Current date: 2026-09-03

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Datestamp limit: 2026-09-03 (0 days ago)

Created/updated limit: 2026-08-27 (7 days ago)

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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-09-03&until=2026-09-03&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 755

Keyword score statistics

score 11 -- 1 abstracts

score 9 -- 1 abstracts

score 7 -- 3 abstracts

score 6 -- 2 abstracts

score 5 -- 3 abstracts

score 4 -- 6 abstracts

score 3 -- 6 abstracts

score 2 -- 21 abstracts

in total -- 43 abstracts

Articles that appeared on 2026-09-03

[abstract 1 / 43] Wow! (score: 11)
arXiv:2609.02550 [pdf, ps, other]

Title: Are JET speeds governed by accretion modes?

Authors: Hong Tu, Xinwu Cao, Andrzej A. Zdziarski,

Comments: 11 pages, 3 figures

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Relativistic JETs are observed in both stellar-mass BLACK HOLE X-ray binaries (BHXRBs) and ACTIVE GALACTIC NUCLEi (AGNs), yet their bulk Lorentz factors differ systematically---those in BLACK HOLE X-ray binaries are typically below $\sim2$, whereas AGN JETs can reach $\sim50$. The origin of this discrepancy remains unclear. Searching the literature, we compile a sample of 333 AGNs with well-measured JET component motions, consisting of 270 QUASARs, 47 BL Lac objects, 10 FR I, and 6 FR II galaxies. We find that QUASARs/FR\,IIs exhibit minimal bulk Lorentz factors ranging from $\sim$1.0 to 41.5, with a mean of 11.5 (median 9.5). In contrast, BL Lac objects/FR\,Is show $Γ_{\rm JET}\sim$1.0--21.9, averaging 4.2 (median 1.5). These values, particularly the median, closely resemble those of BHXRBs, implying a strong correlation between JET speed and accretion mode. The Lorentz factor of a MAGNETically driven JET is mainly determined by the ratio of the MAGNETic pressure to rest mass energy density at the JET base. In BL Lacs/FRIs/BHXRBs, the field is maintained by the advection-dominated accretion flow (ADAF), and the gas at the ADAF surface is MAGNETically driven into the JETs. In QUASARs/FRIIs, the field is maintained by the disc, while the JET base is connected to the corona. Our model calculations show that the disc field is always much stronger than that of the ADAF, and therefore leads to a larger $Γ_{\rm JET}$, which can explain the systematic difference in $Γ_{\rm JET}$ between these two types of sources.

[abstract 2 / 43] Wow! (score: 9)
arXiv:2609.02867 [pdf, ps, other]

Title: Magnetized accretion onto rapidly spinning binary BLACK HOLEs: mini-disk thermodynamics, MAGNETic transport, and dual JETs

Authors: Luciano Combi, Manuela Campanelli, Sean M. Ressler, Alexander J. Dittmann, Federico Cattorini,

Comments: 26 pages, 20 figures. Comments welcome!

Subjects: astro-ph.HE gr-qc

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Supermassive binary BLACK HOLEs embedded in gas-rich environments are promising multi-messenger sources for pulsar timing arrays and future space-borne gravitational-wave interferometers. Their electroMAGNETic emission is governed by nonlinear plasma dynamics around the binary and is expected to inherit variability associated with the orbital motion thereof. Because ACTIVE GALACTIC NUCLEi are intrinsically stochastic, identifying robust binary signatures requires predictive models that connect large-scale circumbinary flows to the BLACK HOLEs. Previous RELATIVISTIC simulations of accreting binaries have mostly focused on smaller separations and lower spins. We perform three-dimensional general RELATIVISTIC MAGNETohydrodynamic simulations of a relaxed, MAGNETized circumbinary disk accreting onto an equal-mass binary BLACK HOLE with a separation of $30$ gravitational radii and dimensionless spin $χ=0.9$. At these separations, the mini-disks around each BLACK HOLE are persistent mass reservoirs but still show pronounced amplitude modulations governed by the eccentric circumbinary disk and the sloshing gas between the mini-disks. We analyze how the MAGNETic flux is transported from the circumbinary disk to the horizons, launching powerful dual JETs with energy extraction efficiencies reaching $\approx 40\%$. The horizon-threading flux and JET luminosity alternate between the two BLACK HOLEs, producing an on-off dual-JET state. The wide JET funnels interact above the binary and form a persistent current sheet favorable to RECONNECTion. We explore the influence of mini-disk thermodynamics, comparing efficient and inefficient cooling inside the cavity. Hotter mini-disks are less massive, exhibit weaker coherent periodicity, and launch less luminous JETs despite comparable horizon-threading MAGNETic flux.

[abstract 3 / 43] Wow! (score: 7)
arXiv:2509.03576 [pdf, ps, other]

Title: How similar are narrow-line Seyfert 1 galaxies and high-z type 1 AGN?

Authors: Marco Berton, Emilia Järvelä, Alessia Tortosa, Chiara Mazzucchelli,

Comments: 18 pages, 8 figures. Published in the Open Journal of Astrophysics

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

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

The recent observations of highly accreting supermassive BLACK HOLEs (SMBH) at very high redshift ($z>$4) with the James Webb Space Telescope (\textit{JWST}) allowed us to shed light for the very first time on the early evolutionary phases of ACTIVE GALACTIC NUCLEi (AGN). Perhaps unsurprisingly, several of the physical properties observed in these new objects, including those known as little red dots (LRDs), are closely reminiscent of the low-mass and high-Eddington AGN in the local Universe, and in particular of the class of narrow-line Seyfert 1 (NLS1) galaxies. However, some differences also emerged, likely due to the radically different evolutionary path and the environment where LRDs and NLS1s live. In this work, we review the multiwavelength properties of local NLS1s and briefly compare them with type 1 AGN found at high-$z$, showing that despite some differences, the study of NLS1s can be extremely useful to better understand the extreme accretion physics of high-$z$ QUASARs and the early stages of AGN evolution. The goal of this review is to provide the high-z community a handbook to compare their new sources with those already known in the local Universe, and to give the low-z community a starting point to venture in the early phases of AGN evolution.

[abstract 4 / 43] Wow! (score: 7)
arXiv:2603.23144 [pdf, ps, other]

Title: The Persistent Radio Sources and Multi-wavelength Counterparts of Fast Radio Bursts in Massive Binary Systems

Authors: Z. Y. Zhao, Q. Wu, F. Y. Wang, Z. G. Dai,

Comments: 40 pages, 13 figures, 2 tables, accepted for publication in ApJ

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Fast radio bursts (FRBs) are millisecond-duration pulses originating from cosmological distances. Multi-wavelength counterparts associated with FRBs are important for unveiling their physical origins. Recent observations provide strong evidence that the sources of some active FRBs are residing in massive star binaries. In this paper, we study the electroMAGNETic counterparts of FRBs, including persistent radio sources (PRSs) and multi-wavelength emission from MAGNETar wind nebulae (MWNe) or bow shocks in massive binary systems. We find that the PRSs with luminosity $10^{38}-10^{39}$ erg s$^{-1}$ can be generated by young MWN. The age of MAGNETars is a few decades. The observed long-term variation of flux density for PRSs can be explained by the internal MAGNETic field decay of MAGNETars. The bow shock radiation can account for the less luminous PRS with the luminosity $\lesssim 10^{36}$ erg s$^{-1}$. Magnetically powered nebulae may yield detectable keV SYNCHROTRON self-Compton (SSC) X-rays out to $\lesssim 20$ Mpc, whereas rotation-powered systems mainly produce GeV SSC emission detectable only within $\lesssim 0.1$ Mpc. For active MAGNETars in massive binaries, enhanced wind interaction can generate SYNCHROTRON X-rays detectable within $\lesssim 50$ Mpc and GeV-TeV inverse-Compton emission detectable within $\lesssim 1-0.1$ Mpc.

[abstract 5 / 43] Wow! (score: 7)
arXiv:2609.02681 [pdf, ps, other]

Title: Multiwavelength View of Black Hole X-ray Binary SWIFT J151857.0-572147

Authors: Manoj Mandal, Sachindra Naik, Souvik Manik, Sabyasachi Pal,

Comments: Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We investigate multiwavelength timing and spectral properties of the newly discovered BLACK HOLE X-ray binary SWIFT J151857.0-572147 during its 2024 outburst using observations from AstroSat, NUSTAR, NICER, SWIFT, and MeerKAT. The AstroSat/LAXPC20 power density spectrum reveals a $\sim$8 Hz low-frequency QPO with a quality factor of $\sim2.8$. The broadband X-ray spectrum of the source exhibits prominent reflection features, which are modeled to constrain the geometry and physical properties of the accretion disk. The spectral analysis indicates that the source was in the soft/intermediate spectral state, characterized by a steep power law with a photon index of $Γ\approx 2.6$ and a relatively high disk temperature of $\sim0.9$ keV. The reflection modeling suggests a disk inclination of $23-31^{\circ}$ and a highly ionized accretion disk with $\logξ\sim 3.3$-4.0. The MeerKAT monitoring revealed a strong radio variability that closely tracked the hard X-ray evolution, including a bright radio flare during the hard-to-soft state transition, supporting close coupling between the accretion flow and JET activity. Using the quasi-simultaneous AstroSat, SWIFT/XRT and MeerKAT observations, we investigated the radio/X-ray correlation and found that SWIFT J151857.0-572147 follows the established $L_{\rm X}$-$L_{\rm R}$ relation for Galactic BLACK HOLE X-ray binaries. Its location in the $L_{\rm X}$-$L_{\rm R}$ plane is consistent with that of Galactic BLACK HOLE X-ray binaries, further supporting its BLACK HOLE nature.

