Current date: 2026-06-04
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Scoring abstracts
Number of records retrieved: 662
Keyword score statistics
score 10 -- 1 abstracts
score 9 -- 1 abstracts
score 6 -- 1 abstracts
score 5 -- 5 abstracts
score 4 -- 6 abstracts
score 3 -- 9 abstracts
score 2 -- 18 abstracts
in total -- 41 abstracts
Articles that appeared on 2026-06-04
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[abstract 1 / 41] Wow! (score: 10)
- Title: Simulating realistic radio morphologies of Fanaroff-Riley I JETs in a self-regulating cool-core clusterAuthors: Léna Jlassi, Rainer Weinberger, Christoph Pfrommer, Maria Werhahn, Joseph Whittingham, Philipp Girichidis,Comments:Subjects: astro-ph.GA astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Active galactic nucleus (AGN) JETs radiate radio SYNCHROTRON emission displaying a wide range of morphologies. At the same time, they provide heat to prevent cooling flows in cool-core galaxy clusters. We produce mock radio observations of AGN JETs in a self-regulating cool-core galaxy cluster. To this end, we employ MAGNETo-hydrodynamical simulations of an idealised Perseus-like galaxy cluster, in which accretion-powered low-density JETs accelerate COSMIC RAY protons and electrons by means of a sub-grid model. Cosmic ray electron spectra are spatially and temporally evolved along Lagrangian tracer trajectories using the Fokker-Planck solver Crest to produce radio SYNCHROTRON emission. Self-regulated AGN JETs stabilize the cool-core cluster against cooling flows and produce realistic Fanaroff-Riley I (FRI) and disturbed lobe morphologies, in contrast to symmetrical lobe structures obtained with a single JET outburst of fixed power. Our mock radio observations are viewed in a BLAZAR configuration - along the JET axis - and exhibit complex radio-emitting lobe structures despite this. This highlights the strong deflection of light JETs by cold gas structures and suggests that small-scale BLACK HOLE and JET properties cannot be inferred from kpc-scale FRI radio lobe morphologies. Combining self-consistently evolved MAGNETic fields and electron spectra enables us to explain a known observational phenomenon, whereby radio observations of AGN lobes on galaxy cluster scales occasionally display similar spatial extents at different frequencies: in 1-50 $μ$G MAGNETic fields obtained in our cool-core environment, both freshly accelerated and hundreds-of-Myr-old electrons are able to contribute to the 150 MHz - 1.4 GHz frequency range.
[abstract 2 / 41] Wow! (score: 9) - Title: NICER Perspective on TeV Blazar Mrk~421: X-ray Variability and Particle AccelerationAuthors: Sangeetha Kizhakkekalam, Gopal Bhatta, Navaneeth P K, Tek P. Adhikari,Comments: 20 pages, 8 figures, Revised version submitted following referee commentsSubjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Mrk~421 is one of the most fascinating BLAZARs, widely studied across the electroMAGNETic spectrum using observations at various wavebands, from radio to the TeV gamma ray bands. We present the first detailed spectral and timing analysis of the TeV BLAZAR Mrk~421 based on 45 X-ray observations from the \textit{NICER} X-ray telescope, collected over two years from 2022 to 2024. The source exhibits strong X-ray variability across intraday and long-term timescales. During this period, we observe a dramatic change in flux, from $\sim 50$ to $\sim 1380$~cts~s$^{-1}$, representing a $\sim 28$-fold increase. Spectral modeling with power-law, broken power-law, and log-parabolic functions shows that the log-parabola provides the most accurate description of the X-ray spectra. The hardness ratio analysis confirms a \textit{harder-when-brighter} trend, consistent with the anticorrelation between flux and photon index($Γ$). Correlation studies reveal a positive relation between the photon index ($α$) and the curvature parameter ($β$) of the log-parabola model, a negative correlation between $β$ and SYNCHROTRON peak energy ($E_{\mathrm{p}}$), and a positive correlation between $E_{\mathrm{p}}$ and flux. In addition, the observed rapid variability indicates that the X-ray emission originates from a compact region located close to the central engine. Furthermore, using a log-parabolic electron energy distribution within the SYNCHROTRON JET scenario, we simulate the observed anti-correlation between the $E_{\rm p}$ and $β$. These features can be interpreted within the framework of energy-dependent particle acceleration in BLAZAR JETs, which are often associated with turbulence, strong MAGNETic fields, and RELATIVISTIC outflows.
[abstract 3 / 41] Yes (score: 6) - Title: Radiation-induced electron spin POLARIZATION in ultraRELATIVISTIC kinetic turbulenceAuthors: Peng Liu, Karen Z. Hatsagortsyan, Christoph H. Keitel, Zheng Gong,Comments: Comments are welcomeSubjects: physics.plasm-ph astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Electron spin POLARIZATION in radiative plasmas with ultraRELATIVISTIC kinetic turbulence under highly MAGNETized conditions is investigated using particle-in-cell simulations. We observe that a significant spin POLARIZATION can be sustained when the leptons undergo energetic photon emission accompanied by spin flips during the nonequilibrium turbulent evolution.By analyzing the time evolution of spatially dependent spin POLARIZATION, we identify an electroMAGNETic (EM) regime of kinetic turbulence, distinct from the well-known density-dominated regime characterized by vortex currents and MAGNETic islands. While in the latter regime the spin POLARIZATION exists only transiently, in the EM regime significant anisotropic net POLARIZATION emerges and persists in non-dissipative scenarios. The correlation between spin signals and turbulence features is leveraged to introduce the characteristic parameter delimiting the EM regime via the ratio of electric and MAGNETic energy densities and to gain insight into complex plasma turbulence. This study demonstrates the versatility of a spin-resolved study of the plasma turbulence in extreme environments, such as BLACK HOLEs and MAGNETar MAGNETospheres.
[abstract 4 / 41] Yes (score: 5) - Title: Captured are circularized: A RELATIVISTIC treatment of extreme mass ratio inspirals crossing accretion disksAuthors: Yuhe Zeng, Zhen Pan,Comments: 15 pages, 14 figuresSubjects: astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
A small body orbiting around an accreting massive object and periodically crossing its accretion disk is a common configuration in astrophysics. In this work, we investigate the secular evolution of extreme mass-ratio inspirals (EMRIs), in which a stellar-mass object (SMO), e.g., a star or a stellar-mass BLACK HOLE (sBH), collides with the accretion disk of a central supermassive BLACK HOLE (SMBH), within a fully RELATIVISTIC framework. We find (1) the disk always tends to align the SMO no matter what the initial orbital inclination $ι$ relative to the disk is, (2) the final orbital eccentricity of the SMO captured by the disk is always low though the orbital eccentricity may temporarily grow when the orbital inclination $ι$ is large and the SMO is an sBH, and (3) via collisions with the accretion disk only, only a small fraction of sBHs that are initially close to the SMBH and close to the disk can be captured by the disk within typical disk lifetime of ACTIVE GALACTIC NUCLEi. Two-body scatterings between SMOs in the nuclear stellar cluster play an essential role in randomly kicking sBHs towards the disk and boosting the capture rate.
[abstract 5 / 41] Yes (score: 5) - Title: Blackholistic 2026 meeting reportAuthors: Rob Fender, Jane Dai, Erin Kara, Sera Markoff, Francesca Panessa, Jiri Svoboda, Heino Falcke,Comments: We encourage all who are interested in the subject matter of this meeting to visit our talks and poster archive at https://blackholesoxford2026.web.ox.ac.uk/programmeSubjects: astro-ph.HECreated: 2026-06-01; Updated: 2026-06-04; Datestamp: 2026-06-04
Accretion and RELATIVISTIC JET formation take place across the BLACK HOLE mass range, from BLACK HOLEs of just a few solar masses to those in excess of ten billion. Despite the enormous range in scales, qualitative similarities and quantitative scalings appear to connect the entire population. In March 2026, researchers from across the BLACK HOLE mass spectrum met in Oxford to educate, explore and forge new research directions. This is a brief report on the meeting and an opportunity to advertise the archive of talks, discussion sessions and posters.
[abstract 6 / 41] Yes (score: 5) - Title: Multifrequency Synthesis via CHIBI: Colorful Hierarchical Interferometric Bayesian ImagingAuthors: Erandi Chavez, Paul Tiede, Sara Issaoun, Michael D. Johnson, Dominic Pesce, Yuh Tsunetoe, Daniel C. M. Palumbo,Comments: 26 pages, 18 figures, to be published in ApJSubjects: astro-ph.IM astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
From MAGNETized plasma of RELATIVISTIC JETs to dust grains within protoplanetary disks, we study the emission mechanisms of radio sources via their rich spectral structure. Multifrequency Synthesis (MFS) is a technique in which interferometric data at multiple frequencies are imaged simultaneously, resulting in a denser sampling of spatial scales, higher imaging fidelity, and tighter constraints on the source's spectral structure and evolution. We describe a new method of MFS imaging reconstruction in a hierarchical interferometric Bayesian inference framework, CHIBI. The model parametrization is based on the spectral behavior of SYNCHROTRON radiation, the emission mechanism dominating the radio emission observed from galactic nuclei. We show results of this method on observations of JET sources from the MOJAVE catalog with the Very Long Baseline Array, and showcase the prospects for MFS imaging of M87* with simulated data from the Event Horizon Telescope (EHT) and future expansions such as the next generation EHT and the Black Hole Explorer. These demonstrations highlight the benefit of MFS to reconstruct higher-fidelity images and spectral index maps, producing scientifically richer results in a statistically grounded framework, implemented in Comrade.jl.
