Current date: 2026-07-03

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Datestamp limit: 2026-07-03 (0 days ago)

Created/updated limit: 2026-06-26 (7 days ago)

Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics

Setting default set: physics

OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-07-03&until=2026-07-03&set=physics&metadataPrefix=arXiv

Scoring abstracts

Number of records retrieved: 713

Keyword score statistics

score 9 -- 1 abstracts

score 8 -- 1 abstracts

score 6 -- 3 abstracts

score 5 -- 2 abstracts

score 4 -- 4 abstracts

score 3 -- 9 abstracts

score 2 -- 18 abstracts

in total -- 38 abstracts

Articles that appeared on 2026-07-03

[abstract 1 / 38] Wow! (score: 9)
arXiv:2607.01941 [pdf, ps, other]

Title: Colour evolution in the radio afterglow of GRB 241025A

Authors: S. Giarratana, O. S. Salafia, L. Nava, G. Ghirlanda, M. Giroletti, S. Antier, M. Pillas, T. Hussenot-Desenonges, A. Iskandar, M. Tanasan, G. Oganesyan, N. Di Lalla, N. Omodei,

Comments: Accepted for publication in A&A

Subjects: astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We present the observing campaign of the afterglow of GRB241025A, a GAMMA-RAY BURST (GRB) whose prompt emission has been simultaneously detected by SWIFT, Einstein Probe, FERMI/GBM, SVOM, Konus-Wind and VZLUSAT-2 3U CubeSat. Our multi-wavelength campaign comprises radio, near-infrared, Optical and X-ray observations. The afterglow was clearly detected in all bands. We performed a semi-empirical fit of the data, showing that the afterglow behaviour can be reasonably reproduced by a single component, i.e. an ultra-RELATIVISTIC shock. However, the results from the semi-empirical fit are inconsistent with the predicted evolution from the standard afterglow model in the slow cooling regime. Specifically, we found that at early times the SYNCHROTRON self-absorption frequency $ν_a$ should be at higher frequencies with respect to the ones sampled by our campaign, in order to explain the observed colour evolution in radio, namely the spectral evolution in time. To reconcile the prediction from the standard model with the observed data set, we fit the observations with a semi-analytical model, including a multiplicative factor $τ_{enh}$ to the optical depth which, in turn, artificially increases $ν_a$. We found that the radio colour evolution, together with the near-infrared, optical and X-ray emission, can be described reasonably well by a forward shock from a structured JET, provided that the optical depth in the shocked material is enhanced by a factor $τ_{enh}=500$. We suggest that such enhancement in the optical depth can result from a population of cold electrons in the downstream material, i.e. electrons that were not accelerated by FERMI I process at the shock front, in agreement with the theoretical expectations previously reported in the literature. Overall, our work underscores the importance of systematic, multi-frequency, multi-epoch radio follow-ups of these extreme events.

[abstract 2 / 38] Wow! (score: 8)
arXiv:2607.01820 [pdf, ps, other]

Title: Polarization Architecture of Steady GRMHD Jets from the Horizon to Infinity

Authors: Zhenyu Zhang, Yehui Hou, Yu Song, Yosuke Mizuno, Bin Chen,

Comments: 22 pages, 8 figures

Subjects: astro-ph.HE gr-qc

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We develop a semi-analytic framework for stationary, axisymmetric GRMHD JETs that efficiently generates resolved polarized images from the near-horizon region out to $\sim 10^5\,r_g$ across a broad parameter space, enabling rapid exploration of how gravity and MAGNETohydrodynamic flows imprint scale-dependent signatures on JET morphology and POLARIZATION. We identify a new scale-dependent separation in polarimetric diagnostics. Outside the photon ring, plasma loading strongly modifies the POLARIZATION-angle profile of the integrated JET-layer emission through inertia-driven winding of the MAGNETic field. At large image-plane radii, the POLARIZATION angle follows a power-law in radius, with an index determined by the JET collimation profile. Near the horizon, in contrast, JETs converge to a universal POLARIZATION pattern controlled solely by BLACK HOLE spin. This convergence is hierarchical: differences in velocity and MAGNETic-field structure are erased first, whereas collimation-dependent differences persist to smaller radii, thereby allowing these effects to be disentangled. These results establish a largely achromatic polarimetric diagnostic that connects GRMHD JET dynamics to resolved image structure, with direct implications for high-resolution polarimetry and for constraining BLACK HOLE spin and JET formation.

[abstract 3 / 38] Yes (score: 6)
arXiv:2605.12448 [pdf, ps, other]

Title: Precessing Black Hole Jets and Galactic Fossils

Authors: Maria J. Rodriguez,

Comments: 44 pages, 8 Figures

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

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

The Galactic Center gamma-ray excess (GCE) -- a surplus of gamma-ray radiation around SgrA$^{\star}$ -- has remained without a consensus interpretation for more than fifteen years. Dark-matter annihilation and unresolved millisecond-pulsar populations remain the leading candidates, yet neither connects the excess to the past activity of SgrA$^{\star}$ traced by the FERMI and eROSITA bubbles. We propose a common-origin scenario in which a contribution to the GCE arises as a fossil hadronic imprint of the same SgrA$^{\star}$ outburst associated with the bubbles. We develop a model of SgrA$^{\star}$ with a precessing paraboloidal Blandford-Znajek (BZ) JET launched from a tilted, MAGNETically arrested accretion disc during a ~ 7.5 Myr active phase ending ~2.6 Myr ago. In this picture, the JET drives the bipolar expansion of the FERMI/eROSITA bubbles -- contributing, alongside wider-angle outflows, to their observed extent -- and injects hadronic COSMIC RAYs at the Galactic Center. We couple the analytic BZ injection to a two-zone diffusion numerical solver to compute the resulting GCE surface brightness and verify internal consistency: the proton Larmor radius remains small compared to the JET coherence scale, ensuring MAGNETic confinement of the cosmic-ray population, while attenuation of the produced $γ$ rays in the interstellar medium is negligible, leaving the medium effectively transparent. Isolating the JET contribution alone yields a spin-dependent, irreducible hadronic floor: for a SgrA$^{\star}$ spin of a$^{\star} = 0.9$, we find a robust floor at the few-percent to $\sim 10\%$ level of the observed GCE surface brightness across the inner ten degrees, highlighting a previously unexplored component relevant for comprehensive models of the GCE.

[abstract 4 / 38] Yes (score: 6)
arXiv:2607.01606 [pdf, ps, other]

Title: X-ray Fourier lag-frequency spectra modulated by stochastic turbulent acceleration in the JETs of high-frequency-peaked BL Lac

Authors: Guang-Cheng Xiao, Wen Hu, Da-Guo Jiang, Jun-Xian Wang, Zhen-Yi Cai, Da-Hai Yan, Fang-Wu Lu,

Comments: 17 pages, 10 figures, published in PRD

Subjects: astro-ph.HE hep-ph

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

X-ray interband time lags are key diagnostics of JET physics and are frequently detected in high-frequency peaked BL Lac (HBL) objects at different epochs with various X-ray telescopes. In this work, we theoretically investigate Fourier lag-frequency spectra using a generic one-zone leptonic model incorporating the stochastic turbulent acceleration (STA), which plays a crucial role in shaping the emitted photon spectra. We demonstrate that the competition between STA, radiative cooling, and escape processes not only gives rise to two well-defined time-lag regimes: hard/positive and soft/negative lags, but also reveals the existence of a transition between the two regimes. Our results indicate that time lags in the transitional and soft-lag regimes can be clearly amplified and modified by STA's suppression of high-energy electron cooling, and nonlinear SYNCHROTRON self-Compton (SSC) cooling can further amplify the emergence of time lags. We conclude that the adopted model offers a unifying quantitative framework for interpreting the diverse time-lag signatures observed in the X-ray flares of HBLs. Additionally, SSC cooling effects can account for the relatively large lags observed in TeV-bright flares, as well as the observed trend between lag amplitude and flare duration: the larger the flare duration, the larger the lag.

