Current date: 2026-08-18
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Datestamp limit: 2026-08-18 (0 days ago)
Created/updated limit: 2026-08-11 (7 days ago)
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Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics
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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-08-18&until=2026-08-18&set=physics&metadataPrefix=arXiv
Scoring abstracts
Number of records retrieved: 1140
Keyword score statistics
score 11 -- 2 abstracts
score 10 -- 2 abstracts
score 9 -- 1 abstracts
score 8 -- 2 abstracts
score 7 -- 2 abstracts
score 6 -- 4 abstracts
score 5 -- 7 abstracts
score 4 -- 8 abstracts
score 3 -- 9 abstracts
score 2 -- 17 abstracts
in total -- 54 abstracts
Articles that appeared on 2026-08-18
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[abstract 1 / 54] Wow! (score: 11)
- Title: Decoding the JET of BL Lacertae using RELATIVISTIC MAGNETo-hydrodynamicsAuthors: G. F. Paraschos, J. A. Kramer, I. Liodakis, S. G. Jorstad, A. P. Marscher, I. Myserlis, I. Agudo, N. R. MacDonald,Comments: 9 pages, 5 figures, accepted by A&ASubjects: astro-ph.HE astro-ph.GACreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
Blazars are a highly variable subclass of ACTIVE GALACTIC NUCLEi, whose RELATIVISTIC JET is pointed towards our line of sight at a small angle. Their variability is often characterised by multi-band flares. BL Lacertae (BL Lac), the namesake of a BLAZAR subclass recently exhibited the highest recorded linearly polarised optical flare. We investigate the origin of this flare via very-long-baseline interferometry observations. Our analysis shows that the sweeping, helical motion of the BL Lac JET, which is known to exhibit kink-like instabilities, can explain the observed flux density spike and polarisation angle rotation, as also confirmed by our state-of-the-art RELATIVISTIC MAGNETo-hydrodynamic simulations. As a by-product of these simulations we find that baryon loading of the JET is required to optimally replicate the observed JET morphology.
[abstract 2 / 54] Wow! (score: 11) - Title: An ALMA view of the Jet-Arc CO clouds toward the TeV $γ$-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microQUASAR JETs, the very powerful cosmic-ray accelerator in the Galactic diskAuthors: Yasuo Fukui, Kisetsu Tsuge, Hidetoshi Sano, G. R. Bhuvana, Rin I. Yamada, Ryoji Matsumoto, Yuta Asahina, Tsuyoshi Inoue, Tim Lukas Holch, Emma de Oña Wilhelmi,Comments: 6 pages, 3 figures, 1 table. Submitted to PASJ as a LetterSubjects: astro-ph.HE astro-ph.GACreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
The TeV $γ$-ray source HESS J1023-575 (HESSJ 1023 hereafter) is one of the brightest H.E.S.S. sources near the young massive cluster Westerlund 2. HESS J1023 shows a remarkable positional alignment with the Jet and Arc CO clouds on its eastern and western sides over 170 pc length. We have carried out sub-pc scale observations of the CO clouds with ALMA and have discovered that the clouds consist of numerous thin filamentary features of $\sim$0.5 pc width and 10--20 pc length at distance of 7.5 kpc, which are well aligned with the Jet-Arc axis. Based on the MAGNETo-hydrodynamical model of microQUASAR JETs launched from {the center of the $γ$-ray source} HESS J1023-575, we present an interpretation that the thin filamentary clouds are the footprints of the microQUASAR JETs on the HI gas. The model also explains the dissimilar Jet vs. Arc clouds in terms of HI density difference on each side. By using the density of the CO and HI gas and the $γ$-ray luminosity, we have calculated the COSMIC RAY proton energy $W_{\rm p}$ to be 7$\times$10$^{48}$ erg under the hadronic scheme, which is ten times larger than those derived in the TeV $γ$-ray SNRs RX J1713.7-3946 and RX J0852.0-4622. It is likely that HESS~J1023 has been active over 1-10 Myr, which is significantly longer than the duration of COSMIC RAY acceleration of the SNRs. HESS~J1023 is therefore an outstanding source of COSMIC RAYs equivalent to at least 1000 SNRs, and is possibly the most powerful CR accelerator in the Galactic disk. A high energy compact source in HESS~J1023, which is likely a Myr-old BLACK HOLE or neutron star, remains veiled due to heavy extinction.
[abstract 3 / 54] Wow! (score: 10) - Title: Synchrotron-Regulated Relativistic Magnetohydrodynamic Turbulence: Emission, Polarization, and Faraday RotationAuthors: Xiaochen Sun, Luca Comisso, Lorenzo Sironi, Anatoly Spitkovsky, Alexander Philippov,Comments: Submitted to AAS journalSubjects: astro-ph.HECreated: 2026-08-14; Updated: 2026-08-18; Datestamp: 2026-08-18
Relativistic MAGNETized plasmas in many high-energy astrophysical systems are both turbulent and strongly radiative, yet their nonlinear dynamics and radiative outcomes remain poorly understood. Here we present results from three-dimensional driven turbulence simulations in RELATIVISTIC MAGNETohydrodynamics with SYNCHROTRON cooling. We compute Faraday rotation measures, synthetic SYNCHROTRON spectra and linear POLARIZATION maps from the simulated turbulence. The balance between energy injection from turbulent driving and SYNCHROTRON cooling keeps the plasma, on average, RELATIVISTICally hot, thereby influencing the rotation measure. Synchrotron cooling triggers the thermal instability and drives the plasma into hot dilute and cold dense phases, which enhances the spatial and temporal variability of SYNCHROTRON emission, especially at high frequencies. These diagnostics show qualitative similarities to observations of fast radio bursts, pulsar wind nebulae, and BLAZARs, suggesting that turbulence may play an important role in shaping emission and propagation effects around high-energy sources.
[abstract 4 / 54] Wow! (score: 10) - Title: VAPOLA - A multiyear, multiband POLARIZATION survey of AGNs and Sgr A* at millimeter wavelengths with ALMA II. Spectropolarimetric properties and their evolution from 2017 to 2023Authors: Douglas Carlos, Ciriaco Goddi, Alejandro Mus, Nicola Marchili, Kazi L. J. Rygl, Ezequiel Albentosa-Ruíz, Iván Martí-Vidal, The Event Horizon Telescope Collaboration,Comments:Subjects: astro-ph.GACreated: 2026-08-14; Updated: 2026-08-18; Datestamp: 2026-08-18
We present a systematic analysis of the spectropolarimetric properties of a sample of 39 ACTIVE GALACTIC NUCLEi and Sagittarius A* observed with the Atacama Large Millimeter/submillimeter Array during five VLBI campaigns between 2017 and 2023. We characterize the compact cores in total intensity and POLARIZATION, focusing on the behavior or the linear POLARIZATION fraction (LP), electric vector position angle (EVPA), and Faraday rotation measure (RM) over time and spectral domains. We investigate both individual objects--such as M87, Sgr A*, 3C273, and 3C279--and ensemble properties of different source classes, including flat-spectrum radio QUASARs, BLLac objects, and other active galaxies. While total intensity and spectral index are generally stable on weekly timescales, POLARIZATION properties often exhibit strong variability, with significant day-to-day changes in LP, EVPA, and RM. Several sources display large EVPA rotations accompanied by variations in LP and RM, in some cases coinciding with flaring activity. We observe that the magnitude of RM increases with observing frequency for all sources for which we have reliable multi-band measurements, consistent with Faraday rotation arising in a MAGNETized sheath surrounding the RELATIVISTIC JET, although an origin in the accretion flow--particularly in the case of Sgr A*--cannot be ruled out.
[abstract 5 / 54] Wow! (score: 9) - Title: Jet Power, Bulk Lorentz Factor, Black Hole Spin, and Magnetic Field of Accretion Disk in Jetted Active Galactic Nuclei: A Large Gamma-Ray Emission SampleAuthors: Dingrong Xiong, Junhui Fan, Feng Yuan, Jun-Xian Wang, Minfeng Gu, Yongquan Xue, Jirong Mao, Liang Chen, Rui Xue, Xu-Liang Fan, Yongyun Chen, Nan Ding, Fei Guo, Jia-Wen Li, Dahai Yan, Y. G. Zheng, Jinming Bai,Comments: 25 pages, 11 figures, 3 tables, accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
We present a catalog of physical parameters for powerful JET-accretion disk-BLACK HOLE systems in one of the largest samples of gamma-ray emitting JETted ACTIVE GALACTIC NUCLEi (AGNs), including JET kinetic and radiative powers, JET radiative efficiencies, bulk Lorentz factors, BLACK HOLE spins, accretion-disk MAGNETic fields and Compton dominance. Comparing JET kinetic power estimators for BLAZARs, values derived from spectral energy distribution (SED) fitting tend to exceed those estimated via cavity power and other scaling relations. For radiatively efficient AGNs, most sources are inferred to possess high spins; for radiatively inefficient AGNs, many potentially have high spins, though some may differ. This indicates that BLACK HOLE spin does not effectively distinguish radiatively efficient from inefficient JETted AGNs. Our results suggest accretion-disk MAGNETic field strength as a key discriminator, proposing a tentative dividing value of $\approx 10^{3.9}$ Gauss between radiatively efficient and inefficient populations. Jet power and bulk Lorentz factor exhibit significant correlations with BLACK HOLE mass in radiatively efficient AGNs, while weak-to-moderate correlations are observed in radiatively inefficient AGNs within narrow accretion-rate bins. Our analysis reveals that JET power correlates with both disk luminosity and MAGNETic field strength. Furthermore, correlations linking Eddington ratio and Compton dominance with JET properties are consistent with the JET-accretion connection. Finally, JET radiative power and bulk Lorentz factor show a potential dependence on BLACK HOLE spin. These results are consistent with the scenario in which JETs are powered and accelerated by energy extraction from rapidly spinning BLACK HOLEs via accretion-disk MAGNETic fields.
[abstract 6 / 54] Wow! (score: 8) - Title: Magnetic rigidity reveals the PeVatron acceleration region in SS 433Authors: Jie Liao, Wancheng Xu, Lang Cui, Pak-Hin Thomas Tam, Xi Yan, Linuo Yang, Ruo-yu Liu, Liang Chen, Ning Chang, Yong-Feng Huang, Long Ji, Ashutosh Tripathi, Felix Aharonian,Comments: 32 pages, 10 figures, 1 table. Submitted, comments are welcomeSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
PeVatrons are cosmic accelerators capable of driving particles to petaelectronvolt (PeV) energies. Recently, microQUASAR JETs have emerged as compelling Galactic PeVatron candidates. This is especially the case for SS 433 as its $>100$ TeV gamma-ray emission is spatially coincident with an atomic cloud. However, the exact region where PeV protons are accelerated and injected within these JETs remains unresolved. Here we report, using archival, multi-frequency VLBA observations, the MAGNETic field profile $B(H)$ along the SS 433 inner JET on tens of AU scale, where $H$ is the distance from the central compact object. We find that the field declines as $B(H) \propto H^{-0.50\pm0.12}$, demonstrating that the MAGNETic rigidity $B(H)R_{\rm acc}$ grows with $H$ for a conical JET. This implies the Hillas limit ($E_{\rm max} \propto BH$) to lie well beyond a PeV at a few hundred-AU scale, which becomes a highly potential site for accelerating protons to energies $E_{\rm cut} \simeq 2.6$ PeV inferred from the LHAASO gamma-ray spectrum. These results reveal a hidden PeVatron within the baryonic ejecta of microQUASAR SS 433, well upstream of the extended TeV-emitting lobes.
[abstract 7 / 54] Wow! (score: 8) - Title: Polarization of GRB standard X-ray afterglow and its detection prospects by eXTPAuthors: Jun-Xi Lin, Zelin Ren, Mi-Xiang Lan, Ming-Yu Ge, Zi-Gao Dai, Xue-Feng Wu, Shuang-Nan Zhang,Comments: 8 pages, 5 figures, 2 tables, A&A acceptedSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
The POLARIZATION signatures of Gamma-ray Burst (GRB) afterglows serve as a powerful diagnostic tool for studying their environments and JET physics. This work systematically investigates the X-ray (2--8~keV) POLARIZATION properties of standard GRB afterglows and assesses their detectability with the Polarimetry Focusing Array aboard the enhanced X-ray Timing and Polarimetry (eXTP) satellite. A Morris global sensitivity analysis is first conducted to identify the dominant parameters, which are then assigned observationally motivated probability distributions. In particular, the isotropic energy, half-opening angle, and initial Lorentz factor are sampled jointly via a Gaussian copula to reproduce the empirical Ghirlanda and Liang correlations. Monte Carlo simulations of $10^{3}$ afterglows are performed and validated against the observed 10~keV flux distributions of a selected FERMI--SWIFT sample (K--S $p = 0.29$ at $10^{3}~\mathrm{s}$ and $p = 0.18$ at $10^{4}~\mathrm{s}$). The simulations yield an overall POLARIZATION event rate of $\lesssim 1.5\%$ for standard GRB X-ray afterglows with eXTP/PFA, reflecting the intrinsically low POLARIZATION produced by a random MAGNETic field confined to the shock plane. The optimal detection window occurs near the JET break at late times, when the PD peaks. For exceptionally luminous events such as GRB~221009A, however, the PD remains above the MDP over the full interval $10^{3}$--$10^{6}~\mathrm{s}$, demonstrating that eXTP/PFA can capture nearly the entire POLARIZATION evolution for such rare, bright bursts.
