Current date: 2026-07-17
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Created/updated limit: 2026-07-10 (7 days ago)
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Number of records retrieved: 764
Keyword score statistics
score 7 -- 1 abstracts
score 6 -- 1 abstracts
score 5 -- 6 abstracts
score 4 -- 6 abstracts
score 3 -- 7 abstracts
score 2 -- 23 abstracts
in total -- 44 abstracts
Articles that appeared on 2026-07-17
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[abstract 1 / 44] Wow! (score: 7)
- Title: Signatures of Black Hole Spin in Horizon-Scale PolarimetryAuthors: George N. Wong, Daniel C. M. Palumbo, Zachary Gelles, Andrew Chael,Comments: 33 pages, 8 figures. prepared for a Galaxies special issue on black hole spinSubjects: astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
The angular momentum of a BLACK HOLE, usually expressed in terms of a dimensionless "spin," both shapes the strong-field spacetime and provides a reservoir of rotational energy that can be exchanged with surrounding plasma. Very long baseline interferometry (VLBI) has now begun to resolve polarized emission on event-horizon scales. We distinguish polarimetric signatures of spin arising primarily from photon propagation in the Kerr spacetime from those mediated by horizon-threading electroMAGNETic fields and MAGNETized plasma dynamics. We trace the inference from VLBI correlations through Stokes images and compact summary statistics to constraints on the source and, ultimately, on spin. Within this framework, we review diagnostics linked to horizon regularity and MAGNETic-field winding, MAGNETically arrested accretion, electroMAGNETic energy extraction, JET-base and light-cylinder structure, and horizon and photon-ring POLARIZATION. Current Event Horizon Telescope observations constrain MAGNETic-field geometry, variability, source orientation, MAGNETic flux state, and aspects of the disk-JET connection more robustly than they constrain spin magnitude or sense. Future observing and modeling programs should prioritize combinations of polarimetric diagnostics with complementary systematics and test whether a common spin-dependent interpretation is supported across independent data products and plausible source models.
[abstract 2 / 44] Yes (score: 6) - Title: Observation of A Solar Like Magnetic Reconnection Event in an AGN Corona with XRISMAuthors: Gal Vardi, Ehud Behar, Liyi Gu, Jelle Kaastra, Matteo Guainazzi, Missagh Mehdipour, Keigo Fukumura, Jon Miller, Ari Laor, Erin Kara, Megan E. Eckart, Misaki Mizumoto, Christos Panagiotou, Chen Li, Ogawa Shoji, Matilde Signorini, Keqin Zhao,Comments: Accepted to ApjL. Added Figure 4Subjects: astro-ph.HE astro-ph.SRCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The X-ray source in AGN is commonly referred to as the corona by analogy to stellar coronae. The similarities between the two suggest that the heating mechanism of AGN coronae is MAGNETic RECONNECTion -- as in cool stars -- but this has not yet been directly observed. This work presents the first observational evidence for a MAGNETic RECONNECTion flare in an AGN corona. We report on a flare in NGC 3783, which was observed with XRISM/Xtend and XMM-Newton/EPIC-PN exhibiting distinct temporal evolution in soft ($<2.0\,$keV) and hard ($>2.0\,$keV) X-rays. An Ultra-Fast Outflow (UFO) was detected during the event. The flare features the Neupert effect -- a temporal signature of the hard light curve correlating with the time derivative of the soft light curve, which shows that the flare is powered by MAGNETic RECONNECTion, The Neupert effect is widely observed in the Sun, with Coronal Mass Ejections (CMEs) playing a role analogous to the UFO. We derive an upper limit of $30 \, R_g$ on the height of the MAGNETic loop from which the flare originates. Using the UFO's measured properties to characterize the MAGNETic field, we obtain $B > 1.3 \times 10^4\,$G for the field annihilated during the flare from total energy considerations, and $B \approx 500\,$G for the momentary MAGNETic field during RECONNECTion from a dynamical consideration.
[abstract 3 / 44] Yes (score: 5) - Title: Short-Duration Gamma-ray Burst and Afterglow Rates in the Rubin and Roman EraAuthors: Tzvetelina Dimitrova, Nathaniel Butler,Comments: ApJ acceptedSubjects: astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
Short-duration GAMMA-RAY BURST (sGRB) afterglows that follow BNS-gravitational wave (GW) events are essential for understanding the tension between the observed sGRB rate and BNS merger rate, heightened by the recent conclusion of aLIGO O4 with no new confirmed BNS detections. Using a probabilistic sGRB world model derived from a source BNS merger population, we simulate afterglow emission with AfterglowPy to investigate detection prospects of afterglows in the new era of optical surveys, and probe their multi-messenger implications. The predicted sGRB/BNS association is strongly dependent on sGRB beaming, which may be constrained by orphan afterglows (OA) - that arise from events with no prompt $γ$-ray detection. We conclude that the Vera C. Rubin Observatory's Large Synoptic Survey Telescope (LSST) may detect an afterglow sample sufficient in constraining sGRB JETting, with an estimated $5.3^{+1.7}_{-1.2}$ on-axis afterglow and $11^{+5}_{-3}$ OA detections per year; while the deep sensitivity of the Roman Space Telescope appears promising for probing the faint end of afterglow events in targeted follow-up strategies. The detection of afterglows in upcoming LIGO runs is possible but challenging, as we predict fewer than $\approx 1.4$ LSST or Roman discoverable events per year within the projected aLIGO O5 BNS range across all considered JET models and observing scenarios. We update previous sGRB-BNS rate predictions, finding that continued non-detection of a BNS in O5 would require revisiting key assumptions underlying sGRB-BNS models.
[abstract 4 / 44] Yes (score: 5) - Title: Ultra-long simulations of collisionless RELATIVISTIC shocks in front-comoving frame: evidence for a steady state and its propertiesAuthors: Mikhail Garasev, Evgeny Derishev,Comments: 16 pages, 12 figuresSubjects: astro-ph.HE physics.plasm-phCreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
We present a series of unprecedently long 2D3V PIC simulations of unMAGNETized RELATIVISTIC $e^{-}e^{+}$-pair shocks performed in a front-comoving frame. By implementing a moving-wall boundary condition in the downstream together with continuous injection at the upstream boundary, we maintain a fixed simulation domain size, opening the way to perform substantially longer simulations. Our longest runs extend beyond $100000\,ω_p^{-1}$, exceeding the duration of the previously published simulations by a factor of several. Across a diverse set of simulations -- varying upstream/downstream lengths, transverse sizes, and particle-per-cell counts -- we find strong evidence that the shock approaches an asymptotic, time-independent state. In the downstream region, the steady state depends only on the upstream temperature at the injection boundary and does not depend on a particular numerical realization. The upstream precursor evolves slower and retains a dependence on the simulation's upstream length, that may be of minor observational consequence, since radiation from astrophysical shocks predominantly originates from the downstream region. We also find that FERMI-type acceleration is limited in energy and a true power-law tail never forms. Another important finding is that the downstream MAGNETic field has a soliton-like structure, where individual MAGNETic domains evolve independently, each comprising a compact, highly MAGNETized core embedded within an extended, weakly MAGNETized region. The MAGNETic-field distribution around the centers of these spots has approximately Lorentzian profile.
[abstract 5 / 44] Yes (score: 5) - Title: A structure-preserving Numerical Method for the Compressible Resistive-Hall-MHD SystemAuthors: Murtazo Nazarov, Rafael Rodriguez-Velasco, Ignacio Tomas,Comments: 37 pages, 7 figuresSubjects: math.NA cs.NA physics.comp-ph physics.plasm-phCreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
In this paper, we present a structure-preserving method for the compressible resistive Hall-MAGNETohydrodynamics (MHD) model. The differential operator is split into two parts: a hydrodynamic part consisting of the compressible Euler equations, and a MAGNETic part consisting of a system coupling the Lorentz force and the induction equation. The method uses continuous Lagrange elements for the Euler part and a curl-conforming finite element space for the MAGNETic part. The hydrodynamic part preserves the positivity of the density and internal energy, the conservation of total energy, and the minimum principle for the specific entropy. Owing to the choice of finite elements, the MAGNETic part preserves the divergence involution constraint. The fluid part is solved using explicit strong-stability-preserving Runge-Kutta (SSP-RK) methods, whereas the MAGNETic part is solved by Crank-Nicholson method, which requires using Newton's method. Coercivity estimates for the Jacobian of the corresponding Newton iteration are presented. We introduce a high-order artificial resistivity to improve the conditioning of the nonlinear residual and the invertibility of the Jacobian. Several challenging benchmarks, including a smooth whistler wave, the Orszag-Tang vortex for comparing resistive MHD with resistive Hall-MHD, and a MAGNETic RECONNECTion problem, are solved to validate the robustness and accuracy of the method.