[abstract 5 / 38] Yes (score: 6)
arXiv:2607.02366 [pdf, ps, other]

Title: The Road to Identifying the Earliest Radio-Powerful AGN with the SKA

Authors: Jose Afonso, Stergios Amarantidis, Stas Shabala, Ross J. Turner, Luca Ighina, Mojtaba Raouf, Nuno Covas, Pedro Martins, Nick Seymour, Alessandro Caccianiga, Alexander Hedge, Jess W. Broderick, Davi Barbosa, Isabella Prandoni, Sabyasachi Pal, Bruno Arsioli, Luis Barroso, Rodrigo Carvajal, João Tiago, Andrew Hopkins, Manuela Magliocchetti, Israel Matute, Ciro Pappalardo,

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Afonso01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes

Subjects: astro-ph.GA

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

The Epoch of Reionization (EoR) is one of the most pivotal frontiers in modern astrophysics, marking the emergence of the first galaxies, stars, and supermassive BLACK HOLEs (SMBHs). Despite insights from the Atacama Large Millimetre/submillimetre Array and the James Webb Space Telescope, we still struggle to explain how $\sim10^{9}$ M$_\odot$ SMBHs powering luminous ACTIVE GALACTIC NUCLEi (AGN) already exist by $z\sim7$. The recent discovery of powerful radio emission from some of these early AGN is notable, offering new constraints on early black-hole accretion and, with the Square Kilometre Array Observatory (SKAO), the prospect of directly probing neutral hydrogen through 21-cm absorption studies. Yet progress remains slow: only a few radio-powerful AGN are known at $z>6$, far fewer than theoretical predictions suggest, raising questions about whether this reflects intrinsic properties or selection biases and incomplete spectral information. In this chapter we synthesise predictions from state-of-the-art hydrodynamical and semi-analytic simulations with observational constraints from SKAO pathfinder facilities. These models suggest the existence of a substantial, still-undetected population of radio-powerful AGN in the EoR, but show that present surveys are limited by selection biases and incomplete radio spectral information. We discuss a physically motivated strategy for identifying high-redshift radio AGN, based on broadband radio spectral energy distributions, spectral curvature, dynamical JET evolution, and radio-only redshift estimation, offering a transformative alternative to traditional empirical approaches. Finally, we justify how the sensitivity and spectral coverage of the SKAO will allow fine-frequency sampling across the 50 MHz - 15 GHz range, revolutionising our ability to identify the earliest radio-powerful AGN and probe the earliest SMBHs.

[abstract 6 / 38] Yes (score: 5)
arXiv:2411.08525 [pdf, ps, other]

Title: The study of an interaction between the JET and an interstellar medium around knot E and knot F of RADIO GALAXy M87 by Chandra

Authors: S. Osone,

Comments: 16 pages, 3 figures. arXiv admin note: text overlap with arXiv:2307.12039:precession is considered for image analysis(v2)

Subjects: astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

The JET may compress an interstellar medium and soft X-ray outside the JET may be absorbed by a compressed interstellar medium and thermal emission heated by a shock is expected inside the JET. I analyze X ray image of the surroundings of the JET of M87 by Chandra. There is an original work for an image analysis. In this time, I select data for an image analysis by a removal of a pile up event completely and a precession consideration. I confirm a dip in soft X ray outside the JET between knot E and knot F with 224 ks archival data. I analyze X ray energy spectra for knot E and knot F with 480 ks archival data by Chandra in order to search for thermal emission. However, X ray energy spectra for knot E and knot F are well described with SYNCHROTRON emission.

[abstract 7 / 38] Yes (score: 5)
arXiv:2607.01369 [pdf, ps, other]

Title: Constraining the near-source RELATIVISTIC wind medium using Fast Radio Burst circular POLARIZATION data

Authors: Om Gupta, Pawan Kumar, Paz Beniamini,

Comments: Comments encouraged. 21 pages, 10 figures, 1 table. Submitted for review

Subjects: astro-ph.HE

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

Fast Radio Bursts (FRBs) exhibit diverse spectro-temporal characteristics, which can probe vital propagation and source physics via Stokes polarimetry. We investigate whether the circular POLARIZATION (Stokes $V$) observed in some bursts is produced by Faraday conversion in the near-source wind of MAGNETars rather than being intrinsic to the source. Our calculation includes the increase in the effective mass of $e^\pm$ in the presence of the FRB wave. We find that Faraday conversion in the MAGNETar wind can explain the broad range of observed circular POLARIZATION in FRBs, including its frequent non-detection. Observationally derived upper limits on $V$ provide stringent constraints on the wind luminosity, MAGNETization, bulk Lorentz factor, and effective particle mass when ions are present. When available, frequency resolved Stokes spectra offer direct estimates of the wind environment. The Stokes parameters can undergo rapid oscillations with frequency in the high-wind/low-FRB-luminosity regime, resulting in Stokes-V dePOLARIZATION. Bursts with significantly lower luminosities than typical FRBs can also develop measurable circular POLARIZATION, within the model framework. Additionally, separate zones are favored for significant circular POLARIZATION and rotation measure, when the model is applicable. The model constrains instantaneous wind parameters for several sources, including FRB 20201124A, FRB 20180301A, and SGR 1935+2154. This work represents the first instance in which properties of winds from compact objects associated with FRBs are inferred from POLARIZATION data.

[abstract 8 / 38] Yes (score: 4)
arXiv:2603.08119 [pdf, ps, other]

Title: Impact of Resonant Compton Scattering on Magnetar X-Ray Polarization with QED Vacuum Resonance

Authors: Tu Guo, Dong Lai,

Comments: 13pages, 7 figures, submitted to ApJ

Subjects: astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Recent obeservations have revealed significant soft X-ray POLARIZATIONs from several quiescent MAGNETars, including the intriguing $90^°$ POLARIZATION angle (PA) swing as a function of photon energy for some sources. We present a general semi-analytical framework for calculating energy-dependent soft X-ray POLARIZATION signatures from MAGNETars, consistently incorporating both QED vacuum resonance in the atmosphere and resonant Compton scattering (RCS) in the MAGNETosphere. Starting from the polarized radiative transfer equation for RCS and treating vacuum-resonance-induced mode conversion as an input, we employ a first-order approximation in RCS optical depth to evaluate the effect of different MAGNETospheric plasma density (which depends on MAGNETic twist), drift velocity and temperature, and viewing geometry on the observed radiation. Our analysis reveals that MAGNETic twist and plasma drift velocity are the critical parameters controlling the impact of RCS on both the absolute POLARIZATION degree and its variation across the soft X-ray spectrum. We find that sufficiently strong RCS can wash out the PA swing caused by vacuum resonance. Furthermore, in addition to the QED vacuum resonance effect, significant RELATIVISTIC signatures arising from plasma drift velocity ($β_0 \gtrsim 0.5$) may introduce an extra $90^\circ$ PA swing in the spectrum. Our calculation framework, based on single-scattering approximation, bypasses the need for complex, multi-dimensional Monte Carlo simulations, providing an analytical pathway for modeling full-surface emission and rotational-phase-resolved radiation from MAGNETic neutron stars, in support of current and future X-ray POLARIZATION missions.

