Current date: 2026-08-04
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Scoring abstracts
Number of records retrieved: 959
Keyword score statistics
score 13 -- 1 abstracts
score 7 -- 3 abstracts
score 6 -- 1 abstracts
score 5 -- 2 abstracts
score 4 -- 10 abstracts
score 3 -- 12 abstracts
score 2 -- 23 abstracts
in total -- 52 abstracts
Articles that appeared on 2026-08-04
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[abstract 1 / 52] Wow! (score: 13)
- Title: Radio-Gamma-Ray Properties and High-Energy Implications for FERMI BlazarsAuthors: Xu-Hong Ye, Wen-Xin Yang, Guo-Hai Chen, Zhi-Yuan Pei, Yong-Yun Chen, Yi Liu, Denis Bastieri, Jun-Hui Fan,Comments: 9 pages, 5 figures, accepted by MNRASSubjects: astro-ph.HECreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Radio and $γ$-ray emissions in BLAZARs, a subclass of ACTIVE GALACTIC NUCLEi (AGNs), provide important insight into their high-energy radiation processes. We studied the relation between radio and $γ$-ray emissions using a large sample of 1687 \textit{FERMI} BLAZARs, based on the Radio Fundamental Catalogue and the latest Third Data Release of the Fourth \textit{FERMI} AGN Catalogue. A clear correlation between radio and $γ$-ray fluxes for both BL Lacertae objects (BL Lacs) and flat-spectrum radio QUASARs (FSRQs) suggests a SYNCHROTRON self-Compton (SSC) contribution to both subclasses. The ratio of $γ$-ray and radio emissions, $γ$-ray loudness ($G_{\rm r}$), is further examined with the $γ$-ray photon index ($Γ_γ$) and the SYNCHROTRON peak frequency ($ν_{\rm{peak}}$). An anti-correlation between $G_{\rm r}$ and $Γ_γ$ is explained by the shift of the spectral energy distribution rather than the Compton cooling effect. We found that $G_{\rm r}$ shows a positive dependence on $ν_{\rm{peak}}$ for low-SYNCHROTRON-peaked BL Lacs (LBLs) and FSRQs, in line with the SSC-contributed scenario, although additional external Compton contributions may account for the substantial scatter observed in LBLs and FSRQs. In contrast, high-SYNCHROTRON-peaked BL Lacs (HBLs) reach the plateau of $G_{\rm r}$ between $\log (ν_{\rm peak}/{\rm Hz}) \simeq15.5-16$, possibly indicating the transition from the Thomson to the Klein--Nishina (KN) regime. Interpreting this feature within a one-zone SSC framework could constrain the MAGNETic field strength of $-4.14 < \log (B/{\rm G}) < -1.69$ for those HBLs affected by the KN suppression.
[abstract 2 / 52] Wow! (score: 7) - Title: Polarization Angle Swings in Blazars Detected in the Millimeter-wave with the South Pole TelescopeAuthors: A. Simpson, E. Anderes, A. J. Anderson, B. Ansarinejad, M. Archipley, L. Balkenhol, D. R. Barron, P. S. Barry, K. Benabed, A. N. Bender, B. A. Benson, F. Bianchini, L. E. Bleem, S. Bocquet, F. R. Bouchet, E. Camphuis, M. G. Campitiello, J. E. Carlstrom, J. Carron, C. L. Chang, P. M. Chichura, A. Chokshi, T. -L. Chou, A. Coerver, T. M. Crawford, C. Daley, T. de Haan, K. R. Dibert, M. A. Dobbs, M. Doohan, D. Dutcher, C. Feng, K. R. Ferguson, N. C. Ferree, K. Fichman, A. Foster, S. Galli, A. E. Gambrel, A. K. Gao, F. Ge, F. Guidi, S. Guns, N. W. Halverson, A. D. Hincks, E. Hivon, G. P. Holder, W. L. Holzapfel, J. C. Hood, A. Hryciuk, N. Huang, E. Järvelä, T. Jhaveri, F. Kéruzoré, A. R. Khalife, L. Knox, K. Kornoelje, C. -L. Kuo, K. Levy, Y. Li, A. E. Lowitz, C. Lu, G. P. Lynch, X. Ma, T. J. Maccarone, G. Madejski, A. S. Maniyar, E. S. Martsen, F. Menanteau, M. Millea, J. Montgomery, Y. Nakato, T. Natoli, A. Ouellette, Z. Pan, K. A. Phadke, A. W. Pollak, K. Prabhu, W. Quan, M. Rahimi, A. Rahlin, C. L. Reichardt, M. Rouble, J. E. Ruhl, A. C. Silva Oliveira, J. A. Sobrin, A. A. Stark, C. Tandoi, C. Trendafilova, J. D. Vieira, A. G. Vieregg, A. Vitrier, Y. Wan, N. Whitehorn, W. L. K. Wu, M. R. Young, J. A. Zebrowski,Comments: To be submitted to ApJSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
We present the first systematic search for electric vector position angle (EVPA) swings in the millimeter-wave (mm-wave) emission of BLAZARs, using five years of observations from the South Pole Telescope SPT-3G camera at 95 and 150 GHz, and investigate their connection to gamma-ray flares. Of the 168 bright sources in the ~1500 square degrees SPT-3G Main Field, eight have sufficient POLARIZATION signal-to-noise for reliable EVPA measurement, four of which have continuous FERMI LAT gamma-ray detections. We detect EVPA swings in all four gamma-ray-active BLAZARs and in none of the remaining four, consistent with the established connection between EVPA swings and high-energy emission seen at optical wavelengths. The observed swing amplitudes and rotation rates are smaller than those found in optical studies, consistent with mm-wave EVPA variability being slower than at shorter wavelengths. Random walk simulations of the POLARIZATION angle using a multi-cell model fail to reproduce both the number, amplitude, and duration of the observed swings, suggesting that this mechanism is insufficient to explain the observed swing population. Analysis of EVPA variability on one-week timescales is consistent with the anti-correlation between POLARIZATION degree and EVPA rotation rate previously observed at optical wavelengths. Of the 14 detected swings, eight are within 30 days of a gamma-ray flare. While many individual swing-flare associations are found to have a very low probability of happening by chance, the full ensembles of 95 and 150 GHz swing time lags with respect to gamma-ray flares are found to be consistent with random coincidence.
[abstract 3 / 52] Wow! (score: 7) - Title: Evidence for a bursty $γ$-ray QPO in the neutrino-associated FSRQ PKS 1424$-$418 using Fast Template Periodograms and Machine LearningAuthors: Aaron A. Maldonado, Alberto Domínguez, Adithiya Dinesh, Alba Rico, Pablo Peñil, Sara Buson, Marco Ajello,Comments: Submitted to A\&A on April 24 (currently under review)Subjects: astro-ph.HE astro-ph.GACreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Standard frequency-domain searches for quasi-periodic oscillations (QPOs) in ACTIVE GALACTIC NUCLEi generally assume sinusoidal variability. However, $γ$-ray BLAZAR emission often shows asymmetric flares and localized bursts, causing spectral leakage that can reduce the sensitivity of conventional methods to non-sinusoidal periodic signals. We analyze a blind sample of 100 high-cadence (7-day binned) FERMI-LAT BLAZAR light curves. After baseline detrending with Singular Spectrum Analysis, we apply the Fast Template Periodogram using three template families: a sinusoid, a Gaussian burst, and an empirical asymmetric template derived from PG 1553+113. Candidate signals are then evaluated with a Random Forest classifier trained on $5\times10^4$ simulated light curves to distinguish genuine periodic phase structure from stochastic red noise. We identify nine $>3σ$ periodicity candidates. Three persistent QPOs, including PG 1553+113, are recovered by all template models, whereas six additional candidates are strongly suppressed under the standard sinusoidal assumption but become detectable with morphology-aware templates. Machine learning validation rejects five of these as lacking stable phase coherence. The remaining candidate, PKS 1424$-$418, shows a structurally stable 4.8-year periodicity with a source-specific significance of $3.76σ$ (approximately $2.4σ$ after accounting for the trial factor of the 100-source sample). These results demonstrate that morphology-aware periodograms, combined with structural machine learning validation, improve the detection of burst-dominated QPOs that are difficult to identify with traditional harmonic searches.
[abstract 4 / 52] Wow! (score: 7) - Title: Submillimeter Detectability of Gravitational-Wave Counterparts from Neutron-Star Mergers with the Xue-shan-mu-chang 15-meter TelescopeAuthors: Di Xiao,Comments: 24 pages, 6 figures, accepted by ApJSubjects: astro-ph.HECreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Submillimeter (sub-mm) follow-up of binary neutron star (BNS) mergers provides unique constraints on the early-time energetics and environments of RELATIVISTIC outflows, capturing the spectral evolution at epochs where centimeter-band emission is often still optically thick or yet to peak. However, the practical scientific yield depends on instrument-specific thresholds, the observing cadence, and the distinct temporal contributions from isotropic ejecta versus beamed RELATIVISTIC JETs. With the upcoming Xue-shan-mu-chang 15-meter SubMillimeter Telescope (XSMT), facility-specific forecasts are needed to test for sustained engine energy injection, as expected for a long-lived MAGNETar remnant rather than a promptly formed BLACK HOLE. We present a unified numerical framework that couples engine-driven ejecta dynamics to non-thermal SYNCHROTRON emission, accounting for SYNCHROTRON self-absorption and deep-Newtonian effects. Adopting fixed 5$σ$ (1 h) point-source thresholds of 1.5/2.9/10.2 mJy at 230/345/460 GHz, we construct parameter-space detectability maps and estimate event rates based on current BNS merger-rate priors. For a fiducial local event at 40 Mpc, we find that a MAGNETar-boosted ejecta afterglow peaks on timescales of weeks to months and remains detectable long enough to allow delayed follow-up, with an expected all-sky rate of $\dot N_{\rm ej} \approx 0.05$--1.7 yr$^{-1}$ at 230 GHz for $f_{\rm mag}=1$; this rate is an upper limit and scales linearly with the long-lived MAGNETar fraction. Conversely, while RELATIVISTIC JETs produce intense early-time signals, their detection is constrained by narrow beaming and fleeting visibility. Our framework provides a quantitative basis for prioritizing gravitational-wave triggers and maximizing the scientific yield of XSMT in the multi-messenger era.
