamak. Using the hybrid kinetic-MHD model implemented in the NIMROD code, the excitation of these modes and their properties are investigated in an advanced tokamak configuration with reversed MAGNETic shear in the core region. The dominant TAE/EPM is found to exhibit odd parity with an anti-ballooning structure when the plasma has elongated, non-circular two-dimensional shaping. As the plasma shaping becomes more circular with reduced elongation, the mode parity undergoes a transition to even parity accompanied by a ballooning structure. These results may help explain the dominant parity of TAE/EPMs observed in advanced tokamak configurations with different plasma shaping.

[abstract 15 / 36] (score: 3)
arXiv:2512.17358 [pdf, ps, other]

Title: Origin of Quasi-Periodic Oscillations and Accretion Process in X-Ray Binaries around Quantum Lee-Wick Black Hole

Authors: Orhan Donmez, G. Mustafa, M. Yousaf, Faisal Javed, Ikhtiyor Saidov, Farruh Atamurotov,

Comments: 28 pages, 18 figures

Subjects: gr-qc astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

In this study, we investigate the accretion dynamics and test particle motion around a non-rotating, spherically symmetric Lee-Wick BLACK HOLE (BH) to reveal how the model parameters affect orbital stability and the quasi-periodic oscillations (QPOs) observed in X-ray binary systems. The spacetime geometry, characterized by the BH mass and the coupling parameters $S_1$ and $S_2$, includes exponential and oscillatory corrections arising from the Lee-Wick terms. Using the effective potential approach, we derive specific energy, angular momentum, epicyclic frequencies, and the locations of the innermost stable circular orbits (ISCOs) of test particles. In addition to the analytical analysis, we explore the effects of the Lee-Wick spacetime parameters on the shock-cone morphology produced by Bondi-Hoyle-Lyttleton (BHL) accretion. To this end, we perform general RELATIVISTIC hydrodynamic simulations in two characteristic regimes: Block-1 (weak Lee-Wick regime) and Block-2 (strong Lee-Wick regime). The results show that Block-1 solutions closely resemble the Schwarzschild case, while Block-2 models develop denser and asymmetric shock cones accompanied by stronger QPOs activity, shifting from low-frequency to high-frequency QPOs. These variations yield distinct observational signatures that may be detectable in high-resolution X-ray timing data. Our analytical and numerical findings demonstrate that the Lee-Wick parameters $S_1$ and $S_2$ cause measurable changes in the morphology of the accretion flow and in the frequency ratios near the BH. This suggests that future multi-wavelength observations could provide an important avenue to test higher-derivative gravity theories.

[abstract 16 / 36] (score: 3)
arXiv:2512.17441 [pdf, ps, other]

Title: On Signatures of a Possible New Physics Resonance in Atmospheric Air Showers Using a Parameterized Model

Authors: Jiri Kvita,

Comments: 27 pages, 16 figures

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

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

We present a parameterized model of atmospheric particle showers initiated by COSMIC RAYs. Few physics shower parameters are tuned in a comparison to the Conex generator. Resulting shower properties are studied, with a comment on the cases where multiple shower maxima develop. Finally, we implement simple models of new physics resonance of masses of 100 GeV and 1 TeV and examine their effects on the shower profile, depth and maximum variation in dependence of the decay channel of the hypothetical resonance. It is shown that a new resonance effects can appear at the energy threshold and can persist for about a decade in $\log_{10} E/\mathrm{eV}$. Various assumed decay modes of the hypothetical resonance have different effects on the direction and shape of the modified average shower depth as function of the energy, with possible implications for current or future measurements. It is shown that, within the presented model, the visibility of the resonance in modified shower depth strongly depends on the resonance width. A significant modification at 10\% width gradually diminishes towards the percent-level width. We propose that looking at the 2D distributions of the two first individual shower moments can also reveal signatures of new physics.

[abstract 17 / 36] (score: 3)
arXiv:2512.17664 [pdf, ps, other]

Title: Validating the performance of the Radio Neutrino Observatory in Greenland using cosmic-ray air showers