[abstract 9 / 38] Yes (score: 4)
arXiv:2607.01479 [pdf, ps, other]

Title: Radiative filtering unifies broad-line phenomenology in ACTIVE GALACTIC NUCLEi

Authors: Mohammad Hassan Naddaf,

Comments: 12 pages, 5 figures, as Letter to Astrophysical Journal

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

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

Broad emission lines (BELs) are a defining feature of ACTIVE GALACTIC NUCLEi (AGNs), yet they weaken or disappear in both very low- and very high-accretion systems. These regimes are typically treated separately, and a unified physical explanation has remained elusive. Here we show that this behavior arises if line formation is governed not by the intrinsic luminosity of the central engine, but by the ionizing radiation field that survives filtering before reaching the broad-line region (BLR). In this picture, line production depends on the product of intrinsic ionizing capability and an effective transmission. Because the former increases from low accretion rates while the latter declines at high accretion rates, the effective ionizing field naturally develops a finite and non-universal window for BEL formation. This framework unifies the absence or extreme faintness of BELs in low-luminosity AGNs, LINERs, and weak-line QUASARs (WLQs), and accounts for the Baldwin effect and the $R_{\rm Fe}$ trend. It also necessarily implies the breakdown of standard BLR-based scaling relations in extreme accretion regimes. We show that a minimal quantitative realization reproduces this behavior across black-hole mass, accretion rate, and radiative efficiency. These results suggest that AGN emission-line phenomenology is governed by global regulation of the ionizing radiation field rather than by mere presence or condition of local gas.

[abstract 10 / 38] Yes (score: 4)
arXiv:2607.01644 [pdf, ps, other]

Title: Numerical Investigation of Efficient Electron Acceleration at an Unsteady Solar Flare Loop-Top

Authors: Yoshiaki Sato, Takafumi Kaneko, Noriyuki Narukage, Shinsuke Takasao,

Comments: 17 pages, 7 figures, 3 tables; accepted for publication in The Astrophysical Journal

Subjects: astro-ph.SR

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Using MAGNETohydrodynamic (MHD) fields and guiding-center test-particle calculations, this study investigates how time-dependent loop-top dynamics modulate the adiabatic energization of electrons in a solar flare. Our results indicate that a time-varying loop-top structure enhances acceleration efficiency compared to a quasi-steady one. In the quasi-steady velocity field, the net acceleration is suppressed due to the decelerating effect of betatron cooling. Conversely, in the unsteady velocity field, the betatron mechanism readily accelerates electrons within the compressed MAGNETic field at the edge of the loop-top. These findings suggest that the acceleration of electrons at the loop-top is driven not only by the static shape of the MAGNETic structure but also by dynamic events such as plasmoid collisions. While previous studies have primarily focused on acceleration processes within the RECONNECTion outflow, such as at termination shocks or within plasmoids, our research highlights the importance of the acceleration and deceleration processes at the exit point where electrons escape from the loop-top.

[abstract 11 / 38] Yes (score: 4)
arXiv:2607.02064 [pdf, ps, other]

Title: Testing Gravity with Binary Pulsars in the SKA Era

Authors: V. Venkatraman Krishnan, L. Shao, V. Balakrishnan, A. Carleo, M. Colom i Bernadich, A. Corongiu, A. Deller, P. C. C. Freire, M. Geyer, E. Hackmann, H. Hu, Z. Hu, M. Kramer, J. Kunz, K. Liu, M. E. Lower, X. Miao, D. Perrodin, D. S. Pillay, A. Possenti, S. Ransom, I. Stairs, B. Stappers, The SKA Pulsar Science Working Group,

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/VenkatramanKrishnan01. Advancing Astrophysics with the SKAII(AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes. An earlier version of this chapter was published in the Open Journal of Astrophysics with Arxiv ID: arXiv:2512.16161

Subjects: astro-ph.HE gr-qc

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Binary (and trinary) radio pulsars are natural laboratories in space for understanding gravity in the strong field regime, with many unique and precise tests carried out so far, including the most precise tests of the strong equivalence principle and of the radiative properties of gravity. The Square Kilometre Array (SKA) telescope, with its high sensitivity in the Southern Hemisphere, will vastly improve the timing precision of recycled pulsars, allowing for a deeper search of potential deviations from general relativity (GR) in currently known systems. A Galactic census of pulsars will, in addition, will yield the discovery of dozens of RELATIVISTIC pulsar systems, including potentially pulsar -- BLACK HOLE binaries, which can be used to test the cosmic censorship hypothesis and the ``no-hair'' theorem. Aspects of gravitation to be explored include tests of strong equivalence principles, gravitational dipole radiation, extra field components of gravitation, gravitoMAGNETism, and spacetime symmetries. In this chapter, we describe the kinds of gravity tests possible with binary pulsar and outline the features and abilities that SKA must possess to best contribute to this science.

[abstract 12 / 38] (score: 3)
arXiv:2509.25141 [pdf, ps, other]

Title: Quasinormal spectra of higher dimensional regular BLACK HOLEs in theories with infinite curvature corrections

Authors: Juan Pablo Arbelaez,

Comments: 18 pages, 3 figures

Subjects: gr-qc

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We investigate the quasinormal modes of massless scalar and electroMAGNETic test fields propagating on several families of higher-dimensional regular BLACK HOLEs arising in gravitational theories with an infinite tower of higher-curvature corrections to Einstein gravity. Using the Wentzel--Kramers--Brillouin (WKB) method supplemented by Padé approximants, we compute the fundamental modes and derive compact analytic expressions in the eikonal regime. For all models considered, positive higher-curvature coupling reduces both the oscillation frequencies and damping rates relative to the corresponding singular general-RELATIVISTIC limit. Since our analysis is restricted to test-field perturbations on fixed regular black-hole backgrounds, these results should be interpreted as geometric and phenomenological signatures of the background geometry rather than as gravitational perturbations of the full higher-curvature theory. Our results provide further insight into how quantum-gravity-inspired corrections and regularity conditions may affect black-hole ringdown signals.

[abstract 13 / 38] (score: 3)
arXiv:2602.17514 [pdf, ps, other]

Title: Kinetic route to helicity-constrained decay

Authors: Dion Li,

Comments: Proof-reviewed version accepted for publication in APS Open Science; main conclusions unchanged. 25 pages, 9 figures, 1 table

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

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Through two-dimensional, three-velocity-component particle-in-cell simulations of freely decaying subion turbulence, intermittent localized regions with $\mathbf{E} \cdot \mathbf{B} \neq 0$ are found, in the early electron-scale interaction phase, to be statistically associated with decreases in $|H_{V_s}|$, the fixed-gauge structure-integrated MAGNETic-helicity diagnostic. This structure-level behavior coincides with a decline of the Saffman helicity-variance plateau value $I_H$. Motivated by these observations, we propose a source-compensated, history-dependent helicity density that satisfies an exact local balance identity by construction, enabling Saffman-type two-point correlation integrals, which, under standard flux-decorrelation assumptions, can exhibit intermediate-scale plateaus that are roughly time independent. In the simulations, such plateaus are observed to remain approximately invariant over the measured kinetic interval even as $I_H$ evolves during the early kinetic stage. Under approximate single-scale self-similarity, the plateau behavior of the MAGNETic integral is consistent with the two-dimensional decay constraint $BL \sim \text{const}$. For initially net-helical configurations, we observe rapid development of mixed-signed MAGNETic-helicity patches and a decrease of the global fractional helicity, such that the decay over the kinetic interval is again most consistent with the cancellation-dominated scaling constraint.