[abstract 6 / 43] Yes (score: 6)
arXiv:2609.02742 [pdf, ps, other]

Title: An Exact Engine for Black-Hole Jets

Authors: Yu Wang,

Comments: 17 pages, 5 figures, 1 table. Invited submission to the inaugural issue of "Astronomy Communications", published by the Purple Mountain Observatory, Chinese Academy of Sciences (PMO, CAS) and the University of Science and Technology of China (USTC)

Subjects: astro-ph.HE gr-qc

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

For fifty years the Blandford--Znajek mechanism has been a mechanism and not an exact solution: force-free electrodynamics on a prescribed metric, with the JET's own field carrying no weight. Here that field gravitates. A split monopole weighs as much as a MAGNETic monopole, so its self-gravity is the MAGNETic Reissner--Nordström geometry; two copies glued across an equatorial current sheet put hole, disk and JET-driving flux into one spacetime, and force-free plasma makes a MAGNETosphere of it. Three things then follow that no test-field calculation can see. First, a steady JET is impossible. A stationary horizon cannot be heated but a slipping MAGNETosphere necessarily heats it, so the only stationary state is a dead one corotating with the hole, and a working JET is a BLACK HOLE in decay at rates the field equations fix rather than assume. Second, flux enters the laws of black-hole mechanics as a charge, sharing one extremality budget with spin. That budget caps the JET power at $c^5/48G$ whatever the mass. Third, the lifetime output is finite: a maximally spinning hole delivers $1-e^{1/4}/\sqrt2=9.2\%$ of its mass and grows its horizon area by exactly $\sqrt e$. The horizon's own moment of inertia vanishes with the irrational exponent $(\sqrt{17}-1)/2$ set by the near-horizon throat, and what is left is a rotating hole whose angular momentum has passed to its own field.

[abstract 7 / 43] Yes (score: 6)
arXiv:2609.02853 [pdf, ps, other]

Title: LHAASO-WCDA observed a $\sim$ 5 days TeV-delayed flaring event in BLAZAR 1ES 1959+650

Authors: Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, J. Blunier, A. V. Bukevich, C. M. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, E. S. Chen, G. H. Chen, H. K. Chen, L. F. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, X. B. Chen, X. J. Chen, X. P. Chen, Yang Chen, Yong Chen, N. Cheng, Q. Y. Cheng, Y. D. Cheng, Y. H. Chi, M. Y. Cui, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, L. X. Dai, Z. G. Dai, Danzengluobu, Y. X. Diao, A. J. Dong, X. D. Duan, J. H. Fan, Y. Z. Fan, J. Fang, J. H. Fang, K. Fang, C. F. Feng, H. Feng, L. Feng, S. H. Feng, X. T. Feng, Y. Feng, Y. L. Feng, S. Gabici, B. Gao, Q. Gao, W. Gao, C. Ge, M. M. Ge, T. T. Ge, L. S. Geng, G. Giacinti, G. H. Gong, Q. B. Gou, M. H. Gu, W. M. Gu, F. L. Guo, J. Guo, K. J. Guo, X. L. Guo, Y. Q. Guo, R. P. Han, O. A. Hannuksela, M. Hasan, H. H. He, H. N. He, J. Y. He, X. Y. He, Y. He, S. Hernández-Cadena, C. Hou, X. Hou, H. B. Hu, S. C. Hu, D. H. Huang, F. Huang, J. J. Huang, X. L. Huang, X. T. Huang, X. Y. Huang, Y. Huang, Z. J. Huang, A. Inventar, X. L. Ji, H. Y. Jia, K. Jia, S. M. Jia, H. B. Jiang, K. Jiang, X. W. Jiang, Z. J. Jiang, C. C. Jin, M. Jin, S. Kaci, M. M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, K. Kurinov, W. H. Lei, Cheng Li, C. K. Li, Cong Li, D. Li, F. Li, H. B. Li, H. C. Li, Jian Li, Jie Li, K. Li, L. Li, R. L. Li, T. Y. Li, W. L. Li, X. R. Li, X. Y. Li, Y. Li, Zhe Li, Zhuo Li, E. W. Liang, Y. F. Liang, S. J. Lin, B. Liu, C. Liu, D. Liu, D. B. Liu, H. Liu, J. Liu, J. L. Liu, J. R. Liu, M. Y. Liu, Q. Liu, R. Y. Liu, S. M. Liu, T. Liu, W. Liu, Y. Liu, Y. Liu, Yuan Liu, Y. N. Liu, Y. Q. Lou, Q. Luo, Y. Luo, H. K. Lv, B. Q. Ma, L. L. Ma, X. H. Ma, I. O. Maliy, J. R. Mao, Z. Min, W. Mitthumsiri, Y. Mizuno, G. B. Mou, A. Neronov, C. -Y. Ng, K. C. Y. Ng, M. Y. Ni, L. Nie, L. J. Ou, Z. W. Ou, H. W. Pan, P. Pattarakijwanich, Z. Y. Pei, D. Y. Peng, J. C. Qi, M. Y. Qi, J. J. Qin, H. Qu, A. Raza, C. Y. Ren, M. Q. Ruan, D. Ruffolo, A. Sáiz, D. Savchenko, D. Semikoz, L. Shao, O. Shchegolev, Y. Z. Shen, X. D. Sheng, F. W. Shu, H. C. Song, Yu. V. Stenkin, Y. Su, C. Y. Sun, D. X. Sun, H. Sun, J. X. Sun, M. Sun, Q. N. Sun, X. N. Sun, Z. B. Sun, N. H. Tabasam, J. Takata, P. H. T. Tam, H. B. Tan, Q. W. Tang, R. Tang, Z. B. Tang, L. Tao, W. W. Tian, C. N. Tong, L. H. Wan, C. Wang, D. H. Wang, G. W. Wang, H. G. Wang, J. C. Wang, J. F. Wang, J. S. Wang, K. Wang, Kai Wang, Kai Wang, L. P. Wang, L. Y. Wang, W. Wang, X. G. Wang, X. J. Wang, X. Y. Wang, Y. Wang, Y. D. Wang, Z. H. Wang, Z. X. Wang, Zheng Wang, D. M. Wei, J. J. Wei, Y. J. Wei, T. Wen, S. S. Weng, C. Y. Wu, H. R. Wu, Q. W. Wu, S. Wu, X. F. Wu, Y. S. Wu, S. Q. Xi, J. Xia, G. M. Xiang, D. X. Xiao, G. Xiao, Y. F. Xiao, B. H. Xie, F. Xie, Y. L. Xin, H. D. Xing, Y. Xing, D. R. Xiong, B. N. Xu, C. Y. Xu, D. L. Xu, R. X. Xu, S. S. Xu, L. Xue, D. H. Yan, T. Yan, C. Yang, C. Y. Yang, F. F. Yang, L. L. Yang, M. J. Yang, R. Z. Yang, W. X. Yang, Z. H. Yang, Z. G. Yao, X. A. Ye, L. Q. Yin, N. Yin, X. H. You, Z. Y. You, Y. H. Yu, Q. Yuan, W. M. Yuan, H. Yue, H. D. Zeng, T. X. Zeng, W. Zeng, X. T. Zeng, M. Zha, B. Zhang, B. B. Zhang, B. T. Zhang, C. Zhang, H. Zhang, H. M. Zhang, H. Y. Zhang, J. Zhang, J. L. Zhang, J. Y. Zhang, L. Y. Zhang, Li Zhang, P. F. Zhang, R. Zhang, R. Y. Zhang, S. R. Zhang, S. S. Zhang, S. Y. Zhang, W. Zhang, X. Zhang, X. L. Zhang, X. P. Zhang, Yi Zhang, Yong Zhang, Z. P. Zhang, H. S. Zhao, J. Zhao, L. Zhao, L. Z. Zhao, X. H. Zhao, F. Zheng, T. C. Zheng, B. Zhou, H. Zhou, J. N. Zhou, L. Zhou, M. Zhou, P. Zhou, R. Zhou, X. X. Zhou, X. X. Zhou, B. Y. Zhu, C. G. Zhu, F. R. Zhu, H. Zhu, K. J. Zhu, Y. F. Zhu, Z. F. Zhu, Y. C. Zou, X. Zuo,

Comments: 15 pages,5 figures

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We report a day-scale hard lag between GeV and TeV $γ$-ray emission from the HBL 1ES~1959+650 in early 2024. Since the LHAASO-WCDA real-time monitoring system began operation in late 2023, multiple TeV flares from this source have been triggered, including the 1st trigger flare on 2024 February 9. A Bayesian-block analysis of the WCDA light curve identifies three TeV flares in 2024. For the second triggered flare, a discrete cross-correlation analysis reveals a $>3\,σ$ correlation (relative to uncorrelated red-noise simulations) at a time delay of $Δt = 5.0_{-2.1}^{+2.1}$ days, with the TeV emission lagging the GeV. Time-resolved spectroscopy shows that this flare has the softest TeV spectrum among these flares (intrinsic spectral index $Γ=3.16\pm0.18$), while the 1st trigger flare is harder ($Γ=2.48\pm0.21$). The observed five-day hard lag is difficult to reconcile with a purely cooling-driven temporal ordering and is consistent with scenarios in which particle energization and/or transport may contribute to the evolution. However, the current data do not uniquely identify the underlying mechanism.

[abstract 8 / 43] Yes (score: 5)
arXiv:2607.05245 [pdf, ps, other]

Title: Geminga and Monogem in the CTAO Era: Probing TeV Halos and Cosmic-Ray Transport

Authors: Youyou Li, Oscar Macias, Manuela Vecchi, Shinichiro Ando,

Comments:

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

TeV halos around Geminga and Monogem (B0656+14) reveal regions of strongly suppressed diffusion near middle-aged pulsars. Determining the sizes and MAGNETic-field strengths of these slow-diffusion zones is important for modelling lepton transport and assessing their contribution to the local positron excess. The Cherenkov Telescope Array Observatory (CTAO) will provide arcminute-scale imaging of extended gamma-ray emission. We construct two-zone diffusion models for Geminga and Monogem with GALPROP v57, injecting electrons and positrons according to the pulsar spin-down history and following their propagation through an evolving slow-diffusion bubble and the ambient interstellar medium. Calibrating to HAWC and FERMI-LAT measurements, we forward-fold the models through official CTAO instrument response functions, including realistic diffuse and instrumental backgrounds. For 50 h observations, both halos are detected with high significance ($\sim 13$--$30,σ$) from either site. Under optimistic background assumptions, CTAO can distinguish changes of $Δγ_1 \simeq 0.2$ in the high-energy injection index and $ΔB \simeq 2,μ{\rm G}$ in MAGNETic-field strength. For Monogem, compact bubbles with $R_{\rm SDZ}\approx30,{\rm pc}$ can be distinguished from extended ($\gtrsim50,{\rm pc}$) cases, although very large bubbles remain degenerate because of the finite field of view. Using an alternative Galactic diffuse template in the fit changes detection significances and parameter sensitivities by $\lesssim10%$, indicating robustness against plausible diffuse-background mismodelling.