Authors: S. Agarwal, J. A. Aguilar, N. Alden, S. Ali, P. Allison, M. Betts, D. Besson, A. Bishop, O. Botner, S. Bouma, S. Buitink, R. Camphyn, J. Chan, S. Chiche, B. A. Clark, A. Coleman, K. Couberly, S. de Kockere, K. D. de Vries, C. Deaconu, P. Giri, C. Glaser, T. Glüsenkamp, H. Gui, A. Hallgren, S. Hallmann, J. C. Hanson, K. Helbing, B. Hendricks, J. Henrichs, N. Heyer, C. Hornhuber, E. Huesca Santiago, K. Hughes, A. Jaitly, T. Karg, A. Karle, J. L. Kelley, C. Kopper, M. Korntheuer, M. Kowalski, I. Kravchenko, R. Krebs, M. Kugelmeier, D. Kullgren, R. Lahmann, C. -H. Liu, Y. Liu, M. J. Marsee, K. Mulrey, M. Muzio, A. Nelles, A. Novikov, A. Nozdrina, E. Oberla, B. Oeyen, N. Punsuebsay, L. Pyras, M. Ravn, A. Rifaie, D. Ryckbosch, F. Schlüter, O. Scholten, D. Seckel, M. F. H. Seikh, Z. S. Selcuk, J. Stachurska, J. Stoffels, S. Toscano, D. Tosi, J. Tutt, D. J. Van Den Broeck, N. van Eijndhoven, A. G. Vieregg, A. Vijai, D. Washington, C. Welling, D. R. Williams, P. Windischhofer, S. Wissel, R. Young, A. Zink,

Comments:

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

The Radio Neutrino Observatory in Greenland (RNO-G) is currently under construction with the aim to detect neutrinos with energies beyond $\sim 10\,\mathrm{PeV}$. A critical part of early detector commissioning is the study of detector characteristics and potential backgrounds, for which COSMIC RAYs play a crucial role. In this article, we report that the number of COSMIC RAYs detected with RNO-G's shallow antennas is consistent with expectations. We further verified the agreement in the observed cosmic-ray signal shape with expectations from simulations after careful treatment of the detector systematics. Finally, we find that the reconstructed arrival direction, energy, and POLARIZATION of the cosmic-ray candidates agrees with expectations. Throughout this study, we identified detector shortcomings that are mitigated going forward. Overall, the analysis presented here is an essential first step towards validating the detector and high-fidelity neutrino detection with RNO-G in the future.

[abstract 18 / 36] (score: 3)
arXiv:2512.17760 [pdf, ps, other]

Title: Constraining the Prompt Atmospheric Neutrino Flux Combining IceCube's Cascade and Track Samples

Authors: R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J. M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, J. Baines-Holmes, A. Balagopal V., S. W. Barwick, S. Bash, 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, I. Bodo, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, M. A. Campana, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Z. Chen, D. Chirkin, S. Choi, B. A. Clark, P. Coleman, G. H. Collin, 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. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, L. Fischer, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, G. Garg, 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, C. Haack, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Ha Minh, 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, 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. Jeong, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, M. Karl, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, H. Kimku, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, 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, J. Krishnamoorthi, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, N. Lad, 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, J. Madsen, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mari{ş}, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, S. Mechbal, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, M. Moulai, D. Mousadi, E. Moyaux, T. Mukherjee, R. Naab, M. Nakos, U. Naumann, J. Necker, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, M. Plum, A. Pontén, V. Poojyam, Y. Popovych, M. Prado Rodriguez, 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, S. Reusch, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, 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, P. Schaile, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. G. Schröder, L. Schumacher, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, 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, S. Tilav, K. Tollefson, S. Toscano, D. Tosi, A. Trettin, A. K. Upadhyay, 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. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, 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, M. Wolf, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman,

Comments:

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

The IceCube Neutrino Observatory has observed a diffuse flux of high-energy astrophysical neutrinos for more than a decade. A relevant background to the astrophysical flux is prompt atmospheric neutrinos, originating from the decay of charmed mesons produced in cosmic-ray-induced air showers. The production rate of charmed mesons in the very forward phase space of hadronic interactions, and consequently, the prompt neutrino flux, remains uncertain and has not yet been observed by neutrino detectors. An accurate measurement of this flux would enhance our understanding of fundamental particle physics such as hadronic interactions in high-energy cosmic-ray-induced air showers and the nucleon structure. Furthermore, an experimental characterization of this background flux will improve the precision of astrophysical neutrino flux spectral measurements. In this work, we perform a combined fit of cascade-like and track-like neutrino events in IceCube to constrain the prompt atmospheric neutrino flux. Given that the prompt flux is a sub-dominant contribution, treating systematic uncertainties arising from the potential mis-modeling of the conventional and astrophysical neutrino fluxes is critical for its measurement. Our analysis yields a non-zero best-fit result, which is, however, consistent with the null hypothesis of no prompt flux within one standard deviation. Consequently, we establish an upper bound on the flux at $4\times 10^{-16}$ (GeV m$^2$ s sr)$^{-1}$ at 10 TeV.