[abstract 5 / 52] Yes (score: 6) - Title: Day-timescale Quasi-periodic Oscillations of the Gev BL Lac RX J0805.4+7534 with TESSAuthors: Xin-Shun Jin, Ting-Feng Yi, Yangwei Zhang, Yuncai Shen, Junjie Wang, Lisheng Mao, Liang Dong,Comments: 13 pages, 4 figures. accepted for publication in RAASubjects: astro-ph.HECreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
This paper reports for the first time the detection of quasi-periodic oscillations (QPOs) in the light curves of the BL Lacertae object RX J0805.4+7534. The Transiting Exoplanetary Survey Satellite (TESS) observed this source in seven sectors of the sky, and we extracted the light curves for these sectors using a custom method. The presence of QPO signals was found in these light curves. To detecte the periodicity and assess the statistical significance of the QPO signals, we employed two methods: Lomb-Scargle periodograms and Weighted Wavelet \textit{Z}-transform. Both of these different methods yielded consistent results. \textcolor{red}{\sout{The results showed signals with day-timescale QPO in sectors 20, 26, 53, and 73, with confidence levels exceeding $3σ$, and three of the sectors exhibited a ~3.8 days QPO. To explain these rapid quasi-periodic changes, we discuss several possible explanations. We propose that the QPO signal might be due to the rotation of hot spots on circular orbits within the accretion disk.}}\textcolor{blue}{The results show that QPO signals exist in sectors 20, 26, and 53, with the confidence levels exceeding 99.73\%. The QPOs in sectors 20 and 26 are $\sim 3.8$ days and have a global significance of 95\%. To explain these rapid quasi-periodic variations, we discussed several possible physical scenarios. The most possible one is the kink instability in RELATIVISTIC JETs. The other possible scenario is the rotation of hot-spots in the innermost accretion disk. Based on the hot-spot orbital model hypothesis, the mass of the BLACK HOLE at the center of this BL Lac object wes estimated. The validity of these two explanations requires further observational data to verify. However, since the radiation of BL Lac objects primarily originates from JETs, we prefer the kink instability in RELATIVISTIC JETs to be the cause of this rapid QPO.
[abstract 6 / 52] Yes (score: 5) - Title: An extreme case of X-ray reflection in the symbiotic V648 CarAuthors: Jherssica Freitas, Raimundo Lopes de Oliveira, Koji Mukai,Comments: Accepted for publication in ApJSubjects: astro-ph.SR astro-ph.HECreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
V648 Car is a $δ$-type symbiotic star known for its strong hard thermal X-ray emission, heavy local photoelectric absorption, and stochastic variability. We analyze NUSTAR observations, complemented by nearly contemporaneous SWIFT/XRT observations, to check for the expected presence and physical implications of Compton reflection in its X-ray spectrum. The spectra were fitted with X-ray models that accounted for thermal plasma components, different prescriptions to quantify the intrinsic absorption, the presence of the fluorescent iron line at 6.4 keV, and a reflection component. Our results reveal a strong Compton reflection contribution, accounting for approximately 37% of the total unabsorbed flux in the 3-50 keV band. The inclusion of reflection significantly improves the spectral fits and reduces the value for the maximum plasma temperature by a factor of 2 (from about 49 keV to 25 keV). If the maximum temperature is attributed to strong shock of a Keplerian flow, the inferred white dwarf mass decreases from about 20% (from $1.2$ to $0.95\,M_{\odot}$), demonstrating that neglecting reflection can lead to significant overestimates of this parameter. Reflection models yield high reflection scaling factors ($R \sim 2$), inconsistent with a simple picture of a primary X-ray source above a reflecting disk. The timing analysis reveals stochastic flickering variability with no evidence for coherent periodic modulations, thus the accreting object is likely a non-MAGNETic white dwarf. We propose a multiple-reflection model to explain the extraordinary strength of reflection features in V648 Car.
[abstract 7 / 52] Yes (score: 5) - Title: Simulations of ElectroMAGNETic Cascades in the Intergalactic Medium with Plasma Instabilities: the grplinst CodeAuthors: Rafael Alves Batista, Andrey Saveliev,Comments: 17 pages, 3 figures; submitted to Frontiers in Astronomy and Space Science, research topic: The Role of Plasmas and Cosmic Magnetism in High-energy Astroparticle PhysicsSubjects: astro-ph.HECreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
ElectroMAGNETic cascades initiated by TeV gamma rays from distant BLAZARs provide one of the cleanest indirect probes of the intergalactic medium and, in particular, of intergalactic MAGNETic fields. However, their interpretation is not completely clear because of an open theoretical question: the extent to which the electron-positron beams generated in the cascade can lose energy through collective plasma processes. If this occurs before inverse Compton scattering produces secondary gamma rays, then the cascade is quenched. Here we present grplinst, a plugin for the CRPropa framework that models plasma-instability cooling acting on electrons and positrons during propagation. We describe the implementation of several prescriptions proposed in the literature, and present illustrative examples. The code is suitable both for bracketing theoretical uncertainties and for performing systematic studies of how plasma-instability assumptions propagate into gamma-ray observables and inferred intergalactic MAGNETic-field constraints, which is essential for interpreting current and forthcoming observations by high-energy gamma-ray observatories.
[abstract 8 / 52] Yes (score: 4) - Title: Numerical analysis of three-dimensional MAGNETohydrodynamic effects in an inductively coupled plasma wind tunnelAuthors: Sanjeev Kumar, Alessandro Munafo, Daniel J Bodony, Marco Panesi,Comments: 36 pages, 22 figuresSubjects: physics.plasm-ph physics.flu-dynCreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
This paper introduces a three-dimensional model for the 350 kW Plasmatron X inductively coupled plasma facility at the University of Illinois Urbana-Champaign, designed for testing high-temperature materials. Simulations of the facility have been performed using a three-dimensional, multiphysics computational framework, which reveals pronounced three-dimensional characteristics within the facility. The analysis of the plasma and electroMAGNETic field in the torch region reveals the influence of the helical coils, which cause a non-axisymmetric distribution of the plasma discharge. Additionally, simulations of the torch-chamber configuration at two operating pressures have been conducted to examine the impact of plasma asymmetry in the torch on JET characteristics in the chamber. The results indicate an unsteady, three-dimensional behavior of the plasma JET at high pressure. Spectral Proper Orthogonal Decomposition (SPOD) has been performed on the unsteady flow field to identify the dominant modes and their associated frequencies. At low pressure, a steady, supersonic, nearly axisymmetric plasma JET forms with consistent flow properties, such as temperature and velocity. However, strong non-equilibrium effects at low pressures lead to substantial deviations in species concentrations from axial symmetry despite having an almost axisymmetric distribution for quantities such as velocity and temperatures.
[abstract 9 / 52] Yes (score: 4) - Title: Measurement of the COSMIC RAY nickel energy spectrum from 10 GeV/n to 2 TeV/n with the DAMPEAuthors: F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. V. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong, G. Donvito, J. L. Duan, K. K. Duan, R. R. Fan, Y. Z. Fan, F. Fang, K. Fang, C. Q. Feng, L. Feng, S. Fogliacco, J. M. Frieden, P. Fusco, M. Gao, F. Gargano, E. Ghose, K. Gong, Y. Z. Gong, D. Y. Guo, J. H. Guo, S. X. Han, Y. M. Hu, G. S. Huang, X. Y. Huang, Y. Y. Huang, M. Ionica, L. Y. Jiang, W. Jiang, Y. Z. Jiang, J. Kong, A. Kotenko, D. Kyratzis, S. J. Lei, B. Li, M. B. Li, W. L. Li, W. H. Li, X. Li, X. Q. Li, Y. M. Liang, C. M. Liu, H. Liu, J. Liu, S. B. Liu, Y. Liu, F. Loparco, M. Ma, P. X. Ma, T. Ma, X. Y. Ma, G. Marsella, M. N. Mazziotta, D. Mo, Y. Nie, X. Y. Niu, A. Parenti, W. X. Peng, X. Y. Peng, C. Perrina, E. Putti Garcia, R. Qiao, J. N. Rao, Y. Rong, A. Serpolla, R. Sarkar, P. Savina, Z. Shangguan, W. H. Shen, Z. Q. Shen, Z. T. Shen, L. Silveri, J. X. Song, H. Su, M. Su, H. R. Sun, Z. Y. Sun, A. Surdo, X. J. Teng, A. Tykhonov, G. F. Wang, J. Z. Wang, L. G. Wang, S. Wang, X. L. Wang, Y. F. Wang, D. M. Wei, J. J. Wei, Y. F. Wei, D. Wu, J. Wu, S. S. Wu, X. Wu, Z. Q. Xia, Z. Xiong, E. H. Xu, H. T. Xu, J. Xu, Z. H. Xu, Z. Z. Xu, Z. L. Xu, G. F. Xue, M. Y. Yan, H. B. Yang, P. Yang, Y. Q. Yang, H. J. Yao, Y. H. Yu, Q. Yuan, C. Yue, J. J. Zang, S. X. Zhang, W. Z. Zhang, Y. Zhang, Y. P. Zhang, Y. Zhang, Y. J. Zhang, Y. Q. Zhang, Y. L. Zhang, Z. Zhang, Z. Y. Zhang, C. Zhao, H. Y. Zhao, X. F. Zhao, C. Y. Zhou, X. Zhu, Y. Zhu,Comments:Subjects: astro-ph.HECreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Nickel, one of the most tightly bound nuclei alongside iron, is the most abundant heavy element beyond iron in COSMIC RAYs. With DAMPE's excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of cosmic-ray nickel spectrum from 10 GeV/n to 2 TeV/n with nine years of flight data. The nickel spectrum is consistent with a single power law with spectral index -2.60 +/- 0.03 from 40 GeV/n to 1 TeV/n. This work provides an accurate measurement of differential flux of nickel with kinetic energy extending to TeV/n for the first time.
[abstract 10 / 52] Yes (score: 4) - Title: Implications of low neutron star merger rates for GAMMA-RAY BURSTs, r-process production and Galactic double neutron starsAuthors: Maya Fishbach, Alexander P. Ji, Wen-fai Fong, Tom Y. Wu, Jillian C. Rastinejad, Aditya Vijaykumar, Hsin-Yu Chen,Comments: updated to match version accepted by ApJLSubjects: astro-ph.HE gr-qcCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
The first multimessenger discovery of a binary neutron star (BNS) merger, GW170817, proved that such mergers can source short GAMMA-RAY BURSTs (SGRBs) and produce r-process elements. The initial merger rate from this single event was found to be broadly consistent with the SGRB rate, the Milky Way (MW) r-process mass, and the Galactic population of double neutron star (DNS) systems that will merge in a Hubble time. However, only one additional BNS merger has been detected since, and the BNS merger rate has been consistently revised downwards with recent gravitational wave (GW) catalog updates. Analyzing GWTC-4, we find a total BNS merger rate of $28$--$300\,\mathrm{Gpc}^{-3}\,\mathrm{yr}^{-1}$ consisting of $53^{+176}_{-49}\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$ in GW170817-like $\sim(1.3,1.3)\,M_\odot$ BNSs (90\% credibility). We revisit the consistency of the BNS merger rate with SGRBs, r-process and Galactic DNSs. In all cases, there is an emerging tension with the BNS (and EM-bright neutron star--BLACK HOLE, NSBH) merger rate. Comparing to a BNS merger rate of $100\,\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$, the cosmological SGRB rate is a factor of 3.6--18 higher (despite kilonova followup of SGRBs implying a significant fraction of SGRBs are of BNS origin), the r-process rate is a factor of 0.9--4.1 higher (even though we consider only r-process elements above the second peak), and the rate inferred from Galactic DNSs is a factor of 2.3--5.1 higher than the BNS rate. We discuss how various uncertainties in the inferred rates either alleviate or exacerbate this tension, which point to the various physical processes that can be constrained by such rate comparisons.