[abstract 6 / 44] Yes (score: 5) - Title: Einstein Probe Fast X-ray Transients Extend the Physical Parameter Space of Relativistic JetsAuthors: Connery Chen, Yihan Wang, Bing Zhang,Comments: Accepted for publication in ApJLSubjects: astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
Fast X-ray Transients (FXTs) detected by the Einstein Probe (EP) mission possess exceptionally low spectral peak energies compared to typical long (Type II) GRBs. Some of these extragalactic transients show phenomenological similarities to X-ray flashes (XRFs), but the physical origins of FXTs remain uncertain. In this work, we investigate EP-detected FXTs using various JET structures relevant to Type II GRBs and test the hypothesis that these FXTs belong to the intrinsically same population of known GRBs but viewed at large angles from the JET axis. We apply detectability estimates to evaluate their distribution in the observed E_iso-E_p plane. We find that standard single- and multi-component JET structures can reproduce the energetics of off-axis events such as GRB 170817A and low-luminosity GRBs (llGRBs), while also yielding energetics consistent with XRFs at the lower end of the E_iso-E_p continuum for moderately off-axis observers. However, viewing-angle effects of standard Type II GRBs alone cannot account for the E_p values observed in some energetic FXTs. This tension suggests that EP-detected FXTs are unlikely to be explained solely as classical GRBs viewed off-axis, and may instead probe RELATIVISTIC explosions in a previously underexplored region of parameter space. In particular, these transients may be associated with lower Lorentz factors, reduced angular momentum in the collapsing core, or alternative JET structures and emission mechanisms. Our results motivate further studies to test these scenarios and constrain the physical properties of FXT progenitors and their outflows.
[abstract 7 / 44] Yes (score: 5) - Title: Black-Hole Spin Measurements from X-ray Reflection Spectroscopy: Quality Criteria and Community RecommendationsAuthors: Javier A. Garcia, Riley Connors, Laura W. Brenneman, James F. Steiner,Comments: 20 pages, 3 figures. Paper for the 2025 Wake Forest workshop Recent Progress on Black Hole Spin Measurements Across the Electromagnetic and Gravitational SpectraSubjects: astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
X-ray reflection spectroscopy provides one of the most powerful electroMAGNETic methods for measuring the dimensionless spin of accreting BLACK HOLEs. It has yielded spin constraints for stellar-mass BLACK HOLEs in X-ray binaries and supermassive BLACK HOLEs in ACTIVE GALACTIC NUCLEi, and is central to the science goals of current and future X-ray observatories. However, the technique is subject to observational and modeling systematics, including continuum-reflection degeneracy, limited spectral coverage, unresolved distant reflection or absorption, detector effects, source variability, accretion-state dependence, and assumptions inherent to reflection models. Motivated by discussions at the 2025 Wake Forest workshop *Recent Progress on Black Hole Spin Measurements Across the ElectroMAGNETic and Gravitational Spectra*, we propose a practical framework for evaluating whether published reflection-based spin measurements should be considered robust, provisional, or not assessable from the available information. The framework is built on three principles: **detectability**, requiring an unambiguous RELATIVISTIC reflection signal; **uniqueness**, requiring that the RELATIVISTIC component be distinguishable from the continuum, distant reflection, absorption, and instrumental effects; and **robustness**, requiring that the inferred spin remain stable against reasonable changes in model assumptions, data selection, and accretion-state treatment. We translate these principles into assessment criteria, a quality-classification scheme, and a reporting checklist for future studies. Calibration of these criteria through dedicated simulations is outlined here and deferred to a companion paper. Our goal is to establish a reproducible path toward a community-maintained compilation of reliable BLACK HOLE spin measurements for the high-throughput, high-resolution era of X-ray astronomy.
[abstract 8 / 44] Yes (score: 5) - Title: An asymptotic-preserving five-moment two-species plasma model coupled to an external MAGNETohydrodynamic solverAuthors: Magnus Deisenhofer, Aleksandr Mustonen, Simon Lautenbach, Rainer Grauer,Comments: 21 pages, 10 FiguresSubjects: physics.plasm-ph physics.comp-phCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
Accurately modeling collisionless space plasmas requires capturing small-scale kinetic effects while keeping global-scale simulations computationally tractable. Traditional multiscale approaches often rely on localized MAGNETohydrodynamics (MHD)-particle-in-cell (PIC) coupling or dynamic model hierarchies. In this work, we extend an established, adaptive multi-model hierarchy spanning from fully kinetic Vlasov descriptions to fluid models by introducing an asymptotic-preserving (AP) strategy that couples a two-species, five-moment fluid description with an ideal MHD solver. This coupling is the final critical step toward enabling efficient global simulations because the kinetic-scale physics in nonideal regions is entirely handled by finer models in the hierarchy. Kinetic descriptions natively solve Maxwell's equations and thus capture fast plasma waves, oscillations, and light waves, which are absent in the MHD dynamics. To address this difference without sacrificing computational efficiency, our AP framework seamlessly projects these fast dynamics onto the slow MHD dynamics, ensuring rigorous consistency at the model interfaces. We detail the AP two-fluid formulation, the variable-coupling interface, and its integration into external frameworks. Finally, we demonstrate the validity and robustness of the fully coupled framework, from kinetics to ideal MHD, through MAGNETic RECONNECTion simulations.
[abstract 9 / 44] Yes (score: 4) - Title: Gravitational Wave Astronomy With TianQinAuthors: En-Kun Li, Shuai Liu, Alejandro Torres-Orjuela, Xian Chen, Kohei Inayoshi, Long Wang, Yi-Ming Hu, Pau Amaro-Seoane, Abbas Askar, Cosimo Bambi, Pedro R. Capelo, Hong-Yu Chen, Alvin J. K. Chua, Enrique Condés-Breña, Lixin Dai, Debtroy Das, Andrea Derdzinski, Hui-Min Fan, Michiko Fujii, Jie Gao, Mudit Garg, Hongwei Ge, Mirek Giersz, Shun-Jia Huang, Arkadiusz Hypki, Zheng-Cheng Liang, Bin Liu, Dongdong Liu, Miaoxin Liu, Yunqi Liu, Lucio Mayer, Nicola R. Napolitano, Peng Peng, Yong Shao, Swarnim Shashank, Rongfeng Shen, Hiromichi Tagawa, Ataru Tanikawa, Martina Toscani, Verónica Vázquez-Aceves, Hai-Tian Wang, Han Wang, Shu-Xu Yi, Jian-dong Zhang, Xue-Ting Zhang, Lianggui Zhu, Lorenz Zwick, Song Huang, Jianwei Mei, Yan Wang, Yi Xie, Jiajun Zhang, Jun Luo,Comments: TianQin Gravitational Wave Whitepaper, 73 pages, 30 figures. Update to match published versionSubjects: astro-ph.GA astro-ph.CO astro-ph.HE gr-qcCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The opening of the gravitational wave window has significantly enhanced our capacity to explore the universe's most extreme and dynamic sector. In the mHz frequency range, a diverse range of compact objects, from the most massive BLACK HOLEs at the farthest reaches of the Universe to the lightest white dwarfs in our cosmic backyard, generate a complex and dynamic symphony of gravitational wave signals. Once recorded by gravitational wave detectors, these unique fingerprints have the potential to decipher the birth and growth of cosmic structures over a wide range of scales, from stellar binaries and stellar clusters to galaxies and large-scale structures. The TianQin space-borne gravitational wave mission is scheduled for launch in the 2030s, with an operational lifespan of five years. It will facilitate pivotal insights into the history of our universe. This document presents a concise overview of the detectable sources of TianQin, outlining their characteristics, the challenges they present, and the expected impact of the TianQin observatory on our understanding of them.
[abstract 10 / 44] Yes (score: 4) - Title: Revealing the $χ_{\rm eff}$-$q$ Correlation among Coalescing Binary Black Holes and Tentative Evidence for AGN-driven Hierarchical MergersAuthors: Yin-Jie Li, Yuan-Zhu Wang, Shao-Peng Tang, Tong Chen, Yi-Zhong Fan,Comments: 14 pages, 9 figures, comments welcome!Subjects: astro-ph.HE astro-ph.GACreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The origin of the correlation between the effective spins ($χ_{\rm eff}$) and mass ratios ($q$) of LIGO-Virgo-KAGRA's binary BLACK HOLEs (BBHs) is still an open question. Motivated by the recent identification of two subpopulations of the BBHs, in this work we investigate the potential $χ_{\rm eff}-q$ correlation for each subpopulation. Surprisingly, the $χ_{\rm eff}$-$q$ correlation {either significantly weakens or disappears} for the low-mass subpopulation if we introduce a second $χ_{\rm eff}$ distribution for the high-mass subpopulation, which likely originates from hierarchical mergers. {This suggests that the $χ_{\rm eff}$-$q$ correlation in the overall population can be explained by the superposition of two distinct subpopulations.} {We find Bayesian evidence strongly favoring two separate $χ_{\rm eff}$ distributions over a single mass-ratio-dependent distribution, with Bayes factors $\ln\mathcal{B}>4.2$.} The first subpopulation has a narrow $χ_{\rm eff}$ distribution peaking at $\sim0.05$, whose primary-mass function {showing a rapid decline beyond} $\sim 40M_{\odot}$, in agreement with first-generation BBHs. The second $χ_{\rm eff}$ distribution is broad and peaks at $μ_{χ,2} \sim 0.4$, aligning with predictions for hierarchical mergers in ACTIVE GALACTIC NUCLEus (AGN) disks. {However, we cannot exclude negative $χ_{\rm eff}$values in the second subpopulation, suggesting hierarchical mergers might occur both in AGN disks and stellar clusters. Furthermore, the inferred second $χ_{\rm eff}$ distribution might alternatively arise from other formation channels, such as stable mass transfer or chemically homogeneous evolution, if not interpreted as hierarchical mergers.}
[abstract 11 / 44] Yes (score: 4) - Title: Aligned Hierarchical Black Hole Mergers in Active-Galactic-Nuclei Disks Revealed by GWTC-4Authors: Yin-Jie Li, Yuan-Zhu Wang, Shao-Peng Tang, Yi-Zhong Fan,Comments: 7 pages, 3 figures (main text) + 8 pages, 9 figures (Supplemental Material). Accepted for publication in PRLSubjects: astro-ph.HE astro-ph.CO gr-qcCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The ACTIVE GALACTIC NUCLEus (AGN) accretion disks are ideal sites for hierarchical BLACK HOLE (BH) mergers. To robustly probe such a possibility, we analyze binary BLACK HOLE mergers in the GWTC-4 with a flexible mixture population model for component masses, spin magnitudes, and spin tilt angles, and identify two distinct subpopulations. In the second subpopulation characterized by high spin magnitudes $χ\sim 0.8$ as well as the broad mass distribution up to $\gtrsim 150M_\odot$, we find a pronounced preference for spins aligned with the orbital angular momentum: an isotropic tilt distribution is strongly disfavored (logarithmic Bayes factor = 4.5). The aligned events account for $\sim 0.57^{+0.23}_{-0.31}$ of the second subpopulation, corresponding to a local rate of $\sim 0.25^{+0.38}_{-0.16} ~ {\rm Gpc}^{-3} {\rm yr}^{-1}$ (all values reflect central 90\% credible intervals). These notable features naturally arise from hierarchical mergers embedded in AGN disks, where gas torques may effectively align spins. Our results suggest that AGN-disk hierarchical assembly may be one important channel for the present gravitational-wave sample, and provide concrete, testable predictions for future detection.