[abstract 8 / 54] Wow! (score: 7) - Title: Interpretations of the $10\%$ POLARIZATION observed in the early forward-shock afterglow of GRB 091208Authors: Yang liu, Mi-Xiang Lan,Comments: 6 pages, 3 figuresSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
The $\sim10\%$ optical POLARIZATION observed at the early stage of GRB 091208B comes from the forward shock emission, which is higher than the conventionally predicted value. Polarizations of the forward shock radiation would depend on the observational geometry and the post-shock MAGNETic field structure. This MAGNETic field could arise either from the compression of a pre-existing MAGNETic field (i.e., the MAGNETic field in the outer medium) or from the shock-generated instabilities. In this paper, we use a SYNCHROTRON radiation model to fit the light curve and POLARIZATION observations of GRB 091208B. Two scenarios are considered: one is the case of a slightly off-axis observer, and the other is with a large-scale ordered MAGNETic field component in the burst environment. We found both scenarios could interpret the observations of GRB 091208B. For the slightly off-axis observation scenario, the observational angle is restricted to be within the range of (1.02, 1.05) times the JET half-opening angle. For the large-scale ordered MAGNETic field component scenario, the ratio between the ordered component to the random component is constrained to be around 1.
[abstract 9 / 54] Wow! (score: 7) - Title: Year-timescale changes in AGN radio luminosity as seen by the ASKAP Variables and Slow Transients SurveyAuthors: Chloe Klare, Charlotte Ward, Dougal Dobie, David Kaplan, Akash Anumarlapudi, Tara Murphy, Joshua Pritchard, Laura N. Driessen, Igor Andreoni,Comments: 54 pages, 17 figures. Submitted to ApJSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
A few dozen previously radio-quiet ACTIVE GALACTIC NUCLEi (AGN) have been observed to transition to radio-loud at 1-3 GHz frequencies over timescales of more than a decade, and this has has been interpreted to be due to newly launched JETs. We identified 101 compact radio sources out of a sample of 64,972 non-BLAZAR AGN which increased in flux density by 80-1800% over 1-6 years in the 887.5 MHz Australian SKA Pathfinder Variables and Slow Transients survey. We obtained optical spectra and radio SEDs using new observations and archival survey data. We determined 60 sources were consistent with extrinsic variability due to refractive interstellar scintillation and 41 were variable due to intrinsic causes, with 26 continuously brightening and two transitioning from radio-quiet to radio-loud. We concluded that young radio JETs launched by either tidal disruption events or changes in the accretion properties were responsible for the continuously brightening AGN. These sources were non-variable at higher frequencies over the same time period, as expected for an expanding emission region. Fourteen sources had inverted or peaked SEDs initially which either flattened below the turnover or evolved into steep SEDs, consistent with young, expanding JETs. Twelve sources had non-variable steep or gigahertz-peaked SEDs, which suggested these hosted more slowly evolving JETs. We investigated the previously discovered AGN with newly launched JETs, and found several have faded at multiple frequencies, which suggested the observed radio-loudness was temporary, rather than the onset of a sustained period of radio activity.
[abstract 10 / 54] Yes (score: 6) - Title: Eclipses of Nearby Millimeter-Bright Galactic Nuclei by Stars in Nuclear Star ClustersAuthors: Michal Zajaček,Comments: 24 pages, 15 figures, 5 tables; accepted for publication by the AAS journalsSubjects: astro-ph.GA astro-ph.HECreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
It is of a general interest to look for signatures of stellar bodies orbiting supermassive BLACK HOLEs (SMBHs) in galactic nuclei other than the Galactic center. Previously stellar transits were analyzed in UV, optical, and X-ray domains as well as potential microlensing signatures due to more compact bodies orbiting SMBH accretion disks. Here we complement previous studies by considering nearby ($z=0.001$) millimeter-bright ACTIVE GALACTIC NUCLEi targeted by different facilities in the millimeter domain. At these wavelengths the JET base and the nuclear ring are sufficiently compact so that they can be occulted by large evolved stars in dense nuclear star clusters. We find that in the millimeter domain evolved stars with stellar radii of $\gtrsim 500\,R_{\odot}$ can cause eclipses with the relative depth of $\sim 10-40\%$. Typical recurrence timescales are at least 10 years and the eclipse durations are $\sim 10$ days. Towards lower frequencies the eclipse temporal profiles become shallower and broader while towards higher frequencies they are deeper and narrower. Although expected to be rare due to selection effects and evolved stars being prone to tidal disruption, eclipses of millimeter radio cores can be applied to estimate the distance of the extragalactic star from the SMBH and its stellar radius. In case the eclipse is recurring, we provide a relation for estimating the SMBH mass.
[abstract 11 / 54] Yes (score: 6) - Title: Low-mass X-ray binaries as a probe of Kerr-MOG BLACK HOLE spacetimeAuthors: Bakhodirkhon Saidov, Bakhtiyor Narzilloev, Ibrar Hussain, Bobomurat Ahmedov,Comments:Subjects: gr-qc astro-ph.HECreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
We investigate the astrophysical implications of rotating BLACK HOLEs in modified gravity by studying the Kerr-MOG spacetime and applying it to several stellar-mass BLACK HOLE candidates: A0620-00, H1743-322, XTE J1550-564, GRS1124-683, GRO J1655-40, and GRS1915+105. The Kerr-MOG geometry is characterized by the BLACK HOLE mass, the spin parameter $a$, and the modified gravity parameter $α$. We analyze how the presence of the MOG parameter modifies the spacetime structure and the location of the innermost stable circular orbit (ISCO). Within the Novikov--Thorne accretion disk model, we show that $α$ significantly affects the radiative efficiency of accretion disks and introduces a degeneracy between the spin and the modified gravity parameter. Using observational estimates of radiative efficiencies inferred from the continuum-fitting method, we constrain the allowed regions in the $(a,α)$ parameter space for each source. We further examine the RELATIVISTIC JET power using the Blandford--Znajek mechanism and compare the theoretical predictions with the observed transient JET energetics, considering two representative JET Lorentz factors, $Γ=2$ and $Γ=5$. By combining the constraints from the radiative efficiency and JET power, we identify regions where both observables can be simultaneously reproduced. For several sources significant overlap regions appear, while for the highly spinning source GRS1915+105 the compatibility occurs only within a narrow range of Kerr--MOG parameters. These results suggest that the Kerr--MOG spacetime can provide a viable framework for interpreting the observed properties of several BLACK HOLE X-ray binaries.
[abstract 12 / 54] Yes (score: 6) - Title: The detection prospects of the POLARIZATIONs in the plateau phase of GRB afterglow by eXTPAuthors: Shu-Ting Wu, Mi-Xiang Lan, Zelin Ren, Ming-Yu Ge, Xue-Feng Wu, Zi-Gao Dai,Comments: 13 pages, 7 figuresSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
Approximately (20-50)$\%$ of the GAMMA-RAY BURST (GRB) X-ray afterglows exhibit the shallow decay features. Two popular energy-injection models had been proposed to interpret such observational phenomenons, the RELATIVISTIC wind bubble (RWB) model with a Poynting-flux injection and the structured ejecta (SE) model with a dynamical energy injection. Polarization predictions of the two models had been investigated and can be used as a test of the two models. However, the impacts of the parameters on the model predictions were not studied and the comparisons with the detection ability of the forthcoming mission, enhanced X-ray Timing and Polarimetry (eXTP), had not been discussed. We considered the above issues and found that influences of the model parameters on the predicted POLARIZATIONs of the two models are very limited. To perform a feasible POLARIZATION detection during the plateau phase, the priority ToO response is required. The detection probability of the GRB plateau phase is about $1/3$ for one pointing under the priority ToO. The POLARIZATION detection probability would depend on the ratio between the Poynting-flux injection to the dynamical energy injection, which is unclear currently. The predicted flux density and POLARIZATION degree (PD) of the RWB model could be well above the threshold flux and minimal detectable POLARIZATION degree of the polarimetry focusing array (PFA) on board eXTP, while the predicted PDs of the SE model would be difficult to be detected by eXTP/PFA. Therefore, a detection of a significant POLARIZATION signal during the GRB plateau phase would prefer the RWB model and the injected energy would be in the form of the Poynting flux, while a non detection of the polarized signal would indicate a dynamical energy injection of the SE model.
[abstract 13 / 54] Yes (score: 6) - Title: Cosmogenic neutrinos from FRII galaxies as potential origin of the ultra-high-energy KM3-230213A eventAuthors: Denis Allard, Bruny Baret, Noémie Globus, Etienne Parizot,Comments: 13 pages, 8 figures + Appendix : 4 pages, 3 figuresSubjects: astro-ph.HECreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Aim : We investigate whether the ultra-high-energy neutrino KM3-230213A can be interpreted as a cosmogenic neutrino produced by ultra-high-energy COSMIC RAYs (UHECRs) accelerated in the lobes of FRII RADIO GALAXies. Method : We model the UHECR, cosmogenic neutrino and photon fluxes expected at Earth using a recent luminosity-dependent density evolution of RADIO GALAXies, empirical relations between radio luminosity and JET kinetic power, and standard assumptions for the UHECR output of FRII lobes. The FRII contribution to the UHECR population is derived self-consistently from the observed luminosity function, rather than imposed as a fixed normalization. The propagation of UHECRs and the production of secondary particles are computed with well-established numerical tools. Results : The predicted cosmogenic neutrino flux is compatible with that inferred from the detection of KM3-230213A, while remaining consistent with current UHECR and gamma-ray constraints. According to our models, the full GRAND observatory ($200\,000~\rm km^2$) should detect between $\sim50$ and $\sim135$ neutrinos above $10^{17}$~eV in ten years, allowing the diffuse UHE neutrino spectrum to be characterized. In contrast, the detection of individual FRII sources or statistically significant correlations with FRII catalogs is likely to remain challenging. At the highest energies, UHECR composition and anisotropy measurements, in particular those related to the nearby RADIO GALAXy Cygnus~A, should provide complementary tests of this scenario. More generally, progress will likely rely on the combination of multimessenger observations with improved astrophysical constraints on particle acceleration and JET composition in FRII RADIO GALAXies.
[abstract 14 / 54] Yes (score: 5) - Title: Acceleration of RELATIVISTIC protons in a solar wind perturbed by a coronal mass ejectionAuthors: Ahmed Houeibib, Filippo Pantellini, Lea Griton,Comments:Subjects: astro-ph.SR astro-ph.HE physics.space-phCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
We investigated the impact of a coronal mass ejection (CME) on the transport and acceleration of RELATIVISTIC protons in the solar wind using a coupled 3D MAGNETohydrodynamics (MHD) simulation and a test-particle approach. The CME is driven by a spheromak injected into a Parker solar wind at a heliocentric distance of 0.139 AU. We integrated the trajectories of 5 GeV protons, injected toward the CME from 3 AU, in the guiding-center approximation and scattered the particles in velocity space with a mean free path $λ_{\|}$. Our results show that the CME can increase the protons' energy by several gigaelectronvolts. The acceleration occurs while particles stream along the portion of a MAGNETic field line downstream of the quasi-perpendicular portion of the CME-driven shock. In our configuration, the maximum energy gain, which is on the order of a few percent per passage through the acceleration region, occurs when the shock approaches 0.3 AU. Large energy gains require multiple passes through the acceleration region, made possible by the combined action of the mirror force and pitch-angle scattering. The efficiency of the acceleration on timescales on the order of hours scales as $λ_{\|}^{-3/2}$. Energy spectra harden with decreasing parallel mean free path $λ_{\|}$.