[abstract 19 / 36] (score: 3)
arXiv:2512.17770 [pdf, ps, other]

Title: Magnetic field spreading from stellar and galactic dynamos into the exterior

Authors: Axel Brandenburg, Oindrila Ghosh, Franco Vazza, Andrii Neronov,

Comments: 15 pages, 8 figures, 1 table, submitted to ApJ

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

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

The exteriors of stellar and galactic dynamos are usually modeled as a current-free potential field. A more realistic description might be that of a force-free MAGNETic field. Here, we suggest that, in the absence of outflows, neither of those reflect the actual behavior when the MAGNETic field spreads diffusively into a more poorly conducting turbulent exterior outside dynamo. In particular, we show that the usual ordering of the dipole MAGNETic field being the most slowly decaying one is altered, and that the quadrupole can develop a toroidal component that decays even more slowly with radial distance. This behavior is best seen for spherical dynamo volumes and becomes more complicated for oblate ones. In either case, however, those fields are confined within a MAGNETosphere beyond which the field drops exponentially. The MAGNETosphere expands ballistically (i.e., linearly in time $t$) during the exponential growth phase of the dynamo, but diffusively proportional to $t^{1/2}$ during the saturated phase. We demonstrate that the Faraday displacement current, which plays a role in a vacuum, can safely be neglected in all cases. For quadrupolar configurations, the SYNCHROTRON emission from the MAGNETosphere is found to be constant along concentric rings. The total and the polarized radio emissions from the dipolar or the quadrupolar configurations display large scale radial trends that are potentially distinguishable with existing radio telescopes. The superposition of MAGNETic fields from galaxies in the outskirts of the voids between galaxy clusters can therefore not explain the void MAGNETization of the intergalactic medium, reinforcing the conventional expectation that those fields are of primordial origin.

[abstract 20 / 36] (score: 2)
arXiv:2304.13630 [pdf, ps, other]

Title: Nonlinear Hall effect in the stationary cylinder with a radial heat flux

Authors: G. S. Bisnovatyi-Kogan, M. V. Glushikhina,

Comments: 15 pages, 14 figures

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

A conducting cylinder with a uniform MAGNETic field along its axis and radial temperature gradient is considered at the stationary state. At large temperature gradients the azimuthal Hall electrical current creates the axial MAGNETic field which strength may be comparable with the original one. It is shown, that the MAGNETic field, generated by the azimuthal Hall current, leads to the decrease of MAGNETic field originated by external sources, and this suppression increases with increase of the electromotive force, connected with a thermodiffusion. Obtained results can help to investigate influence of the Hall current on the coupled MAGNETo-thermal evolution of MAGNETic and electric fields in neutron stars, white dwarfs, and, possibly, in a laboratory facilities.

[abstract 21 / 36] (score: 2)
arXiv:2409.17229 [pdf, ps, other]

Title: Environment matters: stronger MAGNETic fields in satellite galaxies

Authors: Maria Werhahn, Rüdiger Pakmor, Rebekka Bieri, Freeke van de Voort, Rosie Y. Talbot, Volker Springel,

Comments: Published in MNRAS, 2025, Vol. 540, Issue 4, pp. 3431-3440. Updated author manuscript with minor clarifications to the abstract, additional analysis in Section 3, and two new figures in new Appendices B and C (11 pages, 7 figures)

Subjects: astro-ph.GA

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Magnetic fields are ubiquitous in the universe and an important component of the interstellar medium. It is crucial to accurately model and understand their properties in different environments and across all mass ranges of galaxies to interpret observables related to MAGNETic fields correctly. However, the assessment of the role of MAGNETic fields in galaxy evolution is often hampered by limited numerical resolution in cosmological simulations, in particular for satellite galaxies. To this end, we study the MAGNETic fields in high-resolution cosmological zoom simulations of disk galaxies (with $M_{200}\approx10^{10}$ to $10^{13}\,\mathrm{M}_\odot$) and their satellites within the Auriga galaxy formation model including COSMIC RAYs. We find significantly higher MAGNETic field strengths in satellite galaxies compared to isolated dwarfs with a similar mass or star-formation rate, in particular after they had their first close encounter with their host galaxy. These are stronger on average by factors of 2-8 when compared at the same total mass, with a large scatter, ranging up to factors of $\sim$15. While this result is ubiquitous and independent of resolution in the satellites that are past their first infall, there seems to be a wide range of amplification mechanisms acting together. Our result highlights the importance of considering the environment of dwarf galaxies when interpreting their MAGNETic field properties as well as related observables such as their gamma-ray and radio emission, the latter being particularly relevant for future observations such as with the SKA observatory.