[abstract 9 / 43] Yes (score: 5)
arXiv:2609.02151 [pdf, ps, other]

Title: Electron acceleration by turbulent RECONNECTion in solar flares

Authors: Zining Ren, Xin Cheng, Yulei Wang, Mingde Ding,

Comments: 13 pages, 9 figures; Accepted for publication in ApJ

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Solar flares can release MAGNETic energy explosively in the corona and produce high-energy particles on short timescales. However, how and where these particles are accelerated remains an open question. Here, we investigate the acceleration and transport of electrons during self-developed three-dimensional turbulent RECONNECTion of solar flares by solving Parker's transport equation in the framework of high-resolution MHD simulations. We find that thermal electrons at both the flare current sheet and loop top are rapidly accelerated up to ~90keV, with energy spectra exhibiting a power-law feature. Although the population of accelerated electrons at the flare loop top is larger than that at the current sheet, their spectral indices are similar, close to the values usually observed. More importantly, the acceleration is achieved by turbulence-driven compression structures of various scales rather than the supposed termination shock, particularly at the flare loop top. A portion of compression structures even forms shocks. These results highlight the critical role of turbulent RECONNECTion in accelerating electrons, thereby shedding new light on the acceleration and transport of particles in other high-energy phenomena.

[abstract 10 / 43] Yes (score: 5)
arXiv:2609.02533 [pdf, ps, other]

Title: Stars as triggers of interstellar gas entrainment in RELATIVISTIC JETs

Authors: B. Longo, M. Perucho, J. M. Martí, V. Bosch-Ramon, Y. Hoche,

Comments:

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Low-power extragalactic JETs are known to be decelerated and dissipate large amounts of energy within their host galaxies. However, the exact process by which this occurs is still elusive. The aim of this work is to probe the role of stars as triggers of JET mass-loading, deceleration and dissipation in Fanaroff-Riley type I RADIO GALAXies. This is motivated by a theoretical model that proposes that stars interacting with the JET boundaries could facilitate entrainment of interstellar medium (ISM) gas into JETs, favouring mixing and dissipation. We have performed a numerical experiment of stars entering a RELATIVISTIC flow, using a RELATIVISTIC hydrodynamics code. Our setup is limited to the interaction of three stars with the JET boundary, in order to assess the results in a limited, controlled, environment, although this number of stars may be plausible in the inner kpc-region of a massive galaxy. Our results allow us to estimate the amount of entrained ISM gas as the stars enter the JET. We show that the entrainment temporally induced on scales of tens of parsecs and thousands of years by evolved stars is comparable to the initial JET mass rate. The way in which this entrainment happens is by the creation of a low pressure region behind the stellar objects, which drags ambient gas into the JET flow. Our results confirm that stars interacting with the JET boundaries, and acting as catalysts of ISM/shear gas entrainment, can significantly contribute to JET mass-load and deceleration.

[abstract 11 / 43] Yes (score: 4)
arXiv:2605.13011 [pdf, ps, other]

Title: No Measurable Changes in Radio and X-ray Emission Surrounding Glitches in the Young Pulsar PSR J2229+6114

Authors: Wenke Xia, Robert A. Main, Mason Ng, Victoria M. Kaspi, Jason W. Hessels, Alyssa Cassity, Abigail K. Denney, Emmanuel Fonseca, Deborah C. Good, Ajay Kumar, Lars Kunkel, Bradley W. Meyers, Aaron B. Pearlman, Ingrid Stairs,

Comments: 14 pages, 8 figures. Accepted for publication in ApJ

Subjects: astro-ph.HE

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

We present our first result from an ongoing pulsar glitch monitoring campaign at the Canadian Hydrogen Intensity Mapping Experiment (CHIME), in which we analyzed the radio and X-ray emission surrounding four glitches in PSR~J2229+6114. Using daily CHIME observations, we detected a glitch in PSR~J2229+6114 in near-real time and triggered an X-ray follow-up with the Nuclear Spectroscopic Telescope Array (NUSTAR) two days after the glitch. We identified three additional glitch events in archival CHIME/Pulsar observations that coincided with an independent X-ray observing campaign with the Neutron star Interior Composition Explorer (NICER).. Our data show there is no measurable change in the source's X-ray and radio emission during the four glitch events, in stark contrast to the post-glitch activity in high-MAGNETic-field, rotation-powered pulsars (RPPs), which have been observed to exhibit MAGNETar-like X-ray outbursts immediately after large glitches. Those high-MAGNETic-field (high-$B$) RPPs are considered transitional objects between ordinary RPPs and MAGNETars, thereby leading to a unifying neutron star model in which the inferred dipolar surface MAGNETic field strength serves as a unifying parameter. However, such a model remains challenged, in part, by the lack of constraints near the low-$B$ end of the high-$B$ regime, and our result provides additional evidence that MAGNETar-like post-glitch activity is likely more common among high-$B$ RPPs.

[abstract 12 / 43] Yes (score: 4)
arXiv:2606.02748 [pdf, ps, other]

Title: Elemental COSMIC RAY spectra reveal two populations of Galactic sources and an immediate transition to an extragalactic component after the knee

Authors: Timur A. Dzhatdoev, Anatoly A. Semenov,

Comments: 13 pages, 11 figures, 3 tables. Joint fit added (Sect. 5); some mistakes corrected in Discussion/Conclusions

Subjects: astro-ph.HE

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

The energy spectra for individual elements and/or for groups of elements in COSMIC RAYs (CR) in the energy range between 100 $\times$ Z GeV and 10$^{3}$ $\times$ Z PeV (where Z is the charge number of the nucleus) have a number of features, including two steepenings ("knees") with the rigidity-dependent energies $E_{k1} \approx$ 15 $\times$ Z TeV and $E_{k2} \approx$ 3 $\times$ Z PeV and three hardenings ("ankles") at $E_{a1} \approx$ 500 $\times$ Z GeV; for protons $E_{a2-p} \approx$ 150 TeV and $E_{ a3-p} \approx$ 50 PeV. While the values of $E_{a1}$ for different nuclei are rigidity-dependent, the values of $E_{a2}$ (and probably of $E_{a3}$) are not: $E_{a2-He} \approx$ 1 PeV for Helium. The recent advances in precision measurements of the elemental CR spectra in the DAMPE and LHAASO experiments, and, to some extent, in IceTop and other experiments, make it possible, for the first time, to clarify the origin of the aforementioned spectral features. We show that the elemental CR spectra are reasonably well described with a sum of three components: 1) a low-energy Galactic component with a convex spectral shape reflecting the accelerated particle spectrum in the source; this component peters out after the TeV knee, 2) a high-energy Galactic component including the PeV knee, and 3) an extragalactic component. There is no need for any third, additional component of Galactic COSMIC RAYs in the energy range between 10 PeV and 1 EeV.

[abstract 13 / 43] Yes (score: 4)
arXiv:2609.00613 [pdf, ps, other]

Title: Nanohertz Gravitational-Wave Constraints on Supermassive Binary Black Holes at Cosmic Dawn

Authors: Yiqin Chen, Shi-Yi Zhao, Xingjiang Zhu, N. D. Ramesh Bhat, Jacob Cardinal Tremblay, Małgorzata Curyło, Valentina Di Marco, George Hobbs, Wenhua Ling, Rami F. Mandow, Richard N. Manchester, Saurav Mishra, Daniel J. Reardon, Sparrow Roch, Christopher J. Russell, Ryan M. Shannon, Jingbo Wang, Shuangqiang Wang, Andrew Zic,

Comments: 9 pages, 4 figures; Accepted for publication in PRL

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

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

Standard continuous gravitational-wave searches with pulsar timing arrays (PTAs) neglect cosmological redshift, restricting their applicability to the local Universe. We introduce a redshift-aware PTA framework and apply it to the Parkes PTA Data Release 3, deriving the first direct constraints on supermassive binary BLACK HOLEs (SMBBHs) at the cosmic dawn. Evaluating our limits across a broad redshift range, we observationally establish the non-monotonic mass-redshift exclusion boundary driven by the theoretical ``redshift bias", demonstrating how PTAs can effectively probe sources at extreme distances. Redshift-aware targeted searches toward high-redshift systems, including the ultraluminous QUASAR J0100+2802 ($z=6.327$) and the JWST-discovered galaxy JADES-GS-z14-0 ($z=14.32$), rigorously exclude SMBBHs with chirp masses $\mathcal{M}_c \gtrsim 10^{10} M_\odot$ across the nanohertz frequency band. Finally, we demonstrate that high-redshift binaries can be robustly detected and localized, allowing for the accurate measurement of their intrinsic properties. Our results provide the tightest constraints to date on SMBBHs at $z > 6$ and establish a practical framework for probing early-Universe BLACK HOLE assembly.