[abstract 7 / 41] Yes (score: 5) - Title: Recurrent Coronal Jets and QPPs: Periodic Reconnection and Localized Heating Across Quiet-Sun to Active RegionsAuthors: Sudheer K. Mishra, Kartika Sangal, Balveer Singh, Ayumi Asai, A. K. Srivastava, Ding Yuan,Comments: 17 pages, 8 figures, 1 table; Accepted for publication in the Philosophical Transactions of the Royal Society of London Series ASubjects: astro-ph.SRCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
We analyze quasi-periodic pulsations (QPPs) in recurrent coronal JETs driven by periodic MAGNETic RECONNECTion associated with successive flux emergence in the fan-spine MAGNETic topologies. Using the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), we investigate three long-lived recurring JETs spanning quiet Sun to moderate-field-strength regions, each exhibiting recurrent eruptions linked to episodic RECONNECTion. Wavelet analysis of multithermal AIA EUV JET-base light curves detects QPPs with periods of 6-13 min, exceeding typical p-mode oscillation periods. Distance-time analysis reveals quasi-periodic propagating ridges, interpreted as recurrent field-aligned plasma ejections, and morphological similarities to slow MAGNEToacoustic waves, which cannot be entirely excluded. However, the dominant photospheric unsigned flux periodicities of 10-32 min at the JET source regions favor the RECONNECTion-driven interpretation. DEM analysis confirms multithermal plasma with the hottest emission concentrated near the JET base, and the QPP periods fall well below both radiative and conductive cooling timescales, implying persistent localized heating within the fan-spine configuration. These results demonstrate that periodic RECONNECTion in fan-spine topologies drives recurrent JET eruptions and contributes to localized coronal heating across the quiet Sun, moderate-field strength regions, and active regions.
[abstract 8 / 41] Yes (score: 5) - Title: $E_{\rm peak}$-$α$ Correlation in Time Resolved GRB Spectra: A Bottom-Up Approach with Optically Thin Inverse Compton Scattering ModelAuthors: Pragyan Pratim Bordoloi, Ayush Shivkumar, Shabnam Iyyani,Comments: This manuscript has already been submitted to the Astrophysical Journal. No review has come yetSubjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Gamma-ray bursts (GRBs) are the brightest explosions in the Universe, yet the origin of their emission remains uncertain. Time-resolved spectral analysis offers key insights into the evolution of spectral shapes, constraining both radiation mechanisms and emission-site microphysics. Observationally, GRB spectra are well described by the empirical Band function, characterized by the peak energy ($E_{\mathrm{peak}}$) and low-energy spectral index ($α$). We investigate the temporal evolution of spectra produced by optically thin inverse-Compton scattering (ICS) within a standard fireball JET framework, focusing on the scenarios that can produce the two commonly observed spectral evolution patterns: hard-to-soft evolution and intensity tracking, within a single emission pulse. The evolution is analysed using both Bayesian block and constant-fluence binning, with the observed spectrum modeled consistently using the Band function. Using this bottom-up approach, we find that optically thin ICS yields a positive $E_{\mathrm{peak}}$-$α$ correlation, with $α$ evolving from hard (Planck-like, $> +0.5$) to softer ($< -0.67$) values. Such hard $α$ values are inconsistent with standard SYNCHROTRON emission. This characteristic evolution in the $E_{\mathrm{peak}}$-$α$ plane, therefore, provides a diagnostic signature of optically thin ICS as the dominant radiation mechanism during the prompt phase of GRBs. Furthermore, this type of smooth evolution of $α$ within a single pulse does not require invoking a transition between different radiation mechanisms, unless additional observational evidence supports such a change.
[abstract 9 / 41] Yes (score: 4) - Title: Inferring the stochastic gravitational-wave background from eccentric stellar-mass binary BLACK HOLEs with spaceborne detectorsAuthors: Zheng-Cheng Liang, Zhi-Yuan Li, Yi-Ming Hu,Comments: 13 pages, 4 figuresSubjects: gr-qc astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
The stochastic gravitational-wave background (SGWB) from eccentric stellar-mass binary BLACK HOLEs (SBBHs) holds crucial clues to their origins. For the first time, we employ a Bayesian framework to assess the detectability and distinguishing features of such an SGWB with spaceborne detectors, while accounting for contamination from the Galactic foreground. Our analysis covers eccentric SBBHs from three formation channels: isolated binary evolution, dynamical assembly in globular clusters (GCs), and in ACTIVE GALACTIC NUCLEi (AGNs). We find that TianQin, Laser Interferometry Space Antenna (LISA), and Taiji can detect the SGWBs from both isolated and GC-formed SBBHs after four years of operation, with the corresponding SNRs of around 10, 60, and 170. However, these backgrounds are spectrally degenerate with a strictly power-law SGWB. Furthermore, highly eccentric SBBHs formed in AGNs yield an SGWB marked by a spectral turnover and sharp decline. While this feature lowers the SNR by approximately an order of magnitude, it can enable a clear distinction from the strictly power-law background using LISA and Taiji.
[abstract 10 / 41] Yes (score: 4) - Title: XRISM detection of the 6.4 keV Fe K$α$ line in the RADIO GALAXy Cygnus AAuthors: Anwesh Majumder, T. Heckman, L. Gu, A. Simionescu, B. R. McNamara, A. Ptak, E. Hodges-Kluck, M. Yukita, M. W. Wise, N. Roy,Comments: 10 pages, 4 figures. Accepted for publication in ApJSubjects: astro-ph.HE astro-ph.COCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
We detail the spectral analysis of a 170 ks XRISM Resolve observation of the core of Cygnus A. The high spectral resolution of Resolve have enabled us to probe the inner accretion region of Cygnus A by analyzing the 6.4 keV Fe K$α$ line complex. We find that it consists of two Keplerian broadened components. (1) A broad component with a velocity dispersion of $3400^{+800}_{-600}$ km s$^{-1}$ and (2) a narrow component of $440^{+60}_{-50}$ km s$^{-1}$. For an inclination of $50^{\circ}-85^{\circ}$, constrained by VLBI, we find that the broad component arises from a distance of $\sim 0.1-0.17$ pc ($800-1400$ gravitational radii) and the narrow component from $\sim 6-10$ pc ($50,000-80,000$ gravitational radii) from the central BLACK HOLE depending on the inclination angle. Our result suggests that the origin of the broad component is consistent with the broad line region and the narrow component from the torus of Cygnus A. We also find a potential emission line possibly from intermediate ionized Fe XVII with a very low dispersion ($<80$ km s$^{-1}$) that originates from either the outer edge of the torus or the narrow line region. Finally, we find that the Fe K edge is redshifted compared to the Fe K$α$ line components, suggesting a line of sight bulk velocity of $470 \pm 100$ km s$^{-1}$. Such a shift may be due to an inflowing wind or relative motion between the two components originating from the near and far side of an inflowing torus, respectively.
[abstract 11 / 41] Yes (score: 4) - Title: The role of major mergers in triggering super-Eddington accretionAuthors: Riccardo Caleno, Tommaso Zana, Raffaella Schneider, Alessandro Lupi, Pedro R. Capelo, Lucio Mayer, Alessandro Trinca, Rosa Valiante, Marta Volonteri,Comments: 12+2 pages, 8 figures; submitted to A&ASubjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
JWST observations have opened a new era in the exploration of the high-redshift Universe, revealing BLACK HOLEs (BHs) with masses of several million solar masses already at $z>8$, challenging our understanding of their growth mechanisms. In this context, super-Eddington (SE) accretion has emerged as a promising solution and has been widely adopted in both numerical simulations and semi-analytical models. In this work, we investigate whether a major merger between two relatively low-mass halos ($M_{\rm halo}\sim10^9\,\mathrm{M_\odot}$) at high redshift can trigger episodes of sustained SE accretion, with particular focus on the role of BH feedback. We employ state-of-the-art, high-resolution cosmological zoom-in simulations of a major merger at $z\sim11$. We explore different prescriptions for BH seeding and feedback, including physically motivated radiative and kinetic models (winds and JETs) across the three main accretion regimes: advection-dominated accretion flows (ADAF), radiatively efficient sub-Eddington accretion, and SE accretion. For the relatively low-mass halos studied here, our feedback prescription efficiently suppresses gas accretion, preventing substantial BH growth. We find that, although the merger drives gas inflows towards the central regions, this is not sufficient to trigger sustained SE accretion. Post-merger SE accretion episodes are observed only when BH feedback is entirely switched off. Amongst the feedback channels considered, kinetic feedback is the primary mechanism regulating BH growth. Moreover, the only significant SE accretion episodes occur immediately after BH seeding, while the merger itself does not produce a substantial enhancement of the accretion rate.
[abstract 12 / 41] Yes (score: 4) - Title: Temporal Invariance Is an Illusion: Time-Dependent Influences of the Galactic Magnetic Field on UHECR ObservationsAuthors: Veronika Vašíčková, Leonel Morejón, Karl-Heinz Kampert,Comments: 13 pages, 8 figures excl. appendix, or 18 pages, 12 figures incl. appendixSubjects: astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Understanding the origin of the Ultra-High-Energy Cosmic Rays (UHECRs) requires explaining the features of their energy spectrum, mass composition, and arrival directions. Current modeling approaches neglect the time evolution of UHECR observables, a factor that is particularly important in the case of bursting UHECR sources. This study focuses on the influence of time delays caused by the galactic MAGNETic field (GMF) on the spectrum and arrival directions of UHECRs observed on Earth. Using CRPropa 3.2, we investigate the rigidity-dependence of the residence time of extragalactic COSMIC RAYs entering our Galaxy. We find that UHECRs entering the Milky Way can experience delays of hundreds of kiloyears relative to light, and we demonstrate that these delays significantly alter the UHECR observables. Notably, a cutoff emerges in the transient scenario within the rigidity range of $10^{18}-10^{19}$ V, which coincides with the spectral break observed in data. We find a progressive shift in composition favoring heavier nuclei, as well as a delay distribution that is correlated with GMF strength. This causes the particles to be less correlated with their initial direction the larger their delays. A dipole-like anisotropy develops over timescales of about $\sim$100 kyr in certain bursts scenarios. Our results provide an alternative explanation for the UHECR spectral cutoff that does not invoke limits on source acceleration. This could potentially revise existing constraints.
