Current date: 2026-07-29
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Number of records retrieved: 797
Keyword score statistics
score 12 -- 1 abstracts
score 10 -- 1 abstracts
score 7 -- 3 abstracts
score 6 -- 2 abstracts
score 4 -- 5 abstracts
score 3 -- 10 abstracts
score 2 -- 21 abstracts
in total -- 43 abstracts
Articles that appeared on 2026-07-29
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[abstract 1 / 43] Wow! (score: 12)
- Title: A Possible Short-Timescale Optical Quasi-Periodic Oscillation in PKS\,0805$-$07 from High-Cadence TESS ObservationsAuthors: Sikandar Akbar, Zahir Shah, Athar A. Dar, Naseer Iqbal,Comments: Published in JHEAPSubjects: astro-ph.HECreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
We present a timing analysis of the high-cadence optical light curve of the high-redshift flat-spectrum radio QUASAR PKS\,0805$-$07 obtained during \textit{TESS} Sector~34 (MJD~=~59230.90--59239.90). We search for short-timescale quasi-periodic oscillations (QPOs) using complementary time-series techniques, including the Lomb--Scargle periodogram (LSP) and the weighted wavelet $Z$-transform (WWZ), and evaluate their significance against red-noise variability using Monte Carlo simulations. The LSP reveals a dominant modulation at $f \approx 0.6\,\mathrm{d^{-1}}$ ($P \approx 1.7$\,d) exceeding the $99.99\%$ confidence level, while the WWZ independently recovers a consistent timescale at the $\sim$99.9\% level and shows that the signal is temporally localized rather than persistent. The modulation spans $\sim$5 coherent cycles, indicating a transient feature. However, the significance only marginally exceeds the highest WWZ confidence threshold, and the limited number of cycles is insufficient for a firm confirmation. In a disk-based scenario, orbital motion of a hotspot near the innermost stable circular orbit implies a BLACK HOLE mass of $M_{\rm BH} \sim 7.2 \times 10^{8}\,M_\odot$, consistent with typical FSRQ values. Alternatively, MAGNETohydrodynamic kink instabilities in the RELATIVISTIC JET can naturally produce day-scale variability for standard BLAZAR parameters and account for its transient character. Compact SMBH binary and tidal disruption event scenarios are disfavoured by the JET-dominated nature of the source, the optical rather than X-ray character of the modulation, and a BLACK HOLE mass well above that of confirmed QPE hosts. The candidate modulation is consistent with a compact, short-lived structure embedded within stochastic JET variability, and high-cadence multiwavelength monitoring will be essential to confirm its recurrence and constrain its physical origin.
[abstract 2 / 43] Wow! (score: 10) - Title: From compact JETs to extended lobes: radio morphologies of distant QUASARs at z > 4Authors: K. É. Gabányi, M. Kunert-Bajraszewska, A. Krauze, S. Frey, M. Krezinger, Z. Paragi, H. Cao, T. An, L. I. Gurvits, K. Perger, T. Sbarrato, K. Rozgonyi,Comments: 17 pages, 11 figures, accepted for publication in Astronomy and AstrophysicsSubjects: astro-ph.GACreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
High-redshift QUASARs play an essential role in studying the growth and evolution of supermassive BLACK HOLEs and ACTIVE GALACTIC NUCLEi (AGN). Radio-loud QUASARs additionally enable us to investigate the interactions between the JETs and their environment. We aimed to reveal the radio morphology of three radio QUASARs at redshifts z>4 that contain milliarcsecond (mas) scale compact radio features according to previous very long baseline interferometry (VLBI) observations, but show significant flux density at arcsecond scales, indicating the presence of extended radio structure that cannot be sampled by the highest-resolution observations. We analysed radio interferometric data obtained at various angular resolutions and multiple frequencies, including observations made by the international Low-Frequency Array and the enhanced Multi-Element Remotely-Linked Interferometer Network. We also re-imaged archival European VLBI Network observations of our targets. Two QUASARs (J0813+3508 and J1231+3816) exhibit complex radio structures with hotspots, extended to tens of kpc. They resemble Fanaroff--Riley II-type RADIO GALAXies with extremely bent JET morphology. The third object (J1548+3335) shows a one-sided structure of $\lesssim 10$ kpc size. There was no sign of RELATIVISTIC boosting at its previous mas-scale resolution radio observations. Its radio power and (inferred) linear size derived from the lower-resolution observations are similar to the known high-power compact steep-spectrum sources. We found that the previously detected mas-scale compact radio features are related to the centres of the AGN or in one case to one of the hotspots in an extended lobe.
[abstract 3 / 43] Wow! (score: 7) - Title: On Lorentz Variability of Magnetically Dominated Relativistic OutflowsAuthors: V. I. Berezhiani, N. L. Shatashvili, A. G. Tevzadze,Comments: 16 pages, 2 figures. Accepted for publication in Physica ScriptaSubjects: astro-ph.HE physics.plasm-phCreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
We show that MAGNETized RELATIVISTIC outflows can exhibit a RELATIVISTIC effect in which Lorentz transformation maps spatially extended MAGNETic field structure into apparent temporal variability in the observer's frame. Using a force-free Beltrami configurations as representative equilibria of MAGNETically dominated outflows, we demonstrate that Lorentz mapping of stationary helical MAGNETic field produces quasi-periodic modulation of observable electroMAGNETic signatures, without invoking intrinsic plasma variability. The same mechanism naturally generates temporal evolution of the observed POLARIZATION properties, producing smooth, generally aperiodic POLARIZATION-angle swings in the observer's frame. This effect may be described as an aberration of force-free MAGNETic fields under Lorentz transformation. The characteristic frequency of the time variability is determined by the helical wave-number of the MAGNETic field, the viewing angle, and the bulk Lorentz factor of the JET outflow, and scales linearly with $Γ$. This establishes a purely kinematic RELATIVISTIC origin of variability and introduces the concept of MAGNETic Lorentz seismology: the inference of MAGNETic field structure in RELATIVISTIC outflows directly from observed temporal variability.
[abstract 4 / 43] Wow! (score: 7) - Title: Time-dependent photospheric radiative transfer in structured GRB JETs: spectral evolution and POLARIZATION diagnosticsAuthors: Yue Xu, Ming Jin, Qingwen Tang,Comments: Published in The Astrophysical Journal; revised to match the published versionSubjects: astro-ph.HECreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Photospheric emission from RELATIVISTIC GAMMA-RAY BURST (GRB) JETs is a promising mechanism for producing the Band-like spectra observed in the prompt phase, yet the connections between JET structure, dissipation location, and POLARIZATION signatures remain unclear.We investigate time-dependent photospheric radiation transfer in structured RELATIVISTIC JETs by coupling two-dimensional axisymmetric special RELATIVISTIC hydrodynamic (SRHD) simulations with Monte Carlo photon propagation.Photon escape and subphotospheric dissipation are characterized using the residual line-of-sight optical depth tau_out evaluated along each photon trajectory, allowing a direction-dependent treatment of photon decoupling in structured JETs. The radiative transfer includes Klein-Nishina Compton scattering and POLARIZATION evolution using the Mueller matrix formalism.We perform a systematic parameter study exploring the effects of viewing angle, electron-positron pair loading (Zpm), and the optical-depth window of subphotospheric dissipation. The model produces time-resolved spectra, peak-energy evolution Epk(t), Band parameters, POLARIZATION degree Pi(E,t), and last-scattering statistics.We find that JET angular structure and the geometry of the line-of-sight optical depth strongly regulate spectral evolution and POLARIZATION signatures. The dissipation depth and pair loading jointly control the stability of Epk, the formation of high-energy spectral tails, and the energy dependence of POLARIZATION. These results provide quantitative predictions for GRB prompt-emission spectra and POLARIZATION that can be tested with current and upcoming high-energy polarimeters.
[abstract 5 / 43] Wow! (score: 7) - Title: Observational Tests of Sgr A*'s State of the Accretion FlowAuthors: F. Yusef-Zadeh, R. G. Arendt, H. Bushouse, C. J. Chandler, D. Kunneriath, S. M. Ressler, M. Wardle,Comments: 5 pages, one figure, Traversing the Galactic Center in Space and Time, Proceedings IAU Symposium No. 405, M. Zajacek, T. Jerabkova, V. Karas, R. Schodel & P. Sukova, edsSubjects: astro-ph.GACreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
General RELATIVISTIC MAGNETo-hydrodynamic (GRMHD) simulations of the possibly MAGNETically arrested disk (MAD) of the accretion flow of Sgr A* predict short and long time variability, lumpiness in the flow, strong MAGNETic fields, RECONNECTion driving flux eruptions and a JET aligned with its spin angular momentum. We carried out simultaneous multi-wavelength observations with the objective of placing some constraints on these predictions. Our analysis supports most of the predictions of the MAD picture of the flow. It is not clear if there is evidence for a JET, but this could be the result of confusion in the complex region surrounding Sgr A*. Also, the geometry of the MAGNETic fields, which accelerate particles to produce X-ray emission via inverse Compton Scattering (ICS), appears to be consistent with a hybrid state where the accretion flow is represented by MAD-like MAGNETic field strength and with Standard and Normal Evolution-like (SANE-like) MAGNETic field geometry.