[abstract 14 / 43] Yes (score: 4)
arXiv:2609.01711 [pdf, ps, other]

Title: JWST Reveals a Candidate Supermassive Black Hole Binary at z=4.3 in the Brightest Sub-millimeter Galaxy in COSMOS-Web

Authors: Jed McKinney, Ansh Gupta, Julian B. Munoz, John Chisholm, Caitlin M. Casey, Stephanie M. Urbano Stawinski, Olivia Cooper, Erini Lambrides, Hollis Akins, Maximilien Franco, Archana Aravindan, Seiji Fujimoto, Kohei Inayoshi, Andreas L. Faisst, Jeyhan S. Kartaltepe, Michael Boylan-Kolchin,

Comments: 17 pages, 12 figures, accepted to ApJL

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

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

We present JWST/NIRSpec PRISM and G395M grating spectroscopy for AzTEC-1, a massive sub-mm bright galaxy at $z=4.34$ in the COSMOS extragalactic field. The PRISM spectrum reveals strong H$α$, a significant Balmer break, and no H$β$ detection, indicating a $100-400$ Myr-old stellar population and high dust attenuation. BPT line ratios indicate the presence of an Active Galactic Nucleus (AGN). Decomposing narrow and broad line components, we recover broad, blueshifted H$α$ with a velocity offset of $1245{\,\rm km\,s^{-1}}$ from the systemic narrow line velocity and with FWHM$\,\sim2500\,{\rm km\,s^{-1}}$. AzTEC-1's smooth morphology and stellar age is suggestive of a past merger-induced starburst period that would have brought in a second supermassive BLACK HOLE, raising the possibility for a binary supermassive BLACK HOLE system. In this scenario, we assume that the lower mass BLACK HOLE hosts a broad line region orbiting a quiescent primary. Evidence for an extended outflow is not found in the 2D spectrum, NIRCam imaging, resolved ALMA observations of dust continuum, or CO, [C II]$_{157\,μ\rm m}$ and [N II]$_{\rm 205\,μm}$ kinematics. AzTEC-1's high central gas mass surface density and dynamically unstable gas disk indicates that massive gas clouds external to the candidate binary SMBH's orbit might have played a role in stalling infall from $\sim10$ Myr to $\sim100$ Myr through dynamical torques, which has been theorized to occur in the nuclei of massive galaxies like AzTEC-1. If the supermassive BLACK HOLE binary is confirmed, AzTEC-1 would be an excellent laboratory into the astrophysics driving low-frequency gravitational wave detections.

[abstract 15 / 43] Yes (score: 4)
arXiv:2609.01977 [pdf, ps, other]

Title: Inflationary Magnetogenesis with f(R) Gravity: Dynamics, Constraints, and Observational Signatures during Reheating

Authors: Shuang Liu, Bo-yu Zhao, Yu Li, Yao-chuan Wang,

Comments: 13 pages, 8 figures

Subjects: astro-ph.CO gr-qc

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Inflationary MAGNETogenesis provides a promising mechanism for generating primordial large-scale MAGNETic fields, but faces challenges. In this paper, we extend the Ratra model to a non-minimal $f(R)$ gravity framework, appearing in the Lagrangian in the form $f^2(η) F_{μν}F^{μν}$, to break the conformal invariance of the standard electroMAGNETic action. Focusing on the post-inflationary reheating epoch, we derive analytic expressions for the MAGNETic and electric energy density spectra by constructing a broken-power-law evolution for the scale factor and the coupling function across the inflation-to-reheating transition. Three key theoretical constraints are imposed on the model parameter space: the strong coupling condition, the backreaction constraint, and the CMB isotropy requirement. Through numerical calculations, we obtain predictions for the present-day MAGNETic field strength $B_0$ and coherence length $L_{c0}$ for various combinations of the inflationary energy scale $H_f$ and the reheating temperature $T_r$. We further incorporate the nonlinear effects of MAGNETohydrodynamic (MHD) turbulence after reheating, including the inverse transfer process, which significantly enhances the coherence length (up to $0.1$ Mpc) while reducing the field strength by several orders of magnitude. By comparing with observational constraints from radio observations and FERMI-LAT gamma-ray data, we demonstrate that the inflationary energy scale $H_f$, the reheating temperature $T_r$, the parameter $β$, and the e-folds numbers $N_f$, $N_r$ must satisfy stringent joint constraints. This work provides a viable theoretical framework for inflationary MAGNETogenesis that simultaneously satisfies theoretical consistency conditions and current observational bounds.

[abstract 16 / 43] Yes (score: 4)
arXiv:2609.02619 [pdf, ps, other]

Title: Vortex promoters in MHD duct flow

Authors: Andreu Queralt, Dmitry Krasnov, Yuri Kolesnikov, JörgSchumacher,

Comments:

Subjects: physics.flu-dyn

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We use 3D direct numerical simulations to study the effects of vortex promoters in liquid metal duct flow to sustain Q2D states which are formed in the presence of strong MAGNETic fields, such as those present in cooling blankets of fusion reactors. Both for electrically insulating and conducting walls. In case of insulating walls, disturbances are found to be sustained. For conducting walls, the disturbances may be extinguished immediately and replaced by a Walker- or Hunt-type flow with its own JET-detachment instability. Furthermore, we add heat transfer by imposing constant heat flux at the Shercliff walls. We classify and compare possible configurations with respect to their turbulent transport properties. For conducting ducts, no additional effect is observed. For insulating ducts in horizontal position, we observe a small effect. For vertical ducts, the buoyancy forces have a significant impact due to buoyancy-driven instabilities, which produce intermittent fluctuations. The analysis of the turbulent kinetic energy (TKE) and the Nusselt number show that flows with the largest TKE may not have the best heat transfer performance. This is caused by side JETs removing heat faster than mixing the bulk flow. The buoyancy force and wall conductance ratio are found to play a key role in determining the flow structure. Part of our work is a parametric study at fixed Reynolds, Hartmann and Prandtl numbers, which allows us eventually to compose a phase diagram showcasing the different flow regimes.

[abstract 17 / 43] (score: 3)
arXiv:2604.20971 [pdf, ps, other]

Title: Chaotic migration of LISA Extreme Mass Ratio Inspirals in a turbulent accretion disk: effect on waveform de-phasing

Authors: Mudit Garg, Lucio Mayer, Yinhao Wu, Yacine Ali-Haïmoud, Douglas N. C. Lin,

Comments: Accepted by ApJL. 16 pages, 5 figures

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Gravitational wave (GW) detector LISA will observe near-coalescence extreme mass ratio inspirals (EMRIs), which typically form in galactic central accretion disks. Torques from the disk can alter the GW-driven inspiral trajectory of an embedded EMRI from the vacuum expectation, leading to potentially observable GW dephasing ($Δψ_{\rm gas}$). So far, all studies compute $Δψ_{\rm gas}$ for a thin, laminar disk, with negligible flow turbulence, whereby the disk exerts the well-understood linear torque ($T_{\rm lin}$). However, these disks must be turbulent due to MAGNETo-rotational instability in the inner regions. Hence, we present a proof-of-concept general prescription for the turbulent torque ($T_{\rm turb}$) acting on an EMRI by modeling it as a Gaussian distribution around $T_{\rm lin}$, inspired by recent global simulations that study such torques. We compute $Δψ_{\rm gas}$ for the ``golden'' circular EMRI with total source mass $M=10^6~{\rm M}_\odot$ and mass ratio $q=5\times10^{-5}$ in its final four-year evolution at redshift $z=0.276$ and signal-to-noise ratio (SNR) $=50$ by varying turbulence amplitude $C$ ($=1$ in the aforementioned study), maximum correlation timescale ($N_{\rm max}$), Eddington ratio ${\rm f}_{\rm Edd}$, disk aspect ratio $h_0$, and turbo-viscous coefficient $α$ in a reasonable parameters space. For $N_{\rm max}=100$ orbits, we find that for $C\gtrsim{10}$, ${\rm f}_{\rm Edd}\gtrsim0.3$, $h_0\gtrsim0.03$, and $α\gtrsim0.1$, dephasings due to $T_{\rm lin}$ are unobservable but could become detectable ($Δψ_{\rm gas}>8/$SNR) if EMRIs experience turbulent torques. Hence, this work motivates running MHD simulations of accretion disks with embedded early-inspiral LISA EMRIs over long timescales to understand the imprint of the turbulent environment on their orbital parameters and gravitational waveforms.

[abstract 18 / 43] (score: 3)
arXiv:2606.10283 [pdf, ps, other]

Title: First Principles Magnetohydrodynamical Theory for the Expanding Box Model: Effects on Expansion-Induced Alfvén Wave Reflection

Authors: Sebastián Saldivia, Nicolás Villarroel-Sepúlveda, Sebastián Echeverría-Veas, Felipe A. Asenjo, Pablo S. Moya,

Comments: 21 pages, 5 figures

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

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

The Expanding Box Model (EBM) has been widely employed to simulate multiscale plasma phenomena in the expanding solar wind by transforming the MHD equations to a co-moving, non-inertial frame. However, traditional formulations have suffered from historical ambiguity regarding the physical separation between the co-moving and inertial reference frames, primarily arising from a classical approximation of an invariant MAGNETic field between them. To resolve this inconsistency, we reformulate the EBM from first principles using a fully covariant approach. Here, we model the expanding solar wind frame as an anisotropic expanding spacetime metric, allowing us to incorporate radial acceleration profiles and differential transverse expansion, ensuring that all physical fields are correctly transformed by expansion. We demonstrate that asymmetries identified in previous EBM-MHD literature are direct consequences of neglecting the tensorial scaling of the MAGNETic field. Our covariant treatment eliminates these residues, restoring symmetry in the co-moving frame. Projecting our system back into the inertial frame clarifies the distinction between local plasma dynamics and plasma expansion, revealing the anisotropy of the Parker spiral as a geometric projection. Furthermore, linear wave analysis using Elsässer variables reveals that plasma expansion induces a low-frequency cutoff and geometric damping. Numerical integration demonstrates that expansion drives the reflection of Alfvén waves, generating counter-propagating modes primarily at low frequencies relative to the expansion rate, while high frequencies converge to the WKB approximation. This provides a consistent foundation for simulations, establishing that expansion can serve as a source of counter-propagating waves necessary to drive solar wind turbulence at low frequencies.

[abstract 19 / 43] (score: 3)
arXiv:2606.24706 [pdf, ps, other]

Title: IAU Symposium 405: Traversing the Galactic Center in Space and Time

Authors: Michal Zajaček, Bożena Czerny, Martin Mondek, Samik Mitra, Matúš Labaj, Tomáš Ondro, Jan Janík, Jiří Dušek,

Comments: 5 pages, 1 figure, concise meeting report of the Galactic Center workshop 2026 (IAU Symposium 405, https://gc2026.muni.cz/); accepted version, in print in Nature Astronomy

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

The Galactic Center is often identified with its central supermassive BLACK HOLE, Sgr A*. Yet the BLACK HOLE governs gravitationally only the innermost few parsecs of the Milky Way, while the surrounding Nuclear Star Cluster, Nuclear Stellar Disc and Central Molecular Zone (CMZ) shape the dynamics of stars and gas on progressively larger scales. Understanding how these components interact is essential not only for reconstructing the history of our own Galaxy, but also for interpreting galactic nuclei more generally.