[abstract 13 / 41] Yes (score: 4) - Title: Shape of U: Measuring the Curvature of the Universe with Gravitational WavesAuthors: Arindam Sharma, Ish Gupta, Anuradha Gupta,Comments: 15 pages, 7 figuresSubjects: gr-qc astro-ph.CO astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Gravitational waves (GWs) from compact binary mergers are standard sirens that can measure distances across the Universe without external calibrators. When an electroMAGNETic counterpart enables an independent redshift measurement, such "bright sirens" can be used to probe the expansion history of the Universe and constrain cosmological models. In this work, we investigate the ability of future GW observatories to measure the spatial curvature parameter, $Ω_{\rm k}$, in a non-flat $Λ$CDM cosmology. We focus on intermediate-mass binary BLACK HOLE mergers (with masses similar to GW231123) as bright siren sources, motivated by their detectability to high redshifts with next-generation ground-based detectors and by the possibility that mergers in ACTIVE GALACTIC NUCLEus disks may produce electroMAGNETic counterparts. Using Fisher matrix forecasts, we find that a network consisting of two Cosmic Explorer detectors and Einstein Telescope can constrain $Ω_{\rm k}$ to a $1σ$ uncertainty of $0.029$ with these bright sirens. We further show that multiband observations with LISA or the Lunar Gravitational Wave Antenna do not significantly improve these cosmological constraints, because the additional signal-to-noise ratios accumulated in their bands are modest. Further, a population of binary neutron stars as bright sirens provides substantially broader constraints on $Ω_{\rm k}$, with $1σ$ error of $0.055$. Our results show that bright intermediate-mass binary BLACK HOLE and binary neutron star mergers observed with next-generation GW detectors together can provide an independent and informative probe of spatial curvature, with systematics distinct from those of other cosmological observations.
[abstract 14 / 41] Yes (score: 4) - Title: The Extreme Rarity and Physical Properties of Low-redshift AGNs with Balmer AbsorptionAuthors: Jinyi Shangguan, Chang-Hao Chen, Luis C. Ho, Jiwei Liao, Yanqing Liu, Chengzhou Wu, Ruancun Li, Kohei Inayoshi, Linhua Jiang,Comments: 26 pages in the main text, 23 figures, submitted to ApJSubjects: astro-ph.GA astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Balmer absorption lines are increasingly observed in the little red dots (LRDs) discovered by the James Webb Space Telescope, potentially tracing dense circumnuclear gas around rapidly accreting BLACK HOLEs. Motivated by this connection, we search for Balmer absorption using homogeneously analyzed spectra of a representative parent sample of 14,584 low-redshift ($z<0.35$) type 1 ACTIVE GALACTIC NUCLEi selected from the Sloan Digital Sky Survey. We identify seven sources with robust Balmer absorption (occurrence $\sim 0.05\%$) and model them with a partially covering absorber model, accounting for the spectral resolution. By fitting H$α$, H$β$, and H$γ$ simultaneously and tying their optical-depth ratios to theoretical values, we constrain optical depth at the line center ($τ_0$) and the covering factor ($C_f$). All sources with robust modeling require optically thick H$α$ absorption and typically moderate covering factors ($C_f\approx 0.2-0.6$), while the LRD analog J1025 shows $C_f \gtrsim 0.8$ consistent with recent measurements of high-redshift LRDs. The absorbers have modest velocity offsets ($\sim 150-850\,\mathrm{km\,s^{-1}}$) and narrow intrinsic widths ($\sim 20-200\,\mathrm{km\,s^{-1}}$). Multi-epoch spectroscopy of three sources reveals Balmer-absorption variability on both year and month timescales. Three objects exhibit exceptionally weak Fe II emission, high Eddington ratio, and low gas-phase metallicity, an atypically rare combination of properties that might elevate the incidence of Balmer-absorption to $\sim$10%. We argue that low-metallicity conditions may suppress disk winds and help retain dense neutral gas along the line-of-sight in systems of high accretion rate.
[abstract 15 / 41] (score: 3) - Title: Learning collision operators from plasma phase space data using differentiable simulatorsAuthors: Diogo D. Carvalho, Pablo J. Bilbao, Warren B. Mori, Luis O. Silva, E. Paulo Alves,Comments: accepted for publication in Journal of Plasma Physics, code available at https://github.com/diogodcarvalho/ml-pic-collision-operatorsSubjects: physics.plasm-ph cs.LG physics.comp-phCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
We propose a methodology to infer collision operators from phase space data of plasma dynamics. Our approach combines a differentiable kinetic simulator, whose core component in this work is a differentiable Fokker-Planck solver, with a gradient-based optimisation method to learn the collisional operators that best describe the phase space dynamics. We test our method using data from two-dimensional Particle-in-Cell simulations of spatially uniform thermal plasmas, and learn the collision operator that captures the self-consistent electroMAGNETic interaction between finite-size charged particles over a wide variety of simulation parameters. We demonstrate that the learned operators are more accurate than alternative estimates based on particle tracks, while making no prior assumptions about the relevant time scales of the processes and significantly reducing memory requirements. We find that the retrieved operators, obtained in the non-RELATIVISTIC regime, are in excellent agreement with theoretical predictions derived for electrostatic scenarios. Our results show that differentiable simulators offer a powerful and computational efficient approach to infer novel operators for a wide rage of problems, such as electroMAGNETically dominated collisional dynamics and stochastic wave-particle interactions.
[abstract 16 / 41] (score: 3) - Title: Flux Variations of Fast Radio Bursts and Their Persistent Radio Sources: Evidence for a Shared ProgenitorAuthors: Xinming Li, Chenhui Niu, Jiaheng Zhang, Di Li, Bing Zhang, Yuanpei Yang, Pei Wang, Junshuo Zhang, Yongkun Zhang, Ye Li, Jiarui Niu, Xiaoping Zheng, Yunwei Yu, Yi Feng, Bo Zhang, Fayin Wang, Yuhao Zhu, Aming Chen, Zexin Du, Jian Li, Weihong Li, Chenchen Miao, Weiyang Wang, Guanglei Wu, Aiyuan Yang, Jumei Yao, Rushuang Zhao,Comments:Subjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Fast radio bursts (FRBs) are millisecond-duration extragalactic radio transients, some of which are associated with compact persistent radio sources (PRSs), hinting at a physical connection. While several models have been proposed to explain PRSs and their connection to FRBs, direct observational tests remain limited. Here, we report for the first time a correlated trend between the long-term variation of the PRS flux density and the burst energetics of FRB 20190520B and FRB 20240114A, suggesting a physical coupling between the PRS and FRB activity. We further examine additional repeaters with compact PRSs and find no clear correlation between PRS luminosity and burst activity, likely due to the limited observations. These results are consistent with scenarios in which both the PRS and FRB activity may be powered by a common energy reservoir, such as the MAGNETic or rotational energy of a MAGNETar.
[abstract 17 / 41] (score: 3) - Title: Dynamics and detectability of long-lived non-accretion phases for massive BLACK HOLE binaries in cold, thermally regulating disksAuthors: Christopher Tiede, David O'Neill, Daniel J. D'Orazio,Comments: 17 pages and 9 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
We investigate whether the non-accreting phases found in thin, locally isothermal circumbinary disks survive when the disk thermodynamics are evolved self-consistently. We present grid-based hydrodynamics simulations of circumbinary accretion with an energy equation that includes viscous and hydrodynamic heating coupled to radiative blackbody cooling in the high-Mach number regime. We find that, although gas accumulates and heats at the far edge of the circumbinary cavity, the regions that launch accretion streams remain comparatively cold, leading to potentially long-lived suppression of the binary accretion rate as the large-scale feeding rate is reduced towards the Eddington limit. This runaway non-accretion problem, however, is weakened relative to locally isothermal solutions. Despite their low accretion rates, binaries interacting with disks in a non-accreting phase can remain sufficiently luminous and variable at optical and near-infrared frequencies to be detectable in upcoming wide-field surveys like LSST and the Roman Space Telescope. Because of the effective truncation of the surrounding disk, though, such systems are comparatively faint in high energy, photo-ionizing emission, and may therefore appear as intrinsically X-ray-weak AGN with weak or absent emission line features. We additionally suggest an update to grid-based sink prescriptions for approximating mass loss across an unresolved horizon when including an energy conservation equation.
[abstract 18 / 41] (score: 3) - Title: Earliest simultaneous multi-color optical observations of GRB 230328B: from 41 seconds to the host-galaxy identificationAuthors: T. Komesh, A. Pozanenko, N. Pankov, A. Volnova, P. Minaev, R. Gill, D. Berdikhan, B. Grossan, Z. Maksut, Z. Abdullayev, S. Belkin, M. Krugov, A. Moskvitin, K. Baigarin, A. Tursynkan, E. Klunko, A. Tatarnikov, S. Zheltoukhov, V. Rumyantsev, A. Volvach, L. Volvach, O. A. Burkhonov, S. A. Ehgamberdiev, R. Inasaridze, L. Elenin, A. Krylov, M. Zheltobryukhov, S. B. Pandey, A. K. Ror, R. Gupta, V. Swain, V. Bhalerao, G. C. Anupama, S. Barway, R. Sánchez-Ramírez, A. J. Castro-Tirado, S. Antier, P. Beniamini, E. Abdikamalov,Comments:Subjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
We present a multi-wavelength analysis of the long-duration GAMMA-RAY BURST GRB 230328B. FERMI/GBM observations reveal a typical Type II burst with a duration of about 22 s. Using a photometric redshift of about 1.5 derived from the host galaxy, we find that the burst energetics, with an isotropic-equivalent energy of about 6.4*10^52 erg, are consistent with established empirical correlations for long GAMMA-RAY BURSTs. The optical, X-ray, and radio afterglow exhibits a complex temporal evolution, featuring an early onset bump followed by a pronounced late-time achromatic rebrightening at about 4000 s. Through MCMC modeling, we find that the afterglow can be explained by forward shock emission with late energy injection. Broadband spectral energy distribution fitting reveals significant line-of-sight dust extinction, corresponding to a visual extinction of about 0.8 magnitudes, consistent with Milky Way or Large Magellanic Cloud dust properties. The burst originated in a relatively young, highly absorbed S0-type host galaxy, whose morphological analysis suggests that it may be part of a system of interacting galaxies. Finally, late-time optical monitoring reveals no signature of an accompanying SUPERNOVA.