[abstract 12 / 44] Yes (score: 4) - Title: A MINOT-based Study of Gamma-ray emission from SPT-CL J2012-5649/Abell 3667Authors: Siddhant Manna, Shantanu Desai,Comments: Accepted for publication in Phys. Dark Univ . ( 21 pages, 10 Figures, 5 Tables)Subjects: astro-ph.HE astro-ph.COCreated: 2026-07-14; Updated: 2026-07-17; Datestamp: 2026-07-17
We present an analysis of the non-thermal properties of the merging galaxy cluster SPT-CL J2012-5649/Abell~3667 ($z = 0.0556$, $M_{500} = 7.16 \times 10^{14}\ M_\odot$) using the MINOT non-thermal emission modeling framework. The predicted hadronic gamma-ray flux from $pp$ interactions in the $1$--$300\ \mathrm{GeV}$ band is $2.82 \times 10^{-11}\ \mathrm{cm^{-2}\ s^{-1}}$ within $R_{500}$, rising to $1.15 \times 10^{-10}\ \mathrm{cm^{-2}\ s^{-1}}$ at the truncation radius ($3.7\,R_{500}$), in broad agreement with the FERMI-LAT reported flux of $1.3 \times 10^{-10}\ \mathrm{cm^{-2}\ s^{-1}}$. Approximately $76\%$ of the predicted hadronic flux originates from beyond $R_{500}$. The Inverse Compton contribution from cosmic-ray electrons is subdominant relative to the hadronic $π^0$-decay gamma-ray component by a factor of ${\sim}20$ in the $1$--$300\ \mathrm{GeV}$ energy band, and therefore does not contribute significantly to the observable signal. The best fit of the observed FERMI-LAT data is achieved with a hadronic emission assuming a proton spectrum $\propto E^{-3.5}$ and a proton energy density almost in equipartition with the thermal energy density. Even though those parameters may look extreme, they could well be explained by the particle acceleration by low Mach number accretion shocks.
[abstract 13 / 44] Yes (score: 4) - Title: The topology of the MAGNETic field in Abell 2255 out to its virial radius. Results from the LOFAR Galaxy Cluster Ultra-Deep FieldAuthors: A. Botteon, R. J. van Weeren, Y. Hu, F. Vazza, G. Brunetti, K. Rajpurohit, A. Lazarian, T. W. Shimwell, E. De Rubeis, M. Balboni, A. Bonafede, R. Cassano, G. Di Gennaro, F. Gastaldello, M. J. Hardcastle, A. Ignesti, H. J. A. Röttgering,Comments: 15 pages, 10 figures + Appendix. Accepted for publication in A&ASubjects: astro-ph.CO astro-ph.GA astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
We present the LOFAR Galaxy Cluster Ultra-Deep Field, in which 336 h of LOFAR observations at 120$-$168 MHz have been collected on the nearby ($z=0.080$) cluster Abell 2255. This massive and merging system is known to host spectacular radio emission from both cluster galaxies and the intracluster medium. Previous LOFAR observations revealed pervasive diffuse SYNCHROTRON emission extending from the cluster center to its dynamically active outskirts, tracing RELATIVISTIC electrons propagating in large-scale MAGNETic fields. In this work, we present a set of new ultra-deep images at the central frequency of 144 MHz based on the 224 h of data with the best quality, which reach a sensitivity of 24 $μ$Jy beam$^{-1}$ at 7.1" $\times$ 4.3" resolution. These images represent the deepest radio observations of a galaxy cluster obtained to date and provide a glimpse of what should be routinely observed in clusters with SKA-Low in the near future. Using these data, we investigate the topology of the cluster MAGNETic field out to its virial radius by applying the SYNCHROTRON intensity gradient technique. We find that the inferred MAGNETic field exhibits preferential orientations in distinct regions of the cluster, such as in the radio halo extensions (bridges) and in the relics, suggesting that the dynamics of the cluster formation process is shaping the large-scale MAGNETic field. This interpretation is supported by the comparison with the MAGNETic field orientation obtained from cosmological MAGNETohydrodynamic simulations. This work provides the first indication of a coherent, large-scale MAGNETic field topology across an entire galaxy cluster, from core to outskirts, and demonstrates the unique power of ultra-deep, low-frequency observations to trace the structure of cluster MAGNETic fields on megaparsec scales, thereby probing the MAGNETization of the large-scale structure of the Universe.
[abstract 14 / 44] Yes (score: 4) - Title: Spectral study of the outburst decay of the accreting millisecond X-ray pulsar SRGA J144459.2-604207Authors: Amar Deo Chandra,Comments: 16 pages, 7 figuresSubjects: astro-ph.HECreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We study the spectra of the accreting X-ray millisecond pulsar SRGA J144459.2-604207 during the 2024 outburst using the Neutron star Interior Composition Explorer (NICER) and SWIFT observations. The spectra during the outburst decay, reflares, and quiescent state are explored using the absorbed Comptonized model. We find that the spectra during the quiescent state can also be explained using the absorbed power-law and absorbed blackbody model. The spectral evolution of the source is explored as the outburst decays into quiescence. We study the long-term quiescent X-ray activity of the source spanning roughly 45 years and find that the long-term quiescent luminosity may be explained using the deep crustal heating model. We also find that the coronal activity of the companion star alone cannot power the quiescent X-ray luminosity of the source. We place the source on the radio-X-ray luminosity plane and compare its position with other sources. We estimate the propeller luminosity of the source and find that it is smaller than the estimated luminosity during reflares and the quiescent state during the 2024 outburst. Several reflares are detected during the outburst decay, one of which is near-simultaneous with the detection of an ultrafast outflow and radio emission. We explore plausible mechanisms that may power outflow, radio emission and associated JET formation in this accreting binary.
[abstract 15 / 44] (score: 3) - Title: Compressible Navier-Stokes Flow in Schrödinger-Type VariablesAuthors: James R. Beattie, Max Sokolova, Khush Negandhi, Bart Ripperda,Comments: Submitted. 13 pages (main), 4 pages (appendix). 3 figures. Accepted in PRRSubjects: physics.flu-dyn astro-ph.HE physics.plasm-phCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
Fluid equations are nonlinear, dissipative, and non-Hamiltonian, which makes their relation to Schrödinger evolution and quantum algorithms nontrivial. We derive an exact Eulerian Cole-Hopf-type reformulation of isothermal compressible Navier-Stokes (NS) flow in Schrödinger-type amplitude variables. To our knowledge, this gives the first exact Cole-Hopf-type Schrödinger-variable reformulation of compressible NS flow. In two dimensions, a Helmholtz decomposition separates the velocity into compressive and vortical potentials, whose logarithmic transforms yield two scalar imaginary-time Schrödinger-type equations with nonlinear self-consistent potentials. We show that the mixed density-compressive amplitude $Ψ_α=ρ^αΘ^{1-2α}$, where $ρ$ is the density, $Θ$ is the compressive amplitude, and $α\neq 0,\,1/2$, satisfies a nonlinear Schrödinger-type equation with a vector-potential-coupled Laplacian. The transformed system is exactly equivalent to compressible NS and is nonlocal only through Helmholtz and Poisson projections. In three dimensions, the density-carrying equation retains the same vector-potential-coupled structure, while the solenoidal sector admits a compressible analogue of Ohkitani's incompressible NS Cole-Hopf formulation. Unlike unitary hydrodynamic Schrödinger-flow representations, the present equations are imaginary-time heat or drift-diffusion equations with self-consistent potentials, but they remain an exact change of variables for compressible NS. A two-dimensional Kelvin-Helmholtz unstable shear-layer calculation verifies the transformed equations against a direct compressible NS simulation. The formulation exposes operator structures that may be useful for reduced flow descriptions, quantum algorithms for operator evolution, and quantum partial differential equation solvers.