[abstract 6 / 43] Yes (score: 6) - Title: The afterglow of GAMMA-RAY BURST - SUPERNOVA connectionsAuthors: Marco Muccino, Rahim Moradi, Yu Wang,Comments: 8 pages, 3 figures, 1 tableSubjects: astro-ph.HECreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
The X-ray afterglow of several long GAMMA-RAY BURSTs (LGRBs) associated with broad line type Ib/c SUPERNOVAe (SNe) exhibits a standard non-thermal afterglow, commonly attributed to SYNCHROTRON emission from a RELATIVISTIC JET, and an evolving thermal component whose physical origin is still debated. We investigate whether these thermal and non-thermal components can be described within a common analytical framework and whether their temporal evolution can provide insight into the physical connection between RELATIVISTIC JETs and SN ejecta. We combine a phenomenological description of the SYNCHROTRON emission of the non-thermal energy associated with the RELATIVISTIC JET with a diffusion model describing the thermal evolution of the JET-affected portion of the SN ejecta. The resulting coupled system is solved analytically, leading to closed-form expressions for both non-thermal and thermal luminosities. We apply the model to the following systems: GRB 060218A/SN 2006aj and GRB 171205A/SN 2017iuk. The proposed formalism reproduces the main features of both thermal and non-thermal light curves. In both systems, the thermal luminosity follows a temporal evolution similar to that of the non-thermal component up to the plateau phase. The inferred thermal energy stored in the JET-affected ejecta is found to be a fraction of the energy coupled to the observed non-thermal emission. The characteristic timescales obtained from the fits suggest a direct link between the evolution of the JET and the thermal response of the expanding ejecta. Although simplified, the proposed framework provides a unified analytical description of LGRB afterglows and their thermal counterparts and offers a useful tool for investigating the physical connection between RELATIVISTIC JETs and SNe Ib/c.
[abstract 7 / 43] Yes (score: 6) - Title: Compiling the largest multiwavelength database of known changing-look AGN: Prospects in the Rubin eraAuthors: Mariangella Camus, Swayamtrupta Panda,Comments: 24 pages, 13 figures, 7 tables; submitted to AAS journals. The online database hosting the CL-AGN dataset can be accessed at: https://swayamtrupta.github.io/clagn-catalog-public/Subjects: astro-ph.GA astro-ph.HECreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Changing-look ACTIVE GALACTIC NUCLEi (CL-AGN) provide a direct way to study accretion and spectral-state changes on timescales of months to years. Still, the known population remains scattered across heterogeneous literature samples. We present a compilation of a homogenized catalog of known CL-AGN and related candidates, designed as a traceable reference database for time-domain and multiwavelength studies. After coordinate homogenization, duplicate removal, and validation, the optical parent catalog contains 1,438 unique sources, including 987 spectroscopically confirmed CL-AGN and 451 candidate or photometrically selected systems. We augment the catalog with ancillary information from radio/mm, infrared, ultraviolet, X-ray, and gamma-ray data sets using nway and survey-specific quality criteria. The resulting database includes 188 sources in the broad radio layer, 9 RFC/VLBI compact-core matches, 16 sources with ALMA archival coverage, 1,353 infrared counterparts, 918 GALEX ultraviolet matches, and 576 X-ray counterparts. We also identify 9 FERMI-LAT candidate associations. Overall, 1,385 sources have at least one non-optical counterpart, and 75 have coverage across the four main ancillary regimes: radio, infrared, ultraviolet, and X-ray. As a first application, we identify 70 confirmed CL-AGN within the LSST Wide--Fast--Deep footprint and 5 within the Rubin Deep Drilling Fields, and provide the up-to-date, ~116-day ugrizy Rubin lightcurve for SDSS J095902.76+021906.3 (z=0.34579) and discuss the early data inferences. This catalog is envisioned to be community-driven and provides a dynamic, expandable resource for target selection, population comparisons, and future Rubin-era CL-AGN studies.
[abstract 8 / 43] Yes (score: 4) - Title: Vigorous turbulence driven by QUASAR-mode feedback in a cluster coreAuthors: Satoshi Yamada, Shutaro Ueda, Hirofumi Noda, Yutaka Fujita, Misaki Mizumoto, Kentaro Nagamine, Claudio Ricci, Shoji Ogawa, Taiki Kawamuro, Shinya Yamada, Yuichi Terashima, Yoshihiro Ueda,Comments: 29 pages, 9 figures. Published in Nature Astronomy. https://www.nature.com/articles/s41550-026-02939-xSubjects: astro-ph.GA astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
Quasars are among the most luminous objects. They are powered by accretion onto supermassive BLACK HOLEs. They are thought to impact cosmological evolution primarily through energetic winds, known as QUASAR-mode feedback, yet the efficiency and spatial extent of this process remain poorly constrained. Here we present X-Ray Imaging and Spectroscopy Mission (XRISM) observations of H1821+643---the nearest galaxy cluster with a central QUASAR (redshift z = 0.297)---which was a rare opportunity to directly probe QUASAR-mode feedback in the intracluster medium. High-resolution spectroscopy reveals exceptionally broadened Fe XXV emission lines from the intracluster medium, with a velocity dispersion of approximately 300 km/s, far exceeding values observed in nearby cluster cores. These lines originate predominantly at radii of 20-100 kpc from the centre. Assuming that turbulence from a QUASAR-driven shock led to the broadening of the lines, the energy injected by the QUASAR beyond galactic scales ($\gtrsim$20 kpc) is estimated to be $\gtrsim$1-10% of its radiative energy. Notably, this feedback efficiency exceeds previous multiwavelength estimates by orders of magnitude ($\lesssim$0.01%) and reaches the levels required by the latest cosmological hydrodynamical simulations. This finding of vigorous turbulence indicates that QUASAR-mode feedback plays a central role in regulating galaxy and cluster evolution at high redshift.
[abstract 9 / 43] Yes (score: 4) - Title: How massive and clumpy must a QUASAR wind be to create emission line blueshifts?Authors: James H. Matthews,Comments: 12 pages, 6 figures, accepted to MNRASSubjects: astro-ph.GA astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
Blue asymmetries (``Blueshifts'') in the C IV 1550A emission line are common in luminous QUASARs. If they are formed in winds, how much energy, momentum and mass do those winds transport? We address this question by considering how much mass must be supplied through the line-forming region to maintain a given density and ionization state. Using a combination of 1D analytic and 2D numerical models, we find that for blueshifted C IV lines to form in a wind, the wind must have mass outflow rates of $\sim 50 f_V$ times the accretion rate, where $f_V \leq 1$ is the volume filling factor accounting for clumping. Our results therefore disfavour line formation in a smooth disc wind and point towards one of two scenarios: either the wind is clumpy, with required clumping factors suggestively close to those in hot star winds; alternatively, if the mass is instead swept up from the ambient medium, the wind need not be clumpy and MHD and radiative winds can provide the original source of momentum and energy. The power of the outflow depends on the square of the terminal velocity of the flow, $v_\infty$. If the wind is also the BAL outflow, with $v_\infty \sim10,000~{\rm km~s}^{-1}$, the wind power is significant and important for feedback. There are various caveats which moderate our conclusions, motivating i) a better theoretical understanding of wind driving and clump formation physics and ii) improved observational constraints on the physical conditions where the lines are formed.