[abstract 22 / 36] (score: 2)
arXiv:2412.13889 [pdf, ps, other]

Title: X-ray Binaries: a potential dominant contributor to the COSMIC RAY spectral knee structure

Authors: Hua Yue, Jianli Zhang, Yuhai Ge, Lin Nie, Peipei Zhang, Wei Liu, YiQing Guo, Hongbo Hu,

Comments: Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

``PeVatrons" refer to astrophysical sources capable of accelerating particles to energies $\sim$PeV and higher, potentially contributing to the COSMIC RAY spectrum in the knee region. Recently, HAWC and LHAASO have discovered a new type PeVatrons -- X-ray binaries, allowing us to investigate in greater depth of the contributions of these sources to COSMIC RAYs around the knee region. There are hundreds of X-ray binaries in our galaxy observed, which are potential PeVatrons.In this work, we derive the radial distribution of X-ray binaries in the Galaxy. Then we use the DRAGON package to calculate energy spectrum, anisotropy of COSMIC RAYs as well as the resulting diffuse gamma ray emissions, after considering them as factories of COSMIC RAYs in the knee energy bands. Our findings show that the contributions from X-ray binary PeVatrons may be dominant. More X-ray binary PeVatrons can be observed by LHAASO and HAWC in the future, and will confirm the contribution of X-ray binaries to high energy COSMIC RAYs.

[abstract 23 / 36] (score: 2)
arXiv:2501.13601 [pdf, ps, other]

Title: Forecasted Detection Limits on the (Dark) Matter Density in Supermassive Black Hole Binaries for LISA

Authors: Matthias Daniel, Kris Pardo, Laura Sagunski,

Comments: 16 pages, 11 figures. v2: accepted for publication in Phys. Rev. D

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

Created: 2025-12-18; Updated: 2025-12-22; Datestamp: 2025-12-22

Supermassive BLACK HOLE binaries (SMBHBs) are among the most powerful known sources of gravitational waves (GWs). Accordingly, these systems could dominate GW emission in the micro- and millihertz frequency range. Within this domain, SMBHs evolve rapidly and merge with each other. Dynamical friction from stars and gas at the centers of galaxies typically helps to bring together two SMBHs when they are at relatively far separations ($\approx$ kpc $-$ 100 pc), but becomes less efficient at smaller separations. However, DARK MATTER (DM) spikes around SMBHs could enhance dynamical friction at close separations and, thus, shorten the evolution times. In this paper, we simulate the effects of DM spikes on GW signals in the micro- to millihertz frequency range and confirm that the GW signals from SMBHBs with DM spikes can be clearly distinguished from those without any additional matter. Making use of the projected sensitivity curve of the Laser Interferometer Space Antenna (LISA), we forecast upper limits for the (dark) matter density for given future SMBHB observations. We then compare these thresholds with the theoretical density profiles expected for self-interacting DARK MATTER (SIDM) spikes.

[abstract 24 / 36] (score: 2)
arXiv:2502.12237 [pdf, ps, other]

Title: Systematic biases in parameter estimation on LISA binaries: The effect of excluding higher harmonics for non-spinning binaries

Authors: Sophia Yi, Francesco Iacovelli, Sylvain Marsat, Digvijay Wadekar, Emanuele Berti,

Comments: 24 pages, 21 figures, 1 table; revised to match published version

Subjects: gr-qc astro-ph.HE

Created: 2025-12-18; Updated: 2025-12-22; Datestamp: 2025-12-22

The remarkable sensitivity achieved by the planned Laser Interferometer Space Antenna (LISA) will allow us to observe gravitational-wave signals from the mergers of massive BLACK HOLE binaries (MBHBs) with signal-to-noise ratio (SNR) in the hundreds, or even thousands. At such high SNR, our ability to precisely infer the parameters of an MBHB from the detected signal will be limited by the accuracy of the waveform templates we use. In this paper, we explore the systematic biases that arise in parameter estimation if we use waveform templates that do not model radiation in higher-order multipoles. This is an important consideration for the large fraction of high-mass events expected to be observed with LISA. We examine how the biases change for MBHB events with different total masses, mass ratios, and inclination angles. We find that systematic biases due to insufficient mode content are severe for events with total redshifted mass $\gtrsim10^6\,M_\odot$. We then compare several methods of predicting such systematic biases without performing a full Bayesian parameter estimation. In particular, we show that through direct likelihood optimization it is possible to predict systematic biases with remarkable computational efficiency and accuracy. Finally, we devise a method to construct approximate waveforms including angular multipoles with $\ell\geq5$ to better understand how many additional modes (beyond the ones available in current approximants) might be required to perform unbiased parameter estimation on the MBHB signals detected by LISA.