[abstract 16 / 44] (score: 3) - Title: Periodic line-of-sight velocity-driven modulations to gravitational waves emitted by compact binaries in Keplerian outer orbitsAuthors: Avinash Tiwari, Shasvath J. Kapadia, Aditya Vijaykumar, Sourav Chatterjee,Comments:Subjects: gr-qc astro-ph.HECreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The centre of mass (CoM) of compact binary coalescences (CBCs) occurring in the vicinity of a supermassive BLACK HOLE, through interaction with an arbitrary third body (e.g., of stellar mass), or in a dense stellar environment, will undergo a time-varying line-of-sight (LOS) velocity. This in turn leads to a time-varying Doppler shift and corresponding modulations in the shape of the gravitational waves (GWs). The phase and amplitude corrections arising from constant LOS acceleration and its higher-order time derivatives are already known. Specifically, these effects lead to corrections to the GW waveform at $-4n$ post-Newtonian (PN) order, where $n$ is the $n^{th}$ time derivative of the LOS velocity. In the context of a circular or eccentric outer orbit of the CoM of the CBC, these effects can be thought of as approximations to the LOS velocity in the limit: observation duration $\ll$ period of the outer orbit. However, this condition is not necessarily always satisfied. In this {\it paper}, we present phase and amplitude corrections to the GW waveforms arising from a periodic non-RELATIVISTIC LOS velocity for circular and eccentric outer orbits of the CBC's CoM. Specifically, these lead to phase and amplitude modulations at 4 PN order, and reduce to the known corrections for constant kinematic parameters under appropriate limits mentioned above. We also perform a Fisher matrix analysis to forecast constraints on the environment that is sourcing the time-varying LOS velocity, for various future ground and space-based detectors. We further show that constraints acquired using GW waveforms derived in this work improve significantly in comparison to those acquired from approximate methods valid for constant kinematic parameters.
[abstract 17 / 44] (score: 3) - Title: Cosmological $γ$-$γ$ Pair-Production BackgroundAuthors: Mika A. Gelowicz, Thomas Siegert, Saurabh Mittal, Laura Eisenberger, Dimitris Tsatsis, Niklas C. Bauer, Rudi Reinhardt, Patrik Ehrmann, Manja L. Zimmerer, Hiroki Yoneda, Tomohiko Oka, Tristan Bouchet, Manuel R. H. W. Skalka,Comments: 11 pages, 10 figures, 2 tables, accepted by A&ASubjects: astro-ph.CO astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
The origin of positrons is one of the unsolved puzzles in astrophysics as the majority of sources are still unidentified. The Cosmic Photon Background (CPB) is the isotropic radiation spanning the entire electroMAGNETic spectrum. Interactions of the CPB with itself may pose a promising source of positrons and secondary emission. We calculate the electron-positron pair production rate from the $γ$-$γ$ pair-production of the CPB with itself for redshifts $z \leq 10$, and determine the annihilation spectrum, Inverse Compton emission, and bremsstrahlung. The CPB is decomposed into a sum of gray body functions, of which each is being evolved according to source type luminosity functions and redshift. We compute the pair-production rate by integrating the angle- and energy-dependent cross section over the evolving CPB. The pairs produced at each redshift are then propagated towards $z=0$, taking into account a cosmological, intergalactic, energy loss function. The photon emission is calculated per redshift and then line-of-sight integrated towards a contribution of the Cosmic Gamma-Ray Background (CGB) today. The resulting pair-production emissivity increases steeply from $z=0$ of about $2 \times 10^{-36}$ to a peak of $1.8 \times 10^{-31}\,\mathrm{e^\pm\,cm^{-3}\,s^{-1}}$ at $z=2.7$, then declines again. This yields a total cosmic pair-production rate on the order of $10^{54}\,\mathrm{e^\pm\,s^{-1}}$ up to redshift $10$. The secondary emission of pairs experiencing Inverse Compton scattering off the CPB results in a sizable contribution to the CGB. The pairs from cosmological $γ$-$γ$ absorption provide a minimum level of secondary emission which needs to be taken into account for any CGB study. Especially in the range from 1 MeV to 1 GeV, this background can make up 20% of the total CGB emission and may substantially reduce the gap between MeV observations and models.
[abstract 18 / 44] (score: 3) - Title: The plethora of diffuse emission in Abell 2034 as revealed by MeerKAT POLARIZATION observationsAuthors: A. Bonafede, M. Balboni, G. W. Pratt, I. Bartalucci, L. Rudnick, C. J. Riseley, C. Stuardi, B. Hugo, G. Bernardi, M. Brüggen, G. Brunetti, R. Cassano, F. De Gasperin, F. Gastaldello, K. Knowles, F. Loi, T. Shimwell, R. J. van Weeren,Comments: 16 pages, accepted by A&ASubjects: astro-ph.COCreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
We present MeerKAT observations of the galaxy cluster Abell 2034, a massive (M_500=5.21 10^14 solar masses) nearby cluster in a merging state. Previous observations at 144 MHz have shown that the cluster exhibits a plethora of diffuse emission, with multiple diffuse sources of uncertain classification because of the lack of spectral and polarimetric observations. MeerKAT multi-frequency observations, centered at 816 MHz and 1.28 GHz, together with archival low-frequency LOFAR observations at 144 MHz have allowed us to shed light on the properties of these sources. The POLARIZATION properties and spectral index information let us conclude that the cluster hosts one radio relic, a source with a very steep spectrum, previously classified as candidate relic, and filaments of very steep emission around the tailed RADIO GALAXies identified at low frequencies. The presence of a radio halo is confirmed, and its spectrum shows hints for curvature between 144 MHz ad 1.28 GHz. The polarimetric data in the L-band, together with the model of the gas density derived from X-ray observations are used to constrain the MAGNETic field in the intracluster medium. We assume a radially symmetric MAGNETic field model, whose strength declines with the cluster gas density as B(r) ~ n_e(r)^0.5, and normalize its strength within R_500. We find that B_500=1 muG best explains the Faraday depth properties of the cluster, though the detection of sources close to the cluster center would be crucial to discriminate among different values. We conclude that the cluster Abell 2034 shows diffuse emission with complex morphologies that do not follow the historical categories of halos and relics. Deep multi-frequency and polarimetric observations are fundamental to understand their origin.
[abstract 19 / 44] (score: 3) - Title: Multiwavelength study of non-thermal emission in the SWIFT J1834.9-0846/W41 regionAuthors: Manoel F. Sousa, Rita C. Dos Anjos, Vitor de Souza,Comments: This paper has been published in Journal of High Energy AstrophysicsSubjects: astro-ph.HE astro-ph.SR hep-phCreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
We investigate the origin of non-thermal emission from the SWIFT J1834-0846/W41 region by modeling its broadband spectral energy distribution from radio to TeV energies within leptonic and lepto-hadronic frameworks using Markov Chain Monte Carlo sampling. Motivated by morphological studies of HESS J1834-087 suggesting a two-component TeV structure, we explore a single extended source scenario and a configuration comprising a central point-like component embedded within extended emission. Purely leptonic models are disfavored in both scenarios by unrealistically low MAGNETic field strengths, whereas lepto-hadronic solutions yield field intensities and non-thermal energy budgets consistent with an evolved SUPERNOVA remnant undergoing efficient cosmic-ray acceleration. In the two-component scenario, hadronic interactions dominate the extended TeV emission from W41, while the central excess is well described by a leptonic MAGNETar wind nebula powered by SWIFT J1834-0846, implying a short initial spin period of $P_0 \lesssim 0.2$ s. Simulated observations with the Cherenkov Telescope Array Observatory show that 30 h exposures will discriminate between the two morphological configurations and extend spectral measurements beyond $\sim$10 TeV.
[abstract 20 / 44] (score: 3) - Title: Merging galaxies and clusters: Insights into the role of MAGNETic fields and the physics of radio relicsAuthors: Joseph Whittingham,Comments: PhD Thesis, University of Potsdam (2025), xii + 228 pages. Ch. 3-5 reprint arXiv:2011.13947, arXiv:2301.13208, and arXiv:2411.11947, resp. Ch. 6 is expanded in arXiv:2604.06302. Ch. 7 describes major revisions to the CREST and AREPO shock finder implementations; cite this work for these developmentsSubjects: astro-ph.GA astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
Mergers have long been understood to be a driver of galaxy and galaxy cluster evolution. They release tremendous amounts of gravitational potential energy - ~$10^{59}$ and ~$10^{64}$ ergs in galaxies and clusters, respectively - which is dissipated in powerful shock waves. In galaxies especially, the strong tidal effects can have profound effects on the remnant morphology. Although the modelling of mergers has a long history, it is only recently that it has been fully appreciated just how sensitive they are to a range of factors, including the existence of circumgalactic media (CGM), accretion along filaments, and pre-existing MAGNETic fields. Modelling these aspects in a cosmologically-consistent manner necessitates the use of high-resolution cosmological MAGNETohydrodynamic (MHD) simulations. In this work, we use such simulations to investigate two distinct merger-related phenomena: i) MAGNETic fields in galaxy mergers, and ii) the origin of radio relics in galaxy clusters.