[abstract 15 / 54] Yes (score: 5) - Title: GW240925 and GW250207: Astrophysical Calibration of Gravitational-wave DetectorsAuthors: The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration, A. G. Abac, I. Abouelfettouh, F. Acernese, K. Ackley, A. Adam, C. Adamcewicz, S. Adhicary, D. Adhikari, N. Adhikari, R. X. Adhikari, V. K. Adkins, S. Afroz, A. Agapito, D. Agarwal, M. Agathos, N. Aggarwal, S. Aggarwal, O. D. Aguiar, I. -L. Ahrend, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, L. Albers, W. Ali, S. Al-Kershi, C. Alléné, A. Allocca, S. Al-Shammari, P. A. Altin, S. Alvarez-Lopez, W. Amar, O. Amarasinghe, A. Amato, F. Amicucci, C. Amra, C. Anand, A. Ananyeva, S. B. Anderson, W. G. Anderson, M. Andia, M. Ando, M. Andrés-Carcasona, J. L. Andrey, T. Andrić, J. Anglin, J. Anna, S. Ansoldi, J. M. Antelis, S. Antier, M. Aoumi, E. Z. Appavuravther, S. Appert, S. K. Apple, K. Arai, A. Araya, M. C. Araya, M. Arca Sedda, F. Arciprete, J. S. Areeda, N. Aritomi, F. Armato, S. Armstrong, N. Arnaud, M. Arogeti, S. M. Aronson, K. G. Arun, G. Ashton, Y. Aso, L. Asprea, M. Assiduo, S. Assis de Souza Melo, S. M. Aston, P. Astone, F. Attadio, F. Aubin, K. AultONeal, G. Avallone, E. A. Avila, S. Babak, C. Badger, S. Bae, S. Bagnasco, L. Baiotti, R. Bajpai, T. Baka, K. A. Baker, T. Baker, G. Balbi, G. Baldi, N. Baldicchi, M. Ball, G. Ballardin, S. W. Ballmer, S. Banagiri, B. Banerjee, D. Bankar, T. M. Baptiste, P. Baral, M. Baratti, J. C. Barayoga, K. Baric, B. C. Barish, D. Barker, N. Barman, P. Barneo, F. Barone, B. Barr, M. Barrios, L. Barsotti, M. Barsuglia, D. Barta, M. A. Barton, I. Bartos, A. Basalaev, R. Bassiri, A. Basti, M. Bawaj, P. Baxi, J. C. Bayley, A. C. Baylor, P. A. Baynard, M. Bazzan, V. M. Bedakihale, F. Beirnaert, M. Bejger, D. Belardinelli, A. S. Bell, C. Bellani, L. Bellizzi, D. Beltran-Martinez, W. Benoit, I. Bentara, M. Ben Yaala, S. Bera, F. Bergamin, B. K. Berger, S. Bernuzzi, M. Beroiz, C. P. L. Berry, I. Berry, D. Bersanetti, T. Bertheas, A. Bertolini, J. Betzwieser, D. Beveridge, G. Bevilacqua, N. Bevins, R. Bhandare, R. Bhatt, A. Bhattacharjee, D. Bhattacharjee, S. Bhattacharyya, S. Bhaumik, V. Biancalana, A. Bianchi, F. Bianchi, I. A. Bilenko, G. Billingsley, A. Binetti, S. Bini, C. Binu, S. Biot, O. Birnholtz, S. Biscoveanu, A. Bisht, M. Bitossi, M. -A. Bizouard, S. Blaber, J. K. Blackburn, L. A. Blagg, C. D. Blair, D. G. Blair, N. Bode, N. Boettner, P. Bogdan, G. Boileau, M. Boldrini, G. N. Bolingbroke, A. Bolliand, L. D. Bonavena, R. Bondarescu, F. Bondu, V. A. Bonhomme, E. Bonilla, M. S. Bonilla, A. Bonino, R. Bonnand, A. Borchers, N. Borghi, V. Boschi, S. Bose, V. Bossilkov, Y. Bothra, A. Boudon, M. Boyle, A. Bozzi, C. Bradaschia, M. J. Brady, P. R. Brady, A. Branch, M. Branchesi, T. Briant, A. Brillet, M. Brinkmann, P. Brockill, E. Brockmueller, A. F. Brooks, B. C. Brown, D. D. Brown, M. L. Brozzetti, S. Brunett, G. Bruno, R. Bruntz, J. Bryant, Y. Bu, F. Bucci, J. Buchanan, O. 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Panther, M. Panzeri, F. Paoletti, A. Paolone, A. Papadopoulos, E. E. Papalexakis, L. Papalini, G. Papigkiotis, A. Paquis, A. Parisi, B. -J. Park, J. Park, W. Parker, G. Pascale, D. Pascucci, A. Pasqualetti, R. Passaquieti, L. Passenger, D. Passuello, O. Patane, A. V. Patel, D. Pathak, A. Patra, B. Patricelli, B. G. Patterson, K. Paul, S. Paul, E. Payne, T. Pearce, M. Pedraza, A. Pele, F. E. Peña Arellano, X. Peng, Y. Peng, S. Penn, M. D. Penuliar, A. Perego, Z. Pereira, C. Périgois, G. Perna, A. Perreca, J. Perret, S. Perriès, J. W. Perry, S. Peters, S. Petracca, C. Petrillo, H. P. Pfeiffer, H. Pham, K. A. Pham, K. S. Phukon, H. Phurailatpam, M. Piarulli, L. Piccari, O. J. Piccinni, M. Pichot, A. Pied, M. Piendibene, F. Piergiovanni, L. Pierini, G. Pierra, V. Pierro, M. Pietrzak, M. Pillas, L. Pinard, I. M. Pinto, M. Pinto, B. J. Piotrzkowski, M. Pirello, M. D. Pitkin, A. Placidi, E. Placidi, M. L. Planas, W. Plastino, C. Plunkett, R. Poggiani, E. Polini, J. Pomper, L. Pompili, J. Poon, E. Porcelli, A. S. Porter, E. K. Porter, C. Posnansky, R. Poulton, J. Powell, G. S. Prabhu, M. Pracchia, B. K. Pradhan, T. Pradier, A. K. Prajapati, K. Prasai, R. Prasanna, P. Prasia, G. Pratten, A. Praveen, G. Principe, G. A. Prodi, P. Prosperi, P. Prosposito, A. Puecher, J. Pullin, P. Puppo, M. Pürrer, H. Qi, M. Qiao, J. Qin, G. Quéméner, V. Quetschke, P. J. Quinonez, R. Rading, I. Rainho, S. Raja, C. Rajan, B. Rajbhandari, K. E. Ramirez, F. A. Ramis Vidal, M. Ramos Arevalo, A. Ramos-Buades, S. Ranjan, M. Ranjbar, K. Ransom, P. Rapagnani, B. Ratto, A. Ravichandran, A. Ray, V. Raymond, M. Razzano, J. Read, J. Regan, T. Regimbau, T. Reichardt, S. Reid, C. Reissel, D. H. Reitze, A. I. Renzini, B. Revenu, A. Revilla Peña, L. Ricca, F. Ricci, M. Ricci, A. Ricciardone, J. Rice, J. W. Richardson, M. L. Richardson, A. Rijal, K. Riles, H. K. Riley, S. Rinaldi, J. Rittmeyer, C. Robertson, F. Robinet, M. Robinson, A. Rocchi, L. Rolland, J. G. Rollins, A. E. Romano, R. Romano, A. Romero-Rodríguez, I. M. Romero-Shaw, J. H. Romie, S. Ronchini, T. J. Roocke, L. Rosa, T. J. Rosauer, C. A. Rose, D. Rosińska, M. P. Ross, M. Rossello-Sastre, S. Rowan, K. Rowlands, S. K. Roy, S. Roy, D. Rozza, P. Ruggi, N. Ruhama, G. H. Ruiz, E. Ruiz Morales, K. Ruiz-Rocha, V. Russ, S. Sachdev, T. Sadecki, P. Saffarieh, S. Safi-Harb, M. R. Sah, S. Saha, T. Sainrat, S. Sajith Menon, K. Sakai, Y. Sakai, M. Sakellariadou, S. Sakon, O. S. Salafia, F. Salces-Carcoba, L. Salconi, M. Saleem, F. Salemi, M. Sallé, S. U. Salunkhe, S. Salvador, A. Salvarese, A. Samajdar, A. Sanchez, E. J. Sanchez, N. Sanchis-Gual, J. R. Sanders, E. M. Sänger, F. Santoliquido, F. Sarandrea, T. R. Saravanan, N. Sarin, P. Sarkar, A. Sasli, P. Sassi, B. Sassolas, B. S. Sathyaprakash, R. Sato, S. Sato, Yukino Sato, Yu Sato, O. Sauter, R. L. Savage, T. Sawada, H. L. Sawant, S. Sayah, V. Scacco, D. Schaetzl, M. Scheel, A. Schiebelbein, M. G. Schiworski, P. Schmidt, S. Schmidt, R. Schnabel, M. Schneewind, R. M. S. Schofield, K. Schouteden, B. W. Schulte, M. Schulz, B. F. Schutz, E. Schwartz, M. Scialpi, J. Scott, S. M. Scott, R. M. Sedas, T. C. Seetharamu, M. Seglar-Arroyo, Y. Sekiguchi, D. Sellers, N. Sembo, A. S. Sengupta, E. G. Seo, J. W. Seo, V. Sequino, M. Serra, A. Sevrin, T. Shaffer, U. S. Shah, M. A. Shaikh, L. Shao, J. Sharkey, A. K. Sharma, Preeti Sharma, Priyanka Sharma, Ritwik Sharma, Sushant Sharma-Chaudhary, P. Shawhan, N. S. Shcheblanov, E. Sheridan, Z. -H. Shi, R. Shimomura, H. Shinkai, S. Shirke, D. H. Shoemaker, D. M. Shoemaker, R. W. Short, S. ShyamSundar, A. Sider, H. Siegel, V. Sierra, D. Sigg, L. Silenzi, L. Silvestri, M. Simmonds, L. P. Singer, Amitesh Singh, Anika Singh, D. Singh, M. K. Singh, N. Singh, S. Singh, M. R. Sinha, A. M. Sintes, V. Sipala, V. Skliris, B. J. J. Slagmolen, T. J. Slaven-Blair, J. Smetana, D. A. Smith, J. R. Smith, L. Smith, R. J. E. Smith, W. J. Smith, S. Soares de Albuquerque Filho, K. Somiya, I. Song, S. Soni, V. Sordini, F. Sorrentino, H. Sotani, F. Spada, V. Spagnuolo, A. P. Spencer, P. Spinicelli, A. K. Srivastava, F. Stachurski, C. J. Stark, D. A. Steer, N. Steinle, J. Steinlechner, S. Steinlechner, N. Stergioulas, P. Stevens, M. StPierre, M. D. Strong, A. Strunk, A. L. Stuver, M. Suchenek, S. Sudhagar, Y. Sudo, N. Sueltmann, L. Suleiman, K. D. Sullivan, J. Sun, L. Sun, S. Sunil, J. Suresh, B. J. Sutton, P. J. Sutton, K. Suzuki, M. Suzuki, A. Svizzeretto, S. Swain, B. L. Swinkels, A. Syx, M. J. Szczepańczyk, P. Szewczyk, M. Tacca, M. Tagliazucchi, H. Tagoshi, S. C. Tait, K. Takada, H. Takahashi, R. Takahashi, A. Takamori, S. Takano, H. Takeda, K. Takeshita, I. Takimoto Schmiegelow, M. Takou-Ayaoh, C. Talbot, M. Tamaki, N. Tamanini, D. Tanabe, K. Tanaka, S. J. Tanaka, S. Tanioka, D. B. Tanner, W. Tanner, L. Tao, R. D. Tapia, E. N. Tapia San Martín, C. Taranto, A. Taruya, J. D. Tasson, J. G. Tau, A. Tejera, R. Tenorio, H. Themann, A. Theodoropoulos, M. P. Thirugnanasambandam, L. M. Thomas, M. Thomas, P. Thomas, J. E. Thompson, S. R. Thondapu, K. A. Thorne, E. Thrane, J. Tissino, A. Tiwari, Pawan Tiwari, Praveer Tiwari, S. Tiwari, V. Tiwari, E. M. Todd, M. R. Todd, E. Tofani, M. Toffano, A. M. Toivonen, K. Toland, A. E. Tolley, T. Tomaru, V. Tommasini, T. Tomura, H. Tong, C. Tong-Yu, A. Torres-Forné, C. I. Torrie, I. Tosta e Melo, E. Tournefier, M. Trad Nery, A. Trapananti, R. Travaglini, F. Travasso, G. Traylor, M. Trevor, M. C. Tringali, A. Tripathee, G. Troian, A. Trovato, L. Trozzo, R. J. Trudeau, T. Tsang, S. Tsuchida, K. Tsuji, L. Tsukada, K. Turbang, M. Turconi, C. Turski, H. Ubach, A. S. Ubhi, N. Uchikata, T. Uchiyama, R. P. Udall, T. Uehara, K. Ueno, V. Undheim, L. E. Uronen, T. Ushiba, M. Vacatello, H. Vahlbruch, G. Vajente, J. Valencia, M. Valentini, E. Vallejo-Pagès, S. A. Vallejo-Peña, S. Vallero, M. van Dael, E. Van den Bossche, J. F. J. van den Brand, C. Van Den Broeck, M. van der Kolk, M. van der Sluys, A. Van de Walle, J. van Dongen, K. Vandra, M. VanDyke, H. van Haevermaet, J. V. van Heijningen, P. Van Hove, J. Vanier, J. Vanosky, N. van Remortel, M. Vardaro, A. F. Vargas, V. Varma, A. Vecchio, G. Vedovato, J. Veitch, P. J. Veitch, S. Venikoudis, J. Venneberg, R. C. Venterea, P. Verdier, M. Vereecken, D. Verkindt, B. Verma, Y. Verma, S. M. Vermeulen, F. Vetrano, A. Veutro, A. Viceré, S. Vidyant, A. D. Viets, A. Vijaykumar, A. Vilkha, N. Villanueva Espinosa, V. Villa-Ortega, E. T. Vincent, J. -Y. Vinet, S. Viret, S. Vitale, A. Vives, L. Vizmeg, H. Vocca, D. Voigt, E. R. G. von Reis, J. S. A. von Wrangel, W. E. Vossius, L. Vujeva, S. P. Vyatchanin, J. Wack, L. E. Wade, M. Wade, K. J. Wagner, L. Wallace, E. J. Wang, H. Wang, W. H. Wang, Y. F. Wang, Z. Wang, G. Waratkar, R. L. Ward, J. Warner, M. Was, T. Washimi, N. Y. Washington, B. Weaver, S. A. Webster, N. L. Weickhardt, M. Weinert, A. J. Weinstein, R. Weiss, L. Wen, K. Wette, C. Wheeler, J. T. Whelan, B. F. Whiting, C. Whittall, E. G. Wickens, D. Wilken, B. M. Williams, D. Williams, M. J. Williams, N. S. Williams, J. L. Willis, B. Willke, M. Wils, L. Wilson, C. W. Winborn, J. Winterflood, C. C. Wipf, G. Woan, J. Woehler, N. E. Wolfe, H. T. Wong, I. C. F. Wong, K. Wong, T. Wouters, J. L. Wright, M. Wright, B. Wu, C. Wu, D. S. Wu, H. Wu, K. Wu, Q. Wu, Z. Wu, E. Wuchner, D. M. Wysocki, V. A. Xu, Y. Xu, N. Yadav, H. Yamamoto, K. Yamamoto, T. S. Yamamoto, T. Yamamoto, R. Yamazaki, T. Yan, H. Yang, K. Z. Yang, Y. Yang, Z. Yarbrough, J. Yebana, S. -W. Yeh, A. B. Yelikar, X. Yin, J. Yokoyama, T. Yokozawa, S. Yuan, H. Yuzurihara, M. Zanolin, M. Zeeshan, T. Zelenova, J. -P. Zendri, M. Zeoli, M. Zerrad, M. Zevin, H. Zhang, L. Zhang, N. Zhang, R. Zhang, T. Zhang, C. Zhao, Yue Zhao, Yuhang Zhao, Z. -C. Zhao, Y. Zheng, H. Zhong, H. Zhou, H. O. Zhu, Z. -H. Zhu, Z. Zhu, A. B. Zimmerman, L. Zimmermann, M. E. Zucker,Comments: 38 pages (11 pages author list, 7 pages main paper, 8 pages references, 12 pages supplemental material), 15 figures (4 in main text, 11 in supplemental material); data products available from https://doi.org/10.5281/zenodo.18600070Subjects: gr-qc astro-ph.HE astro-ph.IMCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