[abstract 25 / 36] (score: 2)
arXiv:2507.15720 [pdf, ps, other]

Title: Toward RELATIVISTIC inspirals into BLACK HOLEs surrounded by matter

Authors: Lukáš Polcar, Vojtěch Witzany,

Comments:

Subjects: gr-qc

Created: 2025-12-18; Updated: 2025-12-22; Datestamp: 2025-12-22

Extreme mass ratio inspirals, compact objects spiraling into massive BLACK HOLEs, represent key sources for future space-based gravitational-wave detectors such as LISA. The inspirals will occur within rich astrophysical environments containing gravitating matter. Motivated by this, we develop a fully RELATIVISTIC framework for inspirals under the gravitational influence of matter environments. Our approach employs a two-parameter perturbation expansion in the mass ratio and an environmental parameter. This yields a modified Teukolsky equation capturing the leading cross-order. We then implement a simple pole-dipole approximation of an axisymmetric environment through a thin matter shell and restrict to non-rotating BLACK HOLEs. As a result, we obtain a piecewise type D spacetime. This enables the use of Teukolsky-based methods while accounting for junction physics. The presence of the matter shell leads to effectively non-separable boundary conditions for the Teukolsky scalar and introduces mode mixing between adjacent multipoles. Additionally, the shell oscillates under the wave perturbation of the inspiral, contributing to the overall flux. The framework provides novel insights into the global dynamics of gravitational radiation in tidal environments. Furthermore, it represents a complete theoretical foundation for a future computation of inspirals and waveforms in our environmental model.

[abstract 26 / 36] (score: 2)
arXiv:2508.21582 [pdf, ps, other]

Title: Probing Picohertz Gravitational Waves with Pulsars

Authors: Qinyuan Zheng, Chiara M. F. Mingarelli, William DeRocco, Jonathan Nay, Kimberly K. Boddy, Jeff A. Dror,

Comments: 21 pages, 15 figures, 3 tables

Subjects: astro-ph.HE gr-qc

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

With periods much longer than the duration of current pulsar timing surveys, gravitational waves in the picohertz (pHz) regime are not detectable in the typical analysis framework for pulsar timing data. However, signatures of these low-frequency signals persist in the slow variation of pulsar timing parameters. In this work, we present the results of the first Bayesian search for continuous pHz gravitational waves using the drift of two sensitive pulsar timing parameters -- time derivative of pulsar binary orbital period $\dot{P}_b$ and second order time derivative of pulsar spin period $\ddot{P}$. We apply our new technique to a dataset with more than double the number of pulsars as previous searches in this frequency band, achieving an order-of-magnitude sensitivity improvement. No continuous wave signal is detected in current data; however, we show that future observations by the Square Kilometre Array will provide significantly improved sensitivity and the opportunity to observe continuous pHz signals, including the early stages of supermassive BLACK HOLE mergers. We explore the detection prospects for this signal by extending existing population models into the pHz regime, finding that future observations will probe phenomenologically-interesting parameter space. Our new Bayesian technique and leading sensitivity in this frequency domain paves the way for new discoveries in both BLACK HOLE astrophysics and the search for new physics in the early universe.

[abstract 27 / 36] (score: 2)
arXiv:2510.27188 [pdf, ps, other]

Title: Magnetically supramassive and hypermassive compact stars

Authors: Koji Uryu, Shijun Yoshida, Eric Gourgoulhon, Charalampos Markakis, Kotaro Fujisawa, Antonios Tsokaros, Keisuke Taniguchi, Mina Zamani, Lambros Boukas,

Comments: 13 pages

Subjects: gr-qc

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

It is known that the mass of MAGNETized RELATIVISTIC compact star is larger than that of non-MAGNETized one for the same equation of state and central density, albeit the excess of mass is sizable only if the MAGNETic fields are strong enough B~10^17-10^18G. Using our recently developed numerical code COCAL, we systematically compute such compact star solutions in equilibrium associated with mixed poloidal and toroidal MAGNETic fields, and show the MAGNETically supramassive solutions whose masses exceed by more than 10% of the maximum mass of the static and spherically symmetric solutions. For some extremely strong MAGNETic field configurations, we also obtain solutions more massive than the maximum mass of the uniformly rotating solutions at the Kepler (mass-shedding) limit, namely MAGNETically hypermassive solutions.

[abstract 28 / 36] (score: 2)
arXiv:2512.12130 [pdf, ps, other]

Title: Inference of Neutron Star Mass Distributions and the Equation of State from Multi-messenger Observations

Authors: Mahmudul Hasan Anik, Andrew W. Steiner, Richard O'Shaughnessy,

Comments: To be submitted to the Astrophysical Journal; contains 17 pages, 6 figures, 6 tables