[abstract 19 / 41] (score: 3) - Title: NICER detection of a new candidate cyclotron line in the bursting X-ray pulsar GRO J1744-28Authors: Qi Liu, Lingda Kong, Long Ji, Lorenzo Ducci, Xiaohang Dai, Andrea Santangelo, Ce Cai, Shuwang Cui, Mingyu Ge, Shu Zhang, Shuang-Nan Zhang, Lian Tao, Hua Feng, Wei Wang, Valery Suleimanov, Sergey Tsygankov, Juri Poutanen, Alexander Mushtukov,Comments: 9 pages, 10 figures, and 4 tables. Accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.HE astro-ph.SRCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
We report the detection of cyclotron resonant scattering features (CRSFs) in the spectrum of the unique bursting pulsar GRO J1744-28, observed during its recent outburst in 2021 with the Neutron Star Interior Composition Explorer (NICER). Clear pulsations at a frequency of 2.141128 Hz as well as Type II X-ray bursts were observed. The pulse profile exhibits a single-peaked shape in all energy bands, with the pulse fraction showing a positive correlation with energy. We find that the persistent X-ray continuum of the accreting pulsar is well described by typical phenomenological models, and we confirm the presence of the cyclotron line at $\sim$5 keV as reported in previous studies. In addition, we detect a candidate absorption feature with a centroid energy of 2 keV. If confirmed, this feature could be interpreted as a CRSF, which would correspond to a MAGNETic field of $\sim$1.8 $\times 10^{11}$ G. Pulse-phase-resolved analysis also reveals this absorption line around the peak pulse phases. These NICER observations provide tentative evidence for the cyclotron line candidate, establishing GRO J1744-28 as a key laboratory for studying accretion physics in an intermediate-strength MAGNETic field.
[abstract 20 / 41] (score: 3) - Title: Long-term investigation of gamma Cas analogsAuthors: Yael Naze, Robbie Webbe, Myron A. Smith, Christian Motch,Comments: accepted for publication by A&ASubjects: astro-ph.SR astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
The subcategory of gamma Cas analogs gathers Be stars with bright and hard X-ray emission. Long-term variations are expected in such objects for two reasons: their Be disk builds and dissipates, and such stars are suspected long-period binaries. Seven targets are analysed in this paper: five of them benefit from a spectroscopic monitoring in the visible (ESO, TIGRE, and amateur data) and three of them have been repeatedly observed at X-ray wavelengths (using XMM-Newton, Chandra, and SWIFT). Broad-band photometric data are also examined. We confirm the binary status of five targets (HD44458, HD110432, HD119682, HD161103, and HD162718) and propose first orbital solutions for all of them (they remain preliminary for two cases). Their long periods (59-322 d) and small velocity amplitudes (K~5km/s) imply low-mass (~1 M_sol) companions, as in other Be binaries and in agreement with expectations from binary interaction models. In parallel, variations of the X-ray flux are detected in all three targets with a large dataset of X-ray observations. For NGC 6649 9 and HD162718, these changes are modest (a factor of three) and uncorrelated to simultaneous optical broad-band photometry (which remains rather stable). In contrast, SS397 varies by nearly one dex and the largest and best monitored X-ray changes correlate well with optical variations. At minimum flux, SS397 keeps a hard X-ray spectrum despite a nearly normal L_X/L_BOL ratio, which has not been seen yet among gamma Cas analogs. Finally, the photometric behaviours on short timescales of HD161103, SS397, and NGC 6649 9 appear linked to broad frequency groups, as typically found for Be stars. The frequency spectrum of HD162718 displays a complex mix of (isolated) periodicities with the main one at 6.658/d. This target is thus one of the rare gamma Cas analogs to display a strong high-frequency signal typical of beta Cep activity. [summarized]
[abstract 21 / 41] (score: 3) - Title: Granular mass perturbations on the pulsar - supermassive BLACK HOLE systemAuthors: Zexin Hu, Lijing Shao,Comments: 5 pages, 3 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Discovery and timing observations of a radio pulsar orbiting around Sagittarius A*, the supermassive BLACK HOLE (SMBH) in our Galactic Centre (GC), will provide unprecedented opportunities of studying the SMBH spacetime, testing gravity theories, and probing the astrophysical environment in the GC. However, unknown mass distributions might cause timing residuals that are much larger than the timing precision. With extensive numerical simulations, for the first time we find that the perturbations caused by a granular cusp of stellar-mass BLACK HOLEs in the GC lead to post-fit timing residuals of 10-100 s, contrary to traditional wisdom, even for a pulsar in a tight orbit with an orbital period $P_b=0.5\,{\rm yr}$. Such a large timing residual can lead to significant measurement bias or even prevent construction of a phase-connected timing solution for the full orbit. We revisit the idea of extracting SMBH parameters only with data around periastron where the perturbation is small. Under the realistic phase-disconnected assumption, we point out that it is vital to consider the frame-dragging effect in the light propagation, which breaks parameter degeneracy and leads to an order of magnitude improvement for the measurement precision of the SMBH spin.
[abstract 22 / 41] (score: 3) - Title: Cooler Phases of the Circumgalactic Medium Are More Centrally Concentrated: Constraints from Multiphase Absorption LinesAuthors: Weiwen Kong, Zeyu Chen, Enci Wang, Haoran Yu, Kai Wang, Dongdong Shi, Cheqiu Lyu, Yuxuan Zhang, Haoyi Zhang, Haowen Guan,Comments: Submitted to ApJ. Comments welcomeSubjects: astro-ph.GACreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
We present a systematic study of the multiphase circumgalactic medium (CGM) around galaxies and QUASARs, traced by Ca II $λ\lambda3934,3969$, Mg II $λ\lambda2796,2803$, and C IV $λ\lambda1548,1550$, using the Year 1 dataset from the Dark Energy Spectroscopic Instrument. These three doublets trace CGM gas across a range of temperatures, from cold to warm phases, and we employ a stacking technique to measure the corresponding absorption signals using background sources. We show that CGM structure is strongly phase-dependent: ions tracing progressively cooler gas exhibit increasingly steep radial profiles in equivalent width ($W_i$). These trends are broadly consistent with predictions from cosmological simulations, supporting a phase-stratified CGM in which cooler gas is more centrally concentrated. Specifically, halos of emission-line galaxies exhibit a strong radial transition from cool to warm gas, whereas halos of QUASARs show a more uniform distribution, likely regulated by ACTIVE GALACTIC NUCLEi feedback; in contrast, the cold gas traced by Ca II in low-redshift galaxies is tightly confined to inner regions. We further demonstrate that the radial scaling $W_i \propto D^α$ is primarily set by host stellar mass, particularly for the cool-phase medium, suggesting efficient heating processes in massive halos. By jointly leveraging multiple absorption tracers from observations and simulations, we map the CGM from cold to warm phases and place new constraints on the baryon cycle governing galaxy evolution.