GW240925 and GW250207 are two loud gravitational-wave signals from binary BLACK HOLE coalescences observed with network signal-to-noise ratios $\sim 32$ and $\sim 69$, respectively, by the LIGO Hanford--LIGO Livingston--Virgo network. Gravitational-wave signals from coalescing binaries have characteristic phase and amplitude evolution predicted by general relativity. These signal waveforms, together with measured instrumental calibration uncertainties, are used to infer source parameters. However, for sufficiently loud detections it is possible to constrain the calibration of the detectors directly using the signals themselves. We present the first informative astrophysical measurements of gravitational-wave detector calibration. For GW240925, we verify the inference of Hanford calibration from the astrophysical signal through cross-checks with known calibration errors obtained from in-situ measurements. At the time of GW250207, the Hanford detector was not fully stabilized, leading to elevated calibration uncertainties; thus, astrophysical calibration is essential to obtain accurate data and to enable source localization. These well-localized, high signal-to-noise observations have the potential to offer precise measurements of source properties, stringent tests of general relativity, and informative dark siren measurements, provided that calibration uncertainties are properly incorporated. As detector sensitivity improves, astrophysical calibration will become an increasingly valuable complement to in-situ calibration measurements. Obtaining accurate calibration will be essential for precision gravitational-wave science.
[abstract 16 / 54] Yes (score: 5) - Title: Magnetic Prandtl number dependence of plasmoid-mediated RECONNECTionAuthors: Vinay Kumar, Axel Brandenburg,Comments: 29 pages, 15 figures. Comments welcome!Subjects: physics.plasm-ph astro-ph.HE physics.flu-dynCreated: 2026-08-14; Updated: 2026-08-18; Datestamp: 2026-08-18
We investigate the dependence of the plasmoid-mediated MAGNETic RECONNECTion rate on the MAGNETic Prandtl number using two-dimensional MAGNETohydrodynamic simulations of two coalescing MAGNETic islands. For Lundquist numbers below the onset of the plasmoid instability, the RECONNECTion rate follows the expected Sweet-Parker scaling and decreases with increasing MAGNETic Prandtl number. However, once the current sheet becomes plasmoid unstable, the dependence on the MAGNETic Prandtl number weakens considerably. In the fully plasmoid-mediated regime, we find RECONNECTion rates that remain nearly independent of the MAGNETic Prandtl number over the explored parameter range. We show that the largest RECONNECTion rates are associated with strongly non-linear phases involving plasmoid interactions and mergers. We further compare our results with simulations of the boundary-driven Taylor problem, where previous studies reported a stronger MAGNETic Prandtl number dependence, and provide a possible explanation for the differing scalings obtained in the two setups. These results may have implications for RECONNECTion-mediated decay in MAGNETically dominated turbulence and related astrophysical systems.
[abstract 17 / 54] Yes (score: 5) - Title: Magnetic Reconnection and Energy Extraction from a Rotating Black Hole in the Einstein-AdS SU(N)-Nonlinear Sigma ModelAuthors: Muhammad Israr Aslam, Muhammad Nawaz, Abdul Malik Sultan, Ke Wang, Hamood Ur Rehman, Yakup Yildirim,Comments:Subjects: gr-qcCreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
In the present study, we analyze the power and efficiency of energy extraction via MAGNETic RECONNECTion in the rotating Einstein-AdS-SU($N$)-NLSM BLACK HOLE, both in the circular-orbit regime and in the plunging region. Initially, we define the background properties of this spacetime, and then analyze the physical quantities such as the size of the ergoregion, the event horizon, and the boundaries of the ergosphere. We analyze the MAGNETic RECONNECTion process within circular orbits. We plot energy-extraction parameter diagrams and analyze the power and efficiency of energy extraction. Our results indicate that energy extraction remains feasible even at a spin parameter as low as $0.7$, significantly below previously reported thresholds, and the extracted power can exceed that of the Blandford-Znajek mechanism with specific constraints. The coupling constant $K$, AdS radius $l$ and the flavors number $N$, collectively participate in lowering the spin threshold for energy extraction. Consequently, we further investigate the permissible energy extraction region for the energy extraction mechanism in the plunging region, as well as the corresponding power output and efficiency. We observe that the energy extraction is possible even at a spin as low as $0.2$. Importantly, the parameters $N,~K$ and $l$ mainly contribute to lowering the energy extraction spin threshold. This behavior is similar to that in circular orbits. Finally, comparing the plunging region with the circular orbits, we observe that the energy extraction power in the plunging region is higher than in the circular orbits.
[abstract 18 / 54] Yes (score: 5) - Title: A Radio-Bright Local Little Red Dot AnalogAuthors: Luis F. Rodriguez, I. FElix Mirabel, Rosa A. Gonzalez-Lopezlira, Laurent Loinard,Comments: 11 pages, 2 figures. To appear in The Astrophysical JournalSubjects: astro-ph.GACreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
The James Webb Space Telescope revealed the existence in the early Universe ($z >$ 4) of large populations of little red dots (LRDs), compact red luminous sources that host rapidly growing supermassive BLACK HOLEs (SMBHs) surrounded by coeval nuclear starbursts. LRDs have defining properties, one of which is the absence of radio detections. LRDs could be radio-undetected because of their large distances. A way to investigate the radio properties of LRDs is to search for radio emission in their local analogs, the Local Little Red Dot (LLRD) galaxies at $z <$ 1 with analogous properties to LRDs. We report the radio continuum detection of the LLRD analog J204837.26${-}$002437.2 ($z$ = 0.4332, hereinafter J2048). This adds to the previous radio detection of two other LLRDs. However, with a flux density of 3.0$\pm$0.2 mJy at 3.0 GHz, J2048 is two orders of magnitude more radio luminous than the previous detections. The spectral index of $α$ = -0.39$\pm$0.04 is consistent with moderately optically-thick SYNCHROTRON emission. The radio luminosity of J2048 is $1.2 \times 10^{41}~ \mathrm{erg ~s^{-1}}$, in the lower end of the range defined by radio-loud giant elliptical galaxies and QUASARs of $L_R$ = $10^{41-46} ~\mathrm{erg ~s^{-1}}$. The expected radio luminosity of the SMBH associated with J2048 is estimated to be about an order of magnitude larger, suggesting that its radio luminosity could potentially be strongly dimmed. A cosmological ($z >$ 4) LRD with radio luminosity similar to that of J2048 would be detectable using the VLA with moderately long integrations.
[abstract 19 / 54] Yes (score: 5) - Title: A Cross-Band (X-ray $\times$ Optical) Periodicity Search for Supermassive Black Hole Binaries: A Null Result and the First Completeness-Corrected ConstraintAuthors: Karan Akbari,Comments: Accepted for publication in ApJ. 16 pages, 11 figures, 1 table. Code and result tables: doi:10.5281/zenodo.21386388Subjects: astro-ph.HE astro-ph.GA astro-ph.IMCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
We present the first sample-level search for supermassive BLACK HOLE binaries (SMBHBs) requiring coherent quasi-periodicity at a common period in the X-ray and optical bands, over 1194 SWIFT-BAT hard X-ray AGN (Stage 1) and 175 4XMM-DR14 AGN (Stage 2). No source is a co-periodic candidate. Each light curve is modelled as a damped random walk (DRW) and searched with a Lomb-Scargle periodogram and a look-elsewhere-corrected Monte-Carlo significance. Because DRW red noise is largely independent between corona and disc, we require both bands individually significant with periods coincident within 5%, and gate the survivors with the model-independent null-signal-template test of Robnik et al. (2024). Over $P=100$-$900$ d the completeness-corrected 95% upper limit on the co-periodic fraction is amplitude-dependent: $\lesssim 3\%$ for hard-X-ray fractional modulation $\gtrsim 0.3$, $\approx 15\%$ (precision-limited) at 0.2, and uninformative below $\sim 0.15$ (the $ε=1$ floor is 0.25%). The sensitivity is set by the hard X-ray monitoring, not the optical photometry or the statistics, the opposite of the usual assumption. Daily MAXI and RXTE/ASM monitoring of the brightest AGN raises the X-ray completeness 5-8-fold, and the search remains null. Integrated over the BAT black-hole mass function, the expected all-amplitude co-periodic fraction is $\sim 3\times10^{-2}\, f_{\rm bin}\, δ_{\rm mod}$ (modulo a factor $g<1$), with $f_{\rm bin}$ the sub-pc binary fraction, $δ_{\rm mod}$ the modulating duty cycle, and $g$ the fraction reaching recoverable hard-X-ray amplitude, so a null is expected. We deliver a validated cross-band framework and the first completeness-corrected constraint on the co-periodic fraction, ready for the denser X-ray monitoring of Einstein Probe and eROSITA.
[abstract 20 / 54] Yes (score: 5) - Title: The first comprehensive spectral and timing study of the ultra-compact X-ray binary 4U 1812-12 with NICER and NUSTARAuthors: Swarnendu Jana, Aditya S. Mondal, Aru Beri, Gulab C. Dewangan,Comments: 15 pages,13 figures,6 tables,Submitted to ApJSubjects: astro-ph.HECreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
The source 4U 1812-12 is a persistent, weakly variable low-mass X-ray binary containing a neutron star. The source was observed by NICER between 2019 and 2021 and, more recently, by NUSTAR in 2025. During the NICER and NUSTAR observations, the source was detected in a hard spectral state with a bolometric luminosity of $\sim 1.90\times 10^{36}$ ergs s$^{-1}$. Its $3-70$ keV NUSTAR spectrum is characterized by a soft thermal emission from the disc, a hard Comptonized emission from the corona, and its reflection from the accretion disc. The NUSTAR energy spectrum exhibits the clear presence of disc reflection features, fitted using a self-consistent RELATIVISTIC reflection model {\tt relxill}. Our reflection modeling indicates a moderately ionized accretion disc (log\:$ξ\sim2.72$) extending close to the neutron star surface ($R_{in}\lesssim 1.72\:R_{ISCO}$), and viewed through a small inclination angle ($i\sim 25$ degrees). Assuming that the MAGNETic field ($B$) truncates the disc, we found $B\lesssim 2.54\times 10^{8}$ G, comparable to the typical values observed for NS LMXBs. The $1.0-9.5$ keV NICER spectra are also characterized by a soft thermal component and a dominant hard Comptonized component. During NICER observations, the disc temperature exhibits a small variation within $\sim 0.69-0.84$ keV. In contrast, the power law photon index, $Γ$, exhibits a large variation of $\sim 0.8-1.5$, implying a substantial change in the Comptonized emission. Moreover, NICER timing analysis reveals broadband aperiodic variability with significant QPO-like features at $0.379\pm 0.008$ Hz and $0.724\pm 0.025$ Hz, having fractional rms amplitudes of $2.9\pm 0.6\%$ and $4.1\pm 0.5\%$, respectively.