[abstract 10 / 43] Yes (score: 4) - Title: A Systematic Study of Quiescent and Outburst Properties of X-ray-bright Young Stellar Objects Using XMM-NewtonAuthors: Koki Sakuta, Ikuyuki Mitsuishi, Seiya Sasamata, Daigo Nonaka, Mai Yamashita, Shin Toriumi, Takato Tokuno, Yohko Tsuboi, Hiroshi Kobayashi,Comments: Accepted for publication in Astronomy & Astrophysics. 15 pages, 4 figures, 5 tablesSubjects: astro-ph.SRCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Young Stellar Objects (YSOs) exhibit strong X-ray emission, widely attributed to MAGNETic RECONNECTion and MAGNETospheric accretion; however, owing primarily to limited photon statistics, observational tests of these mechanisms have often relied on simplified analyses, leaving room for more precise constraints on their emission processes. We aim to derive the X-ray properties of X-ray-bright YSOs selected from multiple star clusters and investigate their emission mechanisms through an approach from multiple perspectives based on timing and spectroscopic analysis. We performed a systematic search of XMM-Newton archival observations and constructed a sample of 51 X-ray-bright YSOs for timing and spectroscopic analyses. We identified quiescent and outburst phases through timing analysis, performed phase-resolved multi-temperature spectroscopy. Multi-temperature plasma structures are detected in both quiescent and outburst emission. The relationships among the timing and spectral parameters are broadly consistent with a MAGNETic-RECONNECTion scenario. Comparison with Gaia DR3 stellar parameters suggests that MAGNETospheric accretion alone has difficulty explaining most of the fitted X-ray temperatures, although the coolest model components with $kT \lesssim 0.3$ keV may include an accretion-shock contribution. After separating these low-temperature components, the remaining quiescent components show a clearer positive correlation in the $EM$--$kT$ plane, with MAGNETic-loop lengths distributed around $10^{12}$ cm. Neupert-like behavior, the temporal evolution of temperature and emission measure, the Rossby-number activity relation, and positive correlations between quiescent and outburst properties all suggest that MAGNETic RECONNECTion plays a key role in both phases.
[abstract 11 / 43] Yes (score: 4) - Title: Timing and Spectral Analysis of the 2024 Outburst of 2S 1553$-$542 with NUSTAR and NICERAuthors: Haifan Zhu, Wei Wang, Wen Yang, Mariano Mendez, Chenxu Gao, Ziyi Xu, Pengfu Tian,Comments: 23 pages, 10 figures, and 3 tables. Accepted for publication in GalaxiesSubjects: astro-ph.HECreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
We report a timing and spectral study of the 2024 outburst of the Be/X-ray binary pulsar 2S~1553$-$542 using \textit{NUSTAR} and \textit{NICER} observations. From the \textit{NUSTAR} light curve we measure a pulse period of $9.285022\pm0.000001$~s. The energy-resolved pulse profiles are dominated by a single peak and show a wing-like structure most clearly in the $12$--$22$~keV band. The pulsed fraction remains above 60\% and increases with energy. The phase-averaged \textit{NUSTAR} spectrum is described by an absorbed blackbody plus cutoff power-law continuum, together with an iron emission line and a cyclotron absorption feature. Using the \texttt{cyclabs} model, we obtain a cyclotron energy of $E_{\rm cyc}\simeq24.1$~keV, corresponding to a MAGNETic field strength of $B\sim3\times10^{12}$~G. Phase-resolved spectroscopy shows that the continuum and cyclotron-line parameters vary with pulse phase, and that the line becomes poorly constrained around the pulse-wing phase. We also searched the short \textit{NICER} GTIs for transient mHz variability using wavelet analysis and a CEEMDAN-based Hilbert--Huang transform. Localized excesses near $\sim10$~mHz and $\sim20$~mHz are found, but the short exposures, COI effects, red-noise fluctuations, and the lack of a well-constrained Fourier peak limit their significance. We therefore treat them as candidate mHz variability rather than firm mHz QPO detections.
[abstract 12 / 43] Yes (score: 4) - Title: QuickGWecc: Fast Bayesian pipeline for searching eccentric binaries in pulsar timing array dataAuthors: Lankeswar Dey, Bence Bécsy, Abhimanyu Susobhanan, Maria Charisi,Comments: 12 pages, 4 figures, 2 tablesSubjects: astro-ph.HE astro-ph.IMCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Recent pulsar timing array (PTA) results have provided evidence for the presence of a nanohertz gravitational wave (GW) background, most likely originating from a population of supermassive BLACK HOLE binaries (SMBHBs). The next major milestone is the detection of continuous GWs (CGWs) from an individual SMBHB and the identification of its electroMAGNETic counterpart. Typically, searches for CGWs in PTA data assume binaries in circular orbits. However, theoretical studies indicate that binaries emitting GWs in the PTA frequency band may retain significant eccentricity. In this paper, we present a fast and efficient Bayesian pipeline to search for CGWs from individual SMBHBs in RELATIVISTIC eccentric orbits in PTA datasets. Our approach extends the QuickCW framework for circular binaries, in which model parameters are divided into projection and shape parameters. Computational efficiency is achieved by performing many updates of the projection parameters for a fixed set of shape parameters, an operation that is orders of magnitude faster than updating the shape parameters. We validate the pipeline through both detection and upper-limit analyses of simulated PTA datasets. This framework makes the search for eccentric SMBHBs computationally feasible, even in the next-generation PTA datasets with many more pulsars.
[abstract 13 / 43] (score: 3) - Title: Characteristic Decomposition for Relativistic Numerical Simulations: I. HydrodynamicsAuthors: Saul A. Teukolsky,Comments: 20 pages Slightly updated to agree with published versionSubjects: gr-qc astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
The characteristic decomposition for GRMHD is not known in a form useful for current numerical simulations. This prevents us from using the most accurate known computational methods, such as full-wave Riemann solvers. In this paper, we present a new method of finding decompositions. The method is based on transformations from the comoving frame, where the fluid flow is simplest and the decomposition has been known for a long time. The key innovation we introduce is that of quasi-invertible transformations. In this first paper, we introduce these transformations using the simpler example of RELATIVISTIC hydrodynamics. We recover the known decomposition for RELATIVISTIC hydrodynamics in somewhat simpler form than previously derived, and without the need for computer algebra. A new result in this paper is the characteristic decomposition when the the evolution tracks the composition of a fluid in nuclear statistical equilibrium. In Paper II of this series, we apply a quasi-invertible transformation to derive the complete characteristic decomposition for GRMHD in the conserved variables used in simulations.
[abstract 14 / 43] (score: 3) - Title: Intrinsic Nonlocality of Spin- and Polarization-Resolved Probabilities in Strong-Field Quantum ElectrodynamicsAuthors: Samuele Montefiori, Antonino Di Piazza, Tobias Podszus, Christoph H. Keitel, Matteo Tamburini,Comments: 31 pages, 9 figuresSubjects: hep-ph astro-ph.HE physics.plasm-phCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Spin and POLARIZATION are central to precision tests of fundamental physics and for interpreting radiation from astrophysical sources and ultraintense LASER-matter experiments. Here, focusing on the fundamental process of nonlinear Compton scattering, we demonstrate that a key assumption underlying current strong-field quantum electrodynamics (SFQED) models, i.e., that emission can be treated as an instantaneous random event sampled from a local differential rate, is inconsistent once emission angles, electron spin, and/or photon POLARIZATION are resolved. Namely, even in strictly constant and uniform fields, the resulting fully differential distribution is sign-indefinite, yielding negative inferred probabilities. The physical reason is that the photon emission probability builds up over a finite length of the electron trajectory, the formation region, during which the electron direction changes by roughly the same small angle that defines the radiation cone. Therefore, we put forward a new method where we integrate over this formation region analytically to obtain a physically consistent electron spin and photon POLARIZATION model. Simulations of a GeV-class electron-LASER collision accessible at current petawatt facilities and of emission in a pulsar-like MAGNETic field are shown to reveal spin and POLARIZATION patterns that differ even qualitatively from state-of-the-art local models. In particular, our new model predicts substantial angle-dependent circular photon POLARIZATION where the well-known collinear-emission approach yields none, and a pronounced helicity bias in the recoiling electrons absent from current predictions. These findings have direct implications for upcoming strong-field QED experiments and for interpreting polarized radiation from extreme astrophysical environments.
[abstract 15 / 43] (score: 3) - Title: Ion Weibel Instability in the hybrid framework: the optimal resolutionAuthors: Luca Orusa, Taiki Jikei,Comments: 9 pages, 5 figures. Few comments and simulations added, results unchanged. Matches version published by PoPSubjects: physics.plasm-ph astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
The study of collisionless shocks and their role in cosmic-ray acceleration has gained increasing importance through both observations and simulations. Accurately modeling the shock transition region, where particle injection occurs, requires a proper description of the microinstabilities governing its structure. In high-Mach-number shocks, such as those associated with SUPERNOVA remnants, the ion Weibel instability is believed to provide the dominant dissipation mechanism. In this work, we investigate the ion Weibel instability driven by counterstreaming beams in the presence of an external perpendicular MAGNETic field. We employ hybrid simulations, in which ions are treated kinetically while electrons are modeled as a charge-neutralizing fluid. Although hybrid models are widely employed to study collisionless shocks, the resolution requirements needed to accurately capture ion-scale instabilities remain poorly understood. We address this issue by developing a linear theory of the ion Weibel instability tailored to the massless electron assumption of hybrid models and validating it with one- and two-dimensional simulations over a wide range of Alfvénic Mach numbers. We show that hybrid simulations can reliably reproduce the growth, saturation, and POLARIZATION of Weibel-generated MAGNETic fields in weakly MAGNETized regimes, provided that the relevant ion-scale modes are properly resolved. From the scaling of the dominant mode, we derive a minimum spatial resolution required as a function of Alfvénic Mach number. We also demonstrate that excessive resolution introduces unphysical small-scale whistler modes inherent to the massless-electron approximation. We validate the analysis by comparing the results with full particle-in-cell simulations. Together, these results provide practical guidance for hybrid simulations of collisionless shocks and beam-driven plasma systems.