[abstract 11 / 52] Yes (score: 4) - Title: Testing General Relativity with Individual Supermassive Black Hole BinariesAuthors: Qinyuan Zheng, Bjorn Larsen, Ellis Eisenberg, Chiara M. F. Mingarelli,Comments: 23 pages, 11 figures, 3 tables. Accepted to Physical Review DSubjects: gr-qc astro-ph.HECreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
We develop a unified framework for testing gravity beyond General Relativity (GR) with continuous gravitational waves (CWs) from individual supermassive BLACK HOLE binaries (SMBHBs). These long-lived, nearly monochromatic nanohertz signals offer unique strengths for precision tests of gravity, since their coherent phase evolution and inter-pulsar correlations in pulsar timing arrays (PTAs) retain detailed information about departures from GR over cosmological propagation distances. We consider three representative classes of deviations from GR: additional POLARIZATION states, modified dispersion relations, and parity-violating birefringence. For each, we derive the inter-pulsar cross correlation, the modified antenna response, and the propagation-induced pulsar-term phase delay. For non-tensorial POLARIZATIONs, the CW cross correlation scales linearly in the alternative-POLARIZATION amplitude, compared to the quadratic scaling of the gravitational-wave background (GWB), provided the beyond-GR modes are sub-dominant. PTAs are also competitive for modified dispersion relations, where low frequencies enhance both the antenna-pattern modification and the pulsar-term phase delay. Birefringence, by contrast, is suppressed at nanohertz frequencies for most parity-violating theories. We validate the framework with injection-and-recovery simulations for breathing-mode and massive-graviton signals at current observational limits, recovering the injected beyond-GR parameters and distinguishing the CW signal from both correlated and uncorrelated background models. We further show that a pure-GR CW template recovers source parameters without significant bias when beyond-GR physics is present in the data, supporting a two-stage analysis strategy: identify candidates under GR, then test for deviations.
[abstract 12 / 52] Yes (score: 4) - Title: Shrinking the Haystack: One-Class Machine Learning Detection of Magnetosheath Current Sheets in MMS Burst DataAuthors: Deep Ghuge, Daniel J. Gershman, Vadim Uritsky, Julia E. Stawarz,Comments: 28 pages, 10 figures, 2 tables. Submitted to Journal of Geophysical Research: Space PhysicsSubjects: physics.space-phCreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
We present a morphology-first framework for narrowing the search for MAGNETic-RECONNECTion candidates in Magnetospheric Multiscale (MMS) burst-mode data. The target is the small, short, and frequently electron-only RECONNECTing current sheets that occur in turbulent MAGNETosheath plasma. The pipeline operates in two stages. A local frame-quality gate based on minimum-variance analysis first retains only windows whose current-sheet coordinates are well defined. A one-class Deep Support Vector Data Description neural network then scores those windows against a library of 3,000 physically calibrated synthetic current sheets generated by Monte Carlo from a single published reference event. Acceptance into the surrogate library is governed by the second-order structure function $S_2(τ)$: a candidate is admitted only if its multi-scale fingerprint tracks that of the seed event inside a tolerance band, together with a small number of shape-based checks. This $S_2(τ)$-anchored construction defines the in-class distribution directly from a well-understood reference event and sidesteps the absence of a curated negative class in turbulent MAGNETosheath data. Applied to 15 MAGNETosheath turbulence intervals from the literature (1.58 h of burst-mode coverage), the framework compresses 22,775 sliding windows to 270 candidate detections (a 98.8% reduction). Manual visual screening identifies 93 of these as candidate RECONNECTion events and a further 118 as sheet-like, retaining 78% of the queue for follow-up; the candidate-RECONNECTion pool extends well beyond the 22 detections that overlap the published RECONNECTion-event catalog used here as a sanity check. The framework is intended as the data-reduction stage of a broader RECONNECTion-search workflow, offered here as an initial proof of concept before extending the one-class design to additional feature channels.
[abstract 13 / 52] Yes (score: 4) - Title: Gamma Rays from ALP-Photon Conversion and Inverse Compton Reprocessing in Neutron Star MagnetospheresAuthors: Federica Giacchino, Conrado A. Torres, Giorgio Galanti, Bradley J. Kavanagh, Maria A. Pérez-García, Jose M. Diego,Comments: 25 pages, 24 figures, 1 tableSubjects: astro-ph.HE hep-phCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Exploring axion-like particle (ALP) signatures from neutron stars (NSs) in the \emph{FERMI}-LAT energy range remains largely unexplored. Neutron stars with exceptionally strong MAGNETic fields, such as MAGNETars and pulsars with MAGNETar-like MAGNETic fields, provide particularly promising environments for ALP--photon conversion. Magnetars are characterized by surface MAGNETic fields as large as $B_0\sim(10^{14}$--$10^{15})\,\mathrm{G}$; however, despite their extreme MAGNETic fields, no steady MAGNETar emission has been firmly detected in the \emph{FERMI}-LAT energy range, with high-energy activity generally associated with rare flaring episodes. In this work, we investigate ALP production in the interiors of different classes of NSs and the subsequent conversion of ALPs into photons in their MAGNETospheres. The ALP emissivity is determined by the stellar density and temperature $T$, while the conversion probability is enhanced by the strong MAGNETic fields surrounding the star. We further account for photon propagation through the Galactic MAGNETic field, which can provide an additional contribution to the observable photon flux. We investigate the resulting gamma-ray signatures and assess whether ALP-induced emission from NS MAGNETospheres could be detectable at energies $E\gtrsim100,\mathrm{MeV}$ in the \emph{FERMI}-LAT band. In addition, we consider if the reprocessing of the MAGNETospheric photons through inverse Compton scattering can shift part of the emission to higher energies and provide an additional observational signature. We use the resulting fluxes to derive constraints from existing gamma-ray observations and to estimate the sensitivity of future MeV--GeV observations, taking COSI as a representative example.
[abstract 14 / 52] Yes (score: 4) - Title: Identification and Study of Irregular Radio Sources with SKA Continuum SurveysAuthors: Tapan K. Sasmal, Xuelei Chen, Baoqiang Lao, Soumen Kumar Bera, Yougang Wang, Soumen Mondal, Taotao Fang, Renyue Cen,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Sasmal01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopesSubjects: astro-ph.GACreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Radio galaxies show a wide range of morphologies, from regular double-lobed systems to more complex and distorted radio structures. In this chapter, we focus on irregular radio morphologies, defined as sources in which the radio JETs and lobes deviate from a straight and symmetric structure. Bent-tail RADIO GALAXies and winged RADIO GALAXies are two important examples of such sources. Bent-tail RADIO GALAXies show curved JETs or lobes, mainly shaped by the interaction between radio plasma and the dense intracluster or intragroup medium. Winged RADIO GALAXies show faint off-axis emission, which may be related to plasma backflow, JET reorientation, episodic activity, galaxy mergers, or environmental asymmetry. The Square Kilometre Array (SKA) continuum surveys will provide the sensitivity, angular resolution, frequency coverage, and image quality required to identify and study large samples of such irregular RADIO GALAXies. These data will make it possible to detect faint extended structures, including diffuse tails, weak bridges, remnant lobes, and low-surface-brightness wings. The identification and classification of these sources will require a combination of machine-learning methods, quantitative morphology measurements, multi-wavelength host-galaxy association, and expert visual inspection. The study of irregular RADIO GALAXies with SKA data will help to connect radio morphology with host-galaxy properties, Active Galactic Nucleus (AGN) activity, JET power, and surrounding environment. Such studies will provide important insight into JET-environment interactions, AGN feedback, the dynamical state of galaxy groups and clusters, and the evolution of RADIO GALAXies across cosmic time.
[abstract 15 / 52] Yes (score: 4) - Title: The physical mechanism for two rapid changing-look AGNs: SDSS J0225+0030 and SDSS J1723+5504Authors: Shuang-Liang Li, Xinwu Cao, Wei-Min Gu,Comments: 10 pages, 4 figures, 2 tables, accepted by ApJSubjects: astro-ph.GACreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
SDSS J0225+0030 and SDSS J1723+5504 are two turn-on changing-look ACTIVE GALACTIC NUCLEi (CL AGNs) with transition timescales shorter than one year. Such short timescales pose a challenge for the current physical models of CL AGNs. We investigate this issue by exploring two possible mechanisms in this work. First, we consider the effect of a large-scale MAGNETic field on the viscous timescale, which can increase the radial velocity of the accretion disk. However, it is found that the timescale given by this model remains significantly longer than one year. Second, we improve the model of \citet{2025ApJ...988..207L}, which proposed that the inner thin disk in the bright state may form through the collapse of an advection-dominated accretion flow (ADAF) in the dim state, rather than being replaced by the advection of the outer thin disk. We re-estimate the transition radius $R_{\rm tr}$ between the inner ADAF and the outer thin disk through the observed variation of optical flux between the bright state and dim state. It is found that $R_{\rm tr}$ can be significantly reduced in these two objects owing to the lower gas temperature in the inner disk region (of the order of $10^4$ K), resulting from their large BLACK HOLE masses ($\sim 10^9 M_{\odot}$) and small Eddington-scaled mass accretion rates ($\sim 0.01$). The cooling timescales given by the revised model in these two objects are found to be comparable to the observed transition timescales.
[abstract 16 / 52] Yes (score: 4) - Title: Sub-sonic compressible MAGNETohydrodynamic turbulence I. Alfvénic and fast-MAGNETosonic injection, amplitude dependence, and compressibility effectsAuthors: Eleonora Puzzoni, Silvio Sergio Cerri, Dimitri Laveder, Thierry Passot, Pierre-Louis Sulem,Comments:Subjects: physics.plasm-ph astro-ph.GA astro-ph.HECreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
We investigate how sub-sonic compressible MAGNETohydrodynamic (MHD) turbulence properties that are relevant for cosmic-ray (CR) transport in the Galaxy are affected by the nature and amplitude of initial fluctuations, and by the plasma compressibility $β$. We perform 3D simulations of decaying compressible ideal-MHD turbulence at $1024^3$ resolution with the PLUTO code. The level of density fluctuations in fully developed turbulence is insensitive to whether this state is reached starting from Alfvénic or fast-MAGNETosonic perturbations. Fast-MAGNETosonic injection is characterized by an early phase of rapid shock dissipation, followed by a turbulence-dominated decay with a rate comparable to that of the Alfvénic case. The contribution of fast-MAGNETosonic fluctuations in fully developed turbulence remains relevant only when the initial injection consists exclusively of fast modes. Large-amplitude turbulence ($δB/B_0>1$) is characterized by a nearly isotropic Kolmogorov or Iroshnikov-Kraichnan spectrum for Alfvénic or fast-MAGNETosonic injection, respectively. At low amplitudes ($δB/B_0\ll1$), both initial Alfvénic and mixed-wave perturbations lead to strongly anisotropic turbulence with spectra $\propto k_\perp^{-5/3}$ and $\propto k_z^{-2}$ (becoming steeper at $β\gg1$), whereas fast-MAGNETosonic perturbations produce a turbulent state populated by shocks with a nearly isotropic $k^{-2}$ spectrum. Magnetic-field curvature and mirror structures are strongly sensitive to fluctuation amplitude and plasma $β$. The predicted -2.5 power-law scaling emerges only in the large-amplitude regime at high $β$. This work highlights that features of sub-sonic compressible MHD turbulence that may affect CR transport are sensitive to large-scale conditions and to the plasma $β$. Their effect on CR diffusion and field-line random walk is the object of Paper II.