[abstract 14 / 38] (score: 3)
arXiv:2606.04793 [pdf, ps, other]

Title: Cooler Phases of the Circumgalactic Medium Are More Centrally Concentrated: Constraints from Multiphase Absorption Lines

Authors: Weiwen Kong, Zeyu Chen, Enci Wang, Haoran Yu, Kai Wang, Dongdong Shi, Cheqiu Lyu, Yuxuan Zhang, Haoyi Zhang, Haowen Guan,

Comments: Accepted for publication in ApJ. Comments welcome

Subjects: astro-ph.GA

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

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 15 / 38] (score: 3)
arXiv:2607.01325 [pdf, ps, other]

Title: TEQUILA: Mechanism-free polarimetry for astronomy

Authors: Alan M. Watson, Noémie Globus,

Comments: 26 pages. To appear in SPIE Astronomical Telescopes + Instruments 2026

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

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

TEQUILA (Transient Event $Q$, $U$, and $I$ Light Analyzer) is an optical imaging polarimeter developed for the second Nasmyth port of the 1.3-m COLIBRÍ altitude-azimuth telescope at Observatorio Astronómico Nacional in San Pedro Mártir, México (OAN-SPM). TEQUILA uses a CMOS sensor with an on-chip wire-grid micro-polarizer array to obtain simultaneous, single-exposure measurements of the Stokes parameters $I$, $Q$, and $U$ without moving optical components. This mechanism-free instrument, built entirely from commercial components, delivers seeing-limited imaging in a fixed optical band and is optimized for early-time follow-up of transient sources, including GAMMA-RAY BURST afterglows, BLAZARs, and variable young stellar objects. In this paper, we describe the scientific motivation, the instrument design and implementation, the calibration, and initial science results. Sensor characterization reveals a polarimetric structure in the flat field and a low quantum efficiency, which we estimate to be approximately 17%, including losses introduced by the micro-polarizer array. For point sources, TEQUILA achieves absolute polarimetry with RMS uncertainties of 0.15% in pupil-tracking observations and 0.20% in field-tracking observations. In pupil-tracking mode, the observed RMS is fully explained by the measurement and standard-star uncertainties, with no evidence for an additional calibration term. In contrast, field-tracking observations require an additional calibration uncertainty of approximately 0.10%. Calibration for resolved-source polarimetry remains in progress.

[abstract 16 / 38] (score: 3)
arXiv:2607.01330 [pdf, ps, other]

Title: Extreme outflow velocities and weak UV emission lines indicate QUASARs shedding their dust cocoons

Authors: Guozhen Ma, Stefan J. Geier, Johan P. U. Fynbo, Lise Christensen, Andrei Berdyugin, Rasmus Frederiksen, Kasper E. Heintz, Phillip D. Henriksen, Jens-Kristian Krogager, Cédric Ledoux, Vilppu Piirola, Palle Møller, Simone Vejlgaard, Hyunseop Choi,

Comments: 30 pages, 27 figures, accepted for publication in A&A

Subjects: astro-ph.GA

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

The recently discovered low-ionisation broad absorption line (LoBAL) QUASAR GQ 1309$+$2904 is unusual due to its very broad, highly blueshifted absorption troughs and an absence of broad emission lines except for ${\mathrm{H} α}$. In this paper, we present observations of six QUASARs that appear very similar to GQ 1309$+$2904 in the rest-frame ultraviolet (UV). We measure the systemic redshifts of these QUASARs to be $z\approx$ 2.07--3.28 from detected ${\mathrm{H} α}$ emission lines. We confirm that all targets are QUASARs with highly blueshifted BALs possessing high-speed outflows with velocities up to $\sim 0.16\,c$, and five of them are confidently identified as LoBAL QUASARs. Based on ${\mathrm{H} α}$ emission, BLACK HOLE masses and Eddington ratios of these QUASARs are $M_{\mathrm{BH}} \approx 10^{8.7}$--$10^{9.4}\,M_{\odot}$ and $L_{\mathrm{bol}} / L_{\mathrm{Edd}} \approx$ 0.14--0.34, indicating that their central BLACK HOLEs are very massive and active. Every QUASAR in our sample exhibits a very flat or reddened continuum. The spectral shapes of three objects are well-fitted by a normal QUASAR composite reddened by a Small-Magellanic-Cloud-like (SMC-like) extinction curve, while the other three require a steeper extinction law. Broad-band ($BVR$) polarimetry for two of the latter group (plus GQ 1309$+$2904) reveals their low polarisations, consistent with low inclination (more face-on) angles. We propose that these objects are weak emission-line QUASARs (WLQs) observed through the disc wind, caught emerging from their dust cocoons. As QUASARs shed their cocoons, dust grains in the disc wind are shattered into smaller particles, producing the UV-steeper extinction curve observed along the outflow. We present a schematic illustration of this shedding process that can account for the peculiar spectral features observed in our sample.

[abstract 17 / 38] (score: 3)
arXiv:2607.01337 [pdf, ps, other]

Title: A possible high-redshift origin for the short GRB 061201: implications of a compact binary merger beyond cosmic noon

Authors: E. Troja, B. O'Connor, Y. -H. Yang, T. M. Gaudin, M. Yadav, N. Passaleva, S. Dichiara,

Comments: 8 pages, 4 figures, submitted

Subjects: astro-ph.HE

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

Short GAMMA-RAY BURSTs (GRBs) at redshift z>2 remain exceptionally rare, yet they are crucial for tracing compact binary mergers in the early Universe and understanding their role in the production of r-process elements. GRB 061201 is an unusual and still debated event: although its optical afterglow was accurately localized, no secure coincident host galaxy was identified, and the proposed associations with nearby galaxies all require a large separation between the GRB and its birth site. In this work, we revisit GRB 061201 and argue that the observations are more naturally explained if the burst occurred within a faint F322W2~28.4 AB mag galaxy at z>2. By combining constraints from the afterglow and deep near-infrared imaging from JWST, we show that a distant origin provides a coherent explanation of the burst phenomenology. If confirmed, GRB 061201 would represent one of the most distant short GRBs known, extending the observed compact merger population to an epoch when the Universe was only about two billion years old.

[abstract 18 / 38] (score: 3)
arXiv:2607.01357 [pdf, ps, other]

Title: X-ray POLARIZATION in MAGNETized neutron stars

Authors: Tanuman Ghosh, Shiv Sethi,

Comments: 18 pages, 8 figures

Subjects: astro-ph.HE

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

X-ray polarimetry has opened a new window into understanding the physics around MAGNETized compact objects. IXPE detection of linear POLARIZATION from such systems has prompted a new spurt of theoretical modeling. Our study is based on the dominant paradigm that the observed POLARIZATION arises from the scattering of photons around highly MAGNETized systems. Our main focus is the dependence of the POLARIZATION of the scattered light on properties of the incoming light, i.e., geometry and the POLARIZATION state, and the determination of the spectral shape of the polarized light for a wide range of MAGNETic field strengths. We also analyze the impact of vacuum birefringence on photon POLARIZATION. We show that, generically, we expect a higher linear degree of POLARIZATION from MAGNETars as compared to normal pulsars, which is in agreement with IXPE observations. Under some conditions, our study helps to understand the observed degree of POLARIZATION from normal pulsars and low-MAGNETized neutron stars and their spectral dependence. However, we cannot conclusively explain the spectral shape of the observed POLARIZATION for MAGNETars using only a single component emission from scattering in a strong MAGNETic field. This probably points to the system being more complex, e.g., multi-component, than our study allows for. Upcoming X-ray polarimeters with broader energy coverage could probe some of our other predictions, e.g., the spectral shape of the polarized light close to the resonance frequency.

[abstract 19 / 38] (score: 3)
arXiv:2607.01419 [pdf, ps, other]

Title: Vacuum Cherenkov radiation in supercritical MAGNETic fields

Authors: Daniel Gálvez-García, Nora Bretón,

Comments: 16 pages, 5 figures

Subjects: gr-qc

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

In the presence of very intense electroMAGNETic fields, the refractive index of vacuum is modified such that light velocity is less than $c$ and ultraRELATIVISTIC charged particles can be faster than light and can induce Cherenkov radiation. We present the comparison of the Cherenkov radiation produced by the Euler-Heisenberg theory for critical and supercritical MAGNETic fields. We also make the comparison between the Cherenkov and the SYNCHROTRON radiation produced by the charged particles.