[abstract 21 / 54] Yes (score: 4) - Title: Notes on Gravitational PhysicsAuthors: John L. Friedman,Comments: 392 pages. This updated version has minor corrections, replaces or deletes broken links, and includes some additional material on electromagnetism in flat and curved spacetimeSubjects: gr-qc astro-ph.HECreated: 2026-08-14; Updated: 2026-08-18; Datestamp: 2026-08-18
These notes are self-contained, with the first 7 chapters used in a one-semester course with recommended texts by Wald, by Misner, Thorne and Wheeler, and by Schutz. In its treatment of topics covered in these standard texts, the presentation here typically includes steps skipped in Wald or MTW. Treatments of gravitational waves, particle orbits in black-hole backgrounds, the Teukolsky equation, and the initial value equations are motivated in part by the discoveries of gravitational waves from the inspiral and coalescence of binary BLACK HOLEs and neutron stars, advances in numerical relativity, and the expected LISA space-based observatory. The notes begin with a detailed presentation of special relativity with a geometrical orientation, starting with with time dilation and length contraction and including RELATIVISTIC particles, fluids, electroMAGNETism, and curvilinear coordinates. Chaps. 2-5 cover curvature, the Einstein equation, RELATIVISTIC stars, and BLACK HOLEs. Chap. 6, on gravitational waves, includes a discussion of detection and noise. Chap. 7 is a brief introduction to cosmology, deriving the metrics of homogeneous isotropic space, the equations governing a universe with matter, radiation and vacuum energy, and their solutions, and discussions of the cosmological redshift and on using gravitational waves to measure the Hubble constant. Chap. 8, on the initial value problem, has a section on the form of the equations used in numerical relativity. The Newman-Penrose formalism and the Teukolsky equation are covered in Chap. 9. Following that is a chapter on black-hole thermodynamics and a final chapter on the gravitational action and on conserved quantities for asymptotically flat spacetimes, using Noether's theorem. An appendix covers forms, densities, integration, and Cartan calculus.
[abstract 22 / 54] Yes (score: 4) - Title: X-ray thread/Nonthermal Radio Filament associations: Evidence for Interstellar Magnetic ReconnectionAuthors: Q. Daniel Wang,Comments: Submitted to the IAUS 405 proceedings: Traversing the Galactic Center in Space and TimeSubjects: astro-ph.HE physics.space-phCreated: 2026-08-14; Updated: 2026-08-18; Datestamp: 2026-08-18
Nonthermal radio filaments (NTFs), first discovered at 20-centimeter wavelength more than four decades ago, are among the most enigmatic structures at the Galactic Center. They still defy a clear explanation. These striking narrow features trace intense MAGNETic fields and often stand in bold contrast to the Galactic plane. Recent discoveries have revealed surprising associations: some NTFs align well with X-ray threads that seem to exhibit Fe He-$α$ emission. Here, I present preliminary results from an ongoing, collaborative, multi-wavelength study aimed at understanding the origins of these filaments, focusing on testing the MAGNETic RECONNECTion scenario of these associations and shedding new light on the high-energy processes and MAGNETic phenomena operating under extreme conditions at the heart of our Galaxy.
[abstract 23 / 54] Yes (score: 4) - Title: 4U 1538-52 in a Heartbeat: Broadband X-ray Spectral Properties from XMM-Newton and NUSTARAuthors: C. M. Diez, S. Dupourqué, A. -L. Doherty, D. Dickson, A. Zainab, S. Martínez-Núñez, J. M. Torrejón, S. Guillot, A. Rouco Escorial, F. Fürst, P. Kretschmar,Comments: 13 pages, 9 figures, accepted for publication in A&A on 12 Aug. 2026Subjects: astro-ph.HECreated: 2026-08-14; Updated: 2026-08-18; Datestamp: 2026-08-18
Galactic high-mass X-ray binaries (HMXBs) are important systems for studying accretion mechanisms onto compact objects and for investigating the complex stellar winds of massive stars. In particular, HMXBs hosting a neutron star allow us to reveal the structure of the accreted material in X-ray pulsars and consequently to investigate how matter behaves under extreme conditions of pressure and density. These are major scientific goals for XRISM and NewAthena. Here we report on the first out-of-eclipse XMM-Newton observation of the HMXB 4U 1538-52, complemented by NUSTAR coverage. Our campaign aimed to investigate stellar-wind variability and continuum changes with high-resolution spectroscopy at a critical orbital phase: when the neutron star is in inferior conjunction. Thanks to simultaneous observations covering both soft and hard X-rays, we obtain the most detailed X-ray view of the accreted material in 4U 1538-52 to date. In particular, we perform time-resolved spectroscopy down to the pulse period of the neutron star to highlight wind clumping properties and accretion structures. In this dataset, we observe a bright flare reaching $\sim$10$^{37}\,\rm{erg\,s^{-1}}$ probably induced by the accretion of a $10^{20}\,\rm{g}$ clump, followed by a luminosity dip forming a heartbeat-like episode. This event is followed by three local absorption peaks with local variability of the order of the pulse period, and a gradual hardening of the underlying spectrum throughout the observation. This could indicate the presence of both small-scale and large-scale overdense structures in the vicinity of the neutron star, which can be attributed to clumps and filamentary structures embedded in the accretion wake. These observational evidences are further supported and reproduced by 3D hydrodynamic simulations.
[abstract 24 / 54] Yes (score: 4) - Title: Energy Extraction via Magnetic Reconnection from Rotating ModMax Black HolesAuthors: Shi-Hao Wang, Ke-Jian He, Guo-Ping Li, Yuan Meng,Comments: 18pages,16figuresSubjects: gr-qcCreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
Magnetic RECONNECTion has been widely recognized as an important mechanism for extracting energy from rapidly rotating BLACK HOLEs. We find that MAGNETic RECONNECTion can also efficiently extract energy from slowly rotating ModMax BLACK HOLEs. In this paper, we investigate the MAGNETic RECONNECTion process of ModMax BLACK HOLEs in both circular and plunging orbits. First, we analyze the fundamental characteristic quantities of the ModMax BLACK HOLE, including the event horizon, ergosphere radius, and circular photon orbits. The results indicate that the charge parameter $Q$ and screening factor $γ$ exhibit a competing effect on the fundamental characteristic quantities of the ModMax BLACK HOLE. Furthermore, for the extremal ModMax BLACK HOLE, a larger $Q$ and a smaller $γ$ lower the minimum allowed spin parameter $a$. Subsequently, we analyze the parameter space $(r,a)$ for energy extraction in circular and plunging orbits. A larger $Q$ and a smaller $γ$ reduce the region for energy extraction and decrease the minimum spin parameter $a$ required for energy extraction. For circular orbits, the minimum allowed spin parameter is $a\simeq 0.50071$, while for plunging orbits, this threshold further decreases to $a\simeq0.22407$. This proves that energy extraction from lower spin ModMax BLACK HOLEs is theoretically feasible. Finally, we compare the energy extraction region, power, and efficiency between circular and plunging orbits. It is found that these quantities in plunging orbits are always higher than those in circular orbits, indicating that energy extraction from plunging orbits via MAGNETic RECONNECTion may be more efficient.
[abstract 25 / 54] Yes (score: 4) - Title: Hybrid kinetic-MHD simulation on the formation of runaway electron current plateau during a current quench processAuthors: Weimin Fu, Ping Zhu,Comments:Subjects: physics.plasm-phCreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
Runaway electron (RE) generation is of great concern for high-current tokamak operations. A full-f particle-in-cell (PIC) model for RE dynamics has been developed and coupled with the 3D nonlinear extended MAGNETohydrodynamic (MHD) model implemented in the NIMROD code. Our model accounts for RE generation using analytical source terms and advances the RE motion along guiding-center (GC) orbits. The model was employed to simulate the formation of RE current plateau during a disruption, in which the plasma current becomes dominated by the RE current. The model agrees well with several RE codes based on fluid models when the RE GC drifts are ignored. For highly RELATIVISTIC REs, the grad-$B$ and curvature drifts can play a significant role in the RE generation and motion due to the increase in the safety factor profile during the current quench process.
[abstract 26 / 54] Yes (score: 4) - Title: A statistical relation of energy injection plateaus in multi-band afterglows of GAMMA-RAY BURSTsAuthors: Xiao-Yan Li, Tong Liu, Bao-Quan Huang,Comments: 12 pages, 3 figures, 1 table, accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
The origin of the plateau phase in GAMMA-RAY BURST (GRB) afterglows remains under debate, with the energy injection model being one of the most competitive explanations. If the plateau is truly driven by energy injection, the average X-ray and optical luminosities during the plateau phase, $L_{\rm X, plat, ave}$ and $L_{\rm opt, plat, ave}$, should naturally be correlated. Moreover, under this scenario, the scaling relations between the luminosities during the plateau and the normal decay phase are expected to be consistent since they share the same origin, i.e., SYNCHROTRON radiation from the external forward shock. Therefore, simultaneous multi-band observations are essential to verify this mechanism. In this work, we select a sample of 47 GRBs with simultaneous plateaus in both bands. We calculate their time-averaged isotropic luminosities for the plateau and the subsequent normal decay phases. We find a moderate positive correlation $\log L_{\rm X, plat, ave}=m\log L_{\rm opt, plat, ave}+c$ with a slope $m = 0.86 \pm 0.11$ for the plateau phase. This correlation supports the energy injection origin and offers a promising diagnostic approach to test the model. Furthermore, we obtain a similar slope $m = 1.05 \pm 0.05$ for the normal decay phase, which reinforces the idea that both phases share the same physical origin. Notably, the post-plateau data exhibit a systematic downward shift in luminosity, which may indicate the cessation of the central engine.
[abstract 27 / 54] Yes (score: 4) - Title: Coronal gas excitation as a tracer of supermassive BLACK HOLE mass: on the mid-IR coronal [Ne v] linesAuthors: J. S. Elford, A. Prieto, A. Rodríguez-Ardila,Comments: 12 pages, 2 figures with another in the appendix, 1 tableSubjects: astro-ph.GACreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Coronal lines (CL) may be a reliable proxy of supermassive BLACK HOLE (SMBH) masses in ACTIVE GALACTIC NUCLEi (AGN) because the production of these high ionisation potential (IP) lines is sensitive to the shape of the ionising continuum which, for a thin accretion disc, relies on the BLACK HOLE mass. In this work we study the connection between the [Ne\,v] coronal lines and the SMBH mass. We analyse the \textit{Spitzer spectra} of a sample of 27 AGN spanning three orders of magnitude in SMBH mass. Fluxes and the electron density in the coronal gas medium were measured after fitting Gaussians to both the $\rm [Ne\,v]14μm$ and $\rm [Ne\,v]24μm$ lines where detected at high signal to noise. Line fluxes were normalised to the Br$γ_{\rm broad}$ emission from the broad line region. We found strong correlations between the $\rm [Ne\,v]14μm/Brγ_{\rm broad}$ and $\rm [Ne\,v]24μm/Brγ_{\rm broad}$ line ratios and the SMBH mass. For this sample of 27 AGN we find scatters of 0.54 and 0.53 dex, respectively. These correlations support the theory that the coronal gas excitation is sensitive to a range of SMBH masses because of the dependence on the shape of the ionising continuum. The electron densities of the coronal medium are of the order 1000$\rm cm^{-3}$ supporting their nuclear origin. A comparison with density values derived from JWST for a subsample of objects confirm this conclusion. These results further demonstrate the ability to use CL as a SMBH mass proxy, allowing for accurate SMBH mass measurements in AGN.