[abstract 17 / 52] Yes (score: 4) - Title: AGNI: A differentiable MHD stability solver & optimizer for MAGNETic confinement fusion devicesAuthors: Rahul Gaur, Sanket Patil, Prateek Gupta, Djin Patch, Tony Qian,Comments: 25 pages, 8 figures, link to source code will be available in v2Subjects: physics.plasm-phCreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
The existence of an ideal MagnetoHydroDynamic (MHD) equilibrium does not guarantee its stability. Finite toroidal mode number (n) instabilities degrade performance in both tokamaks and stellarators and differentiable stability optimization tools to date have operated only in the infinite-n limit. We present AGNI (Analysis of Global Normal modes in Ideal MHD), a GPU-accelerated, automatically differentiable finite-n ideal MHD stability solver and optimizer. AGNI discretizes the ideal MHD energy principle pseudospectrally in real space using differentiation matrices and geometric coefficients from a DESC equilibrium, giving a variational eigenvalue problem for the plasma displacement, and efficiently finds the most unstable modes. Built on JAX, AGNI yields reverse-mode gradients of the growth rate with respect to boundary-shape and profile parameters without re-solving the equilibrium. We benchmark AGNI against the initial-value code NIMSTELL for a modified Landreman-Buller-Drevlak quasi-helically symmetric equilibrium, recovering the dominant m = n = 4 interchange mode with agreement in both growth rate and eigenfunction structure, and verify the automatic differentiation gradients against central finite differences. We quantify CPU and GPU cost for eigenvalue and gradient evaluation, establish the finite-precision limit on resolving near-marginal eigenvalues, and present a robust scheme to impose incompressibility, one of which is compatible with gradient-based optimization. AGNI will allow us to optimize tokamaks, stellarators, and mirrors against ideal MHD instabilities.
[abstract 18 / 52] (score: 3) - Title: Self-consistent modelling and qualitative comparison of mildly RELATIVISTIC runaway electron dynamics with a closed flux surface formation model during tokamak startupAuthors: Y. Lee, H. -T. Kim, P. C. de Vries, P. Aleynikov, J. Lee, K. Park, T. Park, J. Gwak, G. Nam, W. I. Jeong, K. -D. Lee, J. -G. Bak, J. Jang, J. -W. Juhn, Y. -S. Lee, J. -K. Park, Y. -S. Na,Comments:Subjects: physics.plasm-phCreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
A model for mildly RELATIVISTIC Runaway Electrons (REs) is developed in a reduced-kinetic form and qualitatively compared with radiation characteristics observed in KSTAR ohmic startup. The mildly RELATIVISTIC correction not only alleviates runaway current overestimation but also accounts for the partial parallel confinement of the initial runaway seed under an open-field configuration during early burn-through. The model is self-consistently integrated in the state-of-the-art predictive plasma initiation code DYON (Hyun-Tae Kim et al 2022 Nucl. Fusion 62 126012), hereafter referred to as DYON-RE. DYON-RE provides an improved RE confinement model during the transition from an open to a closed MAGNETic configuration by employing a model-based description of closed flux surface formation validated in multi machines. We show prediction capability of DYON-RE in two representative discharges among KSTAR ohmic startups. DYON-RE reliably predicts key plasma parameters such as plasma current, density, and temperature and also implies the characteristic behavior of the radiative temperature measured by electron cyclotron emission diagnostics in agreement with experimental results. The proposed model offers a framework for designing runaway-free ohmic startup scenarios in CPD and ITER. Future experimental validation will further refine its predictive capabilities and broaden its practical application.
[abstract 19 / 52] (score: 3) - Title: ENGRAVE follow-up of a type IIb SUPERNOVA spatially coincident with the sub-threshold gravitational wave trigger S250818kAuthors: K. Ackley, M. T. Botticella, A. Boye, M. Branchesi, G. Bruni, E. Cappellaro, S. Chaty, T. -W. Chen, F. D'Ammando, V. D'Elia, F. F. De Pasquale, Dimple, R. A. J. Eyles-Ferris, M. Fraser, G. Gianfagna, J. H. Gillanders, G. Greco, M. Gromadzki, C. P. Gutièrrez, A. Hajela, L. Izzo, P. G. Jonker, S. Kobayashi, R. Kotak, G. P. Lamb, G. Leloudas, A. J. Levan, J. D. Lyman, K. Maguire, A. Martin-Carrillo, A. Melandri, M. J. Michałowski, S. R. Oates, F. Onori, B. Patricelli, E. Pian, G. Pignata, S. Piranomonte, L. Piro, Q. Pognan, M. L. Pumo, S. Ronchini, A. Rossi, R. Roy, A. Saccardi, O. S. Salafia, R. Salvaterra, N. Sarin, S. Schulze, S. J. Smartt, R. L. C. Starling, D. Steeghs, N. R. Tanvir, A. L. Thakur, S. D. Vergani, S. Yi, D. R. Young,Comments: Revised versionSubjects: astro-ph.HECreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
The candidate gravitational wave (GW) event S250818k was one of only three non-retracted LIGO-Virgo-KAGRA public alerts issued during the fourth observing run of the network (O4) with a binary neutron star (BNS) merger classification probability exceeding one percent. This triggered a prompt search for a potential electroMAGNETic (EM) counterpart in the large localisation error region (949 deg$^2$ projected in the sky at 90% credible level). The transient SN2025ulz, discovered by the Zwicky Transient Facility (ZTF) during the search, attracted a great deal of attention due to a potential spatial and temporal coincidence, and due to its initial fast decay and featureless spectrum. Here, we report on the follow up of this transient by the ElectroMAGNETic counterparts of gravitational wave sources at the Very Large Telescope (ENGRAVE) Collaboration. We conducted an extensive multi-wavelength observational campaign, which led to the spectral classification of the transient as a type IIb SUPERNOVA (SN), indicating that it is unrelated to the candidate GW event. In this article, we describe our observing strategies, data reduction, and interpretation. All of our results confirm and strengthen our classification of the source, and also show that shock cooling tails associated with type IIb SNe are one of the most prominent contaminants in kilonova searches.
[abstract 20 / 52] (score: 3) - Title: Stellar mergers and chemical element mixing: implications for the metamorphic stellar evolution in AGN disksAuthors: Yanlong Shi, Xiaoshan Huang, Douglas N. C. Lin, Norman Murray,Comments: Revised after a referee report; comments welcomeSubjects: astro-ph.GA astro-ph.HE astro-ph.SRCreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
Chemical mixing during stellar mergers can significantly influence the subsequent evolution of the merger remnant. We perform a suite of three-dimensional hydrodynamical simulations of stellar mergers, each evolved for $\sim100$ stellar dynamical times until the remnant reaches a quasi-hydrostatic equilibrium. The simulations incorporate subgrid-scale diffusion models to capture the turbulent mixing of chemical elements. Starting with an idealized polytropic equation of state (EOS), we first identify the dominant mixing mechanisms and investigate how the merger outcome depends on the mass ratio, relative velocity, impact parameter, and stellar structure. We then extend our simulations to the context of stars embedded in ACTIVE GALACTIC NUCLEus (AGN) disks, using a realistic, composition-dependent EOS and AGN stellar models generated with the stellar evolution code MESA. We find that mergers with both younger metamorphic stars and H-rich accreting AGN stars can substantially rejuvenate old metamorphic stars through efficient core mixing after thermal relaxation. The merger remnants are nitrogen-enriched, with ${\rm N/O}\sim1$--3 and ${\rm N/C}\gtrsim5$, comparable to the abundances observed in the nebula surrounding SN 1987A. During subsequent stellar evolution, the remnants may converge onto the main sequence of isolated metamorphic AGN stars once they reach accretion--wind equilibrium. They may also deposit a significant amount of chemically enriched material into the AGN disk. This work provides a physical framework for connecting hydrodynamical stellar mergers with the long-term evolution of AGN stars and their observational and chemical signatures.
[abstract 21 / 52] (score: 3) - Title: Solar Orbiter SEP Dropout during a Magnetic Cloud with Evidence for Strong Connectivity GradientsAuthors: Radoslav Bucik, Raul Gomez-Herrero, Samuel T. Hart, Maher A. Dayeh, Nariaki V. Nitta,Comments: 10 pages, 5 figures. Accepted version of the paper. Publisher typeset PDF is provided as ancillary fileSubjects: astro-ph.SRCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
We analyze an impulsive solar energetic particle (SEP) event observed by Solar Orbiter at 0.93 au on 2022 December 24 that exhibits a pronounced intensity dropout between approximately 07:15 and 10:00 UT. Pitch-angle distributions show a near-field-aligned beam before the dropout, which disappears abruptly at the dropout onset. At the same time, a weak 100--200 keV component appears at pitch angles of about 90--180 degrees; no comparable enhancement over this pitch-angle range is present at MeV energies. The dropout onset is not accompanied by an abrupt change in the in situ MAGNETic field or solar wind plasma. Solar imaging associates the SEP event with a JET from a compact source. Ballistic back mapping, together with Potential Field Source Surface extrapolations and quasi-separatrix-layer proxy diagnostics, indicates that Solar Orbiter nominally connects to the source region, but lies close to strong connectivity gradients where small displacement may shift the connection to neighboring open field lines. The in situ measurements show that the event occurs during a MAGNETic-cloud passage and that additional dropouts occur later in the event. These results favor an interpretation in which the dropout reflects rapid changes in particle access between adjacent flux tubes, while the MAGNETic cloud may help preserve the sharp SEP intensity gradients between them.
[abstract 22 / 52] (score: 3) - Title: Filling the Shadow: A Propositional Model of Gravastar Accretion in $f(R, L_m, T)$ GravityAuthors: Sandip Dutta,Comments: 11 pages, 7 figuresSubjects: gr-qc hep-thCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
While General Relativity remains our most rigorously tested framework for gravitation, the theoretical persistence of singularities within standard BLACK HOLE solutions continues to motivate the exploration of mathematically regular alternatives. Gravitational vacuum stars (gravastars) offer a non-singular model, substituting the event horizon with a physical, ultra-stiff thin shell. Recent studies have demonstrated that extended theories, such as $f(R, L_m, T)$ gravity, can structurally support these objects by utilizing the non-minimal coupling between geometry and matter. Building upon these static foundations, this paper presents a phenomenological propositional model to explore the dynamic interactions between modified-gravity gravastars and equatorial accretion flows. By numerically solving the modified Tolman-Oppenheimer-Volkoff equations and applying a non-complexifying algorithm, we construct a mathematically regular rotating metric ansatz. We demonstrate that the modified gravity coupling parameter systematically alters the effective potential, shifting the location of the Innermost Stable Circular Orbit (ISCO). Furthermore, we explore the idealized thermodynamics of plasma colliding with the gravastar surface, suggesting a distinct thermal emission that could theoretically produce a ``filled-in'' central shadow in interferometric observations. While acknowledging the challenges of observational degeneracy and the deliberate omission of complex radiation pressure feedback, we offer these geometric and thermal signatures as a transparent conceptual baseline to motivate future general RELATIVISTIC MAGNETohydrodynamic (GRMHD) campaigns.