[abstract 20 / 38] (score: 3)
arXiv:2607.01723 [pdf, ps, other]

Title: Particle dynamics and quasi-periodic oscillations of a Reissner--Nordström-like BLACK HOLE in Kalb--Ramond gravity under an external MAGNETic test field

Authors: Faizuddin Ahmed, Ahmad Al-Badawi, Sardor Murodov, Bekzod Rahmatov, Javlon Rayimbaev,

Comments:

Subjects: gr-qc

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We investigate the dynamics of charged test particles and quasi-periodic oscillations around a Reissner--Nordström-like BLACK HOLE in Kalb--Ramond (KR) gravity in the presence of an external MAGNETic test field. The KR background introduces a Lorentz-violating parameter $\ell$, which modifies the spacetime geometry, horizon structure, circular orbits, and characteristic frequencies of particle motion. In contrast to the standard Wald-type prescription, the MAGNETic-field configuration is constructed from the source-free Maxwell equation on the charged KR background, allowing the MAGNETic profile to be consistently adapted to the modified geometry. We derive the equations of motion, the effective potential, the conditions for circular orbits, and the orbital and radial epicyclic frequencies of charged particles. The results show that the black-hole charge $Q/M$, the KR parameter $\ell$, the specific particle charge $ε$, and the MAGNETic coupling $β=bM$ jointly affect the innermost stable circular orbit (ISCO) and the quasi-periodic oscillation (QPO) frequencies. We then apply the obtained frequencies to the RELATIVISTIC precession model, where the upper QPO frequency is identified with the orbital frequency and the lower one with the periastron-precession frequency. Using the observed twin-peak QPO data of GRO J1655--40, XTE J1550--564, and M82 X-1, we perform a Markov chain Monte Carlo analysis to constrain the model parameters. The obtained posterior constraints indicate that the charged KR black-hole model with an external MAGNETic field can consistently reproduce the observed QPO pairs within the adopted parameter ranges. These findings suggest that QPO observations may serve as a useful phenomenological tool for probing Lorentz-violating black-hole geometries and electroMAGNETic effects in strong-gravity environments.

[abstract 21 / 38] (score: 2)
arXiv:2511.11322 [pdf, ps, other]

Title: Extending the Numerical Flow Iteration to the multi-species Vlasov-Maxwell system through Hamiltonian Splitting

Authors: Rostislav-Paul Wilhelm, Fabio Bacchini, Sebastian Schöps, Manuel Torrilhon, Melina Merkel, Matthias Kirchhart,

Comments:

Subjects: physics.plasm-ph cs.NA math.NA

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

The Numerical Flow Iteration (NuFI) method has recently been proposed as a memory-slim while accurate in phase-space method for the electro-static Vlasov--Poisson system. It stores the temporal evolution of the electric field, instead of the distribution functions, and reconstructs the solution in each time step by following the characteristics backwards in time and reconstructing the solution from the initial distribution. NuFI has been shown to be more accurate than other state-of-the-art electro-static Vlasov solvers given the same amount of degrees of freedom. In this paper, we build on the Hamiltonian structure of the full Vlasov--Maxwell system to extend NuFI to handle electro-MAGNETic kinetic plasma dynamics. We show that the structure-preserving properties of the NuFI time-stepping are preserved when extending to the electro-MAGNETic case. Furthermore we discuss how NuFI can be incorporated into existing Semi-Lagrangian codes as an efficient while accurate subcycling technique.

[abstract 22 / 38] (score: 2)
arXiv:2512.12616 [pdf, ps, other]

Title: A Search for Hard X-ray/Soft $γ$-ray Emission from SPT-CL J2012-5649 (Abell 3667) Using INTEGRAL/ISGRI

Authors: Siddhant Manna, Shantanu Desai, Roman A. Krivonos,

Comments: 13 pages, 1 figure. Accepted for publication in Astronomy Letters

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

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We present a search for hard X-ray/soft $γ$-ray emission from the merging galaxy cluster SPT-CL J2012-5649 (Abell~3667) using archival INTEGRAL/ISGRI observations. This cluster located at $z=0.0556$ hosts prominent radio relics associated with merger-driven shocks, suggesting the presence of RELATIVISTIC electrons capable of producing inverse-Compton (IC) emission in the hard X-ray to soft $γ$-ray regime. We searched for emission in the 30--300~keV energy range using the INTEGRAL Off-line scientific analysis software with a total effective exposure of 2817~s. No significant emission was detected at the cluster position in the aforementioned energy interval. The extracted ISGRI spectrum is consistent with pure background, and no physically meaningful model parameters can be constrained. From the mosaic variance maps, we derive a $3σ$ upper limit of $F_{30-300\,\mathrm{keV}} < 3.63 \times 10^{-10}\,\mathrm{erg\,cm^{-2}\,s^{-1}}$. This limit rules out bright IC scenarios and constrains the efficiency of merger-driven particle acceleration in SPT-CL J2012-5649. Our results provide the most stringent soft $γ$-ray constraint on this system to date and highlight the need for next-generation hard X-ray missions, such as HEX-P or eXTP, to probe IC emission at theoretically predicted levels in merging clusters.

[abstract 23 / 38] (score: 2)
arXiv:2601.13980 [pdf, ps, other]

Title: The Geometry of Flux Surfaces with Quasi-Poloidal Symmetry

Authors: Rishin Madan, Wrick Sengupta, Elizabeth J. Paul, Mohammed Haque, Richard Nies, José Luis Velasco, Amitava Bhattacharjee,

Comments: 44 pages, 12 figures, accepted for publication by Journal of Plasma Physics

Subjects: physics.plasm-ph

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Quasi-poloidal (QP) MAGNETic fields have desirable properties for confining plasma: no radial drift of guiding centres (with positive implications for neoclassical transport), zero Pfirsch-Schlüter current, and a lower level of damping for poloidal flows. Despite their attractive properties, QP fields are not amenable to the near-axis expansion, a major theoretical tool for understanding toroidal fields. In this paper, we provide a novel framework for defining and understanding QP flux surfaces. This framework relies on a simplification that transforms the task of finding a quasi-poloidal flux surface from a 3D problem to a 2D problem. This simplification also applies to asymmetric MAGNETic mirrors with desirable properties. We sketch how this 2D problem can form the basis of an efficient optimisation problem for finding QP flux surfaces. We leverage this 2D problem for theoretical understanding: for instance, we identify a route to finding QP flux surfaces that are naturally flat mirrors (Velasco et al. 2023). The reduced model is qualitatively checked against numerically optimised QP equilibria. These numerical solutions only satisfy QP approximately, but we predictably find that local discrepancies with the reduced model correspond to significant local QP errors, anomalous parallel currents, and field lines deviating from geodesics.

[abstract 24 / 38] (score: 2)
arXiv:2602.03923 [pdf, ps, other]

Title: An emulator for the ionizing photon mean free path in ultra-high resolution simulations: the implications of mean free path measurements for the reionization history

Authors: Hurum Maksora Tohfa, Christopher Cain, Matthew McQuinn, Anson D'Aloisio,

Comments: 25 pages, 8 figures

Subjects: astro-ph.CO

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

Measurements of the mean free path of ionizing photons from high-redshift QUASAR spectra at $z \sim 5$-$6$ constrain the reionization history, but interpreting them requires modeling the kiloparsec-scale clumping that large-volume reionization simulations cannot resolve. We present a deep learning emulator for the mean free path (MFP) trained on high-resolution cosmological radiative transfer simulations of ionization fronts sweeping through small 2 comoving Mpc/h volumes. Using a residual multi-layer perceptron neural network, we predict the MFP at a given redshift as a function of the reionization redshift, photoionization rate, wavelength, and box-scale density, achieving a median relative error of 1.3\% across nearly four orders of magnitude in MFP. Integrating its predictions over box-scale overdensity and an extended reionization history allows the emulator to predict the global MFP. We apply the emulator to extended reionization histories constrained by observed photoionization rates, finding that models prefer late reionization with substantial neutral fractions persisting at $z \lesssim 6$. Fitting a parametric ionization history yields a midpoint of reionization of $z_{\rm re} = 6.58\pm 1.2$ for reionization durations consistent with Planck and kinetic Sunyaev-Zeldovich constraints, and the universe being $10\%$ neutral still at $z < 5.8 ~(6.3)$ at 1~(2)$σ$. Global ionizing emissivity inferences using measurements of the photoionization rate and MFP plus our emulator, which avoids common power-law assumptions, suggest a factor of $2-3$ decline between $z = 6$ and $4.8$, in agreement with previous studies. Our method provides an efficient (and more converged) alternative to large-volume radiative-hydrodynamic simulations of reionization for interpreting MFP measurements, and can also serve as a subgrid prescription for the ionizing opacity within such simulations.