[abstract 28 / 54] Yes (score: 4) - Title: Collisionless Shock Driven by a Supersonic Velocity ShearAuthors: Kazuki Kamiido, Yutaka Ohira,Comments: 5 pages, 5 figureesSubjects: astro-ph.HE physics.plasm-phCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
The long-term evolution of a RELATIVISTIC collisionless velocity shear in an unMAGNETized electron-positron plasma is investigated using a first-principle particle-in-cell simulation. The Alves instability converts the shear kinetic energy into thermal and MAGNETic field energy. The resulting pressures push the plasma, leading to the formation of collisionless shocks. The generated collisionless shocks would accelerate high energy particles, which is a possible solution to the injection problem of shear acceleration. In addition, the collisionless shocks generate a MAGNETic field turbulence that is required for the shear acceleration to work.
[abstract 29 / 54] (score: 3) - Title: Probing Dark Photon Dark Matter with CTAOAuthors: Júlia G. Mamprim, Aion Viana, Vitor de Souza,Comments: 27 pages, 12 figuresSubjects: astro-ph.HECreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
The dark photon is a hypothetical gauge BOSON arising in extensions of the Standard Model, and has emerged as a compelling DARK MATTER candidate. As dark photon DARK MATTER (DPDM), it can interact with electroMAGNETic fields via kinetic mixing, and the inelastic scattering process $γA^{\prime} \to e^+ e^-$ becomes kinematically allowed for gamma rays above a characteristic energy threshold. This interaction imprints unique spectral attenuation features at very-high-energies (VHE), offering an observational probe of DPDM models. Using the Cherenkov Telescope Array Observatory (CTAO) Instrument Response Functions (IRFs), we simulate observations of VHE sources and forecast novel sensitivities to the kinetic mixing parameter for the photon-dark photon scattering process. Our study focuses on three key astrophysical targets: the Crab Nebula and the BLAZARs Markarian 421 and Markarian 501. Additionally, we investigate the impact of DARK MATTER spikes around BLACK HOLEs on the upper limits. For the DARK MATTER spike scenario considered in this work, CTAO observations could probe the DPDM parameter space down to a mixing parameter of $\varepsilon \sim 10^{-8}$ for masses around $m_{A^{\prime}} \sim 10^{-1}\,\textrm{eV}$ through high-energy spectral attenuation, at a $95\%$ confidence level.
[abstract 30 / 54] (score: 3) - Title: A tensor invariant approach to energy flux in MAGNETohydrodynamic turbulenceAuthors: Conan M. Liptrott, Sandra C. Chapman, Bogdan Hnat, Nicholas W. Watkins,Comments:Subjects: physics.plasm-ph physics.flu-dynCreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
A scale-by-scale analysis of energy flux in the turbulent cascade can be performed using the spatially filtered MAGNETohydrodynamic (MHD) equations, while the gradient tensor invariants are widely used to characterize the structure of velocity and MAGNETic fields. Physical mechanisms responsible for energy flux require specific field configurations whose strength is quantified by these tensor invariants. We explore this requirement, showing that the tensor invariants act as proxies for mechanistic energy fluxes under quantifiable conditions. As a special case, the purely hydrodynamic contributions to energy flux can be expressed exactly in terms of the invariants of the velocity gradient tensor. We also show that the invariants bound the available energy flux for distinct physical mechanisms, formalizing the idea that each transfer mechanism requires field configurations with gradients of sufficient strength to support a given energy flux. Results are illustrated using three-dimensional simulations of freely decaying MHD turbulence. These findings advance our understanding of MHD turbulence by revealing key relationships between field topology and energy transfer across scales due to distinct physical mechanisms. They further provide a tool for probing the turbulent cascade using multispacecraft data where local tensor invariants are directly accessible.
[abstract 31 / 54] (score: 3) - Title: Ghostly DLAs in SDSS DR16Authors: Patrick Petitjean,Comments: Published in the Open Journal of AstrophysicsSubjects: astro-ph.GACreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
In Petitjean (2026, A&A 710, 340), we revisited the origin of proximate damped Lyman-alpha absorbers (PDLAs), which trace cold gas within 3000 km/s of the QUASAR redshift, and interpreted their kinematics and physical properties within a unified framework. We showed that most PDLAs are associated with the environment of the AGN and/or the QUASAR host galaxy. We also provided the first census and characterization of absorption systems exhibiting strong absorption from excited levels of atomic ground states among QUASAR-associated absorbers. Among these, ghostly and coronagraphic systems arise in dense, compact gas that partially covers the QUASAR emission regions. Most systems are associated with outflows reaching velocities up to -2000 km/s, while a smaller fraction of inflowing clouds extends to velocities of up to +1200 km/s. In the present work, we provide an updated classification of PDLAs, including a revised catalogue of ghostly systems that more than doubles the number of previously known detections. We investigate the properties of these systems by measuring and discussing the equivalent widths of the detected absorption lines in both stacked spectra and individual ghostly systems. In particular, we show that although most ghostly systems are bona fide DLAs, this is not always the case.
[abstract 32 / 54] (score: 3) - Title: Fitting trends in QUASAR emission and absorption line redshiftsAuthors: Netra K Subramanian, Prasad Subramanian, Nimisha G Kantharia,Comments:Subjects: astro-ph.CO astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
The spectrum of a QUASAR consists of a few emission lines whose wavelengths are shifted by similar redshifts and numerous absorption lines whose wavelengths are shifted by different redshifts. Hence each QUASAR is characterised by an emission line redshift and the absorption lines redshifts are all less than the emission line redshift. The distribution of observed absorption line redshifts ($z_{abs}$) with respect to emission line redshift ($z_{em}$) for a large sample of QUASARs shows a systematic trend as pointed out by \citet{2016arXiv160901593K}. They noticed that increase in $z_{em}$ is accompanied by a monotonic increase in the lowest detected value of $z_{abs}$ and inferred that the emission and absorption lines were all formed in the QUASAR. This study focuses on modeling the systematic trend in the observed $z_{em} \rightarrow z_{abs}$ distribution. We considered the redshift data of absorption lines of singly ionized magnesium (denoted by MgII) and triply ionized carbon (denoted by CIV) for a large sample of QUASARs. We find that the envelope of data points defining the lowest value of the MgII absorption line redshift (which we denote by $z_{MgIImodel}$) for a given $z_{em}$ satisfies $z_{MgIImodel} = (0.418 \pm 0.008) z_{em} - (0.482 \pm 0.02)$ with an $R^2$ value of 0.99. The model can be used to predict the lowest expected MgII absorption line redshift for any $z_{em}$. We find a similar model for the lowest expected redshift of triply ionized carbon lines for any $z_{em}$ which is $z_{CIVmodel} = 0.845 (\pm 0.0002) z_{em} - 0.153 (\pm 0.0006)$.
[abstract 33 / 54] (score: 3) - Title: Impact of a Cold Dark Matter Halo on Magnetic Reconnection and Energy Extraction from Kerr-like Black HolesAuthors: Muhammad Nawaz, Abdul Malik Sultan, Muhammad Israr Aslam, Rabia Saleem, Ke Wang,Comments:Subjects: gr-qcCreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
Recently, Comisso and Asenjo introduced a new energy extraction mechanism based on MAGNETic RECONNECTion. In this paper, we investigate the power and efficiency of MAGNETic RECONNECTion energy extraction in a rotating BLACK HOLE surrounded by a cold DARK MATTER halo. We first examine the properties of the underlying spacetime and its physical quantities, including the event horizon, photon sphere, and ergosphere. We then analyze the allowed energy extraction region and the corresponding energy extraction efficiency for circular orbits. Our results show that energy extraction is feasible for BLACK HOLEs with a spin parameter.
[abstract 34 / 54] (score: 3) - Title: Design and Realization of the LST Main Structure for the Cherenkov Telescope ArrayAuthors: T. Schweizer, J. Eder, H. Wetteskind, C. Jablonski, R. Stadler, R. Mirzoyan, D. Paneque, T. Masahiro, A. Fiasson, N. Geffroy, G. Deleglise, O. Blanch, J. Mundet, R. Garcia, A. J. Penuela Lopez,Comments: 20 pages, 13 figures, SPIE Astronomical Telescopes + Instrumentation 2026, 5 - 10 July 2026, Copenhagen, DenmarkSubjects: astro-ph.IMCreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
The 23 m diameter Large Size Cherenkov Telescope (LST) for CTA, located at 2250 m a.s.l. on the Canary Island of La Palma, is the next-generation Cherenkov telescope following MAGIC, H.E.S.S., and VERITAS. To enable rapid repositioning (180° in 18 s) for GAMMA-RAY BURST observations, the mechanical structure was designed to be ultra- lightweight (110 tons). The space-frame structure consists of slender struts made of carbon fibre, aluminium (dish and camera mast), and steel. The telescope is designed to withstand extreme environmental conditions at the ORM observatory on La Palma, including wind speeds up to 200 km/h, uplift forces, and ice loads of up to 30 tons. We present the structural design developed to meet these functional and environmental requirements. MPP Munich is responsible for the telescope's mechanical structure together with partner institutes in France (LAPP) and Spain (IFAE). The prototype, LST-1, has been operational since 2019, and three additional LSTs are curre1ntly under construction.
[abstract 35 / 54] (score: 3) - Title: A self-consistent solar coronal heating model by Alfvenic wavesAuthors: Hidetaka Kuniyoshi, Richard J. Morton,Comments: Accepted for publication in ApJSubjects: astro-ph.SR physics.plasm-phCreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
Alfvenic waves are prevalent throughout the solar atmosphere and are believed to play an essential role in coronal heating, classified as alternating current (AC) heating in contrast to direct current (DC) heating associated with quasi-static MAGNETic field line braiding. The relative importance of AC versus DC heating depends on the details of the photospheric driver and on the configuration of the MAGNETic field. Moreover, even if AC heating prevails, several wave dissipation mechanisms have been proposed, and which of them dominates remains unclear, as its efficiency depends on plasma compressibility and density inhomogeneity. We address these issues by performing three-dimensional radiative MAGNETohydrodynamic (MHD) simulations of a coronal loop spanning from the upper convection zone to the corona, which self-consistently capture many relevant physical processes. We find that the corona is predominantly heated by AC heating, with Alfven wave turbulence providing the primary contribution, accounting for at least 80% of the entire coronal heating in the present simulation. Our results strongly support the use of Alfven wave turbulence-based models employed in space weather and stellar activity research, such as the Alfven Wave Solar Model (AWSoM) and the Magnetohydrodynamic Algorithm outside a Sphere (MAS).
[abstract 36 / 54] (score: 3) - Title: A NUSTAR Reflection-Spectroscopy Survey of Cygnus X-1Authors: Kshitij Duraphe, Kartik Mandar, Chooda Khanal, Gopal Bhatta,Comments: Under review at ApJSubjects: astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
Relativistic-reflection measurements of Cygnus X-1 disagree on the extent of disk truncation and commonly infer supersolar iron abundances. We analyze a selected sample of 26 archival NUSTAR observations obtained between 2012 and 2024 using two configurations from one reflection-model family, with posterior modes sampled by preconditioned sequential Monte Carlo. In the baseline recovered modes, disk-surface ionization increases with photon index (Pearson r = +0.59), with state medians rising from log xi approximately 3.3 in the hard state to approximately 3.9 in the soft state. The corresponding free-emissivity fits give median inner radii of 6.6, 4.4, and 4.0 R_ISCO in the hard, intermediate, and soft states. Fixing q = 3 moves three of eight soft-state observations to the ISCO and one to 2.4 R_ISCO; four fixed-q fits have lower chi^2 than the sampled free-q solutions, showing that those runs missed higher-likelihood regions. The inferred radii are therefore model- and mode-dependent, and the spectra neither require nor exclude an ISCO disk or R_in greater than or approximately 20 R_ISCO. Baseline fitted abundances span A_Fe = 1.6-8.6, with a median of 4.9. Two observations separated by 7.2 hr yield A_Fe = 1.9 +/- 0.2 and 4.5 +/- 1.0, indicating that fitted abundance is not a direct composition measurement. Fixing A_Fe = 1.6 drives some densities toward the grid boundary and worsens the fits relative to A_Fe = 4.5. The wind parameters remain sensitive to the continuum, abundance, and orbital-phase sampling.