[abstract 16 / 43] (score: 3) - Title: XMAGNET -- Stir before serving: a Lagrangian perspective on mixing-driven condensation in the intracluster mediumAuthors: M. Fournier, P. Grete, M. Brüggen, B. W. O'Shea, G. M. Voit, B. D. Wibking, D. Prasad,Comments: 16 pages, 18 figures, accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
We aim to characterize the thermodynamic and dynamical conditions leading to condensation in cluster cores, and to assess the role of MAGNETic fields. We implement a Monte-Carlo tracer particle algorithm in the GPU-accelerated code AthenaPK, and run a purely hydrodynamical and a MAGNETohydrodynamical (MHD) simulations of an idealized cool-core cluster. We identify the subset of hot ICM tracers that undergo a transition to the cold phase and reconstruct their histories over a lookback time of $300\,\mathrm{Myr}$ prior to condensation. In both runs, the large majority of tracers transitioning to the cold phase follow a thermodynamic pathway driven by mixing, whereby hot ambient gas is entrained onto low-entropy seed clumps that subsequently grow into larger clouds and filaments. In the hydrodynamical run, these seeds form mainly via in-situ cooling at the edges of AGN cavities. In the MHD run, the cold gas cycle is more complex: AGN outflows occasionally shred portions of existing filaments into fragments which are then uplifted, seeding further condensation. In the MHD run, the properties of condensing tracers begin to diverge from the background ICM significantly earlier than in the hydrodynamical run (${\sim}150\,\rm Myr$ before the cooling transition versus ${\sim}30\,\rm Myr$), with vorticity and MAGNETic energy growing together. The turbulent Mach number at condensation is also systematically lower than in the hydrodynamical run. We examine the post-condensation evolution of individual cold structures in the MHD run, namely a massive core filament and two isolated clouds in quiescent regions. We find that MAGNETic tension dominates over ram pressure as the primary drag force, significantly reducing the clouds' terminal velocity. Our results demonstrate that MAGNETic fields substantially impact the assembly history and kinematic properties of the cold phase in cool-core clusters.
[abstract 17 / 43] (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: Main text(+ Appendix): 15(19) pages, 7(9) figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
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 / 43] (score: 3) - Title: Tidal deformation of an accreting compact objectAuthors: Avijit Chowdhury, Chiranjeeb Singha, Kazuharu Bamba, Sumanta Chakraborty,Comments: 18 pages, 7 figures, 1 tableSubjects: gr-qc astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
Tidal deformation of a compact object serves as a sensitive probe of the strong-gravity regime and nature of the compact object. It captures how a compact object responds to the external perturbing field of a companion. In realistic astrophysical settings, compact objects are typically immersed in matter-rich environments, which can significantly alter the response. In this work, we investigate the static deformability of Schwarzschild-like exotic compact objects (ECOs) embedded in a quasi-stationary, self-gravitating thin accretion disk. By modelling the external spacetime with a RELATIVISTIC thin-disk solution, we isolate environmental contributions to the scalar and spin-1 response while maintaining analytical control. We show that, for perfectly reflecting ECOs, the characteristic logarithmic dependence of the scalar and spin-1 response on compactness, set by near-horizon physics, remains intact even in the presence of accretion. The disk primarily amplifies the overall magnitude of the response significantly. These findings highlight that environmental effects can seriously impact tidal signatures, while still permitting, under suitable conditions, the distinguishability of horizonless compact objects from BLACK HOLEs in gravitational-wave observations.
[abstract 19 / 43] (score: 3) - Title: A radio view on Gamma-Loud Protostars: Derivation of JET mechanical luminosityAuthors: Javier Méndez-Gallego, Carlos Carrasco-González, Rubén López-Coto, Iván Agudo, Stefano Menchiari, Rubén Fedriani, Emma de Oña Wilhelmi, Guillem Anglada,Comments: 6 pages, 5 figures. Submitted to arxiv. Comments are welcomeSubjects: astro-ph.HE astro-ph.SRCreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
Context. Gamma-Loud Protostars (GLPs) have been recently reported as Galactic hadronic accelerators whose acceleration site is situated in their protostellar JETs. Theoretical and observational analysis situate radio cm luminosity as a thermal tracer of JET activity, presenting an unique opportunity to study JET properties as accelerators. Aims. We aim to develop a way to estimate the kinetic power of protostellar JETs and compare their energetics with those extracted from the non-thermal gamma-ray side of GLPs. Methods. We combine theoretical and phenomenological relations to estimate the JET mechanical luminosity based on the radio cm luminosity. We relate the resulting values to the non-thermal contribution of GLPs, studying its behaviour and efficiency. Results. The derivation of the JET power successfully reproduces infrared and radio observations. The cosmic-ray energy correlates to the injected mechanical energy, implying an acceleration efficiency of 1--10%. Future radio observations are needed to find the definite accelerators and obtain reliable efficiencies.
[abstract 20 / 43] (score: 3) - Title: Extracting Energy from a Non-Kerr Rotating Spacetime with an Anomalous Quadrupole Moment via Magnetic ReconnectionAuthors: Ke Wang, Xiao-Xiong Zeng,Comments:Subjects: gr-qcCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
This paper investigates how to extract energy from a non-Kerr rotating spacetime with an anomalous quadrupole moment via the MAGNETic RECONNECTion mechanism. Unlike many other rotating spacetimes, this spacetime possesses closed timelike curves, and the corresponding spacetime regions must be excluded when extracting energy. After introducing the event horizon, ergosphere, and closed timelike curves of this spacetime, we deeply analyze the energy per unit enthalpy at infinity for accelerated and decelerated plasmas, the allowed region for energy extraction, and the power and efficiency of energy extraction. The results show that energy extraction is possible for both positive and negative anomalous quadrupole moments, but a positive and small anomalous quadrupole moment corresponds to higher power and efficiency of energy extraction.
[abstract 21 / 43] (score: 3) - Title: Exploring if a coronal dimming event can produce coronal hole-like propertiesAuthors: Adriana De-Sassi, Louise Harra, Krzysztof Barczynski, David H. Brooks, Lakshmi Pradeep Chitta, Ioannis Kontogiannis, Säm Krucker, Cristina H. Mandrini, Eric Priest, Alphonse C. Sterling, Yingjie Zhu,Comments: Accepted for publication in Astronomy & Astrophysics (A&A)Subjects: astro-ph.SRCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Coronal dimmings, or transient coronal holes, are manifested as a sudden reduction in extreme ultraviolet (EUV) and X-ray emission, often following solar eruptions. We investigate whether a dimming event can produce coronal hole-like plasma characteristics by comparing imaging and spectroscopic observations from Solar Orbiter, Hinode, IRIS, and SDO prior and during the dimming. The SDO/AIA 193 Å emission intensity in the dimming region was reduced to the same level as the neighbouring coronal hole within 11 hours. The Doppler velocity measured with Fe XII (corona) decreased from $-0.34^{+0.37}_{-0.27}$ km/s towards a predominant upflow of $-3.2^{+0.4}_{-0.6}$ km/s. The first ionisation potential (FIP) bias was reduced towards photospheric values. We found an increase in the number of automatically detected EUV brightenings near the dimming boundary in SDO/AIA 193 Å which could be a sign of MAGNETic RECONNECTion. In the cooler SDO/AIA 171 Å or Solar Orbiter HRI_EUV 174 Å channel, we did not observe such an increase. Coronal bright points (CBPs) appeared relatively unaffected by the formation of the dimming. The Mg II $k_3$ (chromosphere) Doppler velocities were unchanged, except for a small reduction in the dimming upflows in areas with weak MAGNETic fields ($<20$ G). We find that the dimming only shows partial coronal hole-like properties; specifically, in the coronal emission lines and at temperatures of $>1$ MK. We suggest that this is due to the dimming resulting from plasma depletion only at higher altitudes. Since the CBPs were not significantly impacted by the dimming, we used their MAGNETic loop heights ($\sim 10$ Mm) as the lower limit to the dimming height. Our findings provide new insights into the atmospheric structure of coronal dimmings.