[abstract 20 / 43] (score: 3)
arXiv:2609.02240 [pdf, ps, other]

Title: Instabilities in Cylindrical Geometry Using the Minimalist Approach: Formalism and Rotational Instabilities

Authors: Nektarios Vlahakis,

Comments: Accepted for publication in Universe

Subjects: physics.plasm-ph astro-ph.HE astro-ph.SR physics.flu-dyn

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

The minimalist approach for linear stability analysis is applied to fluids and MAGNETized ideal plasmas in cylindrical geometry. In this approach, the dispersion relation is obtained by integrating a single first-order differential equation - referred to as the principal equation - subject to appropriate boundary conditions. We first derive the principal equation for a general unperturbed state with radially varying density and pressure, axial and azimuthal components of both the velocity and MAGNETic field, and a radially directed gravitational field. We then use this formulation to analyze rotating flows with axial MAGNETic fields, addressing both wall-bounded and interface-driven axisymmetric instabilities. In addition to exact results for selected unperturbed states, we obtain approximate dispersion relations using the WKBJ method in the incompressible and compressible limits. The analysis encompasses centrifugal, MAGNETorotational, and buoyancy-driven instabilities as special cases, and it clarifies how compressibility modifies their stability properties.

[abstract 21 / 43] (score: 3)
arXiv:2609.02395 [pdf, ps, other]

Title: Searching for optical pulsations from spider millisecond pulsars with the fast photometer SiFAP2

Authors: Christian Malacaria, Alessandro Papitto, Filippo Ambrosino, Caterina Ballocco, Riccardo La Placa, Giulia Illiano, Arianna Miraval Zanon, Luigi Stella, Marco Turchetta, James D. Turner, Clara Blanchard, Ignacio Cognard, Lucas Guillemot, Marta Burgay, Paolo d'Avanzo, Aleksandr Burtovoi, Andrea Sanna, Sergio Campana, Massimo Cecconi, Adriano Ghedina, Andrea Possenti, Diego Torres,

Comments: 10 pages, accepted on A&A

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Optical pulsations from millisecond pulsars (MSPs) have recently been discovered from a transitional MSP and an accreting MSP. Evidence for optical pulsations has also been found for a rotation-powered redback MSP. Observations suggest that optical pulsed emission is produced by different mechanisms depending on whether an accretion disk is present in the system or not. We explore a sample of rotation-powered MSPs in close binaries (P$_{orb}<1\,$day, redbacks and black widows), searching for optical periodic signals with the $SiFAP2$ photometer mounted on the $Telescopio\ Nazionale\ Galileo$ (TNG). We perform pulsation searches using the epoch folding method with the most updated (radio or gamma-ray) orbital solution for each system, employing already published solutions or recent observations with Nançay, the Giant Metrewave Radio Telescope, the Parkes Observatory, and $FERMI$-LAT. We update or confirm radio and gamma-ray ephemerides for five of the presented systems. No optical pulsations were detected with a significance exceeding a $3σ$ confidence level in any of our searches, despite often achieving sensitivities on the verge of the instrument's limit. This places correspondingly stringent upper limits on the systems' optical pulsed magnitude and conversion efficiency. Our upper limits are consistent with the pulsed optical luminosity of optical pulsations from the redback PSR J2339-0533. Compared to accreting and transitional MSPs, redback and black widow systems show much lower efficiency in converting their spin down power into pulsed optical emission, supporting the recently advanced idea that the accretion disk around the neutron star plays a role in accelerating the particles responsible for producing bright optical pulsed emission.

[abstract 22 / 43] (score: 3)
arXiv:2609.02809 [pdf, ps, other]

Title: 17 Yr of Magnetar Bursts Observed with the FERMI Gamma-ray Burst Monitor

Authors: Matt Godwin, Özge Keskin, Mustafa Demirer, Yi-Jing Yi, Lin Lin, Oliver J. Roberts, Ersin Göğüş, Yuki Kaneko, Michael Briggs, Matthew G. Baring, Eric Burns, David M. Palmer, Boyan A. Hristov, Bagrat Mailyan, Christian Malacaria, Eva Palafox, Chryssa Kouveliotou, Alexander J. van der Horst, Peter Veres, George Younes,

Comments: 26 pages. Submitted to ApJS

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

The FERMI Gamma-ray Burst Monitor (GBM) has been in operation for over 17 years, during which it has observed more than a thousand bursts from soft gamma repeaters (SGRs), also known as MAGNETars. Serving as a laboratory for extreme physics, MAGNETars are a sub-family of neutron stars characterized by extreme MAGNETic field strength, observed through a combination of persistent and short transient emission across the electroMAGNETic spectrum. We present the comprehensive GBM catalog of SGR short bursts which supersedes the 5-year catalog of Collazzi et al. 2015. The new catalog contains 1254 SGR short bursts observed over 17 years, providing the longest uninterrupted, high-sensitivity all-sky monitoring of MAGNETar bursts with unprecedented spectral and temporal resolution. Our catalog contains bursts from 17 unique Galactic sources, with major contributions by bursts from SGR J1935+2154 and SGR J1550-5418. We present overall characteristics of these bursts, such as the durations, spectral parameters for various photon models, fluxes, as well as their comparison with recently published catalogs of other missions and the previous GBM MAGNETar catalog. The machine readable catalog, as well as burst spectra and response files are made publicly available for the community.

[abstract 23 / 43] (score: 2)
arXiv:2603.20740 [pdf, ps, other]

Title: Southern eROSITA bubble as a forward shock and the low-metallicity CGM. South-east side story

Authors: E. Churazov, I. I. Khabibullin, A. M. Bykov, N. N. Chugai, R. A. Sunyaev, V. P. Utrobin, I. I. Zinchenko,

Comments: A&A, accepted version

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Unlike the complicated X-ray and radio structure observed in the North Polar Spur area, the South-Eastern part of the eROSITA bubbles can be reasonably well described as a propagating forward shock, plausibly created by the transient energy release at the Galactic Center. In this model, the physical radius of the bubble is $R_{\rm b}\sim 7-8\,{\rm kpc}$ and the age of the outburst is $t_{\rm age}\sim 5-8\,{\rm Myr}$. The latter quantity is plausibly a lower limit on the true age. The visible segment of the shock front (located at a distance of $\sim 10-12\,{\rm kpc}$ above the Galactic Disk and at a similar distance from the Sun) is currently expanding with the velocity $\sim 700\,{\rm km\,s^{-1}}$ through the gas with density $n_e\sim 3\times 10^{-4}\,{\rm cm^{-3}}$, and the abundance of heavy elements in this gas is low $Z\sim 0.1-0.2 \times Z_\odot$ (depending on the adopted reference Solar abundances). Unlike constraints derived from the line-of-sight-integrated quantities, these are effectively in situ measurements of the circumgalactic medium (CGM) properties. Given the simplifying assumptions used in deriving the density and abundance, we assign a factor of 2 systematic uncertainty to the final estimates. An eventual decisive test for the shock properties can be provided by the velocity measurements of the X-ray-emitting gas with soft X-ray bolometers. The extended forward shock propagating through low-metallicity gas is a favorable site to accelerate very high-energy COSMIC RAYs, which might contribute to the recently discovered proton-rich Galactic COSMIC RAY component at PeV energies impinging on the Earth's atmosphere.

[abstract 24 / 43] (score: 2)
arXiv:2604.21419 [pdf, ps, other]

Title: Energy Loss of Newborn Magnetars by Schwinger Process

Authors: Chul Min Kim, Sang Pyo Kim, Remo Ruffini, Yu Wang, Shurui Zhang,

Comments: Accepted for publication in the Journal of High Energy Astrophysics

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We investigate electron--positron pair creation through the Schwinger process in newborn MAGNETars with millisecond spin periods and surface dipole fields close to or above the QED critical field, $B_{\rm Q} = 4.414\times10^{13}\,\mathrm{G}$. In the unscreened field scenario, we derive the analytical global pair creation flux and recast it into a compact form with accurate analytic approximations. For a fiducial model with $B_{\rm p} = 10^{14}\,\mathrm{G}$ and $P_0 = 1\,\mathrm{ms}$, the Schwinger channel exceeds the classical Goldreich--Julian particle supply by many orders of magnitude and becomes the dominant source of charges at the earliest stage of the MAGNETar. The associated discharge removes about $90\%$ of the initial rotational energy within 30 ms, suppresses the gravitational-wave loss channel, and implies that the observable millisecond phase is extremely short in this unscreened scenario. The rapid energy release over such a short timescale may also provide a viable power source for astrophysical transients. Extending the same fiducial model to $10^4\,\mathrm{yr}$ gives spin periods of order seconds, linking newborn millisecond MAGNETars to the mature MAGNETar population.

[abstract 25 / 43] (score: 2)
arXiv:2605.05362 [pdf, ps, other]

Title: Constraining Lorentz symmetry breaking in bumblebee gravity with extreme mass-ratio inspirals

Authors: Sheng Long, Zhong-wu Xia, Huajie Gong, Zhoujian Cao, Qiyuan Pan, Jiliang Jing,

Comments: Accepted for publication in Chinese Physics C

Subjects: gr-qc

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

Extreme mass-ratio inspirals (EMRIs), with their long-lived and highly RELATIVISTIC orbital evolution, can probe strong-field spacetime geometry and provide an important means to test general relativity. In this work, we investigate EMRI waveforms in a Schwarzschild-like BLACK HOLE spacetime arising in bumblebee gravity, where Lorentz symmetry breaking (LSB) is characterized by a dimensionless parameter $\ell$. We construct EMRI waveforms within the Augmented Analytic Kludge (AAK) framework using the modified orbital frequencies and fluxes. We find that $\ell$ significantly affects the orbital evolution and thereby modifies the waveform. These modifications grow with increasing $\ell$ and are further enhanced for more eccentric orbits. Furthermore, using Bayesian analysis, we obtain the posterior distributions of EMRI with the parameter $\ell$ included. Our results show that all injected source parameters are recovered within their $1\,σ$ credible intervals. We find that the bumblebee parameter $\ell$ can be constrained with an uncertainty of order $\mathcal{O}(10^{-4})$ by LISA.