[abstract 21 / 44] (score: 3) - Title: SPH methods in the modelling of compact objectsAuthors: Stephan Rosswog,Comments: Living Reviews of Computational Astrophysics; completely revised version; 183 pages; first three chapters are a self-contained review of SPHSubjects: astro-ph.HE gr-qcCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We review the current status of compact object simulations that are based on the Smoothed Particle Hydrodynamics (SPH) method. The first section of this review is dedicated to SPH as a numerical method for Newtonian, ideal gas dynamics and it should be fairly self-contained. It begins with the basics of the method, but also describes recent advances including various meshless derivatives or methods for treating shocks. A separate chapter summarizes general RELATIVISTIC SPH, including its special RELATIVISTIC limit, and it explains in some detail the recent development of full numerical relativity in SPH where matter is evolved together with a dynamical spacetime. The remainder of the review has an astrophysical focus, here we discuss the status of the simulations of white dwarf--white dwarf, neutron star--neutron star and neutron star--BLACK HOLE systems. For each type of system the emphasis is on gravitational-wave-driven mergers, but we also briefly summarize dynamical collisions that can occur in locations with large stellar densities.
[abstract 22 / 44] (score: 2) - Title: Measurement of forward photon production cross-section in pp collisions at $\sqrt{s}$ = 510 GeV with RHICf detectorAuthors: O. Adriani, E. Berti, L. Bonechi, R. D'Alessandro, Y. Goto, B. Hong, Y. Itow, K. Kasahara, M. H. Kim, Y. Kim, J. H. Lee, S. Lee, T. Ljubicic, H. Menjo, I. Nakagawa, A. Ogawa, S. Oh, K. Ohashi, R. Pak, T. Sako, N. Sakurai, K. Sato, R. Seidl, K. Tanida, S. Torii, A. Tricomi,Comments: 21 pages, 7 figuresSubjects: hep-exCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
This study reported the inclusive differential production cross-section of photons in six pseudorapidity regions: 6.1 < $η$ < 6.5, 6.5 < $η$ < 7.0, 7.0 < $η$ <7.5, 7.5 < $η$ <8.0, 8.0 < $η$ < 8.5, and $η$ > 8.5, measured through the RHICf experiment with pp collisions at $\sqrt{s}$ = 510 GeV conducted in June 2017. In addition, the cross-sections in the three regions of the $x_F$-$p_T$ phase space coverage that are same as those of the LHCf results at $\sqrt{s}$ = 7 and 13 TeV were obtained and compared. Considering the uncertainties, the results were observed to be consistent with both the Feynman scaling law and the model predictions of EPOS-LHC, QGSJET-II-04, Sibyll 2.3d, and DPMJET-III 2019.1, although certain models exhibited weak collision energy dependencies.
[abstract 23 / 44] (score: 2) - Title: SEOBNRv5PHM: Next generation of accurate and efficient multipolar precessing-spin effective-one-body waveforms for binary BLACK HOLEsAuthors: Antoni Ramos-Buades, Alessandra Buonanno, Héctor Estellés, Mohammed Khalil, Deyan P. Mihaylov, Serguei Ossokine, Lorenzo Pompili, Mahlet Shiferaw,Comments: Match the journal versionSubjects: gr-qc astro-ph.HECreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
Spin precession is one of the key physical effects that could unveil the origin of the compact binaries detected by ground- and space-based gravitational-wave (GW) detectors, and shed light on their possible formation channels. Efficiently and accurately modeling the GW signals emitted by these systems is crucial to extract their properties. Here, we present SEOBNRv5PHM, a multipolar precessing-spin waveform model within the effective-one-body (EOB) formalism for the full signal (i.e. inspiral, merger and ringdown) of binary BLACK HOLEs (BBHs). In the non-precessing limit, the model reduces to SEOBNRv5HM, which is calibrated to $442$ numerical-relativity (NR) simulations, 13 waveforms from BH perturbation theory, and non-spinning energy flux from second-order gravitational self-force theory. We remark that SEOBNRv5PHM is not calibrated to precessing-spin NR waveforms from the Simulating eXtreme Spacetimes Collaboration. We validate SEOBNRv5PHM by computing the unfaithfulness against 1543 precessing-spin NR waveforms, and find that for 99.8% (84.4%) of the cases, the maximum value, in the total mass range 20-300 $M_\odot$, is below 3% (1%). These numbers reduce to 95.3% (60.8%) when using the previous version of the SEOBNR family, SEOBNRv4PHM, and to 78.2% (38.3%) when using the state-of-the-art frequency-domain multipolar precessing-spin phenomenological IMRPhenomXPHM model. Due to much better computational efficiency of SEOBNRv5PHM compared to SEOBNRv4PHM, we are also able to perform extensive Bayesian parameter estimation on synthetic signals and GW events observed by LIGO-Virgo detectors. We show that SEOBNRv5PHM can be used as a standard tool for inference analyses to extract astrophysical and cosmological information of large catalogues of BBHs.
[abstract 24 / 44] (score: 2) - Title: Hierarchical Black Hole Mergers in Nuclear Star Clusters: A Combined Dynamical-Secular Channel for GW231123-like EventsAuthors: Bin Liu, Dieran Wang, Dong Lai,Comments: 11 pages, 8 figures. Accepted for publication in ApJSubjects: astro-ph.HE gr-qcCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The recent binary BLACK HOLE (BH) merger GW231123, with both components likely in the high-mass gap and with high spins, challenges standard BH binary formation models. It is usually thought that the BHs are of second (or higher) generation (2G), resulting from the mergers of smaller BHs. But the physical processes that produce the merging 2G BH binaries are unclear and highly unconstrained. We show that such 2G mergers can be naturally produced in the nuclear star cluster of Milky Way-like galaxy. The dominant channel combines a sequence of binary-single interactions with secular evolution driven by the central supermassive BH. Our model produces a merger rate consistent with GW231123 and further predicts an abundant population of 2G BH-star (or low-mass BH) binaries; these binaries may observationally manifest as micro tidal disruption events or low-frequency gravitational-wave (GW) sources. Detecting these binaries would provide crucial insights into the dynamical pathways of hierarchical BH assembly.
[abstract 25 / 44] (score: 2) - Title: Dynamics, Ringdown, and Accretion-Driven Multiple Quasi-Periodic Oscillations of Kerr-Bertotti-Robinson Black HolesAuthors: G. Mustafa, Orhan Donmez, Dhruba Jyoti Gogoi, Sushant G. Ghosh, Ibrar Hussain, Chengxun Yuan,Comments: 31 pages, 18 figures. Matches the accepted version at JCAPSubjects: gr-qc hep-thCreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
We study the motion of test particles around the Kerr--Bertotti--Robinson (KBR) BLACK HOLE (BH) and explore how the three defining parameters, the mass $M$, rotation parameter $a$, and MAGNETic parameter $B$ influence their dynamics. We derive analytical expressions for the energy and angular momentum of stable equatorial circular orbits, along with the corresponding radial and latitudinal oscillation frequencies, as functions of $M$, $a$, and $B$. We also examine the key features of the quasi-periodic oscillations (QPOs) of test particles near stable circular orbits, including the precession effects such as periastron precession and the Lense-Thirring effect. We compare our results with those corresponding to the Kerr BH. We find that the particle motion is strongly shaped by the BH parameters. Using a WKB approach, we also study scalar quasinormal modes of rotating KBR BH in an external MAGNETic field and show that the MAGNETic field increases damping, while rotation and angular momentum mainly set the oscillation frequencies. Alternatively, general RELATIVISTIC modeling of Bondi-Hoyle-Lyttleton (BHL) accretion onto rapidly rotating KBR BH shows that two distinct physical structures emerge and cyclically transform into one another over time. These processes produce either a strongly oscillating flip-flop shock cone or a nearly stationary toroidal structure, with their formation governed by the BH spin and MAGNETic curvature. Power spectral analysis shows that these configurations give rise to low- and high-frequency QPO, providing a unified theoretical framework to understand how multiple QPO-like features can arise in rapidly spinning accreting systems.
[abstract 26 / 44] (score: 2) - Title: Quasi-periodic Eruptions from Stellar-mass Black Holes Impacting Accretion Disks in Galactic NucleiAuthors: Kun Liu, Shang-Fei Liu, Zhen Pan, Hongping Deng, Rongfeng Shen, Cong Yu,Comments: 20 pages, 8 figures and 2 tables. Accepted for publication in the Astrophysical Journal LettersSubjects: astro-ph.HECreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We investigate the origins of quasi-periodic eruptions (QPEs) in galactic nuclei using global three-dimensional meshless finite-mass (MFM) simulations. By modeling stellar and black-hole impactors traversing accretion disks under various inclinations and surface densities, we evaluate their consistency with the observed properties of QPEs. Stellar impacts produce highly asymmetric bipolar ejecta with forward outbursts dominating by over an order of magnitude in energy and luminosity due to the star blocking downstream flow and creating a low-density wake. This shock-compression mechanism often renders backward events unobservable, implying one detectable burst per orbit, and challenging the standard assumption of two bursts. It also fails to explain alternating long--short recurrence patterns and places several sources near or within twice the tidal disruption radius for solar-mass stars, raising severe stability concerns. Whereas a stellar-mass BLACK HOLE (sBH) gravitationally focuses and heats disk gas over an effective interaction scale that extends beyond its Bondi radius $R_{\rm B}$ and is naturally bounded by its Hill radius $R_{\rm H}$ during an impact, yielding nearly symmetric ejecta with mild contrasts. This gravitational-drag mechanism generates higher energy budgets at low inclinations due to enhanced mass accumulation. We suggest an ad hoc effective interaction radius $ R_{\rm eff} \simeq 0.5\, R_{\rm B}^{1/3} R_{\rm H}^{2/3} $ to quantify this trend. Incorporating this effective radius substantially increases the energy that sBH-disk collisions can produce compared to previous Bondi-only estimates, improving the viability of stellar-mass BLACK HOLEs as the impactors for a wide range of observed QPE energies and properties.