[abstract 22 / 43] (score: 3) - Title: A new look at old devils. II: New insights on classical RADIO GALAXies from MeerKAT and uGMRTAuthors: Portia P. Legodi, Tiziana Venturi, Dharam V. Lal, Bernie Fanaroff, Oleg M. Smirnov, Simona Giacintucci,Comments: 19 pages, 7 figures, 4 tablesSubjects: astro-ph.GACreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
This paper presents a detailed morphological and spectral analysis of a sample of ten RADIO GALAXies observed with the MeerKAT in L-band ($856\, \text{-}\,1712\ \mathrm{MHz}$) and the upgraded Giant Metrewave Radio Telescope in Band-4 ($550\,\text{-}\,850\ \mathrm{MHz}$). Our main goals are to revisit the current classification scheme for classical RADIO GALAXies and study the properties of new radio features in JETs, lobes and hot spots, which are becoming increasingly numerous due to the sensitivity and imaging capabilities of current radio interferometers, and suggest previous unexplored interaction mechanisms between the radio plasma and the external medium. The sample from the 4C catalogue includes FR I, FR II, wide-angle and narrow-angle tailed sources as well as FR 0 RADIO GALAXies from FR0CAT, with redshifts ranging from $0.04\,\text{-}\,0.20$. The high angular resolution, $\sim4^{\prime\prime}\text{-}10^{\prime\prime}$ total intensity images are presented, revealing complex structures in the JETs, lobes and hotspots of these sources. The integrated spectra of the sources, constructed using flux density measurements from our observations and archival data, reveal spectral breaks and slopes indicative of radiative ageing, with ages spanning $\sim40\,\text{-}\,242\ \mathrm{Myr}$. While the sample broadly confirms the classical FR classification as a useful first-order scheme, the substructures within the radio emission of sources highlight the need for models that incorporate environmental complexity and episodic JET activity to fully describe radio-galaxy evolution.
[abstract 23 / 43] (score: 2) - Title: Rotating Black Holes in a Viable Lorentz-Violating Gravity: Finding Exact Solutions Without TearsAuthors: Deniz O. Devecioglu, Mu-In Park,Comments: Bugs in equation numbers corrected to match the published version in EPJCSubjects: hep-th gr-qcCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
We introduce a two-step procedure for finding Kerr-type rotating BLACK HOLE solutions without tears. Considering the low-energy sector of Horava gravity as a viable Lorentz-violating gravity in four dimensions which admits a different speed of gravity, we find the exact rotating BLACK HOLE solutions (with or without cosmological constant). We find that the singular region extends to r < 0 region from the ring singularity at r = 0 in Boyer-Lindquist coordinates. There are two Killing horizons where g^rr = 0 and the BLACK HOLE thermodynamics laws are still valid. We find the rotating BLACK HOLE solutions with electroMAGNETic charges only when we consider the noble electroMAGNETic couplings, in such a way that the speed of light is the same as the speed of gravity. With the noble choice of couplings, our Lorentz-violating gravity can be consistent with the recently-observed time delay of the coincident GW and GRB signals. Furthermore, in Appendices, we show that (a) the uniqueness of the invariant line element ds^2 under Diff_F, contrary to LV action, (b) the solutions are the Petrov type I with four distinct principal null vectors, and (c) the Hamilton-Jacobi equation for the geodesic particles are not separable.
[abstract 24 / 43] (score: 2) - Title: Precision Joint Constraints on Cosmology and Gravity Using Strongly Lensed Gravitational Wave PopulationsAuthors: Xinguang Ying, Tao Yang,Comments: 8 pages, 5 figuresSubjects: gr-qc astro-ph.COCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
We present a Bayesian framework to jointly constrain the Hubble constant ($H_0$) and the post-Newtonian parameter ($γ$), a key indicator of deviations from general relativity, using the population characteristics of strongly lensed gravitational wave (GW) events from binary BLACK HOLE mergers. Our method extracts cosmological and gravitational information directly from the statistical properties of lensed GW populations, without relying on electroMAGNETic counterparts of the GW events, waveform modeling, and resolved stellar kinematics of the lens galaxy. This establishes lensed GW statistics as a clean and independent probe of cosmic expansion and gravitational physics. Assuming a flat $Λ$CDM cosmology and simulating a GW population observed by the third-generation detector Einstein Telescope, we demonstrate that this method can achieve precision levels of $0.60\%\sim0.99\%$ for $H_0$ and $0.53\%\sim3.3\%$ for $γ$ with various priors of matter density, significantly outperforming existing joint constraints, which typically achieve $2\%$ precision on $H_0$ and $20\%$ precision on $γ$. These results highlight the potential of lensed GW population statistics as a robust and efficient tool for probing both the expansion history of the Universe and the nature of gravity.
[abstract 25 / 43] (score: 2) - Title: Black hole ringdown spectroscopy of curvature-coupled scalar and pseudoscalar fieldsAuthors: Adrian Ka-Wai Chung, Nicolás Yunes,Comments: Match the published versionSubjects: gr-qc astro-ph.HECreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Remnant BLACK HOLEs formed in compact binary coalescences provide a clean setting for probing additional fields coupled to gravity. By analyzing the ringdown signals of the loudest LIGO-Virgo-KAGRA binary-BLACK HOLE mergers, we search for massless curvature-coupled (pseudo)scalar fields arising in extensions to general relativity. We find no evidence for such fields and place 90\% credible upper limits on the coupling length scale, $\ell \lesssim (25$-$45)$ km, corresponding to scales significantly below the horizons of the remnant BLACK HOLEs. These results include the first gravitational-wave constraint on an axidilaton-type coupling. By isolating the ringdown phase and performing extensive robustness checks, our analysis provides a complementary observational probe to existing full-waveform constraints. As the gravitational-wave catalog expands, BLACK HOLE ringdown spectroscopy will enable increasingly sensitive probes of gravity and additional fields using astrophysical BLACK HOLEs.
[abstract 26 / 43] (score: 2) - Title: Characteristic Decomposition for Relativistic Numerical Simulations: II. MagnetohydrodynamicsAuthors: Saul A. Teukolsky,Comments: 21 pages Updated to match published version. Also fixed typos in first and third lines of Eq. 4.32Subjects: gr-qc astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
The characteristic decomposition for GRMHD in the comoving frame of the fluid has been known for a long time. However, it has not been known in the coordinate frame of the simulation and in terms of the conserved variables evolved in typical numerical simulations. This paper applies the method of quasi-invertible transformations developed in Paper I to derive this decomposition. Among other benefits, this will allow us to use the most accurate known computational methods, such as full-wave Riemann solvers. The results turn out to be simpler than expected based on earlier attempts.
[abstract 27 / 43] (score: 2) - Title: Systematic biases in parameter estimation on LISA binaries. II. The effect of excluding higher harmonics for spin-aligned, high-mass binariesAuthors: Sophia Yi, Francesco Iacovelli, Emanuele Berti, Rohit S. Chandramouli, Sylvain Marsat, Digvijay Wadekar, Nicolás Yunes,Comments: 22 pages, 15 figures, 1 table; revised to match published versionSubjects: gr-qc astro-ph.CO astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
The Laser Interferometer Space Antenna (LISA) will observe massive BLACK HOLE binaries (MBHBs) with astoundingly high signal-to-noise ratio, leaving parameter estimation with these signals susceptible to seemingly small waveform errors. Of particular concern for MBHBs are errors due to neglected higher-order modes. We extend Yi et al. [arXiv:2502.12237] to examine errors due to neglected higher-order modes for MBHBs with nonzero (aligned) progenitor spins and total mass up to $10^8\,M_\odot$. For these very massive systems, there can be regions of parameter space in which the $(\ell, |m|)=(2,\,2)$ modes are no longer dominant with respect to higher-order ones. We find that the extent of systematic bias can change significantly when varying the progenitor spins of the binary. We also find that for the heaviest, and therefore shortest, MBHB signals, slight systematic errors can cause severe misinference of the sky localization parameters. We propose an improved likelihood optimization scheme with respect to previous work as a way to predict these effects in a computationally efficient manner.