[abstract 37 / 54] (score: 3) - Title: Microcoulomb-level electron beam and multi-Joule hard X-rays driven by a high-efficiency LASER-plasma acceleratorAuthors: B. Mahieu, L. Ribotte, W. Cayzac, G. Boutoux, R. Parreault, J. Gastineau, E. Lamoine, F. Audo, R. Babjak, D. Batani, N. Blanchot, J. L. Bourgade, M. Brochier, T. Caillaud, P. Canel, S. Cavaro, C. Chappuis, S. Debesset, R. Diaz, E. D Humieres, W. Duchastenier, R. du Jeu, A. Duval, B. Etchessahar, M. Ferri, M. Garandeau, L. Gremillet, V. Henot, E. Journot, J. C. Kieffer, I. Lantuejoul, L. Le Deroff, N. Lemos, C. Rousseaux, F. Scol, K. Ta Phuoc, W. Vaillant, B. Vauzour, M. Vranic, X. Davoine, F. Albert,Comments:Subjects: physics.plasm-phCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
We report on the production of ultrahigh-charge RELATIVISTIC electron beams and the development of a LASER-wakefield acceleration platform at the LMJ facility. Making use of the kilojoule-class, sub-picosecond PETAL LASER pulse focused onto a supersonic helium gas JET, electron beams carrying a total charge beyond 1 $μ$C were generated, with energies up to $\sim$500 MeV. Given the ps-scale LASER pulse duration, an on-target intensity approaching $10^{19}~\mathrm{W/cm^2}$, and a plasma density reaching 2% of the critical density, electron energisation arises from a combination of self-modulated LASER wakefield acceleration (SMLWFA) and direct LASER acceleration (DLA). The resulting electron spectrum exhibits a Maxwellian-like distribution, characteristic of this mixed SMLWFA/DLA regime. The total energy carried by the electron beam is estimated to be up to 17 J, within a sub-ps duration. A broadband Joule-level photon beam was also produced by Bremsstrahlung, demonstrating the potential for future applications. Experimental results are supported by start-to-end numerical simulations, including 3-D particle-in-cell and Monte-Carlo particle transport calculations. These findings pave the way for applications requiring high-charge electron beams, including the generation of high-power secondary radiation or particle sources. The use of these beams to probe matter in high-energy density states driven by the nanosecond-duration LMJ beams represents another promising avenue.
[abstract 38 / 54] (score: 2) - Title: A Multiwavelength View of $ρ$ Oph I: Resolving the X-ray Source Between A and BAuthors: Sean J. Gunderson, Jackson Codd, Walter W. Golay, David P. Huenemoerder, John M. Cannon, J. Alex Fluegel, Philip E. Griffin, Nathalie C. Haurberg, Richard Ignace, Alexandrea Moreno, Pragati Pradhan, Alexis Riggs, James Wetzel, Claude R. Canizares, the MACRO consortium,Comments: Accepted for publication in ApJ, 5 figures, 5 tablesSubjects: astro-ph.SR astro-ph.HECreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
We present a multiwavelength analysis of the central stellar pair of $ρ$ Oph, components A and B. Using recent high-resolution \textit{Chandra X-ray Observatory} observations, we demonstrate with high confidence that the dominant X-ray source is $ρ$ Oph B, while $ρ$ Oph A is comparatively X-ray faint. This result contrasts with earlier \textit{XMM-Newton} observations, which, due to limited spatial resolutions, attributed the X-ray emission to $ρ$ Oph A. An analysis of $ρ$ Oph B's X-ray light curves and spectra reveals properties more consistent with a cool star than a hot star. We therefore propose that $ρ$ Oph B is an Algol-like binary system, consisting of a B-type primary and an active, X-ray-emitting GK-type companion.
[abstract 39 / 54] (score: 2) - Title: A Template-Based Search for Large-Scale-Structure--Correlated Anisotropy in the Nanohertz Gravitational-Wave Background Using the Public NANOGrav 15-Year Data SetAuthors: Yun Fang,Comments: 18 pages, 6 figures; published in Sci. China Phys. Mech. AstronSubjects: astro-ph.CO astro-ph.HECreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Recent PTA analyses reporting evidence for a nanohertz common-spectrum process motivate targeted tests of whether any anisotropic component of the stochastic gravitational-wave background (SGWB) is correlated with the nearby large-scale structure (LSS), as anticipated for an astrophysical background dominated by supermassive BLACK HOLE binaries. We present the first Bayesian PTA likelihood analysis that embeds an externally observed, full-sky galaxy-survey LSS template directly as an overlap-reduction-function (ORF) component. Using the 2MASS Photometric Redshift (2MPZ) galaxy catalog, we construct low-multipole LSS--correlated ORF templates in two redshift slices ($0
[abstract 40 / 54] (score: 2) - Title: Drift-reduced fluid modeling of rapidly rotating plasmasAuthors: Edward A. Tocco, Benjamin D. Dudson, Ian G. Abel, Ben Zhu,Comments:Subjects: physics.plasm-phCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
In this paper, we investigate the effects of rapid rotation (Mach number M ~ 1) on plasma fluid stability, focusing specifically on Kelvin-Helmholtz (KH) and interchange instabilities - including both MAGNETic-curvature-driven (CDI) and rotation-driven (RDI) interchanges. Building on previous studies of shear flow stabilization, we utilize a drift- reduced fluid approach rather than standard MAGNETohydrodynamics to capture finite Larmor-radius effects. To achieve this, the drift-reduced equations were modified to include the centrifugal force and implemented in hermes-3 (Dudson et al. 2024), an extension to the BOUT++ (Dudson et al. 2009) framework. Because plasma rotation both drives the RDI and provides stabilizing shear flow, we find that the global plasma stability is sensitive to background profile characteristics. We identify three distinct regimes of RDI behavior and establish a simple criterion based on the density and velocity profiles to predict RDI susceptibility. This approach is similar to recent local gyrokinetic studies of shear flow that compared instability growth rates to shearing rates (Ivanov et al. 2025). Finally, by examining cases where the plasma is both interchange- and KH-unstable, we find that global KH modes make the plasma less resistant to RDI.
[abstract 41 / 54] (score: 2) - Title: Exploring memory-burdened primordial BLACK HOLEs with ultra-high-energy cosmic-raysAuthors: Antonio Ambrosone, Marco Chianese, Carmelo Evoli,Comments: 11 pages, 5 figures. Published on Physical Review DSubjects: astro-ph.HE hep-phCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Quantum backreaction effects may quench Hawking evaporation through a ``memory burden'', allowing primordial BLACK HOLEs (PBHs) with formation masses well below $10^{15}~\mathrm{g}$ to survive to the present and contribute to the DARK MATTER. We show that ultra-high-energy COSMIC RAYs (UHECRs) provide a powerful and previously unexplored probe of this scenario. We compute the proton and neutron emission from memory-burdened PBHs, including the Galactic-halo contribution and the extragalactic proton component, and confront it with the Pierre Auger Observatory proton spectrum and its EeV neutron limits from the Galactic plane. This yields new constraints on the PBH dark-matter fraction as a function of the PBH formation mass and the evaporation-suppression parameter $k$. For $k\gtrsim 3$ the non-observation of ultra-high-energy protons leads to bounds competitive with those from UHE gamma rays, while neutron limits remain comparable to high-energy neutrino constraints. Our results highlights the key role of multi-messenger astronomy in constraining beyond-the-standard-model scenarios.
[abstract 42 / 54] (score: 2) - Title: Sachs Equations and Plane Waves VI: Penrose LimitsAuthors: Jonathan Holland, George Sparling,Comments: v3: Corrected a name in a referenceSubjects: gr-qcCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Let $(M,g)$ be a Lorentzian manifold whose local space $\mathcal N$ of unparametrized null geodesics is smooth. We show that its Penrose limits assemble into a smooth bundle of plane-wave germs with a canonical gauge-theoretic soldering to spacetime. The incidence correspondence $\mathcal U=\{(x,[γ]):x\inγ\}$ identifies the contact space modulo the tangent space to the sky of $x$ with the screen space at $x$, and identifies the contact line with the weight-two null quotient. These evaluation maps solder the associated-graded Penrose model. A first JET of contact scale fixes the affine scale and a Reeb representative of the weight-two direction. Above the resulting pullback of $J^1\mathcal S$, full neighborhood realizations form a torsor under the group $\mathscr G_>$ of weighted diffeomorphism germs with identity principal part. We also identify the sky-parabolic reduction and its further transverse-Lagrangian reduction to Rosen gauges. The reduction fails precisely where the chosen Lagrangian meets the moving sky, which is the Rosen caustic locus. The trace of the Grassmannian Schwarzian of the sky curve defines a conformally natural projective structure on each null geodesic, and its trace-free part is the Weyl tidal profile of the Penrose germ.
[abstract 43 / 54] (score: 2) - Title: Non-Dynamic Alignment in Magnetohydrodynamic TurbulenceAuthors: Amir Jafari,Comments:Subjects: physics.plasm-ph astro-ph.SR physics.space-phCreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
Dynamic alignment in MHD turbulence is commonly interpreted as a tendency of Elsässer increments to align toward smaller inertial-range scales. This interpretation is based on the amplitude-weighted diagnostic \(\langle A_r\sinθ_r\rangle/\langle A_r\rangle\), where \(A_r\) is the product of the two increment amplitudes and \(θ_r\) is the unweighted folded angle. We show that a decrease of the weighted angle toward smaller scales does not require dynamical alignment but can arise from a retention effect in measurements. At fixed scale, larger amplitudes correlate with smaller angles, making the weighted angle smaller than the unweighted angle without implying that the angular population evolves toward alignment with scale. The same covariance-driven reweighting structure underlies the Price equation in evolutionary biology. Applied here in scale space, it separates angular evolution from redistribution of amplitude weight: a lower measured weighted angle at smaller scales can reflect reweighting even when the unweighted angle remains nearly scale independent. In physical time, the picture predicts that, after matching initial amplitudes, high-amplitude large-angle fluctuations lose a larger amplitude fraction over finite lags than high-amplitude small-angle fluctuations, favoring intense small-angle events in weighted statistics. This retention picture allows perpendicular rms Elsässer increments to scale as \(\ell_\perp^{1/4}\), corresponding to an effective \(k_\perp^{-3/2}\) spectrum, without requiring dynamic alignment of typical fluctuations. We test these results using the Johns Hopkins Turbulence Database and NASA Wind measurements. Mean logarithmic increment amplitudes give steeper typical-amplitude slopes than rms-amplitude fits in both datasets, showing stronger sensitivity of second-order statistics to intermittent intense events.
[abstract 44 / 54] (score: 2) - Title: Spin-valley-layer coupling with dual control via stacking and electric field in antiferroMAGNETic bilayer Janus YIBrAuthors: Bo-Wen Yu,Comments: 8 pages, 6 figuresSubjects: cond-mat.mes-hall cond-mat.mtrl-sciCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
The modification and enhancement of antiferroMAGNETic two-dimensional semiconductor is considered crucial for realizing novel electronic properties and facilitating promising applications. For this purpose, we investigate six antiferroMAGNETic 2D bilayer Janus YIBr structures with different stacking variations by means of first-principles calculation and an effective low-energy model. The calculation of MAGNETic anisotropy energy shows that the direction of easy axis varies with different stacking. First-principles-calculated energy bands reveal that there is a Dirac RELATIVISTIC dispersion relation exists in the valence band in a wide energy window of 0.3 eV at least. The calculations for spin, atom properties and Berry curvature description show that there is spin, valley and layer coupling with spin splitting, valley POLARIZATION and valley Hall and layer Hall effects can be achieved in the bilayer Janus structures. Further analyses of the effect of external electric field can be used to control spin, valley and layer of the hole near the FERMI level and to realize an anomalous valley Hall effect. These can be useful in future exploration for novel properties, control methods and more functionalities in bilayer Janus structures.
[abstract 45 / 54] (score: 2) - Title: Evidence for Azimuthally Anisotropic MgII Absorption around DESI Luminous Red GalaxiesAuthors: Xuanyi Wu, Cheng Li,Comments: 10 pages, 5 figures, 3 table, resubmitted to ApJSubjects: astro-ph.GACreated: 2026-08-15; Updated: 2026-08-18; Datestamp: 2026-08-18
We use luminous red galaxies (LRGs) and background QUASAR spectra from DESI DR1 to measure the mean MgII equivalent width around massive quiescent galaxies as a function of projected radius and azimuth relative to the projected major axis. Our forced-measurement approach assigns a MgII doublet-window EW to every LRG-QUASAR pair, including spectra without individually detected absorbers, and subtracts a redshift-matched random-control signal measured from the same normalized QUASAR spectra. The all-angle profile declines smoothly over $r_p=0.01$-$1.0$ proper Mpc and shows stronger inner absorption at $0.4
[abstract 46 / 54] (score: 2) - Title: Why is GN-z11 Bright, Compact, and Nitrogen Enhanced? Insights from UV Absorption and Emission DiagnosticsAuthors: Minami Nakane, Masami Ouchi,Comments: 22 pages, 11 figures, submitted to ApJSubjects: astro-ph.GACreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
We investigate the UV spectrum of GN-z11, a luminous, compact galaxy with strong nitrogen lines, at $z=10.60$, using deep JWST/NIRSpec high-resolution IFU and medium-resolution MSA spectra assembled from the JADES, SPURS, and GO programs. After optimized reduction and extraction of the IFU data including an evaluation of statistical and systematic uncertainties, we obtain mutually consistent spectra from the high- and medium-resolution observations. After carefully accounting for the data quality limitations, we identify prominent P-Cygni profiles in NV$λ\lambda1238,1243$, SiIV$λ\lambda1394,1403$, and CIV$λ\lambda1548,1550$, together with broad NIV]$λ\lambda1483,1486$ emission (FWHM $\sim1600$ km s$^{-1}$). The P-Cygni profiles resemble those of massive stars such as O-type stars and luminous blue variables (LBVs), while the broad NIV] emission resembles that of nitrogen-sequence Wolf-Rayet (WN) stars. We fit stellar and ACTIVE GALACTIC NUCLEi (AGN) UV spectral models and find that the stellar models are strongly preferred over the AGN models ($Δ$WAIC $=-25$), with the preference driven primarily by the NV P-Cygni profile. These results indicate that the luminous, compact UV continuum of GN-z11 is dominated by massive stars. We derive electron densities from CIII]$λ\lambda1907,1909$, NIII]$λ\lambda1747-1754$, and NIV], with the nitrogen diagnostics extending well beyond the CIII]-based limit and reaching densities of $\gtrsim10^{6.5}$ cm$^{-3}$ for NIV], indicating physically distinct carbon- and nitrogen-emitting nebular components. These findings suggest that the apparent nitrogen enhancement inferred for GN-z11 as a whole may arise when strong narrow nitrogen emission originates from dense gas locally enriched in nitrogen by WN stellar winds and photoionized by nearby massive stars within the same star-forming region.