[abstract 26 / 43] (score: 2)
arXiv:2608.30914 [pdf, ps, other]

Title: Measuring peculiar velocity and tomographic redshift dipole with DESI DR1 catalogs

Authors: Yi-Wen Wu, Jun-Qing Xia,

Comments: 11 pages, 1 figures, 3 tables

Subjects: astro-ph.CO

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

The so-called ``cosmic dipole tension'' challenges the Cosmological Principle by positing a discrepancy between the Solar System's peculiar velocity inferred from the Cosmic Microwave Background (CMB) dipole and that derived from large-scale structure number-count dipoles. Here we provide a high-precision determination of the kinematic dipole using the redshift-dipole method applied to the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI). By exploiting the Doppler-induced modulation of observed redshifts, this estimator is intrinsically less sensitive to imaging systematics and selection-function uncertainties that can bias traditional number-count measurements. We conduct a tomographic analysis of four tracer populations, Bright Galaxy Sample, Luminous Red Galaxies, Emission Line Galaxies, and QUASARs, spanning $0.1

[abstract 27 / 43] (score: 2)
arXiv:2609.01750 [pdf, ps, other]

Title: The Fusion Equilibrium Challenge: Inferring Magnetic Geometry Without Magnetic Diagnostics

Authors: Tapan Ganatma Nakkina, Matthew Waller, Craig Michoski, Brian Sammuli, David R. Hatch, William Boyes, Mitchell Clark, Raffi Nazikian, Sterling Smith,

Comments:

Subjects: physics.plasm-ph

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

Next-generation fusion reactor devices such as SPARC, ARC, and CFETR will operate in extreme neutron environments that compromise the MAGNETic sensors traditionally used to reconstruct plasma equilibria. However, reliable knowledge of the plasma equilibrium--including MAGNETic flux surfaces, safety factor profiles, and shaping parameters--is indispensable for real-time control, disruption avoidance, and physics interpretation. The Fusion Equilibrium Challenge invites the NeurIPS community to confront a deceptively simple but scientifically rigorous inverse problem: reconstruct the two-dimensional poloidal flux function psi(R,Z) and a suite of scalar equilibrium parameters from non-MAGNETic diagnostics alone, namely external poloidal-field coil currents and Thomson-scattering electron temperature/density profiles. The challenge provides the first open-access, harmonized multi-machine benchmark for fusion, releasing a curated dataset of 9,113 DIII-D shots and 2,416 MAST shots--filtered for Thomson-diagnostic availability, feature completeness, and EFIT-reconstruction quality. Each shot is packaged into a standard Parquet file containing approximately 260 (DIII-D) / approximately 80 (MAST) EFIT flux maps and rich high-rate diagnostics. Two complementary awards reward intra-machine reconstruction fidelity (S_model) on DIII-D and zero-shot cross-machine generalization (G_ratio) to the topologically distinct MAST spherical tokamak. We argue that the challenge functions as a benchmark for reactor-ready equilibrium inference and as a probe of how far machine learning can be pushed toward truly machine-agnostic plasma state estimation.

[abstract 28 / 43] (score: 2)
arXiv:2609.01890 [pdf, ps, other]

Title: A novel objective function minimizes resonant trapped energetic particle losses in stellarators

Authors: John Anthony Labbate, Elizabeth J. Paul, Amelia Chambliss,

Comments:

Subjects: physics.plasm-ph

Created: 2026-09-01; Updated: 2026-09-03; Datestamp: 2026-09-03

Near-omnigenous stellarators are susceptible to energetic particle (EP) losses due to resonances between trapped EPs and non-omnigenous perturbations to the MAGNETic field. Existing bounce-averaged objectives such as $Γ_c$, $Γ_δ$ , and $Γ_α$ target the non-resonant misalignment of drift and flux surfaces, but they do not capture resonant convective or diffusive motion. We develop a discrete map theory for the bounce points of trapped EPs in near-omnigenous fields, in which phase-space islands form due to resonance between the precession and bounce frequencies. We introduce $Δ_{res}$, a differentiable, bounce-averaged objective function that penalizes the widths of these islands, promoting phase-space integrability. Optimizing a quasi-axisymmetric configuration using $Δ_{res}$ combined with a two-term quasi-symmetry objective yields a factor-of-four improvement in EP confinement by displacing low-order resonances and forming EP transport barriers. $Δ_{res}$ is a powerful tool to combat both resonant convective and diffusive losses in power plant-relevant stellarators.

[abstract 29 / 43] (score: 2)
arXiv:2609.02037 [pdf, ps, other]

Title: Are Repeaters Prevalent Among the Known Fast Radio Burst Sources?

Authors: Xiao-Fei Dong, Qing Pan, Yong-Feng Huang, Zhi-Bin Zhang, Hao-Xuan Gao, Jin-Jun Geng, Xue-Feng Wu, Lang Cui, Xiu-Juan Li, Song-Bo Zhang, Abdusattar Kurban, Chen-Ran Hu, Chen Deng,

Comments: 14 pages, 6 figures, 2 Tables, Submitted

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Fast radio bursts (FRBs) are millisecond radio pulses of unknown origin. Despite extensive follow-up observations, only $\sim3\%$ of FRBs have been confirmed as repeaters. It remains unclear whether the rest are truly one-off bursts, or essentially repeating sources that have only been detected once due to limited monitoring time. Using the second CHIME/FRB catalog, we test this debate by comparing non-repeaters with two repeater-based subsamples: the first-detected bursts of repeaters and their highest-fluence bursts. A non-parametric method that accounts for selection effects is employed to derive the energy functions and event rates of these samples. All samples are well described by broken power-law energy distributions with comparable break energies ($\sim 5\times10^{38}$ erg), but with significantly different slopes between repeating and non-repeating populations. Their event-rate evolution also differs significantly. Assuming $ρ(z) \propto (1+z)^B$, we have $B = -5.57^{+0.15}_{-0.15}$ for non-repeaters and $B = -8.63^{+0.46}_{-0.41}$ and $-9.10^{+0.55}_{-0.56}$ for the two repeater samples. Size-matched resampling shows that the repeater event-rate indices lie far outside the 5$σ$ range expected from non-repeater subsamples, ruling out sample size as the reason for the observed difference. These results indicate that at least a subset of one-off FRBs are intrinsically non-repeating, implying that repeating sources may represent a distinct and possibly less common population.

[abstract 30 / 43] (score: 2)
arXiv:2609.02053 [pdf, ps, other]

Title: Impact of nuclear triaxial deformation on electroMAGNETic fields in RELATIVISTIC $^{129}\mathrm{Xe}+^{129}\mathrm{Xe}$ collisions

Authors: Maidi Huang, Jin Hu, Yunpeng Liu, Baoyi Chen,

Comments:

Subjects: nucl-th

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

ElectroMAGNETic fields produced in RELATIVISTIC heavy-ion collisions depend sensitively on the initial spatial distribution of nuclear charge. Using the Liénard--Wiechert potential with a triaxially deformed Woods--Saxon density, we calculate the transverse electric and MAGNETic field distributions in $^{129}\mathrm{Xe}+{}^{129}\mathrm{Xe}$ collisions at $\sqrt{s_{NN}}=5.44\text{ TeV}$. We systematically examine how the triaxiality angle $γ$ modifies the field structure at the collision time ($t=0$) in semi-central events, using spherical nuclear collisions as a baseline. The results show that nuclear triaxiality causes distinct spatial redistributions of both electric and MAGNETic fields in the transverse plane. These findings indicate that initial electroMAGNETic fields encode key information on intrinsic nuclear shapes, offering an additional constraint on nuclear deformation and its consequences for field-sensitive observables in heavy-ion collisions.

[abstract 31 / 43] (score: 2)
arXiv:2609.02181 [pdf, ps, other]

Title: Constraints on the Intranight Optical Variability of Intermediate-Mass Black Hole Candidates

Authors: Wenwen Zuo, Hengxiao Guo, Wanling Liu, Wenke Ren, Jingbo Sun, Patricia Arévalo, Luis C. Ho, Alok C. Gupta, Vineet Ojha, Mouyuan Sun, Shuangliang Li, Haicheng Feng, Qi Yuan, Minfeng Gu, Xuebing Wu,

Comments: 22 pages, 12 figures, submitted to ApJ. Comments are welcome

Subjects: astro-ph.GA

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Intermediate-mass BLACK HOLEs (IMBHs) provide a unique regime for studying accretion variability at the low-mass end of the BLACK HOLE population, yet their intranight optical variability (INOV) remains poorly constrained. We present a systematic investigation of INOV in an optically selected sample of IMBH candidates using high-cadence observations from the Zwicky Transient Facility (ZTF). From a parent sample of 1,447 broad H$α$-selected candidates, we identify 64 IMBH candidates (median $f_{\mathrm{AGN}}\sim0.06$) with 163 intranight monitoring sessions. Apparent INOV signals identified by conventional ZTF PSF-fit photometry are largely associated with seeing-dependent changes in the relative contributions of compact nuclear and extended host components, which can mimic intrinsic short-timescale variability. In contrast, no robust INOV is detected with difference-image analysis. An ensemble structure function spanning $Δt\sim0.003$--$1600$ days reveals long-term variability in a small subsample of sources, whereas intrinsic variability remains unresolved at intranight timescales. Monte Carlo simulations further show that ZTF-like single-night monitoring has a low INOV recovery probability ($\sim1.2%$) for the variability amplitudes inferred from the long-term analysis. The recovery probability is primarily controlled by source brightness, AGN contribution, intrinsic variability amplitude, and photometric precision. These results demonstrate that the absence of detected INOV does not imply the absence of rapid accretion variability, but can reflect the limited detectability of low-amplitude signals under current observing capabilities. Our findings highlight the importance of robust photometric methodologies for future high-cadence variability studies of low-mass accreting BLACK HOLEs.