[abstract 23 / 52] (score: 3) - Title: Three-dimensional Magnetic Structures of Ellerman Bombs revealed by SUNRISE III/SCIPAuthors: Yusuke Kawabata, Yukio Katsukawa, Masahito Kubo, Takayoshi Oba, Takuma Matsumoto, Ryohtaroh T. Ishikawa, Yoshihiro Naito, Hirohisa Hara, Toshifumi Shimizu, Fumihiro Uraguchi, Toshihiro Tsuzuki, Kazuya Shinoda, Tomonori Tamura, Yoshinori Suematsu, Carlos Quintero Noda, Jose Carlos del Toro Iniesta, David Orozco Suárez, María Balaguer Jimenez, Sami K. Solanki, Andreas Lagg, Achim Gandorfer, Pietro Bernasconi, Thomas Berkefeld, Alex Feller, Tino L. Riethmüller, Alberto Álvarez-Herrero, H. N. Smitha, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hoelken, Francisco A. Iglesias, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović,Comments: 9 pages, 5 figures. Accepted for publication in the Astrophysical Journal Letters. An animation of Figure 1 is included as an ancillary fileSubjects: astro-ph.SRCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Ellerman bombs (EBs) are widely recognized as photospheric and chromospheric signatures of MAGNETic RECONNECTion. However, the three-dimensional (3D) MAGNETic topology has remained elusive due to the lack of seamless height coverage in observations. Here, we present initial results from the SUNRISE III/SCIP (Sunrise Chromospheric Infrared spectroPolarimeter) observations of an emerging flux region. Exploiting the seeing-free, high-spatial-resolution observations provided by the 1-meter balloon-borne telescope, SCIP achieved seamless multi-line spectropolarimetry from the photosphere to the lower chromosphere. We analyzed the multi-line Stokes profiles of the photospheric Fe I and K I lines and the chromospheric Ca II lines, and applied the Weak Field Approximation to the K I and Ca II lines to reconstruct the 3D MAGNETic field structure. The blue- and red-wing brightenings of the Ca II 8542 Å line appear at spatially offset locations, indicating bi-directional RECONNECTion flows. The reconstructed 3D MAGNETic field reveals that the opposite-polarity field structure reaches different heights in the two events analyzed. In one event, it is confined to the lower layers and is absent at the formation height of Ca II 8542 Å core, which shows no intensity enhancement, whereas in the other event it extends up to the Ca II 8542 Å core formation height, where enhanced line-core intensity is also observed. We interpret this as the RECONNECTion current sheet reaching different altitudes. These results demonstrate that SCIP has successfully resolved the 3D structure of EBs, distinguishing MAGNETic RECONNECTion events occurring at different atmospheric heights.
[abstract 24 / 52] (score: 3) - Title: Metal sign of a large-scale AGN feedback in cool-core cluster MACS J1931.8-2634Authors: Qinnan Zhu, Junjie Mao, Ping Zhou, Yuanyuan Su, Dan Hu,Comments: Accepted for publication in Astronomy & Astrophysics. 7 pages, 5 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
The spatial distribution of metals in the intracluster medium (ICM) is a sensitive tracer of the chemical and dynamical history of galaxy clusters. While most cool-core (CC) clusters exhibit a centrally peaked Fe abundance profile, several outliers show an anomalous central Fe drop, potentially associated with the AGN activities. We revisit the reported large-scale (sim 100 kpc) central Fe drop in the massive CC cluster MACS J1931.8-2634 using new XMM-Newton observations. We aim to verify this feature and search for imprints of AGN feedback on the ICM metallicity distribution. We analyzed sim 170 ks of new XMM-Newton observations and re-analyzed sim 100 ks archived Chandra observations. We derived radial and two-dimensional (2D) Fe abundance maps from CCD spectra. High-resolution RGS spectra were used to constrain the Ne/Fe abundance ratio to test the dust depletion scenario. Spectral fitting was performed in SPEX using an updated atomic database and both single- and multi-temperature collisional ionization equilibrium models. The previously reported central Fe drop is not confirmed in the radial profile from XMM-Newton. However, the 2D Fe distribution is clearly asymmetric: Fe-rich regions are elongated along the axis of the AGN cavities, extending beyond their immediate scale. The Ne/Fe ratio in the core is consistent with solar (${\rm Ne/Fe} = 1.03^{+0.25}_{-0.23}$), arguing against the dust depletion scenario.
[abstract 25 / 52] (score: 3) - Title: Round-Trip Consistency: Bidirectional Diffusion Models Can Predict Their Own Rollout ErrorsAuthors: Alexander Scheinker,Comments:Subjects: stat.ML cs.LG physics.comp-ph physics.plasm-phCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Autoregressive models accumulate error over long rollouts, yet at deployment there is no ground truth to measure it against. We train a single conditional latent diffusion model that steps a dynamical system forward or backward in time via a direction flag, and show that this bidirectionality supplies a measurement-free test-time error signal: rolling forward $i$ steps and then backward $i$ steps must return the model to its start, so the round-trip discrepancy $\mathcal{C}_i$ is a self-supervised proxy for the unobservable rollout error: no ensembles, no held-out data, no governing equations, for one extra rollout. We validate on compressible MAGNETohydrodynamics (MHD), an astrophysical turbulent radiative mixing layer, and natural face videos (CelebV-HQ). On held-out MHD trajectories, $\mathcal{C}_i$ ranks rollout error (Spearman $0.91$-$0.98$ at fixed depth; $0.69 \pm 0.16$ within trajectories), and a simple calibrator fit on training rollouts predicts its magnitude to within $1.14\times$ ($68\%$) and $1.29\times$ ($95\%$) with near-nominal coverage - one nat beyond a depth-only predictor, transferring to all six decoded physical fields. The same signal flags the out-of-distribution Orszag-Tang vortex (AUROC $0.98$; $1.0$ by depth $10$) exactly where sampling-dispersion baselines invert, and it cuts incurred error by $15\%$ at $80\%$ coverage - three times the depth-only baseline. Bidirectional training comes at negative cost, beating direction specialists in both directions, and the backward direction doubles as a fast inverse solver. On LE-PDE-UQ's turbulent Navier-Stokes benchmark, a single bidirectional model reaches accuracy within $1.3\times$ of their ten-model ensemble at a tenth of the training cost, with the best training-free pixel-level calibration. Round-trip consistency turns reversibility into a practical trust signal for generative models.
[abstract 26 / 52] (score: 3) - Title: Signatures of Lorentz violation in bright ring for Sgr A* images by radiation ineffective accretion flowsAuthors: Cuiyu Zhao, Songbai Chen, Jiliang Jing,Comments: 17 pages, 9 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
We have investigated effects of Lorentz violation (LV) on bright ring in Sgr A* images illuminated by the 230 GHz thermal SYNCHROTRON emission from radiation ineffective accretion flows around a rotating LV BLACK HOLE within the low-energy Hořava gravity framework. Our results reveal that the LV parameter reduces the bright ring diameter yet increases its width, luminosity, azimuthal asymmetry and orientation angle. Higher spin parameter strengthens the LV-induced effects on bright ring properties.Increasing disk thickness reduces the ring diameter and enhances the LV parameter's effects on this diameter. The ring width shows no systematic dependence on the disk thickness. These quantities of bright ring display similar trends against BLACK HOLE spin and the LV parameter for the rotating LV BLACK HOLE. Using EHT observational data of Sgr A*, we find that, at fixed disk thickness, the allowed range of the LV parameter first broadens and then contracts with growing BLACK HOLE spin, and shifts toward smaller LV parameter values. In addition, the LV parameter narrows the permitted range of BLACK HOLE spin: negative LV parameter values shift this range to higher spin, while positive values shift it to lower spin. Finally, we probe effects of the LV parameter on the peak position value and the width of the primary image and the $n=1$ photon ring for the rotating LV BLACK HOLE. The peak positions and their widths decrease with the LV parameter, except for a narrow range. The peak position differences for various LV parameter are more pronounced for pure Keplerian accretion flow. In additional, the primary image and the $n=1$ photon ring produced by pure radially free-falling flows are broader than their counterparts generated by pure Keplerian flows.
[abstract 27 / 52] (score: 3) - Title: Spectral decoherence without dePOLARIZATION in curvature radiationAuthors: A. G. Tevzadze, N. L. Shatashvili,Comments: Accepted for publication in Astronomy and Astrophysics (Letter)Subjects: astro-ph.HECreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Context: Fast radio bursts often exhibit strong linear POLARIZATION together with pronounced spectral structure. Yet in coherent curvature radiation, spectral decoherence and dePOLARIZATION are not necessarily simultaneous. Aims: We investigate spectral and POLARIZATION coherence in curvature radiation from extended ultraRELATIVISTIC sources. Methods: Using the coherency matrix formalism together with an asymptotic phase expansion for a uniformly emitting extended source, we derive the spectral and POLARIZATION coherence properties of curvature radiation. Results: We show that spectral decoherence and dePOLARIZATION are governed by distinct physical conditions and therefore develop on separate scales. Retardation phase variations suppress spectral coherence, whereas POLARIZATION remains largely preserved across the RELATIVISTIC beaming cone, naturally producing a broad polarized but spectrally decoherent regime whose extent increases toward higher frequencies and larger Lorentz factors. Conclusions: Spectral decoherence without strong dePOLARIZATION naturally arises in ultraRELATIVISTIC curvature radiation and may explain highly polarized fast radio bursts with strong spectral modulation or narrow band structure.