[abstract 47 / 54] (score: 2) - Title: Radio Monitoring of Classical Novae using the ASKAP Variable and Slow Transients SurveyAuthors: Aishani Majumder, David L. Kaplan, Laura N. Driessen, Ashna Gulati, Tara Murphy, Dougal Dobie,Comments: Accepted for publication in Publications of the Astronomical Society of Australia (PASA)Subjects: astro-ph.HE astro-ph.SRCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
We present a search for radio emission from classical novae at 887.5 MHz using data from the Australian SKA Pathfinder Variable And Slow Transient (VAST) survey. We cross-matched 43 optically discovered classical novae that erupted between 2021 September and 2025 November within the 1200-square-degree Galactic survey footprint, and found three which show significant radio emission: V6598 Sgr, V1716 Sco, and V1723 Sco. To analyse their radio light curves, we use both thermal free-free and non-thermal SYNCHROTRON emission models. We fit the data using the Markov chain Monte Carlo (MCMC) method to constrain parameters, including the ejected mass and ejecta velocities for the thermal models, and mass-loss rate, explosion energy, wind velocity, and filling factor for the non-thermal model. All three novae show evidence of non-thermal SYNCHROTRON emission as the dominant emission mechanism at this frequency. We use a broken power law to describe the radial density structure of a non-uniform circumbinary material, which provides a better fit than a standard wind density profile. This strong early-time SYNCHROTRON emission is strong evidence of shock-driven particle acceleration, which may be related to detections of gamma-rays from all three novae as well. In contrast to earlier studies that used multi-frequency data to distinguish between emission models, our analysis is based on single-frequency radio light curves, which can still provide useful constraints on the dominant emission mechanism when interpreted with physically motivated models
[abstract 48 / 54] (score: 2) - Title: The reddening of NGC 7469 and evidence for variable extinctionAuthors: C. Martin Gaskell, Ananya R. Kamath, Emily I. Kwan, Divya G. Subramonian,Comments: 9 pages, 9 figures. Comments welcomeSubjects: astro-ph.GACreated: 2026-08-16; Updated: 2026-08-18; Datestamp: 2026-08-18
We estimate the reddening of the broad-line region and continuum of the ACTIVE GALACTIC NUCLEus NGC 7469 during the 1996 International AGN Watch multi-wavelength monitoring campaign using seven different reddening indicators. As was found for NGC 5548, these indicators support velocity-integrated broad hydrogen line ratios being close to Case B values. All the indicators point to substantial reddening of E(B-V) = 0.44 +/-0.03 for NGC 7469 during mid-1996. We find evidence for a gradual increase of about 10% in the reddening during the seven weeks of the 1996 campaign. Decades-long optical monitoring before and after the campaign is also consistent with modest changes in the extinction from year to year.
[abstract 49 / 54] (score: 2) - Title: Population-Level Verification of the Black-Hole Area Law with First- and Second-Generation Black HolesAuthors: Shao-Peng Tang, Yin-Jie Li, Yi-Zhong Fan,Comments: 9 pages, 6 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Hawking's area theorem states that the total event-horizon area of classical BLACK HOLEs (BHs) can never decrease. Existing gravitational-wave tests analyze single loud events (GW150914, GW230814, GW250114) and therefore certify the law only for the specific mergers observed. Here we perform the {\it first} population-level test, exploiting the recent decomposition of the GWTC-5 BBHs into a low-spin subpopulation of stellar-collapse origin and a high-spin subpopulation formed through hierarchical mergers of the former. If the high-spin BHs are merger remnants (i.e., second-generation BHs), the area law requires their horizon areas to statistically exceed the total pre-merger areas of the low-spin binaries. Using inspiral-only parameter estimation for 241 events, independent of merger-ringdown modeling, we find that both peaks in the horizon-area distribution of second-generation BHs lie above their first-generation counterparts, with probabilities of $0.9995$ ($3.3σ$) and $0.983$ ($2.1σ$), respectively. The area law thus holds statistically for the quasicircular, moderately spinning mergers that dominate current catalogs, which in turn underpins the robustness of our classification of stellar-collapse and hierarchical-merger BHs.
[abstract 50 / 54] (score: 2) - Title: Modelling of Flowing Plasma in the Magnetic Field of the Small Volume Plasma System ExperimentAuthors: Subhasish Bag, Ashish Ganguli, Vikrant Saxena, Ramesh Narayanan, Debaprasad Sahu,Comments: 23 pages, 31 figuresSubjects: physics.plasm-phCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
A flow model for a MAGNETized plasma has been developed to investigate the flow dynamics in the small volume plasma system (SVPS) experiment. The SVPS experimental conditions require the model to describe a stationary, collisional, quasineutral, axisymmetric plasma. Also, the ions are cold while the electrons are isothermal and in thermal equilibrium, obeying the Boltzmann relation. In a plasma flowing along a MAGNETic field, the velocity of ions along the MAGNETic field lines is much greater than the velocity perpendicular to the field. The latter feature permits a unique ordering of the relevant variables, when the flow equations are transformed to the MAGNETic coordinate system (MCS), where the coordinate axes are parallel and perpendicular to the field lines. The ordering of the flow variables in the MCS allows a further simplification of the flow equations, by permitting their splitting into set of reduced, simplified equations. The SVPS experimental data are used to provide the requisite boundary conditions for initializing and solving the reduced flow equations on a MAGNETic coordinate grid along the different lines of the MCS. An important aspect of the present work is the validation of the splitting scheme used to derive the simplified and reduced flow equations. This is achieved by an in-depth comparison of the predictions from the model equations with the experimental data. The obtained numerical results compare favourably with the SVPS observations and have been discussed rigorously. The model developed here provides a framework for exploring MAGNETized plasma dynamics in the given cylindrically symmetric MAGNETic field configuration and can be further extended to more complex configurations.
[abstract 51 / 54] (score: 2) - Title: Broadband Properties of the Harmonic of Type-C Quasi-periodic Oscillation in MAXI J1348-630Authors: Xin-Lei Wang, Zhen Yan, Jun-Feng Wang, Fu-Guo Xie, Zhan-Yi Liu, Ren-Yi Ma,Comments: 12 pages, 5 figures, accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Harmonics are common features of quasi-periodic oscillations (QPOs) in BLACK HOLE X-ray binaries; however, their physical origins remain poorly understood. Using broadband Insight-HXMT data, we investigated the Type-C QPO harmonic in MAXI J1348-630. The harmonic is significantly detected exclusively during the hard intermediate state and displays prominent energy-dependent properties: while it is strong in the soft X-ray band (< 10 keV) with its fractional rms amplitude even exceeding that of the fundamental QPO, it is much weaker in the hard X-ray band (> 10 keV), where its rms amplitude is generally several times lower than that of the fundamental. Furthermore, the harmonic shows no significant phase coupling with the fundamental in the soft X-ray band, whereas strong coupling is present in the hard X-ray band. These features point to a complex, energy-dependent origin for the harmonic. We propose that the hard X-ray harmonic may arise from nonlinear distortion of the fundamental waveform within the corona, while the soft X-ray harmonic is likely produced via a distinct physical process, such as the reflection emission from the inner disk.
[abstract 52 / 54] (score: 2) - Title: A posteriori correction of Gaia CRF proper motions using conditional probability and zero-parallax priorAuthors: Valeri V. Makarov,Comments: Submitted, under review, version 4Subjects: astro-ph.GACreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Precision of proper motions and positions given in the Gaia Celestial Reference Frame (CRF) catalog can be statistically improved introducing conditional probability based on the prior knowledge of zero parallax for these extremely distant sources. The method developed in this study produces statistically conditioned proper-motion estimates under the assumed per-source Gaussian covariance model. It is demonstrated that thus corrected proper motion vectors of 1.2 million CRF objects in Gaia DR3 show a tighter distribution around zero and a general reduction in the rate of outliers by approximately 15\%. A general vector spherical harmonic fit to degree 4 is produced with the corrected data for a filtered subset of CRF QUASARs with redshifts between 1 and 1.5. This application, predicated on the unknown stochastic component of the global parallax field, shows a 3-sigma change in the estimated magnitude of the Galactocentric acceleration of the solar system barycenter, quantifying the sensitivity of this fundamental determination to the proposed conditioning of proper motions.
[abstract 53 / 54] (score: 2) - Title: Inclination Diffusion in Relativistic Loss ConesAuthors: Wenkang Xin,Comments: 8 pages, 2 figures. Comments welcomeSubjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Relativistic capture and tidal disruption around a spinning BLACK HOLE depend on both the magnitude and direction of the star's angular momentum, yet loss-cone models often assume fixed orbital inclinations by ignoring the associated diffusion. We show that this is not justified: for isotropic two-body relaxation near a small loss threshold, angular-momentum magnitude $L$ and inclination $x = L_{z}/L$ diffuse on comparable timescales, $t_{E} \gg t_{L} \sim t_{x}$. For Kerr capture, retaining inclination diffusion significantly amplifies the prograde--retrograde contrast while leaving the total inclination-integrated flux nearly unchanged. An almost correct integrated flux can hide a badly wrong angular distribution. The three-dimensional diffusion problem nevertheless retains enough angular structure to permit analytic treatment. By representing pericenter removal as a continuous sink, we obtain a closed-form loss flux solution for a nearly linear Kerr tidal-disruption boundary, finding close agreement with phase-resolved calculations. Inclination-dependent loss therefore requires inclination-resolved diffusion even when integrated rates appear robust.
[abstract 54 / 54] (score: 2) - Title: Identifying AGNs from X-ray detections$-$II: Metallicity calibrations for the $\rm N_2O_2$ and $\rm N_2S_2$ diagnosticsAuthors: Mark Armah, O. L. Dors, Rogério Riffel, M. V. Cardaci, G. F. Hägele, Rogemar A. Riffel, J. M. Vílchez,Comments: 18 pages, 8 figures, accepted for publication by MNRAS; DOI: 10.1093/mnras/stag1563Subjects: astro-ph.GACreated: 2026-08-17; Updated: 2026-08-18; Datestamp: 2026-08-18
Emission-line ratios from ions with nearly identical ionization potentials offer a robust solution to the degeneracies inherent to traditional ACTIVE GALACTIC NUCLEi (AGNs) metallicity diagnostics. We introduce new semi-empirical metallicity calibrations for the $\rm N_2O_2$ and $\rm N_2S_2$ diagnostics, explicitly designed to isolate the chemical abundance from the incident radiation field. By coupling an extensive grid of CLOUDY photoionization simulations directly to the intrinsic 2$-$10 keV X-ray luminosity ($L_{\rm X}$) and benchmarking against Seyfert~2 nuclei from the Burst Alert Telescope AGN Spectroscopic Survey (BASS), we establish robust relations valid across the metallicity regime of $8.0 \lesssim 12+\log({\rm O/H}) \lesssim 9.1$ ($0.2 \lesssim Z/Z_{\odot} \lesssim 2.6$). The $\rm N_2O_2$ and $\rm N_2S_2$ indices trace co-spatial emitting volumes within the narrow-line regions (NLRs), enabling this framework to resolve the significant $L_{\rm X}$-driven systematic biases we previously identified in the standard $\rm N_2$ and $\rm N_2O_3$ indices. While the $\rm N_2O_2$ ratio proves to be virtually independent of nebular structural variations, the $\rm N_2S_2$ index exhibits a subtle, yet discernible, electron density ($N_{\rm e}$) susceptibility due to the low critical density ($N_{\rm c}$) of the [S II]$λ\lambda6716,6731$ doublet. Nevertheless, both diagnostics yield highly precise metallicity constraints with tight root-mean-square residual dispersions of $\sim 0.081$ dex for $\rm N_2O_2$ and $\sim 0.121$ dex for $\rm N_2S_2$. We propose the $\rm N_2O_2$ and $\rm N_2S_2$ calibrations as highly optimized, unbiased metallicity tracers for AGNs.
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