[abstract 28 / 43] (score: 2) - Title: Vortex breakdown in a hydro turbine draft tube swirling JETAuthors: Artur Gesla, Eunok Yim,Comments:Subjects: physics.flu-dynCreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
The swirling flow in a Francis type hydropower turbine is known to be susceptible to the formation of a large helical structure, commonly referred to as a vortex rope. This vortex rope can be interpreted as an unstable mode associated with vortex breakdown. This perspective is adopted here in a simplified laminar flow setting. The helical vortex rope mode is shown to bifurcate supercritically from an axisymmetric baseflow in a Hopf bifurcation within a turbine draft tube. When wall friction effects are neglected, a large recirculation region at the axis can form and a range of subcritical solutions is identified for a flow regime corresponding to partial load of the turbine. The existence of these subcritical solutions promotes the emergence of a hysteresis loop. We further describe a regular dynamics of a formation of recirculation bubble at the axis and its destruction due to the emergence of a helical vortex rope at its periphery. Increasing the axial flow discharge towards the regime corresponding to nominal turbine load leads to an unfolding of the steady solutions branch in a transcritical bifurcation. This bifurcation takes place at finite Reynolds number and complements existing evidence of transcritical bifurcation of the swirling JET flows, previously reported only in the inviscid limit.
[abstract 29 / 43] (score: 2) - Title: Radiation-pressure instability is an artifact of constant-$α$ closure. Implications for AGN disk tensionsAuthors: M. H. Naddaf, M. Ghasemnezhad, H. Ghanbarnejad, D. Hutsemékers, B. Czerny,Comments: 9 pages, 3 figures, accepted for publication in A&ASubjects: astro-ph.HE astro-ph.IMCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
The standard $α$-disk formalism parametrizes turbulent angular momentum transport through a dimensionless coefficient $α$, assumed to be spatially and thermodynamically invariant. While analytically convenient, this assumption leads to the well-known thermal and viscous instabilities in radiation-pressure dominated (RPD) regions. We show that this instability is not the consequence of radiation pressure, but is due to enforcing a constant $α$ across distinct thermodynamic regimes. Requiring the steady thin-disk (TD) to remain thermally stable and single-valued in the $\dot{M}$--$Σ$ plane yields a necessary condition on the stress response, expressed as $η_{\rm x} \equiv d\lnα_{\rm x}\,/\,d\ln X > 4/7$, where $X \equiv P_{\rm gas}/P_{\rm rad}$. The resulting viscosity law $α_{\rm x} \equiv α(X)$ emerges directly from the internal consistency of TD equations, without modifying the stress law or invoking any additional physics. $α_{\rm x}$ removes the RPD unstable branch. The disk structure becomes smooth and globally single-valued, with higher $Σ$ and $τ$ in the inner RPD disk, while preserving the standard effective-temperature profile. This increases thermal and inflow timescales, offering a natural route to accretion-state dependent variability without large-amplitude radiation-pressure limit cycles. It also motivates revisiting AGN disk tensions, including microlensing sizes and continuum reverberation lags with improved radiative-transfer modeling. The results show that the RPD instability, and possibly some associated AGN disk tensions, reflect an inconsistent viscosity closure.
[abstract 30 / 43] (score: 2) - Title: S301 and friends: Measuring the spin of Sgr A*Authors: T. Piran, P. Amaro-Seoane, B. Aytac, G. Bourdarot, A. Burkert, D. Calderon, J. Cuadra, F. Eisenhauer, R. Genzel, S. Gillessen, S. Joharle, F. Mang, T. Naab, T. Ott, H. B. Perets, D. C. Ribeiro, M. Sadun Bordoni, R. Sari,Comments:Subjects: astro-ph.GA astro-ph.HECreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
The discovery of S301 (GRAVITY Collaboration et al., 2026) with pericenter distance rp= 280rg and eccentricity e=0.9825, opens the prospect of measuring the spin parameter of Sgr A* through Lense--Thirring (LT) nodal precession. A major obstacle is Newtonian confusion: any non-spherical extended mass distribution can also induce nodal precession. We aim to separate the LT spin signal of S301 from the Newtonian nodal precession. We compare the secular Newtonian torque exerted by a disk or flattened mass distribution on the orbits of S301 and of the apocenter-matched reference stars S2, S55, and S38, using analytic estimates validated by numerical orbit-averaged torque calculations. For a disk or flattened distribution extending beyond the stellar pericenters, the secular Newtonian torque on a highly eccentric orbit is controlled mainly by the apocenter, whereas the LT signal is controlled mainly by the pericenter. Thus stars with apocenters comparable to S301's but much larger pericenters, in particular S2, but also S55, and S38, experience comparable Newtonian torques while having ~ 30 times smaller LT signals (for S2). Their measured precessions, or upper limits on them, can therefore calibrate the mass and orientation of the Newtonian background for subtraction from S301's precession. The Schwarzschild apsidal advance of S301 further rotates the orbit's pericenter relative to any disk, producing a systematic time dependence in the Newtonian contribution, while the LT signal remains fixed by the spin vector. Granularity of the perturber population sets a stochastic floor on this subtraction, which orbit- and star-averaging suppress. With continued GRAVITY+ astrometry and Extremely Large Telescope (ELT) spectroscopy, the in-plane spin projection may be within near-term reach; the full spin vector requires a much longer-term accumulation of the LT apsidal signal.
[abstract 31 / 43] (score: 2) - Title: Coupled GravitoelectroMAGNETic Response of a Magnetically Supported Generalized Hayward Black Hole in Nonlinear ElectrodynamicsAuthors: Anirudh Pradhan, K. Ghaderi, M. Zeyauddin, A. Gulhane,Comments:Subjects: gr-qcCreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
We construct the exterior coupled gravitational and electroMAGNETic response of a MAGNETically supported generalized Hayward BLACK HOLE within a specified nonlinear electrodynamic completion. Both parity sectors reduce to canonical two channel wave systems with explicit potentials and the correct Schwarzschild and effective Reissner--Nordström limits. We compute the quasinormal spectrum, metric and optical characteristics, extremal throat weights, quadrupolar wave conversion, finite bandwidth transfer, and coherent absorption eigenchannels while verifying exterior hyperbolicity and flux conservation. An effective charged operator captures the leading weak core geometry and mode mixing; after its subtraction, the residual hierarchy is consistent with cubic spectral corrections in the primarily electroMAGNETic branch and quartic corrections in the primarily gravitational branch and principal scattering observables. The fundamental quadrupolar branches become intrinsically linewidth separated near $χ\simeq0.70$, whereas parity splitting remains subleading. Metric and optical characteristic families separate monotonically toward extremality. At $χ=0.9$, positive parity reflected conversion reaches $45.8\%$ and remains $40.8\%$ after moderate bandwidth averaging, while coherent incident combinations yield $98.4\%$ bright and $1.3\%$ dark absorption. These independently evaluated observables provide mutually consistent diagnostics of the same nonlinear electrodynamic operator.
[abstract 32 / 43] (score: 2) - Title: Magnetic pressure anisotropy in ultra-dense white dwarfs: Landau quantization and neutronization effectsAuthors: Edson Otoniel, Juan M. Z. Pretel, Victor B. T. Alves, César O. V. Flores, Clésio E. Mota,Comments: 13 pages, 6 figures and 2 tablesSubjects: astro-ph.SR astro-ph.HE gr-qcCreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
Strong MAGNETic fields modify the thermodynamics of white dwarf (WD) matter by quantizing the transverse motion of degenerate electrons into Landau levels and splitting the pressure into components parallel and perpendicular to the MAGNETic field. We investigate how this microscopic pressure anisotropy affects ultra-dense WD sequences when Coulomb lattice contributions, electron capture thresholds, neutron drip limits, and nuclear composition are treated consistently in the equation of state (EoS). The stellar equilibrium structure is obtained by solving an anisotropic extension of the Tolman--Oppenheimer--Volkoff (TOV) equations, where $P_r = P_\parallel$ and $P_t = P_\perp$ denote the radial and tangential pressures, respectively. We compare the post-electron-capture branches with their corresponding pre-capture sequences for pure $^{12}\rm{C}$, $^{16}\rm{O}$, $^{20}\rm{Ne}$, and $^{24}\rm{Mg}$ compositions, as well as for fixed 50/50 C/O, Ne/O, and Mg/Ne mixtures. The EoS predicts $P_\perp < P_\parallel$ in density ranges where only a few Landau levels are occupied. Consequently, pressure anisotropy shifts the stellar sequences toward smaller radii, with only minor changes in the maximum masses. We also find that post-capture configurations cannot be interpreted from the mass--radius plane alone, since the corresponding $M(ρ_c)$ curves reveal unstable portions after the maximum mass is reached. Our results show that strong MAGNETic fields significantly reduce the radii of low-mass WDs, yielding better agreement with the observational data available in the Montreal White Dwarf Database and suggesting that future high-precision observations of massive MAGNETic WDs could help assess the role of MAGNETic pressure anisotropy in determining their masses and radii.