[abstract 28 / 52] (score: 3) - Title: Search for active-sterile neutrino transitions using Pierre Auger Observatory dataAuthors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, M. Ahmed, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin, O. Batalla Cruz, J. P. Behler, C. Berat, M. E. Bertaina, M. Bianciotto, P. L. Biermann, V. Binet, K. Bismark, T. Bister, J. Biteau, J. Blazek, J. Blümer, M. Boháčová, D. Boncioli, C. Bonifazi, N. Borodai, J. Brack, P. G. Brichetto Orquera, S. Buitink, A. Bwembya, T. R. Caba Pineda, K. S. Caballero-Mora, S. Cabana-Freire, L. Caccianiga, J. Caraça-Valente, R. Caruso, A. Castellina, F. Catalani, G. Cataldi, L. Cazon, M. Cerda, B. Čermáková, A. Cermenati, K. Cerny, J. A. Chinellato, J. Chudoba, L. Chytka, R. W. Clay, A. C. Cobos Cerutti, R. Colalillo, R. Conceição, A. Condorelli, G. Consolati, M. Conte, F. Convenga, D. Correia dos Santos, P. J. Costa, C. E. Covault, M. Cristinziani, C. S. Cruz Sanchez, S. Dasso, K. Daumiller, B. R. Dawson, R. M. de Almeida, E. -T. de Boone, B. de Errico, J. de Jesús, S. J. de Jong, J. R. T. de Mello Neto, I. De Mitri, D. de Oliveira Franco, F. de Palma, V. de Souza, E. De Vito, A. Del Popolo, O. Deligny, N. Denner, K. Denner Syrokvas, L. Deval, A. di Matteo, C. Dobrigkeit, J. C. D'Olivo, L. M. Domingues Mendes, T. Dominguez, Y. Dominguez Ballesteros, Q. Dorosti, R. C. dos Anjos, J. Ebr, F. Ellwanger, R. Engel, M. Erdmann, A. Etchegoyen, C. Evoli, H. Falcke, G. Farrar, A. C. Fauth, T. Fehler, F. Feldbusch, A. Fernandes, M. Fernández Alonso, B. Fick, J. M. Figueira, P. Filip, A. Filipčič, B. Flaggs, A. Franco, M. Freitas, T. Fujii, A. Fuster, C. Galea, B. García, C. Gaudu, P. L. Ghia, U. Giaccari, M. Giammarco, C. Glaser, F. Gobbi, F. Gollan, G. Golup, P. F. Gómez Vitale, J. P. Gongora, N. González, D. Góra, A. Gorgi, M. Gottowik, F. Guarino, G. P. Guedes, Y. C. Guerra, L. Gülzow, S. Hahn, P. Hamal, M. R. Hampel, P. Hansen, V. M. Harvey, A. Haungs, M. Havelka, T. Hebbeker, C. Hojvat, J. R. Hörandel, P. Horvath, M. Hrabovský, T. Huege, A. Insolia, P. G. Isar, M. Ismaiel, P. Janecek, V. Jilek, K. -H. Kampert, B. Keilhauer, V. V. Kizakke Covilakam, H. O. Klages, M. Kleifges, A. Klingel, J. Köhler, F. Krieger, M. Kubatova, N. Kunka, B. L. Lago, N. Langner, N. Leal, M. A. Leigui de Oliveira, Y. Lema-Capeans, A. Letessier-Selvon, I. Lhenry-Yvon, L. Lopes, M. Mallamaci, S. Mancuso, D. Mandat, P. Mantsch, A. G. Mariazzi, C. Marinelli, I. C. Mariş, G. Marsella, D. Martello, S. Martinelli, O. Martínez Bravo, A. Martínez-Mendez, M. A. Martins, H. -J. Mathes, J. Matthews, G. Matthiae, E. Mayotte, S. Mayotte, P. O. Mazur, G. Medina-Tanco, D. Melo, A. Menshikov, C. Merx, S. Michal, M. I. Micheletti, L. Miramonti, M. Mogarkar, S. Mollerach, F. Montanet, L. Morejon, K. Mulrey, R. Mussa, W. M. Namasaka, S. Negi, L. Nellen, K. Nguyen, G. Nicora, M. Niechciol, D. Nitz, D. Nosek, A. Novikov, V. Novotny, L. Nožka, A. Nucita, L. A. Núñez, S. E. Nuza, J. Ochoa, M. Olegario, C. Oliveira, L. Östman, M. Palatka, J. Pallotta, G. Parente, T. Paulsen, M. Pech, J. Pękala, R. Pelayo, C. Pérez Bertolli, L. Perrone, S. Petrera, T. Pierog, M. Pimenta, M. Platino, P. Privitera, C. Priyadarshi, M. Prouza, K. Pytel, S. Querchfeld, J. Rautenberg, D. Ravignani, J. V. Reginatto Akim, M. Z. Rennó, A. Reuzki, J. Ridky, F. Riehn, M. Risse, V. Rizi, B. Rocha Moldes, E. Rodriguez, G. Rodriguez Fernandez, J. Rodriguez Rojo, S. Rossoni, M. Roth, E. Roulet, A. C. Rovero, A. Saftoiu, M. Saharan, F. Salamida, H. Salazar, G. Salina, P. Sampathkumar, N. San Martin, J. D. Sanabria Gomez, F. Sánchez, F. M. Sánchez Rodriguez, E. Santos, F. Sarazin, R. Sarmento, R. Sato, P. Savina, V. Scherini, H. Schieler, M. Schimp, D. Schmidt, O. Scholten, H. Schoorlemmer, P. Schovánek, F. G. Schröder, J. Schulte, T. Schulz, S. J. Sciutto, M. Scornavacche, A. Sedoski, S. Sehgal, S. U. Shivashankara, G. Sigl, K. Simkova, F. Simon, R. Šmída, S. Soares Sippert, P. Sommers, S. Stanič, J. Stasielak, P. Stassi, S. Strähnz, M. Straub, T. Suomijärvi, A. D. Supanitsky, Z. Svozilikova, Z. Szadkowski, F. Tairli, A. Tapia, C. Taricco, C. Timmermans, O. Tkachenko, P. Tobiska, C. J. Todero Peixoto, B. Tomé, A. Travaini, P. Travnicek, C. Trimarelli, M. Tueros, M. Unger, R. Uzeiroska-Geyik, L. Vaclavek, M. Vacula, I. Vaiman, J. F. Valdés Galicia, L. Valore, P. van Dillen, E. Varela, V. Vašíčková, A. Vásquez-Ramírez, D. Veberič, I. D. Vergara Quispe, S. Verpoest, V. Verzi, J. Vicha, S. Vorobiov, J. B. Vuta, A. A. Watson, A. Weindl, M. Weitz, L. Wiencke, H. Wilczyński, B. Wundheiler, B. Yue, A. Yushkov, E. Zas, D. Zavrtanik, M. Zavrtanik,Comments: 11 pages, 4 figuresSubjects: hep-ph astro-ph.HE hep-exCreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
We investigate the sensitivity of the Pierre Auger Observatory to physics beyond the Standard Model arising from MAGNETic-moment-induced transitions between active and heavy sterile neutrinos. Such dipole portal interactions can enhance neutrino-nucleon cross sections above a kinematic threshold set by the sterile neutrino mass, leading to observable modifications of neutrino detection rates at ultrahigh energies (UHE). We estimate the impact of these interactions on both down-going and Earth-skimming neutrino detection channels, the contrasting responses of which enable discrimination between an enhanced neutrino flux and a modified interaction cross section. Using the non-observation of UHE neutrino candidates, we derive neutrino-flux-dependent constraints with 90% confidence-level on the transition MAGNETic moment for sterile neutrino masses in the range 1 TeV-100 TeV. Under the assumed flux scenarios, the resulting flavor-independent limits extend existing bounds into previously unexplored parameter space.
[abstract 29 / 52] (score: 3) - Title: Abnormal Nitrogen Abundance in the X-ray Spectrum of Quasi-periodically Erupting Source AT2019wzcAuthors: Tao Wu, Xinwen Shu, Luming Sun, Ning Jiang, Jiazheng Zhu, Wenjie Zhang,Comments: 8 pages, 4 figures, comments welcomeSubjects: astro-ph.HECreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
Quasi-periodic eruptions (QPEs) are rapid, recurring soft X-ray bursts, whose nature is still in dispute. A compelling case of QPEs has emerged in the slowly evolving optical transient AT2019wzc, possibly associated with the tidal disruption of a post-main-sequence star by a supermassive BLACK HOLE. Further evidence of a tidal disruption event (TDE) is crucial to understand the nature of AT2019wzc and establish the link between TDE and QPEs. Here we report the detection of a narrow, blueshifted N VI absorption line in its high-resolution X-ray spectra obtained by XMM-Newton, but weak or undetectable absorption lines from other elements of similar ionization states such as carbon and oxygen. The absorption line features can be reproduced by an ionized gas with ionization parameter $\log ξ\sim 0.3\ {\rm erg~cm~s^{-1}}$ and column density $N_{\rm H}\sim 10^{20}\ {\rm cm^{-2}}$, under the condition of a nitrogen abundance of $11.6_{-7.8}^{+19.6}$ times the solar value. This abnormal nitrogen abundance favors a TDE origin for AT2019wzc, and the absorbing gas may originate from the outflow induced by self-collision of the TDE's debris stream.
[abstract 30 / 52] (score: 2) - Title: Neural Surrogate HMC: On Using Neural Likelihoods for Hamiltonian Monte Carlo in Simulation-Based InferenceAuthors: Linnea M Wolniewicz, Peter Sadowski, Claudio Corti,Comments: 22 pages, 17 figures. Accepted for publication in the Journal of Geophysical Research: Machine Learning and Computation. Published 2026 American Geophysical Union. Further reproduction or electronic distribution is not permittedSubjects: cs.LG astro-ph.HECreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
Bayesian inference methods such as Markov Chain Monte Carlo (MCMC) typically require repeated computations of the likelihood function, but in some scenarios this is infeasible and alternative methods are needed. Simulation-based inference (SBI) methods address this problem by using machine learning to amortize computations. In this work, we highlight a particular synergy between the SBI method of neural likelihood estimation and the classic MCMC method of Hamiltonian Monte Carlo. We show that approximating the likelihood function with a neural network model can provide three distinct advantages: (1) amortizing the computations for MCMC; (2) providing gradients for Hamiltonian Monte Carlo, and (3) smoothing over noisy simulations resulting from numerical instabilities. We provide practical guidelines for defining a prior, sampling a training set, and evaluating convergence. The method is demonstrated in an application modeling the heliospheric transport of galactic COSMIC RAYs, where it enables efficient inference of latent parameters in the Parker equation.
[abstract 31 / 52] (score: 2) - Title: Time lags and their association with the Boundary Layer structure in a Z source GX 349+2Authors: Abhishek M. V. R., Sriram K, Gouse SD,Comments:Subjects: astro-ph.HECreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Studying the cross-correlation function between the soft and hard X-ray emission in Neutron Star Low Mass X-ray Binaries provides crucial insight into the structure and dynamics of the innermost accretion regions. In this work, we investigate the CCF of the Z-source GX 349+2 using an XMM-Newton observation. We noted that asymmetric CCFs with lags of a few hundred secondsbetween soft and hard band LCs in the horizontal branch, whereas CCFs remained symmetric in normal and flaring branches. We also performed a CCF study during the flux transition duration and observed lags of the order of a few tens to hundreds of seconds. Monte Carlo simulations were performed to assess the robustness of these CCFs, confirming their significance at a 95% confidence level. Spectral analysis during the flux transitions further suggests that the inner accretion disk extends close to the last stable orbit. We propose that the observed hard lags arise from the readjustment of the boundary layer/coronal region located near the inner edge of the accretion disk. From the measured lags, we estimate the characteristic size of the boundary layer. We show that the observed lags could also be associated with the depletion timescale of the boundary layer with low viscosity.
[abstract 32 / 52] (score: 2) - Title: Long-lived quasinormal frequencies for regular BLACK HOLE supported by the Einasto profile in the presence of the MAGNETic fieldAuthors: Milena Skvortsova,Comments: 12 pages, 7 figures, the mistakes have been correctedSubjects: gr-qcCreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
We investigate quasinormal modes, grey-body factors, and absorption cross-sections of a massive scalar field in regular black-hole spacetimes supported by the Einasto density profile. The analysis is performed for $\tilde n=1/2$, $1$, and $5$, where the scalar mass $μ$ is treated as an effective parameter induced by an external environment. Quasinormal frequencies are computed with high-order WKB expansions and Padé resummation, and are cross-checked by time-domain evolution. We show that increasing the effective mass and varying the Einasto parameters can strongly suppress the damping rate, leading to long-lived modes and clear quasi-resonant behavior. Grey-body factors obtained from direct WKB transmission and from the QNM-based correspondence agree well in the considered regimes, while their differences remain controlled. Using the transmission coefficients, we derive partial and total absorption cross-sections and demonstrate the expected transition from low-frequency suppression to efficient high-frequency absorption. Our results show that regularity of the core together with environmental parameters leaves a noticeable imprint on both ringdown and scattering observables. Within this setup, the MAGNETic field acts as the physical agent that controls the effective mass scale and therefore governs how close the system can approach the quasi-resonant regime.