[abstract 23 / 41] (score: 3) - Title: Early Multiwavelength Observations of AT 2026fgk: The Luminous Afterglow to Sub-luminous GRB 260310A, Identified Independently of a Gamma-ray TriggerAuthors: K. -R. Hinds, A. Y. Q. Ho, Y. Wagh, R. Jayaraman, D. A. Perley, G. Waratkar, A. Bochenek, B. P. Gompertz, C. Fremling, J. Rastinejad, N. Sarin, G. Schroeder, R. A. Perley, G. P. Srinivasaragavan, K. Ackley, T. Ahumada, M. F. Aller, I. Andreoni, A. Aryan, S. Belkin, E. C. Bellm, S. Ben-Ami, T. de Boer, M. Bremer, R. P. Breton, S. B. Cenko, K. C. Chambers, T. -W. Chen, C. T. Christy, G. Corcoran, L. Cotter, M. W. Coughlin, F. Cuadra, V. D'Elia, K. De, V. S. Dhillon, Dimple, M. J. Dyer, A. R. Escorial, D. K. Galloway, S. Garrappa, J. H. Gillanders, M. A. Gurwell, X. J. Hall, M. E. Huber, S. Ibrahim, J. C. Jaimes, P. Jakobsson, E. Kammoun, M. Kasliwal, G. K. Keating, T. Killestein, R. Konno, R. Kotak, D. Kovaleva, A. Krassilchtchikov, A. Kraus, A. Kumar, R. R. Laher, A. Levan, J. Lyman, A. Martin-Carrillo, Z. McGrath, P. Minguez, G. Mo, M. Nicholl, K. Noysena, A. Nugent, L. K. Nuttall, P. O'Brien, D. O'Neill, E. O. Ofek, G. S. H. Paek, P. V. de la Parra, D. Polishook, A. Ruiz Del Pozo, G. Pugliese, J. Purdum, M. Pursiainen, G. Ramsay, R. Rao, A. C. Readhead, P. Rekhi, R. Riddle, S. Rose, B. Rusholme, A. Sasli, D. Schiminovich, E. Segre, C. Sevilla, Y. M. Shani, M. Shrestha, S. J. Smartt, K. W. Smith, J. Sollerman, N. Sravan, S. Srivastav, D. Steeghs, R. Stein, T. Surti, K. Ulaczyk, J. C. Vel'azquez, R. Wainscoat, J. L. Wise, D. Xu, S. Yang,Comments:Subjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
The origins of sub-luminous ($L_\mathrm{γ,\mathrm{iso}} < 10^{49.5}$\,erg\,s$^{-1}$) GAMMA-RAY BURSTs (GRBs) associated with broad-lined Type~Ic SUPERNOVAe (Ic-BL SNe) are poorly understood, in part due to the low discovery rate and faint afterglows. Here we present the identification of the optical afterglow of FERMI-GBM-detected GRB\,260310A (AT\,2026fgk) as a rapidly rising ($>1\,$mag\,d$^{-1}$), red ($g-r=0.4$\,mag) transient using the Gravitational-wave Optical Transient Observatory, Large Array Survey Telescope, and Zwicky Transient Facility (ZTF) data streams. We present multiwavelength follow-up observations from the first 50\,days, which reveal that GRB 260310A/AT\,2026fgk was sub-luminous ($L_\mathrm{γ,iso}=10^{48.8}\,$erg\,s$^{-1}$); it was the most nearby ($z=0.153$) afterglow identified blindly by an optical survey; and that it is one of the brightest afterglows ever observed at X-ray, optical, and radio (cm to mm) wavelengths. We spectroscopically confirm an underlying Ic-BL SN with properties typical of GRB-SNe ($M_\mathrm{ej}\approx3\,M_\odot$, $E_{\rm K}\approx 10^{52}\,$erg). With basic modeling of the afterglow, including the long optical rise ($\approx10^{3}\,$s), we infer either a low initial Lorentz factor ($Γ_0\approx40$) or a slightly off-axis viewing angle ($\lesssim3^\circ$). The host galaxy's mass and STAR FORMATION rate are similar to the hosts of other sub-luminous GRBs. ZTF's flux-limited survey gives a volumetric rate of AT\,2026fgk-like events of $0.30^{+1.37}_{-0.29}\,$Gpc\,$^{-3}$\,yr$^{-1}$, which is consistent with the on-axis, high luminosity ($L_{\rm γ,iso}>10^{49.5}$\,erg\,s$^{-1}$) long-GRB rate. The similarity in the rates strongly constrains the prevalence of low-$Γ_0$ bursts and the beaming of the initial RELATIVISTIC material in GRBs.
[abstract 24 / 41] (score: 2) - Title: Modeling transport in weakly collisional plasmas using thermodynamic forcingAuthors: Prakriti Pal Choudhury, Archie F. A. Bott,Comments: 28 pages, 15 figures, 1 table, accepted in Physical Review ESubjects: physics.plasm-ph astro-ph.GA astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
How momentum, energy, and MAGNETic fields are transported in the presence of macroscopic gradients is a fundamental question in plasma physics. Answering this question is especially challenging for weakly collisional, MAGNETized plasmas, where macroscopic gradients influence the plasma's microphysical structure. In this paper, we introduce thermodynamic forcing, a new method for systematically modeling how macroscopic gradients in MAGNETized or unMAGNETized plasmas shape the distribution functions of constituent particles. In this method, we propose to apply an anomalous force to those particles inducing the anisotropy that would naturally emerge due to macroscopic gradients in weakly collisional plasmas in which thermal pressure is much larger than MAGNETic pressure. We implement thermodynamic forcing in particle-in-cell (TF-PIC) simulations using a modified Vay particle pusher and validate it against analytic solutions of the equations of motion. We then carry out a series of simulations of electron-proton plasmas with periodic boundary conditions using TF-PIC. First, we confirm that the properties of two electron-scale kinetic instabilities - one driven by a temperature gradient and the other by bulk-velocity gradient - are consistent with previous results. Then, we demonstrate that in the presence of both macroscopic gradients, heat-flux saturation is mediated by the bulk-velocity-gradient-driven electron firehose instability rather than the temperature-gradient-driven whistler instability. This suggests that saturation mechanisms may differ from our current understanding in the presence of multiple free energy sources. This work enables, for the first time, systematic and self-consistent transport modeling in weakly collisional plasmas, with broad applications in astrophysics, LASER-plasma physics, and inertial confinement fusion.
[abstract 25 / 41] (score: 2) - Title: TDE 2025abcr: A Tidal Disruption Event in the Outskirts of a Massive GalaxyAuthors: Robert Stein, Jonathan Carney, Charlotte Ward, Raffaella Margutti, Xander J. Hall, Itai Sfaradi, Igor Andreoni, Ryan Chornock, Suvi Gezari, Geoffrey Mo, Yuhan Yao, Eric C. Bellm, Joshua S. Bloom, Malte Busmann, Ilaria Caiazzo, S. Bradley Cenko, Matthew J. Graham, Steven L. Groom, Daniel Gruen, Erica Hammerstein, Mansi M. Kasliwal, Brendan O'Connor, Antonella Palmese, Josiah Purdum, Jillian C. Rastinejad, Reed Riddle, Ben Rusholme, Jesper Sollerman, Jean J. Somalwar, Sylvain Veilleux,Comments: accepted, 30 pages, 14 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Tidal disruption events (TDEs) have traditionally been discovered in optical sky surveys through targeted searches of nuclear transients. However, it is expected that some TDEs will occur outside the galaxy nucleus, arising from wandering BLACK HOLEs originating in galaxy mergers. Here we present observations of TDE 2025abcr, the first optical TDE discovered in the outskirts of a host galaxy. The TDE was identified by a custom 'off-nuclear' implementation of the ML classifier $\texttt{tdescore}$, which classifies new ZTF transients based on their lightcurves. Follow-up observations confirm that TDE 2025abcr is a TDE-H+He, occurring 9.5$"$ (9.3 kpc projected distance) from the nucleus of a massive galaxy ($\mathrm{M}_{\star}$ = $10^{11.18 \pm 0.03}\mathrm{M}_{\odot}$) with a central BLACK HOLE mass of $10^{8.82 \pm 0.65}\mathrm{M}_{\odot}$. TDE 2025abcr itself was likely disrupted by a much lighter BLACK HOLE ($10^{6.09\pm0.53}\mathrm{M}_{\odot}$, as estimated with peak luminosity scaling relations). The BLACK HOLE was either dynamically ejected from the nucleus or lies at the center of a very faint tidally-stripped dwarf galaxy undergoing a minor merger. Late-time observations of TDE 2025abcr could confirm the origin of this apparent 'wandering' BLACK HOLE. The rate of highly offset ($\gtrsim$3 kpc) TDEs can be constrained to $<$10% of the nuclear TDE rate, but our discovery implies that many dozens of similar sources will be detected by the Vera C. Rubin each year with resolvable offsets.
[abstract 26 / 41] (score: 2) - Title: Bounds on Lorentz invariance violation from muon fluctuations at the Pierre Auger ObservatoryAuthors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin, J. P. Behler, C. Berat, M. E. Bertaina, M. Bianciotto, P. L. Biermann, V. Binet, K. Bismark, T. Bister, J. Biteau, J. Blazek, J. Blümer, M. Boháčová, D. Boncioli, C. Bonifazi, N. Borodai, J. Brack, P. G. Brichetto Orquera, A. Bueno, S. Buitink, M. Büsken, A. Bwembya, K. S. Caballero-Mora, S. Cabana-Freire, L. Caccianiga, J. Caraça-Valente, R. Caruso, A. Castellina, F. Catalani, G. Cataldi, L. Cazon, M. Cerda, B. Čermáková, A. Cermenati, K. Cerny, J. A. Chinellato, J. Chudoba, L. Chytka, R. W. Clay, A. C. Cobos Cerutti, R. Colalillo, R. Conceição, G. Consolati, M. Conte, F. Convenga, D. Correia dos Santos, P. J. Costa, C. E. Covault, M. Cristinziani, C. S. Cruz Sanchez, S. Dasso, K. Daumiller, B. R. Dawson, R. M. de Almeida, E. -T. de Boone, B. de Errico, J. de Jesús, S. J. de Jong, J. R. T. de Mello Neto, I. De Mitri, D. de Oliveira Franco, F. de Palma, V. de Souza, E. De Vito, A. Del Popolo, O. Deligny, N. Denner, K. Denner Syrokvas, L. Deval, A. di Matteo, C. Dobrigkeit, J. C. D'Olivo, L. M. Domingues Mendes, Y. Dominguez Ballesteros, Q. Dorosti, R. C. dos Anjos, J. Ebr, F. Ellwanger, R. Engel, I. Epicoco, M. Erdmann, A. Etchegoyen, C. Evoli, H. Falcke, G. Farrar, A. C. Fauth, T. Fehler, F. Feldbusch, A. Fernandes, M. Fernández Alonso, B. Fick, J. M. Figueira, P. Filip, A. Filipčič, T. Fitoussi, B. Flaggs, A. Franco, M. Freitas, T. Fujii, A. Fuster, C. Galea, B. García, C. Gaudu, P. L. Ghia, U. Giaccari, M. Giammarco, C. Glaser, F. Gobbi, F. Gollan, G. Golup, P. F. Gómez