Subjects: astro-ph.HE

Created: 2025-12-18; Updated: 2025-12-22; Datestamp: 2025-12-22

We construct a combined model to incorporate neutron star (NS) mass measurements with electroMAGNETic mass-radius constraints and gravitational-wave observations using Bayesian inference. We use different mass distributions for three populations depending on the companion stars: double neutron stars, NS - white dwarfs, and low-mass X-ray binaries (LMXB). To observe the effects of different parametrizations, we use two equation of state (EoS) models: a piecewise polytrope and a fixed sound-speed model at high densities in combination with a low-density EoS. Our results show that the mass distributions of these NS populations are distinct and sensitive to the EoS prior choices. In addition, we show for the first time that using a uniform prior on the observable NS maximum mass, rather than a nuisance parameter in the unknown high-density EoS, shifts the posterior maximum mass to larger values. For polytropic EoSs, the maximum mass posterior changes from $M_\mathrm{max}=2.09_{-0.07}^{+0.18} M_\odot$ to $2.15_{-0.10}^{+0.19} M_\odot$ at 90% confidence level. This change in prior also impacts the shape of the mass distribution for NSs in LMXB, shifting the posterior for the population mean from $1.51_{-0.13}^{+0.13} M_\odot$ to $1.62_{-0.12}^{+0.15} M_\odot$ at 68% confidence level.

[abstract 29 / 36] (score: 2)
arXiv:2512.17201 [pdf, ps, other]

Title: Constraining the Nanohertz Gravitational Wave Background with an X-ray Pulsar Timing Array from NICER observations

Authors: Tian-Yong Cao, Shi-jie Zheng, Shu-Xu Yi, Ming-Yu Ge, Yi-Tao Yin, Yao-Ming Duan, Xiang Yang, Wen,

Comments: 10 pages, 5 figures

Subjects: astro-ph.HE gr-qc

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

We present constraints on the nanohertz gravitational wave background (GWB) using X-ray pulsar timing data from the Neutron Star Interior Composition Explorer(\textit{NICER}). By analyzing six millisecond pulsars over a six-year observational baseline, we employed a Bayesian framework to model noise components and search for a common red signal consistent with a GWB from supermassive BLACK HOLE binaries (assuming a spectral index $γ_{\rm gwb}=13/3$). Our results show no significant evidence for a GWB, yielding a 95\% upper limit of $\log_{10}(A_{\rm gwb})<-13.4$. Weak evidence for Hellings-Downs spatial correlations was found (S=2.5), though the signal remains statistically inconclusive. Compared to radio and $γ$-ray pulsar timing arrays, the \textit{NICER} constraint is currently less stringent but demonstrates the feasibility of X-ray timing with \textit{NICER} for GWB studies and highlights the potential for improved sensitivity with future X-ray missions.

[abstract 30 / 36] (score: 2)
arXiv:2512.17204 [pdf, ps, other]

Title: A Search for Binary Black Hole Mergers in LIGO O1-O3 Data with Convolutional Neural Networks

Authors: Ethan Silver, Plamen Krastev, Edo Berger,

Comments:

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

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Since the first detection of gravitational waves in 2015 by LIGO from the binary BLACK HOLE merger GW150914, gravitational wave astronomy has developed significantly, with over 200 compact binary merger events cataloged. The use of neural networks has the potential to significantly speed up the detection, classification, and especially parameter estimation for gravitational wave events, compared to current techniques, quite important for electroMAGNETic follow-up of events. In this work, we present a machine learning pipeline using neural networks to detect gravitational wave events. We generate training data using real LIGO data to train and refine neural networks that can detect binary BLACK HOLE (BBH) mergers, and apply these models to search through LIGO's first three observing runs. We detect 57 out of the 75 total cataloged BBH events with two detectors of data in O1, O2, and O3, with 57 false positives that can mostly be ruled out with parameter inference and human inspection. Finally, we extensively test this pipeline on time-shifted data to characterize its False Alarm Rate (FAR). These results are an important step in developing machine learning-based GW searches, enabling low-latency detection and multi-messenger astronomy.

[abstract 31 / 36] (score: 2)
arXiv:2512.17214 [pdf, ps, other]

Title: Pulsed radio emission from a Central Compact Object

Authors: Lei Zhang, Alessandro Ridolfi, Di Li, Erbil Gugercinoglu, Fernando Camilo, Wynn C. G. Ho, Matthew Bailes, Ping Zhou, Craig O. Heinke, Marcus E. Lower,

Comments:

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

The high MAGNETic fields and rapid spins of young pulsars associated with SUPERNOVA remnants, such as the Crab and the Vela, established the standard pulsar model in which massive stellar explosions produce rapidly rotating, radio-luminous neutron stars. Central Compact Objects (CCOs), identified in X-rays at the centers of other remnants, challenged this view, as decades of searches yielded no radio detections. Here we show that the prototypical young CCO 1E 1207.4-5209 is in fact a faint radio pulsar rotating at the 0.4s X-ray period. Analysis of its POLARIZATION indicates that the radio beam intersects our line of sight near the MAGNETic pole, affirming its radio faintness' being intrinsic. Once its SUPERNOVA remnant dissipates, this source would be misidentified as an apparently gigayear-old pulsar. The CCO's low radio flux density may explain why many SUPERNOVA remnants lack detectable radio pulsars and suggests a hidden population of young, slowly rotating neutron stars.