[abstract 33 / 52] (score: 2) - Title: Low-Order Bessel-Type PID Dynamics in Lithium-Based Tritium Breeding and Heat-Removal SystemsAuthors: S. A. S. Borges, S. D. Campos,Comments: Updated version with improvementsSubjects: physics.plasm-ph nucl-exCreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Lithium plays a dual role in deuterium-tritium fusion systems by enabling tritium breeding in blankets and providing an efficient heat-removal medium in liquid-metal components. However, most existing investigations treat neutronic behavior, JET thermohydraulics, and feedback control as largely decoupled layers, and there is currently no compact analytical framework that simultaneously links lithium-based tritium breeding, JET thermal response, and controller dynamics. In this work, we integrate nuclear cross-section data for deuterium-tritium and lithium reactions with a reduced thermohydraulic model of a liquid-lithium JET and an operator-theoretic formulation of feedback control. The resulting blanket/JET configuration should be interpreted as a conceptual, reduced-order demonstration of how two Li-based subsystems can be coupled in a unified analytical framework, rather than as a fully realistic reactor design in which an IFMIF-type neutron source is directly attached to a self-sufficient power blanket. We derive a low-order model describing JET thermal expansion under deuteron-beam loading and demonstrate that a continuous-time proportional-integral-derivative controller, expressed in operator form, can be locally embedded within a family of Bessel-type differential operators acting on the tritium-inventory tracking error. The results suggest that lithium-based breeding and heat-removal systems admit low-order, proportional-integral-derivative controllable dynamics that can be interpreted in terms of localized Bessel modes, providing a compact analytical framework for guiding future controller design and blanket/JET optimization.
[abstract 34 / 52] (score: 2) - Title: Revisiting the sphaleron and axion production rates in QCD at high temperaturesAuthors: Sayak Guin, Sayantan Sharma,Comments: v3: published versionSubjects: hep-lat astro-ph.CO hep-ph hep-thCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
We report our new lattice results for the sphaleron rate calculated within a thermal effective field theory of soft SU(N) gluons whose momenta are below the MAGNETic scale, where $N=2,3$, for a wide range of temperatures spanning from $0.6$ to $10^{15}$ GeV at sufficiently large volumes. Comparing these results with sphaleron rates in a nonthermal SU(N) plasma where the infrared gluons are overoccupied, we estimate the typical thermalization time for these ultrasoft gluons during the early stages of reheating after inflation. We also calculate the thermal production rate of RELATIVISTIC axions due to these non-perturbatively interacting soft gluons which shows a significant deviation from its perturbative estimate even at the electroweak scale.
[abstract 35 / 52] (score: 2) - Title: Scalar memory from compact binary coalescencesAuthors: Jann Zosso, Silvia Gasparotto, Llibert Aresté Saló, Daniela D. Doneva, Stoytcho S. Yazadjiev,Comments: 16 pages, 5 figuresSubjects: gr-qcCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Gravitational memory provides a distinctive low-frequency probe of gravity, but explicit merger studies beyond general relativity remain limited. In this letter, we investigate memory from binary BLACK HOLE mergers in Ricci-coupled scalar-Gauss-Bonnet gravity, a natural extension of scalar-Gauss-Bonnet theory that admits an additional scalar breathing POLARIZATION. Based on numerical-relativity waveforms of binary BLACK HOLE coalescences, we show that the change in the scalar charge of the system across merger generates a significant scalar-memory contribution. For a GW150914-like system, this effect modifies the memory signal in a gravitational-wave detector on the same observable timescale and by an amount comparable to the pure scalar-Gauss-Bonnet correction to tensor memory. Thus, it can substantially enhance the total deviation from the general-relativity prediction over a broad range of source and detector configurations. We argue that this identifies a general mechanism: whenever a compact-binary merger changes the asymptotic charge of an additional gravitational field, and that field sources an observable extra POLARIZATION, the resulting memory can provide a leading low-frequency signature of new gravitational physics.
[abstract 36 / 52] (score: 2) - Title: Galaxy-cluster-stacked FERMI-LAT, part IV: $\sim70$ GeV WIMP annihilation linesAuthors: Uri Keshet,Comments: Additional robustness testsSubjects: astro-ph.HE astro-ph.CO hep-phCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
The strongest constraints on the velocity-dependent ($p$-wave) annihilation of weakly interacting massive particle (WIMP) DARK MATTER were derived from the deep potential wells of galaxy clusters. Even weaker signals can be extracted from sufficient aggregated clusters, by cross-correlating $γ$-rays with large-scale structure tracers or stacking over extensive cluster catalogs. Three independent such analyses show a similar triad of emission lines in FERMI-LAT data, around 70, 40, and 13 GeV, emerging from featureless spectra in each hemisphere upon cross-correlation with eROSITA maps, and in stacked MCXC, eROSITA, and DESI catalog clusters only once boosted to the cluster frame. These lines fit the anticipated $χχ\toγγ$, $γZ$, and $γh$ annihilation channels of a $\sim70$ GeV WIMP $χ$, detected by composite matched filters at trial-corrected global $Z$-scores reaching $5.6σ$ (cross-correlations) and $2.3σ$ (stacking), with intrinsic $\sim10^{[-20,-19]}$ cm$^3$ s$^{-1}$ channel cross-sections. High-resolution spectra establish six lines and an unresolved ($2$--$3$ line) feature in total, naturally aligned with the anticipated nine channels of two cross-annihilating WIMPs of masses $67.3_{-0.1}^{+0.1}$ and $71.4_{-0.1}^{+0.2}$ GeV (profile-likelihood bounds; $_{-5\%}^{+3\%}$ systematic; $5.3σ$). The Galactic-center GeV excess is broadly consistent with the corresponding broad annihilation continuum.
[abstract 37 / 52] (score: 2) - Title: When the BLACK HOLEs align: a subpopulation of aligned massive binary BLACK HOLEs observed via gravitational wavesAuthors: Stefano Rinaldi, Charmaine Wong, M. Paola Vaccaro, Elvir Mislimi, Otto A. Hannuksela, Samson H. W. Leong, Michela Mapelli,Comments: 9 pages, 6 figures. Resubmitted after implementing referee's commentsSubjects: astro-ph.HECreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
In this work, we investigate the features present in the joint primary mass and effective spin distribution of binary BLACK HOLEs without relying on specific modelling assumptions. We make use of non-parametric methods, flexible models capable of approximating arbitrary probability densities with minimal mathematical assumptions, applying it to the newly released GWTC-5.0. Our analysis supports, albeit with large uncertainties, the presence of at least two separate sub-population of binary BLACK HOLEs showing different effective spin distributions: one of them, preferring positive $χ_\mathrm{eff}$ values, points towards the direction of systems formed in a non-spherically-symmetric, dynamical environment.
[abstract 38 / 52] (score: 2) - Title: No way ou$τ$: Epoch of Reionization Observations Do not Support Large Values of the Optical Depth to ReionizationAuthors: Paulo Montero-Camacho, Yi Mao,Comments: Comments welcome! 8 pages, 5 figures. New version replaces the LambdaT model for the main model used in Ref. [5]Subjects: astro-ph.COCreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
Recent cosmological analyses combining high-redshift cosmic microwave background (CMB) measurements with low-redshift baryon acoustic oscillation (BAO) data have reported a preference for dynamical DARK ENERGY, with the cosmological constant scenario ($Λ$CDM) disfavored at the $\sim 3σ$ level. These analyses, however, typically rely on large-scale CMB POLARIZATION measurements to constrain the optical depth to reionization $τ_{\rm reio}\sim 0.06$, raising the question of whether potential systematics in this dataset could influence the inferred cosmological preference. Excluding large-scale POLARIZATION data substantially weakens the tension with $Λ$CDM to the $\lesssim 2σ$ level, nevertheless at a price of increasing $τ_{\rm reio}$ significantly to $\sim 0.09$. Here, we use a physically motivated Gompertzian reionization framework to perform a self-consistent Bayesian analysis combining CMB (excluding large-scale POLARIZATION data), BAO, and independent measurements of the neutral hydrogen fraction evolution from QUASAR damping wing observations and dark pixel constraints. We derive $τ_{\rm reio} = 0.067 \pm 0.011$ (dynamical DARK ENERGY scenario) in good agreement with cosmological analyses that would include large-scale CMB POLARIZATION data, while the inferred reionization history is consistent with multiple observational constraints. Our analysis recovers a preference for dynamical DARK ENERGY at the $\gtrapprox2σ$ level. These results demonstrate that astrophysical probes of reionization independently recover the optical depth required by CMB POLARIZATION measurements, suggesting that potential systematics in large-scale POLARIZATION alone are unlikely to fully explain the emerging preference for dynamical DARK ENERGY.
[abstract 39 / 52] (score: 2) - Title: Optical Landscapes and High-Energy Collisions in Hairy Horndeski GravityAuthors: Filipe Cattete Alves, Rodrigo Maier,Comments:Subjects: gr-qcCreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
We investigate the null geodesic structure, photon sphere dynamics, and high-energy particle collisions within a class of static, spherically symmetric hairy Horndeski BLACK HOLEs. Characterized by an invariant metric root at $r = 2M$ and a scalar hair parameter $Q$, the spacetime maps onto four distinct geometric domains dictated by the surface gravity $κ|_{2M}$. We derive exact analytical expressions for the photon sphere radius $r_{\text{ph}}$ and its dynamic stability criterion, showing that external circular null orbits remain dynamically unstable across non-extremal regimes. Crucially, we prove that a stable photon sphere arises exclusively in the extremal configuration ($Q = -2M$), where it coincides precisely with the degenerate horizon ($r = 2M$). We argue that this horizon-bound stable photon orbit acts as an infinitely redshifted bound state for light and ultra-RELATIVISTIC particles. Finally, we analyze the Bañados-Silk-West (BSW) effect for infalling timelike test particles, demonstrating that the center-of-mass energy $E_{\text{cm}}$ for critical collisions diverges as $E_{\text{cm}} \propto (r - r_h)^{-1/2}$ strictly at the extremal threshold $Q = -2M$.