[abstract 27 / 44] (score: 2) - Title: Two shadows of a single BLACK HOLE: Vacuum birefringence phenomena within Einstein-nonlinear-electrodynamicsAuthors: Marco A. A. de Paula, Haroldo C. D. Lima, Pedro V. P. Cunha, Carlos A. R. Herdeiro, Luís C. B. Crispino,Comments: 21 pages, 15 figures. To match published versionSubjects: gr-qc hep-thCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
One of the main features of nonlinear electrodynamics is the existence of an effective geometry that describes the geodesic motion of photons. A detailed analysis of the properties of effective geometry is of utmost importance for a better understanding of nonlinear electrodynamics theories and their possible imprints on physics, especially in the context of BLACK HOLEs. We consider a nonlinear electrodynamics model that depends on the two electroMAGNETic scalar invariants and obtain that the motion of photons in nonlinear electrodynamics exhibits \textit{vacuum birefringence}, i.e., photons can propagate along two distinct paths, depending on their POLARIZATION. As a consequence of this phenomenon, we show that static BLACK HOLE solutions sourced by nonlinear electrodynamics can admit two distinct unstable light rings, leading to the formation of two distinct shadows. Moreover, to explore the potential astrophysical relevance of our results, we also compare them with the astrophysical observations for the shadow radius of Sagittarius A*. We place upper limits on the charge-to-mass ratio of the nonlinear electrodynamics-sourced BLACK HOLE. We also show that the motion of photons in this context can be interpreted as nongeodesic curves subjected to a four-force term from the perspective of an observer in the spacetime metric, generalizing previous results in the literature for nonlinear electrodynamics models that depend on a single electroMAGNETic scalar invariant.
[abstract 28 / 44] (score: 2) - Title: Estimating coil features from an equilibriumAuthors: Eduardo Rodriguez, Wrick Sengupta,Comments:Subjects: physics.plasm-phCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We present an explicit theoretical framework for constructing artificial modular coils for vacuum stellarator fields based solely on equilibrium properties, achieved through the formulation of a current potential defined on flux surfaces. Contours of constant Boozer toroidal angle can be directly interpreted as proxy coils, and so we demonstrate that key measures of coil complexity (particularly coil non-planarity) are strongly governed by local MAGNETic field properties. This approach shows promise as predictor for more realistic coil configurations, providing both a pathway towards deeper understanding of equilibrium-coil relationships and a potential practical proxy for coil design.
[abstract 29 / 44] (score: 2) - Title: micrOMEGAs 7: Beyond standard cosmologyAuthors: G. Belanger, A. Belyaev, N. Bernal, F. Boudjema, S. Chakraborti, A. Goudelis, A. Pukhov,Comments: 24 pages, 7 figuresSubjects: hep-phCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We present micrOMEGAs7, a major upgrade of the micrOMEGAs package for the computation of DARK MATTER observables in generic models. This release introduces a generalized treatment of the Boltzmann equations, allowing for user-defined modifications of the Hubble expansion rate, entropy evolution, and non-thermal DARK MATTER production from late-decaying cosmological components, thereby extending the framework beyond the standard radiation-dominated cosmology. The relic density can now be computed in scenarios such as low-temperature reheating, early matter domination, and kination. The new version also improves the treatment of sub-GeV DARK MATTER, in particular annihilation into light mesons through scalar mediators, and provides updated spectra for indirect detection. Several experimental and observational constraints have been implemented or revised, including CMB bounds from Planck on energy injection during recombination and FERMI-LAT limits from dwarf spheroidal galaxies. For direct detection, a recast of recent LZ results has been included, and the code now takes into account effective electroMAGNETic couplings of spin-$1/2$ and spin-1 DARK MATTER. Collider observables have also been extended through the implementation of CMS dilepton resonance constraints on $Z'$ mediators. Additional improvements include a more flexible treatment of effective RELATIVISTIC degrees of freedom and an updated LHAPDF interface.
[abstract 30 / 44] (score: 2) - Title: Identifying and characterizing extragalactic circum-CBC exoplanets with future gravitational-wave detectorsAuthors: Avinash Tiwari, Aditya Vijaykumar, Shasvath J. Kapadia, Sourav Chatterjee,Comments:Subjects: astro-ph.HE gr-qcCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
Exoplanets are high-value targets for a variety of ground and space-based telescopes. All known exoplanets are Galactic, and a fraction of them orbit compact objects. In this work, we investigate the possibility of detecting extragalactic exoplanets orbiting stellar-mass compact binary coalescences (CBCs), such as binary neutron stars, neutron star-BLACK HOLEs, and binary BLACK HOLEs, using future gravitational wave (GW) detectors, including A+ (LIGO in O5), Einstein Telescope, and DECIGO. We use the technique of reconstructing an external potential's profile by extracting information about the centre-of-mass (CoM) kinematics of a CBC encoded in the GWs it emits. In this work, the external potential is provided by the circum-CBC exoplanet, and the resulting signature on the GW waveform comes from the ``wobble'' of the CBC's CoM around the CBC-exoplanet barycentre. As a proof of principle, we consider a few example CBCs detectable with future detectors and a range of circum-CBC exoplanet parameters in circular and eccentric orbits. We find that for a significant fraction of the range of parameters considered, we can identify the presence of a circum-CBC exoplanet by extracting its mass (up to an unknown orbital inclination angle) within a factor $\mathcal{O}(1)$ of its true value, at $68\%$ confidence.
[abstract 31 / 44] (score: 2) - Title: Why gas-focused microJETs are so fast: kinetically resolved, shear-driven flow focusing in vacuumAuthors: Alfonso M. Ganan-Calvo,Comments: 6 pages, 5 figures (18 plots)Subjects: physics.flu-dynCreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
Gas-focused liquid microJETs -- the flow-focusing sample delivery on which serial femtosecond crystallography depends -- reach speeds several times the pressure-driven (Bernoulli) bound, unexplained by continuum, local-equilibrium models that do not resolve the rarefied, hypersonic expansion of the focusing gas. We resolve that expansion with a deterministic kinetic (Shakhov--BGK) solver and couple it to the slender liquid JET. The JET is \emph{shear-driven}, not pressure-driven: the tangential stress of the hypersonic gas supplies nearly all of the axial momentum, accounting for the anomalous speed. The gas does not become ballistic behind the near field -- its stress decays as a power law and it stays coupled -- and its constitutive regime is set by a single rarefaction parameter $δ=D/\ell_0$, the orifice diameter over the source mean free path, through the thermodynamic Deborah number $De_θ\simeq K\!n\,M$ (Knudsen times Mach), whose $De_θ=1$ surface maps where the Newtonian-gas closure fails: the small-$δ$ vacuum corner where crystallography JETs operate. The kinetically computed surface stress is the input for the fully non-Newtonian (viscoelastic-liquid) sequel.
[abstract 32 / 44] (score: 2) - Title: Automated Outlier-Robust Bayesian Profile Fitting for Magnetically Confined Plasmas with Modified Tanh Profiles and Good-and-Bad Gaussian Mixture LikelihoodsAuthors: Jaewook Kim, Jekil Lee, Laurent Jung, Sang-hee Hahn, Sehyun Kwak,Comments: 16 pages, 8 figures; submitted to Nuclear FusionSubjects: physics.plasm-phCreated: 2026-07-13; Updated: 2026-07-17; Datestamp: 2026-07-17
We present an outlier-robust Bayesian approach for automated kinetic profile fitting in MAGNETically confined plasmas with the modified tanh (mtanh) parametrisation and demonstrate its implementation on KSTAR. The method addresses two systematic obstacles: anomalous diagnostic channels can bias least-squares fits, and multimodality of the mtanh cost surface can trap deterministic optimisers in secondary minima. The deployed workflow uses a good-and-bad Gaussian mixture likelihood based on the Box--Tiao formulation as the default outlier-robust likelihood for fitted diagnostic channels, with posterior outlier probabilities retained as channel-level quality indicators. The posterior is sampled with an affine-invariant ensemble MCMC sampler initialised near the result of deterministic maximum a posteriori (MAP)-seeking optimisation, reducing sensitivity to secondary minima on the multimodal mtanh surface. A batch automation layer retrieves diagnostic data from MDSplus and fits arbitrary time slices in parallel for the quantities \(n_e\), \(T_e\), \(T_i\), and \(v_T\) for which the relevant diagnostics are available. Results are written in formats suitable for MDSplus upload and downstream analysis. Representative KSTAR H-mode cases show that the mixture likelihood downweights contaminated measurements while preserving plausible pedestal profiles. The workflow provides a practical basis for future large-scale kinetic profile production for kinetic-EFIT, TRANSP, FASTRAN, and data-driven analysis workflows.