Vitale, J. P. Gongora, J. M. González, N. González, D. Góra, A. Gorgi, M. Gottowik, F. Guarino, G. P. Guedes, Y. C. Guerra, L. Gülzow, S. Hahn, P. Hamal, M. R. Hampel, P. Hansen, V. M. Harvey, A. Haungs, M. Havelka, T. Hebbeker, C. Hojvat, J. R. Hörandel, P. Horvath, M. Hrabovský, T. Huege, A. Insolia, P. G. Isar, M. Ismaiel, P. Janecek, V. Jilek, K. -H. Kampert, B. Keilhauer, A. Khakurdikar, V. V. Kizakke Covilakam, H. O. Klages, M. Kleifges, J. Köhler, F. Krieger, M. Kubatova, N. Kunka, B. L. Lago, N. Langner, N. Leal, M. A. Leigui de Oliveira, Y. Lema-Capeans, A. Letessier-Selvon, I. Lhenry-Yvon, L. Lopes, J. P. Lundquist, M. Mallamaci, S. Mancuso, D. Mandat, P. Mantsch, A. G. Mariazzi, C. Marinelli, I. C. Mariş, G. Marsella, D. Martello, S. Martinelli, O. Martínez Bravo, M. A. Martins, H. -J. Mathes, J. Matthews, G. Matthiae, E. Mayotte, S. Mayotte, P. O. Mazur, G. Medina-Tanco, J. Meinert, D. Melo, A. Menshikov, C. Merx, S. Michal, M. I. Micheletti, L. Miramonti, M. Mogarkar, S. Mollerach, F. Montanet, L. Morejon, K. Mulrey, R. Mussa, W. M. Namasaka, S. Negi, L. Nellen, K. Nguyen, G. Nicora, M. Niechciol, D. Nitz, D. Nosek, A. Novikov, V. Novotny, L. Nožka, A. Nucita, L. A. Núñez, S. E. Nuza, J. Ochoa, M. Olegario, C. Oliveira, L. Östman, M. Palatka, J. Pallotta, S. Panja, G. Parente, T. Paulsen, J. Pawlowsky, M. Pech, J. Pękala, R. Pelayo, V. Pelgrims, C. Pérez Bertolli, L. Perrone, S. Petrera, C. Petrucci, T. Pierog, M. Pimenta, M. Platino, B. Pont, M. Pourmohammad Shahvar, P. Privitera, C. Priyadarshi, M. Prouza, K. Pytel, S. Querchfeld, J. Rautenberg, D. Ravignani, J. V. Reginatto Akim, A. Reuzki, J. Ridky, F. Riehn, M. Risse, V. Rizi, E. Rodriguez, G. Rodriguez Fernandez, J. Rodriguez Rojo, S. Rossoni, M. Roth, E. Roulet, A. C. Rovero, A. Saftoiu, M. Saharan, F. Salamida, H. Salazar, G. Salina, P. Sampathkumar, N. San Martin, J. D. Sanabria Gomez, F. Sánchez, F. M. Sánchez Rodriguez, E. Santos, F. Sarazin, R. Sarmento, R. Sato, P. Savina, V. Scherini, H. Schieler, M. Schimp, D. Schmidt, O. Scholten, H. Schoorlemmer, P. Schovánek, F. G. Schröder, J. Schulte, T. Schulz, S. J. Sciutto, M. Scornavacche, A. Sedoski, S. Sehgal, S. U. Shivashankara, G. Sigl, K. Simkova, F. Simon, R. Šmída, S. Soares Sippert, P. Sommers, M. Stadelmaier, S. Stanič, J. Stasielak, P. Stassi, S. Strähnz, M. Straub, T. Suomijärvi, A. D. Supanitsky, Z. Svozilikova, Z. Szadkowski, F. Tairli, M. Tambone, A. Tapia, C. Taricco, C. Timmermans, O. Tkachenko, P. Tobiska, C. J. Todero Peixoto, B. Tomé, A. Travaini, P. Travnicek, C. Trimarelli, M. Tueros, M. Unger, R. Uzeiroska, L. Vaclavek, M. Vacula, I. Vaiman, J. F. Valdés Galicia, L. Valore, P. van Dillen, E. Varela, V. Vašíčková, A. Vásquez-Ramírez, D. Veberič, I. D. Vergara Quispe, S. Verpoest, V. Verzi, J. Vicha, S. Vorobiov, J. B. Vuta, C. Watanabe, A. A. Watson, A. Weindl, M. Weitz, L. Wiencke, H. Wilczyński, B. Wundheiler, B. Yue, A. Yushkov, E. Zas, D. Zavrtanik, M. Zavrtanik,Comments: 15 pages, 9 figuresSubjects: astro-ph.HE gr-qc hep-phCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Quantum gravity theories often modify spacetime symmetries. In particular, Lorentz invariance may be violated when approaching the Planck scale. Although the scales at which interactions occur in extensive air showers induced by ultra-high-energy COSMIC RAYs in the atmosphere are many orders of magnitude below the Planck scale, these violations might still be observable. In this work, the fluctuations in the number of muons in the extensive air showers measured at the Pierre Auger Observatory are exploited, for the first time, to constrain Lorentz invariance violations. The bounds derived in the hadronic sector are the strongest ever obtained, and do not rely on assumptions about the mass composition of ultra-high-energy COSMIC RAYs. The fluctuations in the number of muons constitute a new and powerful observable to further explore Lorentz invariance in a region of the parameter space not accessible to other observables.
[abstract 27 / 41] (score: 2) - Title: Imprints of primordial MAGNETic fields in gravitational collapse during early structure formationAuthors: Jennifer Schober, Molly Abramson, Sayan Mandal, Salome Mtchedlidze, Tina Kahniashvili,Comments: 17 pages, 14 figures, accepted for publication in A&ASubjects: astro-ph.CO astro-ph.GA hep-ph physics.plasm-phCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Context. Primordial MAGNETic fields (PMFs) generated in the early Universe might have left observable imprints on present-day large-scale structure. However, the spatial scales on which primordial signatures are able to survive the nonlinear processes that accompany structure formation remain unclear. Aims. The aim of this study is to investigate the evolution of the statistical properties of PMFs during the onset of gravitational collapse. Methods. We performed a suite of high-resolution direct numerical simulations of isothermal self-gravitating, MAGNETized gas clouds. By varying the viscosity, we probed different Reynolds-number regimes and follow the coupled evolution of gravitational collapse and MAGNETohydrodynamic turbulence. Results. At sufficiently high Reynolds numbers, turbulence generated during collapse triggers the onset of a small-scale dynamo, which amplifies MAGNETic energy below the Jeans scale and modifies the MAGNETic energy spectrum significantly. The question of whether dynamo amplification dominates the MAGNETic field evolution is determined by the competition between the dynamo growth time and the free-fall time. Conclusions. Our results highlight the importance of resolving the Jeans scale and the associated turbulent inertial range in cosmological MAGNETohydrodynamic (MHD) simulations to accurately capture the interplay between gravitational compression and dynamo amplification and to assess which structures retain memory of primordial fields.
[abstract 28 / 41] (score: 2) - Title: Mapping the nuclear environments of extreme coronal line emitting galaxiesAuthors: Daniel Kynoch, Or Graur, Peter Clark, J. N. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, P. Doel, J. E. Forero-Romero, S. Gontcho A Gontcho, G. Gutierrez, R. Joyce, S. Juneau, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, S. Panda, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, D. Schlegel, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou,Comments: 31 pages, 6 figures. Submitted to MNRASSubjects: astro-ph.GACreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Extreme coronal line emitters (ECLEs) are a rare class of galactic nuclei exhibiting unusually strong high-ionisation forbidden emission lines, and several ECLEs have been linked to tidal disruption events (TDEs). In this work, we compile and analyse optical spectra of 33 ECLEs, dividing them into variable, TDE-linked sources and non-variable, AGN-linked systems. Using multi-epoch spectroscopy from the Sloan Digital Sky Survey, Dark Energy Spectroscopic Instrument, and other facilities, we investigate the evolution of the emission line spectra and measure emission line profiles. Many variable ECLEs have changing spectra in which the highest-ionisation lines (e.g., [Fe X]-[Fe XIV]) appear and fade first, followed by [Fe VII], accompanied by brightening of [O III]. These changes may reflect a softening ionising continuum, the outward propagation of the ionisation front following the TDE flare, or both. Assuming virial motion, we translate line widths into characteristic radial distances, reconstructing the spatial distribution of line-emitting gas. Coronal lines are generally emitted at radii intermediate between the broad line region and the low-ionisation narrow line region. This ionisation stratification is seen in many sources, with similar incidence in variable and non-variable ECLEs, suggesting no apparent difference in circumnuclear gas distributions between active and quiescent nuclei. We find positive correlations between gas distance and BLACK HOLE mass for both [O III] and [Fe VII]: the log(Distance)-log(Mass) relations have slopes $0.63\pm0.08$ and $0.69\pm0.12$, respectively, broadly consistent with a Mass$^{0.5}$ dependence and with characteristic radii set primarily by photoionisation.
[abstract 29 / 41] (score: 2) - Title: Compact quasiaxisymmetric stellarators, a near axisymmetric theoryAuthors: Wrick Sengupta, Rogerio Jorge, Nikita Nikulsin, Stefan Buller, Richard Nies, Andrew Brown, Amitava Bhattacharjee,Comments:Subjects: physics.plasm-phCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
We develop a theory of ridges in compact stellarators with quasiaxisymmetry (QA). The equilibrium with finite plasma currents and pressure is modeled by ideal MAGNETohydrostatics (MHS). Field lines are collimated near sharp ridges, much like X-points, making ridges attractive to divertor designs without the requirement of a rational rotational transform at the divertor. However, unlike X-points, which must cover the entire torus an integer number of times, sharp ridges are typically localized in certain parts of the flux surfaces. Motivated by recent work (Henneberg and Plunk, Phys. Rev. Research 6, L022052) on compact hybrid devices, we develop a perturbative treatment of nearly axisymmetric quasisymmetric devices by expanding in the deviation from perfect axisymmetry. As a result, we can analytically describe the key features of compact QA devices, such as the tendency for ridges to be localized on the inboard side, where the Gaussian curvature is typically negative, and the field strength is maximum. We provide comprehensive numerical evidence in support of our analytical theory.