[abstract 25 / 38] (score: 2)
arXiv:2603.06509 [pdf, ps, other]

Title: An Overview of Relativistic Particle Pushers and their Extension to Arbitrary Order Accuracy

Authors: Holger Schmitz,

Comments: 21 pages, 8 figures, accepted for publication in Journal of Scientific Computing

Subjects: physics.plasm-ph physics.comp-ph

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Particle in Cell (PIC) simulations have become a vital tool for the investigation of kinetic processes in plasma physics. Many of the systems investigated with PIC simulations contain particles with RELATIVISTIC velocities. The correct integration and the knowledge of possible sources of errors in RELATIVISTIC particle trajectories is of importance to accurately judge the validity of the simulation results. Over the past few decades, various new integration schemes for RELATIVISTIC particle trajectories in PIC simulations have been proposed. These are aimed at improving numerical accuracy in specific scenarios. This article presents a comprehensive comparison of particle pushers with a focus on explicit schemes. An important class of these schemes is found to be generalisable to arbitrary high order. A comparison of the fourth order variants of these schemes with their second order counterpart is also presented.

[abstract 26 / 38] (score: 2)
arXiv:2606.10566 [pdf, ps, other]

Title: Discovery of EP J175257.3-351923 as a Candidate Black Hole Low-Mass X-ray Binary

Authors: G. L. Huang, Q. C. Zhao, L. Tao, A. Coleiro, A. Rau, S. Brennan, C . Y. Dai, R. Soria, F. Cangemi, F. Coti Zelati, A. Marino, L. Zhang, S. Guillot, H. Q. Cheng, H. Feng, D. Götz, Y. Huang, Y. F. Huang, D. Y. Li, Z. S. Li, P. Maggi, R. C. Ma, X. Ma, H. W. Pan, N. Rea, J. Wang, Q. Y. Wu, L. P. Xin, W. M. Yuan, Z. H. Yao, G. B. Zhang, W. D. Zhang, S. N. Zhang,

Comments: Accepted for publication in A&A Letters

Subjects: astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We report the discovery of a new X-ray transient, EP J175257.3-351923 (EP250916a), by the Einstein Probe (EP) near the Galactic plane. The outburst lasted for at least 250\,days, reached a peak 2--10 keV flux of $\sim 4 \times 10^{-10}$~erg~cm$^{-2}$~s$^{-1}$, and exhibited a fast-rise exponential-decay (FRED) profile typical of X-ray binary outbursts. The source remained in the hard state throughout the outburst, with only modest variations in the photon index ($\sim 1.6$--$2.2$) and no evidence for a spectral state transition. Broadband spectral modeling suggests a truncated disk, a weak reflection component, and a high-energy cutoff at $\sim 217$~keV, consistent with hard-state accretion in black-hole systems. No reliable optical or radio counterpart is detected within the SWIFT/XRT error circle. The inferred X-ray-to-optical and X-ray-to-radio flux ratios are consistent with a low-mass X-ray binary classification. Neither pulsations nor significant aperiodic variability are detected. Although the compact object cannot yet be firmly identified, the timing, spectral, and multiwavelength evidence favors EP~J175257.3--351923 as a black-hole low-mass X-ray binary candidate, highlighting EP's potential to uncover a faint, previously hidden population of X-ray binaries.

[abstract 27 / 38] (score: 2)
arXiv:2606.31364 [pdf, ps, other]

Title: Establishing Compactness as a Population Observable in Gravitational-Wave Astronomy

Authors: Shrobana Ghosh, Charlie Hoy, Mark Hannam, Frank Ohme,

Comments: 9 pages, 3 figures

Subjects: gr-qc astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Classically, BLACK HOLEs (BHs) are the most compact objects predicted in nature with C=0.5 in the Schwarzschild limit; C is defined as the mass-to-radius ratio in geometric units. In this work we perform a novel measurement on the nature of putative BH mergers in the gravitational wave (GW) data by directly probing the binary's closest approach through an effective compactness parameter. We confidently show all such high-significance signals in GWTC-3 are consistent with the BH hypothesis for the first time. Our hierarchical analysis yields $C_{\rm eff} = 0.5^{+0.3}_{-0.1}$, and we further limit the merger rate of low-compactness exotic binaries to $< 0.7\,{\rm Gpc}^{-3}\,{\rm yr}^{-1}$. This work establishes compactness as a key observable in GW astronomy.

[abstract 28 / 38] (score: 2)
arXiv:2607.01168 [pdf, ps, other]

Title: Stellar Forcing of (exo)Planetary Environments

Authors: Julián D. Alvarado-Gómez, Erika Palmerio, Manuel Güdel, Kosuke Namekata, Konstantin Herbst, N. Eugene Engelbrecht, Antoine Strugarek, Judy J. Chebly, Astrid Veronig, Maria D. Kazachenko, Krisztián Vida, Kristina G. Kislyakova, Katja Poppenhäger, Antonio García-Muñoz, Yuta Notsu, Harish K. Vedantham,

Comments: 132 Pages, 47 Figures, 8 Tables, Submitted to Space Science Reviews, Abstract shortened for arXiv compliance

Subjects: astro-ph.SR astro-ph.EP

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

The environments of exoplanets are fundamentally shaped by the MAGNETic activity of their host stars through radiative, plasma, and particle-driven processes. This article presents a comprehensive overview of the four principal forms of stellar forcing that regulate atmospheric structure, chemistry, escape, and long-term planetary evolution: high-energy radiation, MAGNETized stellar winds, coronal mass ejections, and energetic particles. Using the Sun as a physically resolved benchmark, the discussion extends to increasingly active cool stars to establish a broader picture of star--planet interactions across the main sequence. The article first examines stellar X-ray and extreme ultraviolet emission from chromospheres and coronae, together with variability introduced by flares and MAGNETic RECONNECTion. Particular attention is given to spectroscopic diagnostics, activity scalings with stellar rotation and age, flare energetics, and the observational links between impulsive and gradual phases of MAGNETic energy release. The treatment then shifts to MAGNETized stellar winds, describing the mechanisms that drive them and the role of multidimensional MAGNETohydrodynamic modeling in determining wind structure, angular momentum loss, and planetary interaction regimes. Solar and stellar coronal mass ejections are explored through their diagnostics, flare associations, propagation, and possible suppression by strong stellar MAGNETic fields. Finally, galactic and stellar energetic particles are discussed together with methods for estimating particle environments and their consequences for atmospheric chemistry and climate. The article concludes by outlining future observational and numerical developments needed to connect these coupled stellar forcing processes within a unified exoplanetary framework.