[abstract 33 / 44] (score: 2) - Title: Optimized finite-$β$ tokamak-stellarator hybrid configurations achieved by planar dipole-field coilsAuthors: Yihui Liang, Hengqian Liu, Guodong Yu, Zhenyu Zhou, Caoxiang Zhu, Yao Zhou,Comments:Subjects: physics.plasm-phCreated: 2026-07-14; Updated: 2026-07-17; Datestamp: 2026-07-17
Tokamak--stellarator hybrids seek to combine tokamak-like compactness and confinement with stellarator-like externally generated rotational transform and steady-state operation. In this work, we build on the recent tokamak--stellarator hybrid study using planar dipole-field coils (PDCs) [Yu et al., arXiv:2605.03599], in which the fixed-position, programmable coils on an axisymmetric winding surface generate flexible three-dimensional shaping fields. Using single-stage free-boundary optimization of coil currents and plasma-equilibrium parameters, we construct vacuum and finite-$β$ configurations. The vacuum cases show controllable external transform and MAGNETic well. The finite-$β$ cases accommodate various density, temperature, and pressure profiles, producing quasi-axisymmetric (QA) equilibria with self-consistent bootstrap current, favorable Mercier stability, and reduced demand for external current drive. Re-optimization enables $β$ ramp-up and access to different field-period QA branches with moderate coil-current changes. At large rotational transform, a toroidally omnigenous (TO)-like configuration exhibits more favorable infinite-$n$ ideal-ballooning behavior than a QA reference with matched profiles, even though ballooning stability is not directly optimized for. These results demonstrate that PDCs provide a flexible platform for achieving optimized finite-$β$ hybrid configurations.
[abstract 34 / 44] (score: 2) - Title: Coupled by Design: Computing Kerr-Newman Quasinormal Modes with a Hybrid SpectralPINN SolverAuthors: Alexandre M. Pombo,Comments: 24 pages, 11 figures, public dataset of 12 Kerr-Newman QNM mode branches at Zenodo: 10.5281/zenodo.21359120Subjects: gr-qcCreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
We extend our \texttt{SpectralPINN} solver to the computation of Kerr-Newman quasinormal modes by applying it to solve the system of two coupled master PDEs -- advancing from the single, separable equation of the uncharged Kerr limit to a genuinely coupled two-field problem. The coupling between the gravitational and electroMAGNETic fields gives rise to two families of solutions: the photon-sphere, connecting with Kerr; and near-horizon, disconnected from the Kerr limit, each with two branches of solutions depending on the leading field: the gravitational- and vector-led. Benchmarking against publicly available datasets shows relative frequency errors of $\sim 10^{-4}$ worst case and $\sim10^{-7}$ for most cases. The computed public dataset spans five photon-sphere modes, both gravitational- and vector-led, up to $\ell=4$, as well as two fundamental gravitational-led near-horizon modes. The vector-led photon-sphere branch is computed and systematically characterized for the first time. We apply the dataset and observe the onset of the eigenvalue repulsion reported by Dias \textit{et al.}, to exclude an inter-POLARIZATION repulsion within the resolved domain, and to forecast Einstein Telescope constraints on the black-hole charge-to-mass ratio.
[abstract 35 / 44] (score: 2) - Title: X-Ray Timing Properties of the Black Hole Candidate IGR J17091-3624 During the 2022 Outburst Onset with AstroSatAuthors: Sree Bhattacherjee, Biplob Sarkar,Comments: The manuscript is submitted to the proceedings of the International Conference on Innovative Research in Science, Engineering & Social Sciences 2026, School of Basic and Applied Sciences, The Assam Kaziranga University. Comments are welcome. 14 pages 6 figuresSubjects: astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
We present the evolution of rapid X-ray timing variability in the BLACK HOLE X-ray binary IGR J17091-3624 during the initial phase of its 2022 outburst using a ~3-day-long AstroSat observation. Utilizing the high time-resolution capability of the Large Area X-ray Proportional Counter, we perform a comprehensive study of the evolution of Type-C quasi-periodic oscillations (QPOs) throughout the observation. The QPO centroid frequency evolves from 3.30 to 7.78 Hz, accompanied by the broad-band noise characteristics. We further investigate the energy dependence of the fractional rms variability and time lags, finding that the fractional rms exhibits a positive energy dependence, with its amplitude evolving throughout the observation, while the time lags exhibit the soft-lag behavior and evolve with QPO frequency. These findings provide important insights into the evolution of geometry of the inner accretion flow during the onset phase of the 2022 outburst of IGR J17091-3624.
[abstract 36 / 44] (score: 2) - Title: Temporal Memory in Repeating Fast Radio Bursts: Epsilon-Machine Reconstruction of Causal Structure in Burst TimingAuthors: Tom Kimpson, Joseph O'Leary,Comments: Accepted for publication in MNRAS. 17 pages + appendices, 8 figures, 3 tablesSubjects: astro-ph.HECreated: 2026-07-15; Updated: 2026-07-17; Datestamp: 2026-07-17
The emission mechanism of fast radio bursts (FRBs) remains unknown. Whether the bursts from a repeating FRB arrive at random or in a structured sequence is a key constraint on that mechanism. We apply $\varepsilon$-machine reconstruction, a tool from computational mechanics that infers the minimal model capturing all predictive information in a stochastic process. Applied to the waiting-time sequences of three repeating FRBs (FRB~20121102A and FRB~20201124A from FAST; FRB~20220912A from CHIME), the method yields the statistical complexity $C_μ$, the minimum number of bits required for optimal prediction. Both FAST sources carry roughly one bit of temporal memory (significant against permutation surrogates, $p \leq 0.01$; per-source false-discovery-rate-adjusted $p \leq 0.028$), while FRB~20220912A is consistent with memoryless emission. FRB~20201124A's memory spans hours-to-days across four sessions, FRB~20121102A's spans hours-to-weeks across thirty-nine, and neither source shows defensible within-session predictive memory. For FRB~20121102A the ordering of those sessions is itself predictive (session-shuffle $p = 0.02$), whereas FRB~20201124A's signal reflects the contrast between heterogeneous sessions rather than their order. A simulated windowing test shows that CHIME's short transit observations would suppress comparable structure in the FAST data, leaving FRB~20220912A's null result ambiguous. This first application of $\varepsilon$-machine reconstruction to astrophysical transients yields a model-independent constraint: the bursting of at least two of these repeaters is not memoryless, but is governed by a hidden state that occupies distinct activity-rate regimes varying across observing sessions, behaviour that any viable physical model must reproduce.
[abstract 37 / 44] (score: 2) - Title: Microwave Resonant Discharges for Spatiotemporally Selective Plasma Breakdown Near SurfacesAuthors: Arnav Mohapatra, Joshua K. Goodrich, Thomas C. Underwood,Comments:Subjects: physics.plasm-phCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
Generating non-equilibrium plasmas close to surfaces remains a significant challenge for conventional plasma sources. Existing plasma generation schemes create volumetric discharges with limited spatial selectivity that lead to inefficient energy deposition and poor coupling between reactive intermediates and nearby surfaces. This work establishes tailored resonant field enhancement as a mechanism for prescribing where plasma forms near dielectric surfaces through microwave excitation. In this approach, the geometry, refractive index, and packing configuration of dielectric materials define resonant field structures that interfere constructively and amplify electric fields locally. Plasma forms only within these resonant volumes where the amplified fields exceed the local breakdown threshold, while the surrounding gas remains below breakdown. Microwave pulse shaping then provides dynamic control over these modes and can be used to excite different families of resonances, determine where breakdown occurs, and reconfigure what locations microplasmas occupy from one pulse to the next. We validate this framework through theory, electroMAGNETic simulations, and experiments using a pair of high-permittivity dielectric resonators. These studies identify multiple resonant mode families, demonstrate dynamic repositioning of microplasmas between prescribed breakdown sites, quantify the ignition characteristics of each mode, and confirm that multiple resonant microplasmas remain confined to localized field-enhancement regions during a microwave pulse. Together, these results establish a framework for designing resonant dielectric materials that localize, reconfigure, and control atmospheric-pressure plasmas near surfaces.
[abstract 38 / 44] (score: 2) - Title: Parameter Scan of Multi-Fluid Equilibria in Rotating p-11B Plasmas: Effects on Fusion Power and Bremsstrahlung LossesAuthors: Xingyu Li, Huasheng Xie, Lai Wei, Zhengxiong Wang,Comments: 29 pages, 21 figuresSubjects: physics.plasm-phCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We present VEQ-MF, a fast spectral parameter-scan framework for two-dimensional axisymmetric multi-fluid equilibria with prescribed species-dependent toroidal rotation. The solver couples generalized Boltzmann density responses, quasineutral electrostatic POLARIZATION, and a generalized Grad--Shafranov equation, extending reduced-parameter Grad-Shafranov and VEQ formulations to multi-species rotating equilibria. Rotating $p\text{-}^{11}\text{B}$ spherical-tokamak configurations are used as a demanding test case. Independent scans of the proton and boron rotation frequencies are performed in EHL-2 and EHL-3B geometries. The computed fields are then post-processed to obtain fusion power from a drift-Maxwellian reaction-rate coefficient and bremsstrahlung power from an analytical radiation model. Three in-range EHL-3B finite-difference benchmarks give global stored-energy, bremsstrahlung-power, and fusion-power differences of $1.7$--$3.4\%$, while a representative convergence check shows sub-percent sensitivity to increasing the spectral-parameter number and negligible sensitivity to Gaussian-grid refinement. The core equilibrium solve remains fast for repeated scans, with representative nonzero EHL-3B cases requiring $0.032$--$0.050$~s per point in MATLAB, excluding post-processing, interpolation, plotting, and file export. The scans identify two competing multi-fluid effects. Under iso-rotation, outward boron accumulation increases the volume-integrated $n_e^2$, so the fusion-to-bremsstrahlung power ratio $\mathcal{R}_{\mathrm{fb}}$ decreases with increasing rotation. Species-dependent toroidal rotation weakens centrifugal POLARIZATION and lowers bremsstrahlung power, while the relative toroidal flow in the larger EHL-3B geometry raises the drift-Maxwellian reaction-rate coefficient and thereby modifies fusion power.