[abstract 32 / 36] (score: 2)
arXiv:2512.17407 [pdf, ps, other]

Title: On the essential structure of exact traveling-wave solutions in viscoelastic flow

Authors: Lu Zhu, Rich. R. Kerswell,

Comments:

Subjects: physics.flu-dyn

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

We examine elastic travelling-wave (`arrowhead') solutions in a viscoelastic, unidirectionally body-forced flow, focusing on their existence and morphological changes as the Weissenberg number, $\mathrm{Wi}$, and streamwise duct length, $L$, are varied. We find that branch topology varies from an isola at low $L$ through a two-sided RECONNECTion at intermediate $L$ to a branch which exists at asymptotically large $\mathrm{Wi}$ for larger $L$. At intermediate $L$ more than two arrowhead solutions can coexist at a given $(\mathrm{Wi}, L)$ choice due to extra saddle node bifurcations. Secondly, the canonical arrowhead consists of two legs joined by an arched head that blocks throughflow and traps a counter-rotating vortex pair, while a polymer strand can emerge as a by-product of a strong extensional region attached/detached to the arrowhead arch. Thirdly, a minimal domain length $L_{\min}$ required to sustain an arrowhead is found to vary non-monotonically with $\mathrm{Wi}$; for $\mathrm{Wi}\ge 20$, detached-strand states control $L_{\min}$ with a relation $L_{\min}\approx 0.125\mathrm{Wi}+1.5$. And fourthly, in sufficiently long domains, the upper branch becomes a localised single arrowhead whose streamwise extent depends on $\mathrm{Wi}$, whereas the lower branch can proliferate into a train of arrowheads at high $\mathrm{Wi}$, a phenomenon not previously reported.

[abstract 33 / 36] (score: 2)
arXiv:2512.17550 [pdf, ps, other]

Title: GW231123: Overlapping Gravitational Wave Signals?

Authors: Qian Hu, Harsh Narola, Jef Heynen, Mick Wright, John Veitch, Justin Janquart, Chris Van Den Broeck,

Comments: 7 pages, 3 figures

Subjects: gr-qc astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

The recently discovered gravitational wave event GW231123 was interpreted as the merger of two BLACK HOLEs with a total mass of 190-265 $M_\odot$, making it the heaviest such merger detected to date. Whilst much of the post-discovery literature has focused on its astrophysical origins, primary analyses have exhibited considerable discrepancies in the measurement of source properties between waveform models, which cannot reliably be reproduced by simulations. Such discrepancies may arise when an unaccounted overlapping signal is present in the data, or from phenomena that produce similar effects, such as gravitational lensing or overlapping noise artifacts. In this work, we analyse GW231123 using a flexible model that allows for two overlapping signals, and find that it is favoured over the isolated signal model with Bayes factors of $\sim 10^2 - 10^{4}$, depending on the waveform model. These values lie within the top few per cent of the background distribution. Similar effects are not observed in GW190521, another high-mass event. Under the overlapping signals model, discrepancies in the measurement of source properties between waveform models are largely mitigated, and the two recovered sources show similar properties. Additionally, we find that neglecting an additional signal in overlapping-signal data can lead to discrepancies in the estimated source properties resembling those reported in GW231123.

[abstract 34 / 36] (score: 2)
arXiv:2512.17787 [pdf, ps, other]

Title: Selected topics on: 1) proposal of interpreting the Crab SUPERNOVA with a GRB 2) progress in identifying the seven GRBs episodes 3) the role of Sagittarius A in identifying the DARK MATTER component (the X fermion)

Authors: R. Ruffini, C. Sigismondi, Y. Wang, J. A. Rueda, H. Quevedo, S. Zhang, Y. Aimuratov, P. Chardonnet, M. Della Valle, C. L. Fryer, T. Mirtorabi, R. Moradi, M. Prakapenia, F. Rastegarnia, S. -S. Xue,

Comments:

Subjects: astro-ph.HE

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

As the fiftieth anniversary of our common effort in the field of RELATIVISTIC astrophysics is approaching, we offer a new look to some of our acquired knowledge in a more complete view, which evidence previous unnoticed connections. They are gaining due prominence in reaching a more complete picture evidencing the main results. We outline the history of GRB observations along with a summary of the contributions made by our group to develop the BdHN interpreting model. We show the seven Episodes characterizing the most powerful BdHNe I occurred to date: GRB 190114C and GRB 220101A. New inferences for the explanation of the highest energy radiation in the TeV are presented.