[abstract 29 / 38] (score: 2)
arXiv:2607.01288 [pdf, ps, other]

Title: Pulsar Science with the SKAO

Authors: Bhal Chandra Joshi, Aris Karastergiou, Marta Burgay,

Comments: 13 pages, 2 figures, Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report number AASKAII/Joshi01. Advancing Astrophysics with the SKA II (AASKA II) outlines the transformative scientific advances that will be enabled by the SKA telescopes. An earlier version of this chapter was published in The Open Journal of Astrophysics with arXiv ID: arXiv:2512.16152

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

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

The large instantaneous sensitivity, wide frequency coverage and flexible observation modes, with large number of beams in the sky, are the main features of the SKA observatory's two telescopes, the SKA-Low and the SKA-Mid. Owing to these capabilities, the SKAO telescopes are going to be a game-changer for radio astronomy in general and pulsar astronomy in particular. Eleven chapters in this book describe their impact on different areas of pulsar science. In this overview article each chapter is briefly summarised and the inter-relationship between different pulsar science use cases are explored: new deep surveys, covering the Galactic field, globular clusters and the Galactic centre, will discover thousands of new pulsars; these will form the backbone for studies of neutron star physics and of their environments. The enhanced understanding provided by these studies will feed into the main contributions to fundamental physics from pulsar astronomy: testing RELATIVISTIC gravity, studying gravitational waves in the nano-Hz regime and studying the equation of state of nuclear matter. Synergies with other science cases are also highlighted throughout this overview.

[abstract 30 / 38] (score: 2)
arXiv:2607.01372 [pdf, ps, other]

Title: AI-enabled gravitational-waves searches for binary neutron stars at optimal sensitivity

Authors: Bhavya Gupta, Deep Chatterjee, William Benoit, Ethan Marx, Christina Reissel, Seiya Tsukamoto, Kyungseop Yoon, Michael W. Coughlin, Philip Harris, Erik Katsavounidis,

Comments:

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

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

Gravitational Waves (GWs) represent the newest window of astronomy, furthering our understanding of compact objects like BLACK HOLEs and neutron stars in the Universe. The signal from two merging neutron stars is especially interesting since it brings the prospect of concordant electroMAGNETic and neutrino emissions. Such multi-messenger observations have a transformational impact on fundamental physics, nuclear matter, astrophysics, and gravity. It was first witnessed in 2017 with the detection of the binary neutron star (BNS) merger GW170817. However, searching for BNS signals in real-time in the LIGO-Virgo-KAGRA (LVK) GW detectors presents a computational challenge, as the data streaming out must be matched against $\sim$ million reference waveforms, which requires up to a thousand CPU cores. We present a different approach using neural networks to learn the presence of a signal in the data. Our algorithm, called Aframe, was deployed in the LVK's fourth observing run and was the first artificial intelligence (AI)-enabled search to detect multiple binary BLACK HOLEs (BBHs) live. In this work, we demonstrate that the approach extends to the lower-mass BNS regime, and is the first AI-enabled search that achieves sensitivity comparable to matched-filter pipelines at lower computational and latency costs. The challenge of the longer-duration BNS signals is addressed by heterodyning the data, following which the network architecture used for BBHs is sufficient to distinguish signal versus background. We also show that this analysis requires a single non-flagship GPU for online deployment. Furthermore, the design and adoption of inference-as-a-service tools allow rapid offline analysis using a distributed pool of GPU resources. Hence, aside from the use case of rapid online data analysis, we also establish the use of Aframe for efficient archival data analysis.

[abstract 31 / 38] (score: 2)
arXiv:2607.01475 [pdf, ps, other]

Title: Understanding Non-Gaussian Chorus Wave Statistics via the Benjamin-Feir Index

Authors: D. J. Ratliff, O. Allanson, D. Rasinskaite, J. Stawarz, C. E. J. Watt, S. Chakraborty,

Comments: 14 pages, 3 figures

Subjects: physics.plasm-ph math-ph math.MP

Created: 2026-07-01; Updated: 2026-07-03; Datestamp: 2026-07-03

We derive an extended wave action model for equatorial chorus waves, identifying a wave activity index (a version of the Benjamin-Feir index, BFI) which indicates non-Gaussian frequency spectra emerge when BFI$>$0.5. Global maps of this index indicate the night and dawn sectors ($0<{\rm MLT}<9)$ of the MAGNETosphere as the primary region for non-Gaussian wave statistics to emerge. Comparisons with events measured by the Van Allen probe A demonstrate good qualitative agreement whilst identifying key aspects for model refinement. A key strength of our model that our work highlights is its ability to account for the asymmetric frequency spectra characteristic of non-Gaussian chorus. This work ultimately establishes the first wave activity index that distinguishes Gaussian and non-Gaussian wave scenarios from first principles, providing the groundwork for a threshold-based quantification for use in space weather modelling.

[abstract 32 / 38] (score: 2)
arXiv:2607.01576 [pdf, ps, other]

Title: Signatures of Two Distinct Epochs of FRB 20240114A from January to August 2024 Based on its Energy and Waiting Time Analysis

Authors: Xiao Li, Ying Gu, En-Wei Liang,

Comments: 12 pages, 6 figures, accepted for publication in MNRAS

Subjects: astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

A comprehensive analysis of the energy and waiting time distributions of the bursts from FRB 20240114A detected by the Five-hundred-meter Aperture Spherical Radio Telescope between 28 January and 29 August 2024 is presented. For the full sample, its energy distribution cannot be fitted with the simple power-law (SPL),bent power-law (BPL), thresholded power-law (TPL) or Band function models, and its waiting time distribution excluding intervals shorter than 0.5 s cannot be fitted with the Poisson or Weibull models. Nevertheless, for the subsamples with more than 50 bursts in single-day observations, their energy distributions can be fitted with the BPL or TPL models, and their waiting time distributions are better described by a Weibull model. It is noted that the best-fitting BPL parameter $β$ is approximately invariant within the epochs before and after 21 March 2024, with an average of $\bar β_b = 1.006 \pm 0.074$ and $\bar β_a = 1.236 \pm 0.183$ (one standard deviation), respectively. Most subsamples from the later epoch have a smaller burst rate parameter $r$ in the Weibull model than those from the earlier epoch. The majority of bursts with $E>10^{39}$ erg occurred in the earlier epoch. The energy distributions in the high-energy range ($> 6\times10^{37}$ erg) differ significantly between the two epochs, and power-law fits to $dN/dE$ yield indices of $-1.97_{-0.02}^{+0.02}$ and $-2.34_{-0.06}^{+0.06}$, respectively. The median of the waiting time distribution of the later epoch is larger than that in the earlier epoch. These results suggest that the two epochs may be dominated by different types of bursts, possibly attributed to changes in the physical properties of the emission region.

[abstract 33 / 38] (score: 2)
arXiv:2607.01604 [pdf, ps, other]

Title: Bolometric correction factor and radiative efficiency for the super-Eddington accretion flow in tidal disruption events

Authors: Yongxin Wu, Erlin Qiao, Xuan Fang, Yiyang Lin, Jifeng Liu, Meng Guo,

Comments: 9 pages, 5 figures, accepted for publication in MNRAS

Subjects: astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

The estimate of the bolometric luminosity and the radiative efficiency are two key aspects for understanding the properties of the accretion flow around a supermassive BLACK HOLE (BH). In this paper, we focus on the estimate of the bolometric luminosity and the radiative efficiency of the early super-Eddington accretion flow in tidal disruption events (TDEs). Specifically, we first perform radiation hydrodynamic simulations of super-Eddington accretion flow in TDE environment, and then calculate the corresponding emergent spectra with the method of post processing for the simulation data. Based on the emergent spectra, we calculate the isotropic-equivalent X-ray bolometric correction factor $k_\mathrm{bol}$ and the radiative efficiency $η$ of the super-Eddington accretion flow. We find that both $k_\mathrm{bol}$ and $η$ are BH mass and viewing-angle dependent. $k_\mathrm{bol}$ is in the range of about a few tens to a few thousands, and $η$ is in the range of $\sim 10^{-3}-10^{-1}$ for BH mass in the range of $10^{6-7}M_\odot$ and the viewing angle in the range of $0^{\rm o}-90^{\rm o}$. Finally, we apply the derived $k_\mathrm{bol}$ and $η$ to some specific TDEs to estimate the accreted mass during an event, which can significantly alleviate the so-called missing energy problem in TDEs.