[abstract 33 / 43] (score: 2) - Title: Emergence and Detection of Electron-Scale Current Sheets in Turbulence with MMS Observations and fully kinetic 3D simulationsAuthors: Zachary Davis, Alexandros Chasepis, Colby Haggerty, Luca Comisso, Derek Sikorski,Comments:Subjects: physics.plasm-ph astro-ph.SRCreated: 2026-07-27; Updated: 2026-07-29; Datestamp: 2026-07-29
The solar wind is characterized by turbulence, where a cascade produces intermittent current structures called current sheets (CS) that efficiently dissipate energy into the plasma. These have been studied with in situ spacecraft observations, but single-spacecraft techniques such as the partial variance of increments (PVI) are inherently limited since they lack spatial context. A combined analysis of in situ observations and numerical simulations can provide significant insight into the properties of intermittent structures forming in heliospheric turbulence. Understanding the size and distribution of these structures is crucial in tracing the pathways of energy dissipation and particle energization in space plasma. Using 3D fully kinetic simulations of MAGNETized turbulence, we identify CS via machine learning and find a complex broken-power-law distribution for the CS widths, where the power-law breaks separate ion-scale CS from electron-scale CS. Electron-scale CS dominate, with widths peaking near $2d_e$. Comparing simulations with MMS data, we test PVI as a CS detector and show it can infer CS scale, though oblique crossings inflate inferred sizes. The prevalence of electron-scale sheets suggests they may contribute to plasma heating in aggregate.
[abstract 34 / 43] (score: 2) - Title: Statistical structure of canonical kinetic equilibrium with sheared flowAuthors: Daniel W Crews,Comments: 5 pages, 1 figure (3 panels)Subjects: physics.plasm-ph physics.space-phCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
In isothermal kinetic equilibrium of a plasma with sheared flow, the electrostatic potential is the cumulant generating function of the velocity distribution, encoding all non-Maxwellian statistics. Consequently, of the polynomial-form flux-function equilibrium flows, only the linear one is admissible, and every other equilibrium sheared flow has non-zero cumulants to all orders. The identity is shown for a sheared-flow screw pinch and specialized to the Z pinch, theta pinch, and Harris sheet. A simple sheared-flow Bennett pinch illustrates the principal results, namely weaker MAGNETization yields more non-Maxwellian features, and co- and counter-current flow shear have distinct statistics. The identity also yields a method for initializing kinetic simulations.
[abstract 35 / 43] (score: 2) - Title: Enhanced alpha channeling with spin-polarized fuelAuthors: J. F. Parisi, A. Diallo, J. W. S. Cook,Comments: 36 pages, 29 figuresSubjects: physics.plasm-phCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
The nuclear spin state of deuterium-tritium (D-T) fuel sets both the D-T fusion cross section and the emission direction of the fusion-born alphas and neutrons. We show two ways that spin-polarized fuel (SPF) could enhance alpha channeling, the wave-mediated damping of alpha power onto fuel ions rather than electrons, which is predicted to increase fusion power significantly. First, the enhanced SPF cross section produces more alphas, and second, the perpendicular (to the MAGNETic field) bias of the alphas' kinetic energy couples more efficiently to the perpendicular-resonant channeling waves. The birth anisotropy survives slowing-down and appears as a population inversion of the bulk alpha distribution over a broad region of velocity space, so resonant alphas can drive a suitably tuned channeling wave rather than damp it. Without channeling, SPF roughly doubles the fusion power density through the cross-section boost and its temperature feedback on the reactivity, a well-known result. Our velocity-space calculations find the channeling efficiency about 1.5 times higher for vector-aligned fuel than for unpolarized fuel, and channeling raises the fusion power enhancement to three or four times as the channeling efficiency improves, provided the waves do not depolarize the fuel. A transport model of an ARC-class equilibrium with stiff critical-gradient transport gives an enhancement of 2.2, rising to 3.4 for less stiff transport and to 4.7 in the zero-dimensional model when the critical gradients rise with the hotter ions. Channeling also transports helium quickly to the divertor: at fixed pumping the core helium fraction nearly halves, and a divertor pump several times less selective for helium supports the same core helium dilution. Spin-polarized fuel thus enhances fusion power through the anisotropic alpha distribution, beyond its increase of the reactivity.
[abstract 36 / 43] (score: 2) - Title: Polaris: a flexible stellarator demonstration experiment with simple modular coilsAuthors: Simon P. H. Vincent, Joaquim Loizu, Matthieu Toussaint, Rémy Jacquier, Jérémy Salm, Philippe Guittienne, Matias Habib, Idil Sonmez, Christopher B. Smiet, Erol Balkovic, Rogerio Jorge, Alan G. Goodman, Ivo Furno, Christian Moura, William Matthey-Dorey, Steve Couturier, Frédéric Dolizy,Comments:Subjects: physics.plasm-phCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
We present the design, construction, and first plasma experiments of Polaris, a new small-scale stellarator experiment (major radius R ~ 0.4 m) located at the Swiss Plasma Center. Polaris consists of a relatively large vacuum vessel (~0.5 m^3) predominantly made of glass windows and inside which different sets of MAGNETic coils can be installed. A first modular coil configuration has been designed with six identical, circular, water-cooled copper coils toroidally arranged in an optimal way so that they generate a large volume of MAGNETic surfaces and rotational transform in vacuum (iota ~ 0.3). The total current in each coil goes up to ~ 5 kA, producing a MAGNETic field on-axis of B ~ 0.03 T. An RF antenna specifically designed to operate in vacuum delivers up to 2.5 kW of power to produce plasma via inductive coupling and electron-impact ionization. We present the engineering solutions adopted for the design of Polaris and illustrate the great experimental flexibility it enables. Time-averaged values and fluctuations of plasma density, electron temperature, and floating potential are measured at various toroidal locations, providing insights into the plasma equilibrium, electrostatic turbulence, and associated transport. The glass vacuum chamber of Polaris additionally provides unprecedented optical access to the entire plasma volume. With its original, flexible design, Polaris is a 'stellarator fish-tank', allowing interchangeable coil sets and exploration of various MAGNETic configurations. Furthermore, its low-temperature, low-density, high-neutral-pressure plasmas are relevant to stellarator edge physics, making Polaris a first-of-kind testbed for the fundamental investigation of stellarator edge-relevant physics.
[abstract 37 / 43] (score: 2) - Title: Vortex dynamics and air entrainment in dam break wave impacting on vertical walls: A multiphase lattice Boltzmann studyAuthors: Massimiliano Mustè, Andrea Montessori, Pietro Prestininzi,Comments:Subjects: physics.flu-dyn physics.comp-phCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Air entrainment often plays a crucial role in determining impact loads exerted by free-surface wave flows interacting with structures, yet its modelling is often oversimplified in numerical approaches. In this study a two-phase numerical model, based on the Lattice Boltzmann Method coupled to a conservative Allen--Cahn interface-capturing equation is employed to perform direct numerical simulations of dam-break waves propagating over a dry bed and impacting on vertical walls. Access to high-resolution simulations enables a detailed assessment of how accurately resolving both air--water and solid--water interfaces affects local and overall dynamics, as well as quantities of extreme engineering interest. Indeed, the magnitudes and locations of the pressure peaks are strongly affected by wave front deflection and local aeration induced by a small corner vortex. Additionally, comparisons between no-slip and free-slip implementations suggest that the large air cavity formation, commonly observed as trapped inside the reflected JET falling back onto the incoming flow, may be the result of modeling assumptions rather than intrinsic flow physics, again highlighting the key role of near-wall shear in JET breakup dynamics.
[abstract 38 / 43] (score: 2) - Title: From simulations to observations of cool plasma: What we can learn from synthetic spectraAuthors: V. Jerčić, T. A. Kucera, A. G. M. Pietrow, P. Antolin, J. M. Jenkins,Comments: 13 pages, 13 figures, accepted for publication in A&ASubjects: astro-ph.SRCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Cool plasma of coronal rain or prominences and filaments is ubiquitous in the solar corona. We explored the synthetic spectra of MgII h&k lines in detail and analyse how well a non-adiabatic MAGNETohydrodynamic (MHD) simulation of condensations in the corona matches observations when comparing the synthetic with the observed spectra. We applied, a Python implemented, non-local thermodynamic equilibrium (non-LTE) radiative-transfer framework, Promweaver to create synthetic spectra from a 2.5D MHD simulation created with MPI-AMRVAC. The simulation shows a dynamic system of numerous cold, dense thread-like structures that we compare to observations of the $\textit{Interface Region Imaging Spectrograph}$ (IRIS), with a focus on flare-driven coronal rain. We give a detailed description of the simulation from the aspect of the synthetic spectra. We show how and why the particular spectra form. A single thread already demonstrates great complexity. We further used the quartile analysis to systematically explore the evolution of observables in the observed and the synthetic spectra. This gives an overview of how the parameters change in time and that the changes seen in the simulation fit with the changes seen in observations. The results show that the simulation, in some aspects, matches particularly well to the observations of flare-driven coronal rain. Furthermore, we explored relations of parameters of the simulation and the observables. We find significant correlation between intensity and density, but not with temperature (in the studied temperature range of 5 to 20 kK). As a result, there is also a correlation of intensity and pressure. This relation allows us to further relate intensity and the vertical component of the Lorentz force. This brings us a step closer to a better understanding of the connection between the observed spectra and the atmosphere from which it originates.