[abstract 32 / 43] (score: 2)
arXiv:2609.02211 [pdf, ps, other]

Title: The relationship between solar and stellar tachoclines, dynamos, and spin-down

Authors: Loren I. Matilsky, Lydia Korre, Nicholas Brummell,

Comments: 8 pages, 5 figures, part of the proceedings for Cool Stars 23 held in Tokyo, Japan

Subjects: astro-ph.SR

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

The solar tachocline, a thin shear layer separating the differentially rotating convective zone (CZ) from the underlying rigidly rotating radiative zone (RZ), remains a dynamical mystery. Under the influence of "radiative spreading" (the process by which meridional circulation, baroclinicity, and differential rotation burrow through a stably stratified fluid), the tachocline should have spread significantly by the current age of the Sun. Some unknown torque must therefore rigidify the whole solar interior below the CZ and keep the tachocline confined to a thin layer. At the same time, the spin-down process (through which cool stars shed angular momentum via surface MAGNETic torques) must extract angular momentum from the solar RZ, presenting a second mystery: solar spin-down must be communicated from the near-surface layers to the deep interior, all the while leaving the tachocline intact. In this work, we explicitly analyze the dynamics of radiative spreading in two 3D, spherical-shell, fully nonlinear fluid simulations of a solar-like CZ--RZ system, one without a MAGNETic field (hydrodynamic---HD) and one with a small random seed MAGNETic field (MAGNETohydrodynamic---MHD). We find that radiative spreading is unmitigated in the HD case (as expected), but in the MHD case, a self-excited dynamo not only confines the tachocline, but \textit{also} extracts angular momentum from the RZ, thereby communicating the spin-down downward. We thus speculate that solar and stellar tachoclines may be intimately linked to both the spin-down process and global dynamo.

[abstract 33 / 43] (score: 2)
arXiv:2609.02221 [pdf, ps, other]

Title: Demonstrating the Time-Domain Capabilities of the 4-m International Liquid Mirror Telescope: An Early Census of Transient and Variable Detections

Authors: Kumar Pranshu, Kuntal Misra, Bhavya Ailawadhi, Monalisa Dubey, Naveen Dukiya, Sara Filali, Paul Hickson, Priyanshi Kumari, Gokul Singh Mehra, Vibhore Negi, Jeewan C. Pandey, Anna Pospieszalska-Surdej, Jean Surdej, Sarvesh Kumar Yadav,

Comments: 20 pages, 12 figures, accepted for publication in PASP

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

The PyLMT transient detection pipeline has been operational since November 2023, detecting transient and variable objects in the ILMT images in almost real time. Using the image subtraction technique, nearly 3700 CCD frames have been analyzed by the automated pipeline, generating nearly 23,000 alerts for the detection of verified transient candidates and cataloged variable sources. Around 21,000 of the alerts correspond to known MPC asteroids, nearly 2000 correspond to variable stars (including eclipsing binaries, RR Lyrae, Delta Scuti, T-Tauri, etc.), 509 correspond to variable AGNs (including QSOs, Seyfert galaxies, and BLAZARs), 21 SUPERNOVA candidates, and several other interesting candidates. We provide a concise overview of the detections and their significance, emphasizing the surveys potential contributions to a broad class of astrophysical and scientific cases. A transient detection dashboard called DART was developed using Streamlit to visualize and categorize candidates based on PyLMT and SIMBAD classifications. It includes cone-search functionality and displays key metadata, offering an intuitive interface that is publicly accessible. Our results demonstrate the viability of liquid mirror telescopes such as the ILMT for time-domain astronomy, emphasizing the important role that small-field survey facilities can play in systematic transient science programs.

[abstract 34 / 43] (score: 2)
arXiv:2609.02223 [pdf, ps, other]

Title: Accretion dynamics of thin and thick disks in charged Kalb-Ramond BLACK HOLEs

Authors: Ednaldo L. B. Junior, José Tarciso S. S. Junior, Francisco S. N. Lobo, Jorde A. A. Ramos, Manuel E. Rodrigues, Diego Rubiera-Garcia, Luís F. Dias da Silva, Henrique A. Vieira,

Comments: 17 pages, 14 figures, revtex4-2 style

Subjects: gr-qc

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

In this work, we investigate the accretion properties of an electrically charged, static, spherically symmetric BLACK HOLE in Kalb-Ramond (KR) gravity, where a dimensionless parameter $l$ characterizes spontaneous Lorentz symmetry-breaking. We first constrain the free charge and KR parameter space, $(Q,l)$, by comparing the predicted shadow radius of this family of solutions with the bounds inferred from Event Horizon Telescope observations of Sagittarius A*. The inclusion of electric charge introduces a degeneracy between $Q$ and $l$, enlarging the region compatible with the observed shadow size and yielding the broad constraint $-0.3900 \leq l \leq 0.1898$, with part of the compatible parameter space extending into the naked-singularity sector. We then investigate RELATIVISTIC accretion disks around the charged KR BLACK HOLE within the above constraints. For geometrically thin disks, we compute the time averaged energy flux, temperature distribution, emission spectrum, time averaged torque, and mass-to-radiation conversion efficiency, finding that the radiative output increases for higher values of $l$, while lower values of $l$ suppress it. Furthermore, when coupled with the electric charge this effect is amplified. For geometrically thick, constant-angular momentum tori-shaped disks, Lorentz symmetry-breaking shifts the characteristic orbital radii, compresses the radial extent of equilibrium configurations, narrows the interval supporting finite equilibrium tori, and shifts the stationary-fluid topology toward open and unconfined configurations outside that interval. These results show how charge and spontaneous Lorentz symmetry-breaking jointly affect observational constraints and the structure and emission properties of BLACK HOLE accretion flows, providing potential signatures of KR gravity in the strong-gravity regime.

[abstract 35 / 43] (score: 2)
arXiv:2609.02279 [pdf, ps, other]

Title: Ventilated Cavitation around a sphere through surface air injection at Re = 10,000

Authors: Soundararajan R, Anikesh Pal,

Comments:

Subjects: physics.flu-dyn

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We perform DNS of ventilated cavitation over a sphere at subcritical (Re=10,000). The flow is modeled as a homogeneous mixture of water and air, with the interface tracked using the volume-of-fluid method. Unlike previous numerical investigations, surface tension is explicitly included. Air is injected through a circular strip on the sphere at three locations selected based on the bulk flow dynamics: front (FR025, (18^\circ\leqθ\leq63^\circ)), mid (MD025, MD050, (75^\circ\leqθ\leq104^\circ)), and back (BK025, (120^\circ\leqθ\leq180^\circ)), with (C_q=0.2) and (0.4). The injection location strongly governs cavity inception and stability and alters flow separation in the front- and mid-injection cases. Front injection produces an unsteady bubbly cavity due to vigorous puffing, which fragments the injected air and increases drag by (\sim56%) relative to the single-phase case. In contrast, mid- and back-injection produce stable cavities with distinct leading-edge dynamics. In the mid-injection cases, puffing dominates and, despite delayed flow separation, the cavity detaches from the leading edge of the injection patch. For back injection, the cavity detaches upstream of the injection patch owing to the adverse pressure gradient induced by cavity formation. Kelvin--Helmholtz instabilities and divot formation characterize the back-injection cavity. Stable cavities exhibit strong air entrainment and close through a re-entrant JET. The mid-injection cases achieve (35%) and (25%) drag reduction at (C_q=0.2) and (0.4), respectively, while back injection yields a maximum drag reduction of (46%) relative to the single-phase case.

[abstract 36 / 43] (score: 2)
arXiv:2609.02442 [pdf, ps, other]

Title: Transient discs around isolated accreting neutron stars

Authors: Marina D. Afonina, Anton V. Biryukov, Sergei B. Popov, Arthur G. Suvorov,

Comments: 21 pages, 6 figures, submitted to JHEAP

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Mature, isolated neutron stars can accrete from the interstellar medium. Due to turbulence, the accreted gas can have a substantial angular momentum and form a disc around the compact object. In this paper, we perform a population synthesis of isolated neutron stars in the Milky Way that specifically tracks the possibility of disc formation, which typically requires a low spatial velocity of the compact object ($\lesssim 40$ km s$^{-1}$). In general, weak MAGNETic fields favour disc formation as the MAGNETosphere occupies a smaller volume. Still, even in the case of fields decaying exponentially over a characteristic timescale of $\sim 1.5$ Gyr, we find that for several realistic models of propeller spin-down, only a small fraction of accretors (down to $\sim 0.02$ %) attain discs. However, disc-accreting isolated neutron stars are relatively numerous among the brightest sources. We estimate that their number can reach a few hundred at X-ray fluxes of $\gtrsim 10^{-14}$ erg s$^{-1}$ cm$^{-2}$. We speculate that disc-accreting isolated neutron stars can manifest as long-period radio transient sources via electron cyclotron maser emission, predicting spectra and critical conditions for quenching.

[abstract 37 / 43] (score: 2)
arXiv:2609.02648 [pdf, ps, other]

Title: Can diffuse X-rays be important in driving photoionisation in molecular clouds?

Authors: E. I. Makarenko, A. V. Ivlev, S. Bialy, X. Zheng, B. A. L. Gaches, P. Caselli, M. Padovani, M. C. H. Yeung,

Comments: 8 pages, 10 figures, accepted for publication in Astronomy & Astrophysics

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

The ionisation balance in molecular clouds is regulated by several ionising sources, including COSMIC RAYs, X-rays, and ultraviolet radiation. Their relative importance depends on the local physical conditions and on the shielding column density. We compute the contribution of the large-scale diffuse X-ray radiation field to the ionisation in molecular clouds in the absence of strong local X-ray sources, such as young stars. Our goal is to quantify its significance relative to the Galactic COSMIC RAYs. Using measurements of diffuse X-ray emission from the first eROSITA all-sky survey, we estimate the depth-dependent X-ray ionisation rate in molecular clouds across different Galactic environments. We consider both the observed diffuse field and a deabsorbed field obtained by correcting for foreground Galactic attenuation using HI4PI line-of-sight column densities in a pixel-by-pixel framework. Diffuse Galactic X-rays are unlikely to dominate the ionisation balance in well-shielded molecular gas ($N_{\mathrm{H}} > 5 \times 10^{21} \mathrm{cm^{-2}}$), where COSMIC RAYs remain the primary ionising agent. At low column densities, the deabsorbed diffuse X-ray field produces ionisation rate of $ζ_X \sim 10^{-18}\mathrm{s^{-1}}$ at $N_{\mathrm H} \sim 10^{19}\mathrm{cm^{-2}}$, remaining below the lower end of Galactic COSMIC RAY ionisation rate ($\sim 10^{-17} \mathrm{s^{-1}}$). The X-ray contribution decreases rapidly with increasing shielding, falling to $ζ_{X}\sim10^{-19}\mathrm{s^{-1}}$ by $N_{\rm H}\sim10^{21}\mathrm{cm^{-2}}$ and to $ζ_X \sim5\times10^{-21}\mathrm{s^{-1}}$ by $N_{\rm H}\sim10^{22}\mathrm{cm^{-2}}$. Diffuse X-ray may therefore contribute to the thermal and chemical structure of low-extinction material and should be considered when interpreting ionisation tracers in diffuse or cloud-envelope environments.