[abstract 30 / 41] (score: 2) - Title: Predictions for the X-ray polarisation modulation in Cygnus X-1 from reflection off the stellar companion and its windAuthors: Bert Vander Meulen, Kun Hu, Victoria Grinberg, Henric Krawczynski,Comments: 10 pages, 10 figures, submitted to A&ASubjects: astro-ph.HECreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Context. Cyg X-1 is one of the brightest X-ray binaries and has been observed multiple times with the Imaging X-ray Polarimetry Explorer (IXPE). Recent studies report tentative evidence for a polarisation modulation with the orbital period P, but a half-period (P/2) signal, expected from reflection off the companion star and its stellar wind, has not been reported. Aims. We aim to quantify the reflection-induced variations of the polarisation degree PD and polarisation angle PA in Cyg X-1 as a function of orbital phase and energy, and interpret these in terms of binary geometry and wind structure. Methods. We set up a radiative transfer model combining a general RELATIVISTIC description of the polarised source emission (kerrC) with a focussed stellar wind model for the binary medium. Using the 3D X-ray radiative transfer code SKIRT, we simulate broadband Stokes I, Q, and U fluxes, surface brightness maps, and linear polarisation maps over one binary orbit. Results. We find a prominent double-peaked (P/2) polarisation modulation, with a peak-to-peak PD amplitude of 0.25, 0.81, and 1.24 percentage points in the 2-4, 4-6, and 6-8 keV bands, respectively, with a strong energy dependence. The PA modulation is more modest, with |ΔPA| < 4.6°. Crucially, X-ray reprocessing reduces the overall PD relative to the source polarisation. Conclusions. The modulation is driven by reflection off the companion star and the focussed wind, which induces a polarisation signal that alternately reinforces and counteracts the source polarisation throughout the orbit. The diffuse scattering halo surrounding the source systematically reduces the PD, an effect that should be accounted for in all wind-fed XRBs. The PD amplitude increases with energy as absorption disproportionately attenuates the distant-reflection signal; as the extinction drops, the reflection signal becomes increasingly important.
[abstract 31 / 41] (score: 2) - Title: Periodic Radio and X-ray Emission from an Accreting White Dwarf BinaryAuthors: Kovi Rose, Joshua Pritchard, Tara Murphy, L. N. Driessen, D. L. Kaplan, M. Caleb, Ziteng Wang, A. Zic, I. Andreoni, J. Carney, B. N. Barlow, D. Dobie, M. Gu, G. Heald, D. Huber, E. Lenc, J. K. Leung, W. Lu, R. Momose, M. G. Pedersen, Y. Qu, N. Rea, I. de Ruiter, K. Shaji, G. R. Sivakoff, A. J. M. Thomson, Y. L. Wang, G. J. Yang, F. Zahedy,Comments: Published in Nature AstronomySubjects: astro-ph.HE astro-ph.SRCreated: 2026-06-02; Updated: 2026-06-04; Datestamp: 2026-06-04
Long period radio transients (LPTs) are coherent bursts of polarised radio emission that repeat periodically on timescales of minutes to hours. Little is known about the physical origins of these systems. Astronomers have proposed MAGNETars that rotate slowly and white dwarfs that rapidly orbit with a companion star as potential explanations. While several recent examples appear to support the latter hypothesis, the mechanism generating these bright radio pulses remains poorly understood. Here we report our discovery and classification of the LPT ASKAP J174508.9-505149 as an accreting white dwarf binary. This object has a ~1.3h spectroscopic orbital period and exhibits orbitally-modulated X-ray emission and radio bursts. These elliptically polarised radio bursts drift in emission frequency, potentially due to a longer beat period, and turn off for several hours at a time. Some long period radio transients have been associated with non-interacting white dwarf binaries. We have spectroscopically confirmed this system as an accreting cataclysmic variable, identified through characteristic optical emission lines and an ongoing X-ray outburst. Our results strengthen the link between at least some long period radio transients and white dwarf binaries.
[abstract 32 / 41] (score: 2) - Title: Fast-spinning massive BLACK HOLEs from slowly rotating low-metallicity stars: implications for GW231123Authors: N. H. Ismail, N. Yusof, R. Hirschi, A. Griffiths, M. Á. Aloy, S. Ekström, G. Meynet,Comments: 6 pages (including Appendix) and 2 figures. Submitted to Astronomy & Astrophysics Letter. Comments welcomeSubjects: astro-ph.SRCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
The origin of massive BLACK HOLEs in the early universe remains uncertain and still unexplored. Pop III stars are among the first stellar sources capable of producing such remnants, but their evolution is very sensitive to rotation. We explore how slow initial rotation influences the evolution and BLACK HOLE formation of very massive Pop III stars, and assess their potential to become massive, fast-spinning BLACK HOLEs consistent with GW events such as GW231123. We compute a grid of non-rotating and slowly rotating Pop III stellar models with initial masses of 80, 85, and 90 $M_\odot$ using the GENEC code. Our models include rotationally induced mixing and angular-momentum transport by MAGNETic torques. We analyse the CO core masses and their volume-averaged adiabatic index to assess stability against electron-positron pair creation. From the angular-momentum profiles at the end of He burning, we estimate the resulting BLACK HOLE masses and dimensionless spins under the assumption of direct collapse. Our non-rotating and slowly rotating 80 and 85 $M_\odot$ models develop carbon-oxygen core masses between 31 and 36 $M_\odot$ and have an adiabatic index that remains above 4/3. Our models thus predict that Pop III stars can keep most of their mass and collapse directly to form BLACK HOLEs of 80 to 85 $M_\odot$ with dimensionless spins up to $a_{\rm BH} \lesssim 0.7$. Initially slowly rotating, massive Pop III stars can form very massive, rapidly spinning BLACK HOLEs just below the pair-instability regime. This supports interpreting the lower boundary of the PISN mass gap as a smooth, structure-dependent transition and identifies single-star Pop III evolution as a possible channel for massive fast-spinning BLACK HOLEs observed by gravitational-wave detectors, subject to the uncertain efficiency of internal angular-momentum transport and mass-loss prescriptions.
[abstract 33 / 41] (score: 2) - Title: High-beta runaway transitions in a fluid model of electroMAGNETic ion-temperature-gradient turbulenceAuthors: Y. Zhang, M. Barnes, A. A. Schekochihin, P. G. Ivanov, T. Adkins,Comments:Subjects: physics.plasm-phCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Gyrokinetic simulations of tokamak turbulence indicate that fluctuation levels increase abruptly and dramatically when the plasma beta exceeds a certain critical value. This increase in fluctuation levels coincides with a transition from a state dominated by zonal flow to one in which turbulent eddies form radially-elongated `streamers'. Here we derive from gyrokinetics a minimal fluid model for electroMAGNETic ion-temperature-gradient (ITG) turbulence that captures the key features of this transition. Due to the relative simplicity of the model, we are able to conduct a detailed numerical study of the interplay between the turbulence and the zonal flow across a broad range of values of the plasma beta and the ITG. We find that the transition occurs when the Reynolds stress, which tends to strengthen zonal flows, is overwhelmed by the Maxwell and diaMAGNETic stresses, which tend to weaken them. Power-law scalings of the stress ratios with plasma beta and ITG are obtained, indicating a possible means by which the location of the transition could be predicted with minimal computational cost.
[abstract 34 / 41] (score: 2) - Title: A candidate cyclotron line at 1.89 keV in the ultraluminous X-ray source NGC 4861 X-2Authors: Sinan Allak, Lorenzo Ducci, Valery F. Suleimanov, Andrea Santangelo, Aysun Akyuz, Santina Piraino, Faruk Soydugan, Amar Deo Chandra, Wei Yu,Comments: Accepted for publication in Astronomy & Astrophysics LettersSubjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
In this Letter, we report the detection of an absorption-like feature at ~1.89 keV in Chandra/ACIS spectra of the ultraluminous X-ray source NGC 4861 X-2, based on the deepest observation (ObsID 20992; ~58 ks). The feature is consistently recovered across independent continuum models and significantly improves the fit statistics. Monte Carlo simulations yield a detection significance of ~3.5-4.1 sigma, depending on the adopted continuum, and a blind line scan reveals a single, localized peak at the same energy. The observed properties are consistent with a proton cyclotron resonant scattering feature (CRSF), implying a MAGNETic field strength of B ~(3-4) x 10^14 G. The spectrum is well described by a multicolor disk blackbody (diskbb) with kTin ~0.8 keV or a strongly curved continuum with a low cutoff energy (cutoffpl; Ecut ~1.3 keV). The source shows variability confined to the soft X-ray band in the two Chandra observations where the absorption-like feature is detected. In these observations, a candidate periodic signal at P ~7.4 s is also detected, with a global significance of ~2.5 sigma.
[abstract 35 / 41] (score: 2) - Title: TDEs on FIRE: Illuminating the Cosmic Evolution of Tidal Disruption RatesAuthors: Rudrani Kar Chowdhury, Lixin Dai, Janet N. Y. Chang, Tsang Keung Chan,Comments: Submitted to the AAS journalSubjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Tidal disruption events have been extensively studied in the local universe, but their prevalence at high redshifts remains largely unexplored. Using the FIRE-2 cosmological zoom-in simulations, we compute the per-galaxy tidal disruption rate (TDR) over $z=1-10$, covering BLACK HOLEs from IMBHs to SMBHs. The averaged TDR rises from the early universe, peaks at $\sim 4 \times 10^{-4} \, \text{yr}^{-1}$ near $z \sim 2.5$, and declines to $\sim 10^{-5} \, \text{yr}^{-1}$ at $z=1$. The TDR correlates strongly with host galaxy STAR FORMATION rate and central stellar density at all redshifts. Qualitatively, the TDR trends with the $M_{\rm BH}$ and $M_{\rm gal}$ persist from high redshift to the local universe, suggesting similar BH-galaxy scaling across cosmic time. Satellite galaxies exhibit comparably high TDRs, with their fractional contribution increasing significantly at high redshifts, highlighting their potential for probing IMBHs and early galaxy assembly. This work demonstrates that cosmological simulations offer a promising avenue for constraining the cosmic evolution of the TDR, paving the way for future comparisons with next-generation observations.