[abstract 39 / 43] (score: 2) - Title: High-Frequency Magnetohydrodynamic Waves with Substantial Energy in the Solar Polar CoronaAuthors: Yuhang Gao, Hui Tian, Richard Morton, Tom Van Doorsselaere, Daye Lim, Mingzhe Guo, Jiansen He, Zhenyong Hou,Comments: 14 pages, 4 figures, 1 tableSubjects: astro-ph.SR physics.space-phCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
The acceleration and heating of the fast solar wind remain long-standing challenges in space physics. One type of leading theoretical models requires high-frequency MAGNETohydrodynamic (MHD) waves to transport and dissipate sufficient energy in the corona. However, such high-frequency waves with energetically significant amplitudes have never been unambiguously observed, leaving a key gap between theories and observations. Using high-cadence, high-resolution extreme-ultraviolet imaging from Solar Orbiter's Extreme Ultraviolet Imager, we identify a previously hidden population of high-frequency MHD waves in coronal plumes of the solar polar region. An analysis of the detected propagating kink waves shows that over one-third have periods shorter than 100 s, a population largely undetected by earlier instruments. Power spectral analysis demonstrates that these high-frequency waves carry substantial energy flux, which are significantly underestimated in lower-cadence data. These results suggest that high-frequency MHD waves may contribute importantly to the energy budget of the solar polar corona and could play a role in solar wind acceleration, highlighting the value of high-resolution observations for probing energy transport in MAGNETized space and astrophysical plasmas.
[abstract 40 / 43] (score: 2) - Title: Shear interaction and acceleration of a corotating stream detected by Parker Solar ProbeAuthors: Andrea Verdini, Simone Landi, Emanuele Papini, Luca Franci, Petr Hellinger, Roberto Livi, Orlando Romeo,Comments: 10 pages, Accepted in A&ASubjects: astro-ph.SR physics.plasm-ph physics.space-phCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Recent analysis of Parker Solar Probe (PSP) and Solar Orbiter data indicates that fluctuations energy is transferred to the bulk flow in fast streams of the solar wind at heliocentric distances between 15 and 120 Rsun. To gain insight into this process, we analyze data collected during the inbound orbit of PSP in Encounter 10, when it is in approximate corotation with the Sun and an accelerating stream is detected between 25 and 45 Rsun. The geometry of the flow indicates that a neighboring very fast streams is colliding with the corotating stream, causing large-scale MAGNETic field distortion, density enhancement, and acceleration. However, also deposition of fluctuations' energy can heat and do work on the solar wind plasma, resulting in a radial acceleration. We evaluate the energy lost by fluctuations via radial variation of conserved quantities in the corotating stream and find that it is almost equally partitioned into heating and work. While the heating is marginally consistent with the non-adiabatic decrease of proton temperature, the work exerted on the wind is insufficient to account for the measured solar wind acceleration. Although limited to this event, observations suggest that shear interaction is capable of accelerating slower streams within relatively short distances from the Sun, possibly leaving its imprint as large-scale density and MAGNETic fluctuations.
[abstract 41 / 43] (score: 2) - Title: A systematic assessment of the short-term X-ray behaviour of the $γ$ Cas analoguesAuthors: Robbie Webbe, Yaël Nazé, N. A. Webb,Comments: Accepted for publication in A&ASubjects: astro-ph.SR astro-ph.HECreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Context. Overall, $γ$ Cas analogues represent a class of OBe stars displaying bright and hard X-ray emission. This emission was recently determined to be the result of accretion onto a companion white dwarf (WD), which might possibly be a MAGNETic WD. Aims. We present a systematic review of the properties of $γ$ Cas analogues on short-term (kilosecond, ks) scales to further investigate the nature of the X-ray source. In particular, the presence of periodicities could be associated with the rotation of a MAGNETic WD. Methods. We generated the power spectra and a generalised Fourier algorithm. We applied an epoch folding method, along with Z2n approaches, to 131 X-ray detections of 26 $γ$ Cas analogues and two candidate sources. Results. We identified five sources ($γ$ Cas, $ζ$ Tau, HD45314, V771 Sgr, and $π$ Aqr), with recurrent periodic variability (P $\sim$ 1.2-5.4 ks) across observations. Period values and pulsed fractions are consistent with those reported for intermediate polars. However, while similar periods are found in all exposures of an object, the exact period value or folded light curve shape can vary. We also identify another nine sources displaying periodicities that cannot be confirmed, as there was only one observation available for their analysis. In other cases, periodicities appear (at best) transient and/or marginally significant. Aperiodic variability could be fitted by a power law in 18 of the sources, while the power-law index always is $\sim$ 1, as observed in other accreting WDs. Conclusions. The global properties of the observed short-term X-ray variability of the $γ$ Cas analogues are consistent with those observed from other accreting WD systems.
[abstract 42 / 43] (score: 2) - Title: High-energy neutrino emission from the Milky WayAuthors: R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J. M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, L. Brusa, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. D'\iaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. Fattorini, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häu\ssler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, S. Minji, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, R. Neshat, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, C. Parisel, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, P. Savina, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. Schmitt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, W. Tian, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Velazquez, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, A. Weindl, P. Weigel, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, J. Woodward, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas,Comments:Subjects: astro-ph.HE astro-ph.GA hep-exCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
The Milky Way hosts astrophysical objects that accelerate COSMIC RAYs to energies beyond the reach of terrestrial particle accelerators. It remains a longstanding goal to locate the sites of these powerful Galactic engines and understand how COSMIC RAYs propagate through the Galaxy, leading to the production of high-energy neutrinos. In this paper, we combine event morphologies characteristic of all three neutrino flavours and apply recent improvements in ice modelling, calibration and reconstruction to 12 years of IceCube data. With a predefined, global analysis we establish high-energy neutrino emission from the Galactic plane at 5.7 $σ$ significance. A further study shows that the inner region of the Galaxy is a prominent neutrino source, with 217 shower events with visible energy above 5 TeV compared with an expected background of 154.4 $\pm$ 4.1. These results herald a new era of Galactic multi-messenger astronomy, creating new opportunities to study cosmic-ray propagation and probe neutrino properties over kiloparsec distances.
[abstract 43 / 43] (score: 2) - Title: Understanding the Travel-time Asymmetry of Acoustic Waves in Sunspots With Time-distance HelioseismologyAuthors: Haiyu Li, Tobías Felipe, Elena Khomenko, Hui Tian, Paul Rajaguru, Yuhang Gao,Comments: 17 pages, 8 figuresSubjects: astro-ph.SRCreated: 2026-07-28; Updated: 2026-07-29; Datestamp: 2026-07-29
Mapping the subsurface structure and flow field of sunspots has been a challenging task for helioseismology. In this work, we investigate the propagation of acoustic waves in a sunspot in NOAA active region 11312 using time-distance helioseismology. Travel times of waves traveling into and out of the sunspot are measured as functions of travel distance and azimuthal angle relative to the local radial direction. The same time-distance analysis is also applied to a simulated data based on a MAGNETohydrostatic (MHS) model of sunspot, and forward modeling of travel times is performed using ray tracing based on both the MHS sunspot model and a MAGNETohydrodynamic (MHD) simulation. We find that both ingoing (traveling from the quiet area into the sunspot) and outgoing waves (traveling from the sunspot into the quiet area) have shorter travel times than in the quiet Sun, with travel-time reductions of up to 40 s. The magnitude of the mean time shift is largest for waves traveling along the radial direction at small travel distances. A clear asymmetry is detected between ingoing and outgoing waves: outgoing waves generally exhibit shorter travel times. This asymmetry is strongest for radial direction and small travel distances, with differences exceeding 1 min for 3.5 mHz and 4.5 mHz waves. From the results of both observations and models, our analysis indicates that the overall reduction in travel time could be primarily caused by the combined effects of Wilson depression, MAGNETic field, and wave-speed perturbations, while the ingoing-outgoing asymmetry could be partly attributable to subsurface flows. Although the forward-modeling results reproduce several qualitative features of the observations, quantitative discrepancies remain, highlighting limitations of current sunspot models and ray-theoretical approximations.
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