[abstract 38 / 43] (score: 2)
arXiv:2609.02655 [pdf, ps, other]

Title: Relativistic stellar collapse of initially static configurations

Authors: Keshlan S. Govinder, Megandhren Govender, Sunil Maharaj,

Comments: 18 pages, 8 figures

Subjects: gr-qc

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We study the dynamics of a radiating RELATIVISTIC star in the presence of the electroMAGNETic field and the cosmological constant. The evolution of the model originates from an initially static configuration. The temporal behaviour of the system is governed by a nonlinear second order equation which is studied using a phase plane analysis. We show that in the general case, with all physical parameters present, fold bifurcations arise which are related to nonzero charge and cosmological constant. Our treatment clarifies earlier results and we extend our study to the general solution space. We obtain a more comprehensive understanding of the temporal evolution for a shear-free configuration during collapse.

[abstract 39 / 43] (score: 2)
arXiv:2609.02667 [pdf, ps, other]

Title: Feeding The Little Monster: An Accreting Intermediate-Mass Black Hole In A Minor Merger Secondary Galaxy

Authors: Marko Mićić, Julia St. Pierre,

Comments: Accepted for publication in ApJ. 8 pages, 4 figures, 1 table

Subjects: astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We report the discovery of a luminous supersoft X-ray source associated with the secondary galaxy in a 10:1 minor merger at $z$=0.216. We identified the system in the 3D-HST survey and observed it serendipitously in more than 100 Chandra observations, providing a combined exposure of 6.6 Msec. The secondary galaxy ($\log$ (M$_*$/M$_\odot$)=8.24) exhibits X-ray emission detected exclusively below 2.0 keV, with no significant hard-band photons. Because the source is low-count, we characterize its spectrum using Bayesian hardness-ratio analysis combined with simulations of physically motivated spectral models folded through the Chandra response files. The observed count rates and hardness ratios are reproduced by a thermal accretion-disk spectrum with rest-frame inner-disk temperatures kT$_{in}$=0.18-0.30 keV and luminosities log(L$_X$/erg s$^{-1}$)=40.5-41.2. Interpreted using a standard thin-disk framework, these properties imply a BLACK HOLE mass of M$_\bullet$$\approx 8\times10^{2}$--$5\times10^{3}\,M_\odot$ accreting at $\approx$0.2-0.5 of the Eddington rate. Alternative interpretations involving ultraluminous X-ray supersoft sources are disfavored by the source's luminosity, temperature, lack of variability, and the host galaxy's low star-formation rate. Numerical simulations predict that BLACK HOLEs in smaller, secondary galaxies could experience episodic rapid growth during minor mergers. This discovery provides observational support for this scenario and suggests that minor interactions may be an important channel for assembling supermassive BLACK HOLEs in dwarf galaxies.

[abstract 40 / 43] (score: 2)
arXiv:2609.02674 [pdf, ps, other]

Title: Thermal Quantum Fluctuations in Einstein-Nonlinear Maxwell-Yukawa Black Hole

Authors: M. Mangut,

Comments: This manuscript has been accepted for publication in Annals of Physics

Subjects: gr-qc

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

This study investigates an Einstein-nonlinear electrodynamic BLACK HOLE generated by a Yukawa-screened electroMAGNETic potential and examines its thermal properties through the calculation of the fundamental thermodynamic potentials and variables. The effect of thermal fluctuations on the calculated standard thermodynamic quantities is analyzed through two different correction terms added to the Bekenstein-Hawking entropy. In this work, the thermodynamic behavior in cases where the BLACK HOLE has a relatively large event horizon is investigated using a logarithmic correction term representing corrections arising from quantum fields in constant backgrounds. In addition, thermal fluctuations occurring in cases where the event horizon is small are analyzed through an exponential correction term added to the entropy, reflecting non-perturbative quantum effects. Finally, the thermodynamic functions for all obtained cases are examined graphically, and the stability properties of the BLACK HOLE are discussed in detail.

[abstract 41 / 43] (score: 2)
arXiv:2609.02802 [pdf, ps, other]

Title: GRINTA: a new Probe of the Dynamic Universe

Authors: Lorenzo Natalucci, Philippe Laurent, Marica Branchesi, Mariateresa Fiocchi, Lorraine Hanlon, J. Miguel Mas-Hesse, Aline Meuris, Paul 'O Brien, James C. Rodi, Simone Scaringi, Konrad Skup, Norbert Werner, Silvia Zane, Julia Alfonso-Garzon, Biswajit Banerjee, Patrizia Barria, Anthony J. Bird, Soren Brandt, Gabriele Bruni, Floriane Cangemi, Gianluca Castignani, Eric Chassande-Mottin, Sylvain Chaty, Jerome Chenevez, Alexis Coleiro, Francesco Dazzi, Alessio L. De Santis, Phil Evans, Olivier Godet, Diego Gotz, Rene Hudec, Lucien Kuiper, Angela Malizia, Sheila McBreen, Sandro Mereghetti, Manuela Molina, Filip Munz, David Murphy, Gor Oganesyan, Francesca Panessa, Elena Pian, Jakub Rıpa, Oliver J. Roberts, Samuele Ronchini, Fabian Schussler, Vojtech Simon, Nial Tanvir, Alexey Uliyanov, Nello Vertolli, Stanislav Vıtek, Ugo Zannoni,

Comments: Presented at SPIE Astronomical Telescopes and Instrumentation 2026. 24 pages, 8 figures, 3 tables

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

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

Recent observations of the transient sky at all wavelengths are increasingly revealing the importance of the multi-messenger and multi-wavelength approach. The GRINTA (Gamma-Ray INternational Transient Array Observatory) mission, proposed for launch around the middle of the next decade, is conceived as a small mission with good sensitivity, excellent angular resolution and fast follow-up capability for studying transient sources at timescales from ms to hours, at the same time ensuring optimal integration with multi-messenger networks. The GRINTA mission will carry two complementary payloads to cover in total the 5 keV-10 MeV band, that will detect and localise GAMMA-RAY BURSTs covering $\sim$ half of the sky and will be able to perform imaging surveys with sub-arcmin resolution. GRINTA will operate in synergy with the most powerful electroMAGNETic, gravitational wave and neutrino observatories foreseen to be operational after 2035.

[abstract 42 / 43] (score: 2)
arXiv:2609.02803 [pdf, ps, other]

Title: Global Gyrokinetic Simulations of ElectroMAGNETic Turbulence in STEP

Authors: Daniel Kennedy, Facundo Sheffield, Tobias Görler, Colin Roach, Maurizio Giacomin, Arka Bokshi, David Dickinson, Harry Dudding, Bhavin Patel,

Comments:

Subjects: physics.plasm-ph

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

This paper presents gradient-driven global electroMAGNETic gyrokinetic simulations for a conceptual burning flat-top operating point of STEP [1], STEP-EC-HD, and investigates how non-local effects influence the nonlinear saturation and transport of the electroMAGNETic turbulence at finite $β$. Local gyrokinetic simulations have shown that including $δB_{\parallel}$ is essential for the dominant hybrid kinetic ballooning modes, or hKBMs, to be unstable in STEP [2]. Using the long-wavelength $δB_{\parallel}$ solver [3] implemented in GENE [4], this work demonstrates that the linear mode spectrum can be accurately captured in global geometry, which results in good agreement with an ensemble of local flux-tube simulations. The global framework reproduces the hKBMs identified in [5], while microtearing modes remain challenging to resolve due to their shorter radial scales. Nonlinear simulations reveal clear evidence of an electroMAGNETic transition to states with extremely large heat fluxes, consistent with local simulations and with the predicted loss of zonal-flow regulation for this proposed operating point [6]. These findings establish the capability of global gyrokinetics to capture finite-$β$ dynamics in STEP-like plasmas and motivate future work to identify the conditions governing this transition.

[abstract 43 / 43] (score: 2)
arXiv:2609.02868 [pdf, ps, other]

Title: Inelastic Dark Photon Dark Matter for the LUX-ZEPLIN High-Recoil Event and the Galactic Halo Gamma-Ray Excess

Authors: Kimiko Yamashita,

Comments: 4 pages, 1 figure

Subjects: hep-ph astro-ph.HE

Created: 2026-09-02; Updated: 2026-09-03; Datestamp: 2026-09-03

We show that a single dark-photon DARK MATTER framework can simultaneously account for two recently reported anomalies: the halo-like Galactic gamma-ray excess identified by Totani in 15 years of FERMI-LAT data, and the $E_{\rm nr}=248\pm23\,({\rm stat})\pm23\,({\rm sys})$ keV nuclear-recoil event of interest reported by the LUX-ZEPLIN Collaboration. The DARK MATTER is a $U(1)_X$ dark photon $X$ with mass $m_X=420$ GeV, stabilized by a dark parity that forbids kinetic mixing with the Standard Model photon. A light scalar mediator $ϕ$, already required to explain the Totani excess via Sommerfeld enhancement, is extended to couple a nearly degenerate heavier vector partner $V$ to $X$. The resulting inelastic transition $X+N \to V+N$, with mass splitting $δ\simeq316$~keV close to the kinematic endpoint for $m_X=420$ GeV, naturally reproduces the localized LZ event once the detector energy resolution is included, while leaving the relic abundance and the halo phenomenology of the original Totani-motivated benchmark essentially unchanged.