[abstract 36 / 41] (score: 2) - Title: Fast gravitational waveform models for quasi-circular coalescences of neutron star--BLACK HOLE binariesAuthors: Felip A. Ramis Vidal, Adrian Abac, Marta Colleoni, Tim Dietrich, Pierre Mourier, Alejandra Gonzalez, Ivan Markin, Anna Puecher,Comments: 26 pages, 12 figuresSubjects: gr-qc astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
We present IMRPhenomXHM_NSBH and SEOBNRv5HM_ROM_NRTidalv3_NSBH, the first two frequency-domain models for gravitational-wave signals from quasi-circular, aligned-spin neutron star--BLACK HOLE (NSBH) binaries including higher-order modes beyond the dominant quadrupole. We also present IMRPhenomXPHM_NSBH, an extension of the former model to the spin-precessing case. These models incorporate tidal effects in the gravitational-wave phasing and amplitude using a higher-mode extension of the NRTidalv3 model as well as dedicated amplitude models calibrated to numerical relativity (NR) simulations of NSBH mergers. We test the performance and validity of the new models by comparing them to NR simulations and other existing models for these systems. Finally, we perform parameter estimation studies. The new models show clear improvements over their predecessors in analyses of simulated signals, while yielding results consistent with the literature when applied to real events from the GWTC-3 and GWTC-4 catalogs.
[abstract 37 / 41] (score: 2) - Title: A Reduced-Order Particle-in-Cell Method with Azimuthal Fourier-Decomposed Fields for Nominally Axisymmetric PlasmasAuthors: Shaun Andrews,Comments: 18 pages, 9 figuresSubjects: physics.plasm-ph physics.comp-phCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
A reduced-order Particle-in-Cell method is introduced for kinetic simulation of otherwise axisymmetric cylindrical plasmas that exhibit azimuthal instabilities. The method spatially decomposes all field quantities into a small number of azimuthal Fourier modes, reducing the costly three-dimensional field solve to a family of decoupled independent two-dimensional problems on the meridional plane - one per mode - while particles continue to move in full three-dimensional space. Fields are reconstructed at particle positions by coherent superposition of these modal contributions, preserving complete azimuthal variation at a fraction of the cost of a conventional three-dimensional simulation. The method is validated against the diocotron instability of a hollow electron annulus across three geometrically distinct configurations, recovering linear growth rates and eigenmode structures within 7% of closed-form analytic predictions, and reproducing the non-linear vortex dynamics characteristic of this instability class. A further benchmark against the community-standard Landmark Penning discharge problem recovers the rotating-spoke frequency, radial plasma profiles, and modal energy hierarchy in quantitative agreement with long-time reference simulations, at approximately 640 CPU-hours - a factor of 46 below the median benchmark cost. The approach resolves the gap between computationally prohibitive full three-dimensional kinetic simulation and the physically limited reduced-dimensionality models on which predictive modelling of anomalous transport in MAGNETised plasma devices currently relies.
[abstract 38 / 41] (score: 2) - Title: Bridging Roche Lobe Overflow and micro-TDEs: The Runaway Evolution of Eccentric Mass Transfer in Star-Black Hole BinariesAuthors: Tian-Shun Chen, Dong Lai,Comments: 14 pages, 19 figuresSubjects: astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Binary systems may undergo mass transfer while maintaining significant orbital eccentricities. Stellar-mass BLACK HOLEs (sBHs) can strip stars on eccentric orbits and produce micro-tidal disruption events (micro-TDEs). While previous hydrodynamical studies have focused on compact systems on the verge of disruption, the transition between self-regulated eccentric mass transfer and runaway disruption remains poorly understood. We present SPH simulations of a Sun-like star interacting with a $10\,M_\odot$ sBH across a range of initial eccentricities ($e_0=0.30$--$0.70$) and pericenter distances ($b_0=3.33$--$3.57$ in units of the tidal radius), tracking the systems for tens to over 100 orbital periods. Our results reveal that these binaries can evolve along two distinct pathways, dictated by the competition between mass-transfer-driven stellar expansion and orbital widening: (i) Runaway disruption ($b_0\lesssim 3.45$), in which mass loss at pericenter drives adiabatic expansion of the stellar envelope, leading to unstable Roche-lobe overflow and runaway disruption of the star. The stripped debris forms a thick accretion flow with hyper-Eddington accretion rates onto the sBH, potentially powering fast X-ray/UV or blue/optical transients. (ii) Stable mass transfer ($b_0\gtrsim 3.57$), in which the binary settles into a long-lived, stable mass-transfer phase lasting up to 150 orbits (the limit of our simulation), regulated by orbital expansion from pericenter mass loss. These eccentric mass-transfer events could manifest observationally as repeating, quasi-periodic flares.
[abstract 39 / 41] (score: 2) - Title: A Measurement of the Thermal and Ionization State of the IGM at $z < 0.5$Authors: Teng Hu, Vikram Khaire, Joseph F. Hennawi, Todd M. Tripp, Jose Onorbe, Michael Walther, Zarija Lukic,Comments: 20 pages, 16 figuresSubjects: astro-ph.COCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
We apply a machine-learning-based inference method that exploits the joint Doppler parameter-column density (b-NHI) distribution from Lya forest decomposition to measure the thermal and ionization state of the intergalactic medium (IGM) in four redshift bins spanning z = 0.06 to 0.48, using 82 archival QUASAR spectra from the Cosmic Origin Spectrograph (COS) on board Hubble Space Telescope (HST). Our results show that the low-z IGM (z < 0.5) is extremely hot and nearly isothermal, with log(T0/K) = 4.45 (+0.08 / -0.12) [T0 = 28183 (+5700 / -6804) K] and gamma = 1.06 (+0.13 / -0.09) at z = 0.1. This temperature lies approx 7sigma (and 7 times) above the canonical prediction (log T0 approx 3.60, i.e. T0 ~ 4000 K, with gamma ~ 1.6 at z = 0), where the IGM is expected to have cooled long after He II reionization. We also measure the hydrogen photoionization rate to be log (GammaHI/s^-1) = -13.70 (+0.10 / -0.08) at z = 0.1, which is about approx 4sigma below the range predicted by current UV-background synthesis models (approx -13.3). To investigate the discrepancy between these high temperatures and theoretical models, we assess the impact of small-scale turbulence. By exploring a parameter grid in turbulent velocity (vtur) and GammaHI, we find that a standard IGM thermal and ionization state combined with unresolved turbulence of vtur simeq 15 km s^-1 can successfully reproduce the observed line widths at z = 0.1. Comparisons with high-resolution Space Telescope Imaging Spectrograph (STIS) expanded data indicate that the observed line widths are unlikely to be caused by instrumental resolution effects. Our findings suggest that either new heating mechanisms or unresolved turbulence are required to explain the unexpectedly broad Lya lines observed in the low-z IGM.
[abstract 40 / 41] (score: 2) - Title: CMB Bounds on Primordial Black Holes via Radiation CaptureAuthors: Marzieh Farhang, S. M. S. Movahed,Comments: 6 pages, 4 figuresSubjects: astro-ph.COCreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
We explore the capture of neutrinos and photons in the cosmic neutrino and photon background by primordial BLACK HOLEs (PBHs). We model this phenomenon as a gravitational interaction that effectively modifies the continuity equations for radiation and PBH densities and the cosmic expansion history. We find that the observability of this modified cosmic history is highly sensitive to PBH mass, and only extraordinarily massive PBHs would leave observable trace on the temperature and E-mode POLARIZATION of the cosmic microwave background (CMB). Specifically, Planck data restrict PBH abundance to $f_{\rm pbh}\lesssim 10^{-1}$ for PBH masses above $10^{15} M_\odot$, getting considerably tighter for higher masses. We expect substantial improvement as high-resolution measurements of larger CMB multipoles become available. A future cosmic-variance-limited experiment, with $\ell_{\rm max}=7000$, would set $f_{\rm pbh}\lesssim 10^{-1}-8\times 10^{-5}$ (for the fiducial $Λ$CDM cosmology) across $10^{13}-10^{18}M_\odot$. These constraints would be comparable to the current limits at the high-mass end of the spectrum [Carr et al, 2026]. The gravitational interaction of PBHS with the cosmic background radiation and its imprints on CMB would thus provide an independent complementary probe of extraordinarily massive PBH abundance.
[abstract 41 / 41] (score: 2) - Title: Mapping the STAR FORMATION peak with LIGO A# and Next-Generation detectorsAuthors: Divyajyoti, Stephen Fairhurst, Mark Hannam, Mukesh Kumar Singh,Comments: 14 pages, 9 figuresSubjects: gr-qc astro-ph.HECreated: 2026-06-03; Updated: 2026-06-04; Datestamp: 2026-06-04
Measuring the redshift evolution of STAR FORMATION rate density is crucial in understanding the origin and evolution of galaxies and large scale structure in the universe. It is currently measured with electroMAGNETic probes, however, these probes often track luminosity, which is then converted to STAR FORMATION rate (SFR) depending on various factors such as initial mass function, dust extinction, etc. Gravitational waves provide an independent method to constrain SFR at high redshifts by tracking the redshift evolution obtained from analysis of binary BLACK HOLE mergers. In this study we explore three population models for star-formation combined with an \textit{inverse} time-delay model and demonstrate that it is possible to obtain bounds on the peak of redshift distribution with a network of upgraded LIGO detectors (such as LIGO-A#). For a year of observation, using simulated signals with a merger rate peak at $z_\text{peak}=1.5$, a network of LIGO detectors at A# sensitivity is able to constrain the peak of merger rate with a precision of $\pm 0.1$. Further, we obtain the results with a next-generation network (of Cosmic Explorer and Einstein Telescope) and conclude that the redshift distribution will be extremely well measured, with a precision of $\pm 0.02$, with future detectors.
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