[abstract 34 / 38] (score: 2)
arXiv:2607.02009 [pdf, ps, other]

Title: Research Progress on Solar Small-Scale Dynamo

Authors: Wen-Jie Jiang, Lei Ni, Chun-Lan Jin, Zhi Xu, Mei Zhang,

Comments:

Subjects: astro-ph.SR

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

The small-scale solar dynamo theory, as the core mechanism explaining the origin of the persistent, disperse weak MAGNETic field in the quiet Sun regions, has made significant progress over the past three decades in the fields of observation, theory, and simulation. Breakthrough observations from high-resolution space-based and ground-based telescopes have revealed that the quiet Sun is ubiquitously populated by highly dynamic, mixed-polarity and possibly predominantly horizontal MAGNETic structures with complex topology. These observations confirm that their total MAGNETic flux is substantial, with a high and widely distributed MAGNETic flux emergence rate, strongly suggesting a local dynamo effect independent of the solar cycle and driven by intense turbulence and convection. Theoretical studies indicate that even in the challenging low MAGNETic Prandtl number ( Pm << 1) environment of the solar photosphere and convection zone, turbulent motions can self-excitedly convert kinetic energy into MAGNETic energy through the stretching, folding, and twisting of MAGNETic field lines. MHD simulations have successfully reproduced observed features, demonstrating that a pure small-scale dynamo can operate efficiently and sustain MAGNETic fields even in an open, stratified solar environment incorporating realistic physical processes. Current research strongly suggests that small-scale MAGNETic fields constitute the majority of the MAGNETic energy in the quiet Sun and also influence coronal heating, solar wind acceleration, and radiation distribution. This article conducts a literature review centered on observations, theoretical models, and numerical simulations of the small-scale dynamo, organizing and discussing the relevant research history and progress. Finally, it summarizes the content and provides an outlook on future research from multiple perspectives.

[abstract 35 / 38] (score: 2)
arXiv:2607.02044 [pdf, ps, other]

Title: Energetic particle-mediated interplanetary shocks observed by Solar Orbiter

Authors: D. Trotta, D. Lario, B. Reville, S. Raptis, O. Pezzi, H. Hietala, P. Mostafavi, J. Giacalone, R. F. Wimmer-Schweingruber, P. Kuehl, A. Kollhoff, D. Turner, D. Burgess,

Comments: In review in A&A Letters

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

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

Context: In collisionless shocks, energetic particles can carry sufficient pressure to modify the upstream plasma and the shock structure itself, a regime often invoked in theories of cosmic-ray acceleration but rarely observed in the heliosphere. Aims: We find and characterize {interplanetary} IP shocks where energetic particles dynamically dominate the upstream pressure. Methods: We analyze IP shocks observed by Solar Orbiter inside 1 au and compute the energetic particle pressure $P_{EP}$ from proton measurements above 10\,keV, comparing it with the upstream thermal $P_{Th}$ and MAGNETic $P_{B}$ pressures. Results: We identify four shocks for which $P_{EP} \geq P_{Th} + P_B $. These events correspond to strong and fast shocks in the high-Mach-number tail of the Solar Orbiter shock population. In several cases the $P_{EP}$ increase coincides with a decreasing upstream bulk flow speed in the shock frame, and the resulting particle-mediated foreshocks extend up to $\sim10^5$ {ion inertial lengths} $d_i$. The extent of such energetic particle dominated region depends on shock geometry. Conclusions: These observations provide evidence that accelerated particles can dynamically modify interplanetary shocks. They highlight the importance of the coupling between energetic particles, upstream fluctuations, and shock structure for understanding particle acceleration at collisionless shocks.

[abstract 36 / 38] (score: 2)
arXiv:2607.02110 [pdf, ps, other]

Title: Black Boxes in Black Hole Imaging

Authors: Juliusz Doboszewski, Jamee Elder,

Comments: forthcoming in Synthese, TC: The Philosophy of Experiments

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

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We investigate the epistemic opacity of computer simulations and machine learning methods in the context of BLACK HOLE imaging. We argue that there are forms of opacity-including opacity resulting from the use of machine learning-which do not need to affect the reliability of an inference when it is seen as a part of a broader inferential framework. We propose conditions under which that can plausibly be the case, and discuss how opaque methods can be useful in the context of the (next generation) Event Horizon Telescope. However, we also argue that at least one problematic form of opacity is currently present in BLACK HOLE imaging: GRMHD models of Sagittarius A* are opaque. This form of opacity signals the limitations of current understanding of the models of this source, and constrains the potential uses of ML models in future observations.

[abstract 37 / 38] (score: 2)
arXiv:2607.02228 [pdf, ps, other]

Title: Timing and spectral analysis of the 2025 outburst of 4U 1630$-$47 with \textit{NICER}

Authors: Haifan Zhu, Mariano Méndez, Xiao Chen, Wei Wang,

Comments: 13 pages, 10 figures, accepted for publication in Astronomy & Astrophysics

Subjects: astro-ph.HE

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

We analyzed \textit{NICER} observations of the 2025 outburst of the BLACK HOLE X-ray binary 4U~1630$-$47 to investigate the spectral--timing properties of its transient low-frequency quasi-periodic oscillations (QPOs) and millihertz-scale quasi-regular modulation (QRM). During the rising phase of the outburst, the QPO centroid frequency increased from $\sim 0.24$ Hz to $\sim 3.43$ Hz. Wavelet-based state separation shows that the with-QPO intervals are associated with a higher inner disk temperature and a lower \texttt{diskbb} normalization than the without-QPO intervals, while the photon index ($Γ$) shows weaker changes within the uncertainties. Near the outburst peak, the source displayed a weak QRM at $\sim 0.07$ Hz with a fractional rms amplitude of $\sim 4.7\%$, lower than that of the heartbeat state observed in 2023. Phase-resolved Hilbert--Huang analysis shows that the inner disk temperature is positively correlated with the X-ray flux, the \texttt{diskbb} normalization is anticorrelated, and $Γ$ varies only weakly. Overall, the short-timescale spectral--timing variability is expressed most clearly through the disk-related parameters. The transient QPOs are therefore consistent with short-timescale disk-related variability during the rising phase, whereas the millihertz-scale QRM may represent a weaker heartbeat-like variability mode appearing near the outburst peak.

[abstract 38 / 38] (score: 2)
arXiv:2607.02373 [pdf, ps, other]

Title: Brilliant multi-GeV Compton gamma-ray source seeded by a photon accelerator

Authors: Michael J. Quin, Stepan S. Bulanov, Arkady Gonoskov, Christopher D. Murphy, Mattias Marklund, Alexander G. R. Thomas, Thomas G. Blackburn,

Comments:

Subjects: physics.plasm-ph physics.acc-ph

Created: 2026-07-02; Updated: 2026-07-03; Datestamp: 2026-07-03

High-brilliance sources of polarized gamma rays are widely sought after to pump and probe matter at subatomic length scales. However, existing accelerator facilities and optical LASERs cannot reach a sufficiently high center-of-mass energy to produce polarized, multi-GeV gamma rays from unpolarized electrons via inverse Compton scattering. Here we propose a scheme where the optical LASER photons are first "accelerated" to the extreme ultraviolet in a beam-driven plasma wakefield, then reflected by a plasma mirror back onto a trailing electron beam, producing a flash of gamma rays. Numerical simulations demonstrate this light source can achieve a high peak-brilliance (10^25 photons/s mm^2 mrad^2 0.1% BW) and a high degree of circular (95 %) or linear (77 %) POLARIZATION at multi-GeV photon energies, paving the way for the production of spin-polarized positrons and tests of light-by-light scattering.