[abstract 39 / 44] (score: 2) - Title: Random walks around BLACK HOLEs and low-frequency X-ray variabilityAuthors: Arthur G. Suvorov,Comments: 12 pages, 9 figures. Accepted for publication in Classical and Quantum GravitySubjects: gr-qc astro-ph.HECreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The stochastic dynamics of a grain embedded within a turbulent fluid subject to strong gravitational fields can be formulated as a random walk on a Riemannian manifold. Such curvature-weighted walks provide a framework to model the intrinsic variability of accretion onto compact objects. By solving the relevant Fokker-Planck equation on a BLACK HOLE background, we find the counterintuitive result that the escape probability of a grain is actually higher compared to flat space. This is a consequence of the stretching of radial cells near the event horizon: there is a greater spatial volume for the particle to wander through before being captured. By simulating a large number of grain trajectories, initially distributed on concentric shells with a density profile set by the thin-disc structure equations, we also study particle fluxes through the horizon. Shallower spectral indices emerge at low frequencies relative to flat space, primarily due to time dilation, and steeper ones at high frequencies. We find that Schwarzschild-weighted spectra broadly match observations of low-frequency X-ray variability from systems like Cygnus X-1 in their hard state, suggesting that geometric drifts may be important in describing stochastic accretion processes.
[abstract 40 / 44] (score: 2) - Title: Cosmogenic photon fluxes at ultra-high energiesAuthors: Marcus Niechciol, Chiara Jane Papior, Markus Risse,Comments:Subjects: astro-ph.HECreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
During their propagation, ultra-high energy COSMIC RAYs produce cosmogenic photons. The expected flux level of these photons may vary by orders of magnitude depending on parameters such as the spectrum and composition of COSMIC RAYs at injection or the source distance. We investigate the photon yields for various assumptions on injection parameters. The photon yield is largest for proton-emitting sources at about 15 Mpc distance for cosmogenic photons above $10^{18}$ eV. While the photon yield from protons always exceeds the one from heavier nuclei of the same total energy, the differences are reduced for larger source distances. Then, we quantify the cosmogenic photon fluxes for different source scenarios. We regard mixed-composition scenarios that were found to provide a reasonable description of the data from the Pierre Auger Observatory. In addition, benchmark scenarios leading to comparably high ("maximum") or low ("minimum") photon fluxes are determined assuming pure proton or pure iron primaries. For the mixed-composition scenarios that do not contain initial protons, the predicted cosmogenic photon fluxes are below present experimental limits by more than 1.5 orders of magnitude. In case of a substantial fraction of protons at the highest energies, the related photon flux might be in reach. Certain parameter combinations of pure proton scenarios are constrained already by present photon limits.
[abstract 41 / 44] (score: 2) - Title: Early Near-Infrared Excess and Rapid Disk-Corona Evolution in the Tidal Disruption Event 2024aepdAuthors: Yongxin Wu, Yanan Wang, Thomas M. Reynolds, Shuyuan Wei, Shiyan Zhong, Zikun Lin, Megan Newsome, Sebastian Gomez, Iair Arcavi, Panos Charalampopoulos, Chun Chen, Rongfeng Shen, Ning-Chen Sun, David Aguado, Ismael Pérez-Fournon, Frédérick Poidevin, Zhongnan Dong, Niu Li, Weijian Guo, Hu Zou, Jingbo Sun, Nieves Castro-Rodríguez, Antonio Cabrera-Lavers, Ning Jiang, Hengxiao Guo, J. P. Anderson, Tomás E. Müller-Bravo, Seppo Mattila, Claudia P. Gutiérrez, Amit Kumar, G. Pignata, Xiangkun Liu, R. Dastidar, Brajesh Kumar, Xiaowei Liu, Bin Ma, M. Dennefeld, Francesca Onori, Lydia Makrygianni, Mariusz Gromadzki, Xuan Fang,Comments: Submitted to the Research in Astronomy and Astrophysics (RAA)Subjects: astro-ph.HECreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We present multi-wavelength observations of the tidal disruption event (TDE) 2024aepd, spanning primarily the first $\sim$300 days after discovery. The X-ray spectrum is initially dominated by a thermal disk component accompanied by a hard excess. From $\sim$178 days onward, the spectrum becomes power-law dominated and subsequently hardens, indicating the rapid emergence and strengthening of a hot corona. A prominent near-infrared (NIR) excess is detected as early as $\sim40$ days. Its nearly flat power-law spectrum strongly deviates from the Rayleigh-Jeans tail of the UV-optical blackbody. Although a conventional dust-echo origin cannot be completely ruled out, free-free emission from a reprocessing photospheric envelope provides a more plausible explanation. Moreover, the UV-optical-to-NIR break shifts to higher frequencies as the density-profile index remains nearly constant, implying evolving reprocessing conditions within a broadly unchanged density structure. Together with AT2019azh and TDE 2025abcr, TDE 2024aepd is the third TDE reported to exhibit an early-time NIR excess. A larger sample with early-time NIR coverage is needed to determine whether such excesses are common among TDEs.
[abstract 42 / 44] (score: 2) - Title: The Goldilocks Molecule: H$_{2}$ Emission Lines Can Identify Elusive Dwarf AGNAuthors: Morgan Micharski, Chris Richardson,Comments: Accepted to RNAASSubjects: astro-ph.GACreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We propose using H$_{2}$ emission lines as a novel diagnostic to identify dwarf AGN by running photoionization models incorporating active intermediate-mass BLACK HOLEs and using an observed WISE dwarf AGN as a template. Though many dwarf AGN would be incorrectly classified as star-forming if the H$_{2}$~2.12~$μ$m/Br$γ$ ratio is used, ratios between H$_{2}$ emission lines can reveal active IMBHs in cases where log $n_{\text{H}} \gtrsim 4.0$. This includes the case where $M_{\text{BH}} = 10^3~M_{\odot}$, even though the optical strong lines and NIR coronal lines would likely go undetected. We conclude that H$_{2}$ emission lines show promise in detecting the most elusive IMBHs.
[abstract 43 / 44] (score: 2) - Title: Testing the Isotropy of the Universe with the CHIME/FRB Catalog IAuthors: Jun-Yi Shen, Yuan-Chuan Zou,Comments: 14 pages, 3 figures, submitted to JCAPSubjects: astro-ph.HE astro-ph.COCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
We test the isotropy of the Universe using 536 Fast Radio Bursts (FRBs) from the first CHIME/FRB catalog, employing two complementary statistical methods: the two-point angular correlation function (2PACF) and the sigma-map method, with observational biases corrected using CHIME injection data. Both analyses are consistent with the isotropic expectation, but are limited by the small sample size. The 2PACF suffers from an ill-conditioned covariance matrix, preventing robust parameter inference. The sigma-map angular power spectrum shows no statistically significant directional anisotropy, though the uncertainties at low multipoles remain large. Future FRB surveys are expected to improve these limitations.
[abstract 44 / 44] (score: 2) - Title: SWIFT gives a new BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew EpochsAuthors: S. Ronchini, T. Parsotan, J. DeLaunay, J. A. Kennea,Comments:Subjects: astro-ph.HE astro-ph.IM gr-qcCreated: 2026-07-16; Updated: 2026-07-17; Datestamp: 2026-07-17
The Burst Alert Telescope (BAT) onboard the Neil Gehrels SWIFT Observatory is capable of localizing gamma-ray transients with arcminute precision, enabling rapid multi-wavelength follow-up. However, onboard triggering is disabled during spacecraft slews, preventing the autonomous detection and localization of transients occurring during these intervals. We present here BAT-GLIMPSE, a fully autonomous, open-source pipeline for the low-latency localization of transient gamma-ray sources in SWIFT-BAT data. Making use of the BatAnalysis package, the pipeline combines coded-mask imaging and mosaic techniques, automatically selecting the appropriate analysis according to the spacecraft attitude and enabling localization searches during both pointing observations and spacecraft slews. We validate the performance of BAT-GLIMPSE on a sample of 66 GRBs reported in GUANO circulars. The pipeline successfully recovers arcminute positions for 43 events, consistent with published localizations, with typical offsets of $\lesssim5$ arcminutes. Approximately $88\%$ of the GRBs occurring during spacecraft slews are recovered through imaging or mosaic analyses. During the fourth LIGO-Virgo-KAGRA observing run, the role of BAT-GLIMPSE was crucial in the search for gamma-ray counterparts of gravitational waves, particularly in response to pre-merger alerts which triggered the slew of the SWIFT spacecraft with extremely low latency. Operating synergistically with NITRATES, BAT-GLIMPSE fills the critical gap left by slew intervals and, together, the two pipelines are estimated to double the onboard arcminute-localization rate of SWIFT-BAT, unlocking the full potential of the SWIFT mission for time-domain and multi-messenger astrophysics.
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