[abstract 35 / 36] (score: 2)
arXiv:2512.17811 [pdf, ps, other]

Title: Investigating the AGN variability timescale -- BLACK HOLE mass relationship with Gaia, SDSS and ZTF

Authors: Adrien Hélias, Sarah C. Gallagher, Pauline Barmby,

Comments: 16 pages, 13 figures, accepted for publication in ApJ

Subjects: astro-ph.GA

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

Active galactic nuclei (AGNs) exhibit variability in their luminosities with timescales that correlate with the mass of the BLACK HOLE at the centre of the AGN. Presently, the empirical correlation lacks sufficient precision to confidently convert these timescales into BLACK HOLE masses, especially at the low-mass end. To find more AGNs with timescale measurements, we study a very large catalog of AGNs from the Gaia Data Release 3 called GLEAN (Gaia variabLE AgN; 872228 objects). We identify GLEAN objects with optical spectra from the Sloan Digital Sky Survey DR17 and light curves from the Zwicky Transient Facility (ZTF) DR21. After fitting the light curves with a damped random walk model, we find that the GLEAN light curves have insufficient sampling to extract reliable amplitude and timescale measurements outside the range of 50-100 days. On the other hand, well-sampled ZTF light curves allow more accurate estimations of these parameters. The fractional variability amplitude is an effective, model-independent metric for measuring variability amplitude, but only when derived from high-quality light curves. We provide a catalog of 127 GLEAN AGNs with spectroscopic virial BLACK HOLE masses, and variability amplitudes and timescales. Though we do not find any low-mass BLACK HOLEs in this AGN sample, we confirm a relationship between the damped random walk timescale and the BLACK HOLE mass that is consistent with previous studies.

[abstract 36 / 36] (score: 2)
arXiv:2512.17865 [pdf, ps, other]

Title: Constraining primordial non-Gaussianity from DESI DR1 QUASARs and Planck PR4 CMB Lensing

Authors: Sofia Chiarenza, Alex Krolewski, Marco Bonici, Edmond Chaussidon, Roger de Belsunce, Will Percival, Jessica Nicole Aguilar, Steven Ahlen, Anton Baleato Lizancos, Davide Bianchi, David Brooks, Todd Claybaugh, Andrei Cuceu, Kyle Dawson, Axel de la Macorra, Peter Doel, Simone Ferraro, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Hiram K. Herrera-Alcantar, Klaus Honscheid, Dragan Huterer, Mustapha Ishak, Dick Joyce, David Kirkby, Anthony Kremin, Ofer Lahav, Claire Lamman, Martin Landriau, Laurent Le Guillou, Michael Levi, Marc Manera, Paul Martini, Aaron Meisner, Ramon Miquel, Seshadri Nadathur, Jeffrey A. Newman, Gustavo Niz, Nathalie Palanque-Delabrouille, Claire Poppett, Francisco Prada, Ignasi Pérez-Ràfols, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Hee-Jong Seo, Joseph Harry Silber, David Sprayberry, Gregory Tarlé, Benjamin Alan Weaver, Christophe Yèche, Rongpu Zhou, Hu Zou,

Comments: 42 pages, 17 figures, 11 tables. Comments are welcome

Subjects: astro-ph.CO

Created: 2025-12-19; Updated: 2025-12-22; Datestamp: 2025-12-22

We present the first measurement of local-type primordial non-Gaussianity from the cross-correlation between $1.2$ million spectroscopically confirmed QUASARs from the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI) and the Planck PR4 CMB lensing reconstructions. The analysis is performed in three tomographic redshift bins covering $0.8 < z < 3.5$, covering a sky fraction of $\sim 20\%$. We adopt a catalog-based pseudo-$C_\ell$ estimator and apply linear imaging weights validated on noiseless mocks. Compared to previous analyses using photometric QUASAR samples, our results benefit from the high purity of the DESI spectroscopic sample, the reduced noise of PR4 lensing, and the absence of excess large-scale power in the spectroscopic QUASAR auto-correlation. Fitting simultaneously for the non-Gaussianity parameter $f_{\mathrm{NL}}$ and the linear bias amplitude in each redshift bin, we obtain $f_{\mathrm{NL}} = 2^{+28}_{-34}$ for a response parameter $p=1.6$, and $f_{\mathrm{NL}} = 6^{+20}_{-24}$ for $p=1.0$. These results improve the constraints on $f_{\mathrm{NL}}$ by $\sim 35\%$ compared to the previous analysis based on the Legacy Imaging Survey DR9. Our results demonstrate the statistical power of DESI QUASARs for probing inflationary physics, and highlight the promise of future DESI data releases.