[abstract 40 / 52] (score: 2) - Title: Adaptive Hybrid Modeling of Collisionless Plasma Shocks and Ion AccelerationAuthors: Yuri A. Omelchenko, Igor V. Sokolov, Lulu Zhao, Keheng Zhu,Comments: Submitted to The Astrophysical Journal. 9 figures, 1 tableSubjects: physics.space-ph astro-ph.SRCreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
We present a novel efficient technique for hybrid (kinetic ions, quasi-neutral fluid electrons) simulations of non-RELATIVISTIC MAGNETized collisionless plasma shocks, frequently observed near the Sun, in the solar system, and beyond. This Adaptive Frame-Of-Reference Algorithm (AFORA) enables multi-dimensional simulations of plasma shocks along with concomitant ion acceleration in the shock frame, where shock evolution remains quasi-steady. Compared to moving shocks, this technique allows us to reduce the simulation time and domain size to a minimum while achieving converged shock dynamics and spectra of energetic ions. Using an event-driven (asynchronous) hybrid code, HYPERS, we demonstrate this approach in two spatial dimensions for different orientations of the background MAGNETic field with respect to the shock normal. Our results show excellent agreement of simulation shocks with observations of interplanetary (IP) shocks. We verify that different shock configurations (quasi-parallel, oblique, and quasi-perpendicular) convert bulk plasma flow energy into ion acceleration with varying degrees of efficiency. These findings underscore the importance of efficient and robust numerical algorithms for future high-resolution modeling of plasma shocks and ion acceleration in three dimensions. In addition to enabling efficient computational studies of collisionless shocks in general, this work paves the way for accurate prediction of seed populations of Solar Energetic Particles (SEPs), generated by coronal mass ejection (CME) shocks. The characteristics of seed ions can be used as inputs to Fokker-Planck models that simulate long-term transport and acceleration of ions along MAGNETic field lines through their interactions with background solar wind turbulence.
[abstract 41 / 52] (score: 2) - Title: A Review of How Supermassive Black Hole Binaries Can Be Detected and Characterized through Gravitational Lensing of Background StarsAuthors: Mu'allim Yakubu,Comments: 11 Pages. Review ArticleSubjects: astro-ph.GACreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
Supermassive BLACK HOLE binaries are an inevitable outcome of hierarchical galaxy mergers, but their sub-parsec evolutionary phase between the kpc separations resolvable by direct imaging and the millihertz gravitational-wave regime targeted by LISA remains observationally elusive. Gravitational lensing of background stars by SMBH binaries has emerged as a powerful complement to periodic variability searches, periodic Doppler-boost signals, and circumbinary accretion hydrodynamic models. Two distinct lensing channels are reviewed: (i) the gravitational lensing of Milky Way bulge stars by the central Sgr A-star binary, whose secondary image is now within reach of ELT-class instruments; and (ii) the recently introduced Quasi-Periodic Lensing of Starlight (QPLS) mechanism, in which the rotation of caustics produced by a non-active SMBH binary magnifies individual bright stars in its host galaxy on the orbital period of the binary. The QPLS framework predicts 1-50 (190-5000) binaries per cubic parsec with periods below 10 yr and redshift z less than 0.3, opening a multimessenger window onto pulsar timing array sources and LISA-band events. After outlining the theoretical foundation, microlensing formalism, observational status, and the synergy with pulsar timing arrays and LISA, we identify outstanding challenges and project the field into the LSST era.
[abstract 42 / 52] (score: 2) - Title: On the ideal stability of the sheared-flow Z pinchAuthors: Daniel W. Crews, Jackson C. Turner,Comments: 20 pages, 16 figuresSubjects: physics.plasm-ph physics.flu-dynCreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
Sheared-flow Z-pinch stability has been studied within ideal MHD primarily through growth rate calculations, which find that even trans-Alfvénic sheared flows apparently fail to suppress the kink instability. Trans-Alfvénic sheared flow does stabilize the MHD kink but also excites shear-driven instabilities characteristic of high-Reynolds-number supersonic flow. This distinction is evident from the dispersion relations underlying the growth rates, computed here as the analytic dispersion function in the complex-frequency plane. Regularization splits this function into adiabatic and resonant parts describing how discrete modes emerge from and interact with the continuous spectrum. The Doppler-shifted flow continuum interacts with the interchange and kink instabilities in distinct ways. For interchange, the continuum overlaps the instability branch at all wavenumbers, so even sub-Alfvénic sheared flow stabilizes profiles modestly beyond the interchange threshold. The kink, by contrast, is shielded from the continuum by a frequency gap, and trans-Alfvénic flow is required to Doppler-shift the continuum into resonance with it, giving a geometric picture of the stabilization threshold. But shear-driven instabilities arise at this same threshold, including reflection modes and an acoustic kink. It is these shear-driven modes, not the original MHD instabilities, that dominate the ideal-MHD spectrum in trans-Alfvénic conditions. The ideal analysis thus describes the stabilization mechanism while showing that the stability of the sheared-flow Z pinch ultimately rests on non-ideal physics, including finite orbit width and dissipation.
[abstract 43 / 52] (score: 2) - Title: The generation of spiral density waves by MRI in accretion discsAuthors: G. Mamatsashvili, D. Kobaidze, W. Mouhali, T. Lehner, L. Burdiladze,Comments: 14 pages, 6 figures, accepted for publication in MNRASSubjects: astro-ph.EP astro-ph.HE astro-ph.SRCreated: 2026-07-31; Updated: 2026-08-04; Datestamp: 2026-08-04
We investigate the linear dynamics of non-axisymmetric perturbations in Keplerian discs subject to a weak uniform vertical MAGNETic field in the shearing box approximation. Perturbations are decomposed into shearing waves and evolved by numerically integrating the linearized ideal MHD equations. The disc flow supports three basic perturbation modes: two incompressible modes - MAGNETic mode that undergoes MAGNETorotational instability (MRI) and inertia-MAGNETic waves - and compressible spiral density waves. The MAGNETic mode and inertia-MAGNETic waves have a low frequency of the order of Alfvén and orbital frequencies, respectively, while density waves have high-frequency. We introduce mode eigenfunctions and governing modal equations to analyze the dynamics of individual modes. For non-axisymmetric modes, the modal equations are coupled due to the shear of the Keplerian rotation of the disc, giving rise to a new shear-induced linear mode coupling process, which is rooted in the non-self-adjoint nature of shear flows. We focus on the generation of density waves by the dominant MRI-unstable MAGNETic mode. We show that initially imposed MAGNETic mode undergoes MRI growth and abruptly excites density waves when its radial wavenumber crosses zero. The density wave-MRI coupling is most efficient when the azimuthal and vertical wavelengths of perturbations are comparable to the disc scale height. Since density waves are compressible, whereas MRI is incompressible, this wave excitation process can also be regarded as a linear mechanism generating compressible motions via MRI-driven incompressible ones. Its implications for compressible nonzero net vertical field MRI-turbulence are also discussed.
[abstract 44 / 52] (score: 2) - Title: Evading Cauchy Horizon Excision in Scalarized Regular Black HolesAuthors: Ernesto Contreras, Pedro Bargueño, Arthur G. Suvorov,Comments: 9 pages, 2 figures. Accepted for publication in Phys. Rev. DSubjects: gr-qc astro-ph.HE hep-thCreated: 2026-08-01; Updated: 2026-08-04; Datestamp: 2026-08-04
Spontaneous scalarization provides a dynamical mechanism to evade the no-hair paradigm, but it has been argued to generically eliminate the Cauchy horizon in charged BLACK HOLEs. We show that this obstruction is not universal, but instead follows from the sign-definite structure of the Einstein-Maxwell source term. Within the $P$-dual formulation of nonlinear electrodynamics, we derive a general condition under which the effective scalar source changes sign between the horizons, allowing the integral constraint to be satisfied without destroying the Cauchy horizon. This establishes that the fate of the Cauchy horizon depends on the electroMAGNETic coupling and identifies candidate theories where scalarized horizons may persist. The resulting framework opens the possibility of studying scalarization in the inter-horizon region and its interplay with mass inflation.
[abstract 45 / 52] (score: 2) - Title: Unified remnant models for aligned-spin, precessing, and eccentric binary BLACK HOLE mergersAuthors: Tousif Islam, Digvijay Wadekar, Gaurav Khanna,Comments: Models are available through https://github.com/tousifislam/gwModels/Subjects: gr-qc astro-ph.HECreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Using approximately $5000$ numerical-relativity (NR) simulations spanning mass ratios up to $q=128$ and $1200$ black-hole-perturbation-theory (BHPT) simulations extending to $q=1000$, we present fully analytic models for the remnant properties of quasi-circular binary BLACK HOLE mergers. The models gwModelRemS (for final mass, final spin, peak luminosity, and recoil kick) and gwModelRemP (for final mass, final spin, and peak luminosity) describe nonprecessing and precessing binaries, respectively. Our approach combines analytic insights from post-Newtonian theory and point-particle limits with a data-driven fitting framework which also includes validation-guided AI-agent-assisted optimization. The resulting fits outperform existing analytic models and achieve accuracies comparable to data-driven models within their domains of validity. We also construct gwModelRemP\_flow, a normalizing-flow model for recoil kicks from precessing binaries, marginalized over the in-plane spin orientations. This model additionally utilizes an enlarged low-fidelity training set, beyond the available NR and BHPT simulations, constructed through a waveform-based data-augmentation procedure. We also include simple eccentric extensions through leading-order dependence on eccentricity and orbital anomaly. The models span the equal-mass to extreme-mass-ratio regimes and are publicly available through the gwModels package for applications in gravitational-wave astronomy, astrophysical population studies, and cosmology.
[abstract 46 / 52] (score: 2) - Title: VLT/MUSE Study of Close AGN Pairs and Host Galaxies in the Local Universe. I. Overview of the Ionized GasAuthors: Xiaoyu Xu, Zhiyuan Li, Meicun Hou, Junfeng Wang, Fuyan Bian, Yan-Mei Chen,Comments: 20+15 pages, 5+11 figures, 5+1 tables, accepted for publication in ApJSSubjects: astro-ph.GACreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Studying AGN pairs and their host galaxies is essential for understanding the interplay between galaxy mergers and key internal processes such as supermassive BLACK HOLE fueling and feedback. We cross-match between the Big Multi-AGN Catalog (The Big MAC) and the public data archive of the VLT/MUSE, and obtain 12 AGN pair candidates in the local universe ($z\lesssim0.1$) with a projected distance $r_{\rm p}\leq 20\rm\,kpc$. Using the archival VLT/MUSE data, we present a spatially resolved study of the ionized gas kinematics and ionization properties of these 12 AGN pair candidates. By decomposing the optical emission lines into two Gaussian components, we try to separate gas associated with disk rotation from non-circular motions. We further identify dominant ionization mechanisms using spatially resolved BPT diagnostics. We find that both nuclei in 4 of the 12 systems are classified as Seyfert or LINER. In addition, three nuclei are classified as star-forming or composite in the optical diagnostics, but are identified as AGNs at other wavelengths. Kinematically, regularly rotating ionized gas disks are detected in 16 of 24 nuclei. Prominent tidal features traced by ionized gas are also detected in 9 systems. Ionized gas outflows are widespread and are detected in 18 nuclei. Finally, for three nuclei (Mrk 739A, NGC 7592B, and J1544+0446A), we find evidence for fading AGN activity over the past several $10^{4}\rm\, yr$, based on optical emission-line ratios and an assumed AGN photoionization model.
[abstract 47 / 52] (score: 2) - Title: Two-fluid boundary turbulence simulations in reversed field pinch plasmasAuthors: M. Giacomin, B. Momo, I. Predebon, N. Vianello, M. Zuin,Comments:Subjects: physics.plasm-phCreated: 2026-08-02; Updated: 2026-08-04; Datestamp: 2026-08-04
Turbulent transport in MAGNETic confinement fusion devices governs the overall plasma confinement properties and regulates the plasma-material interaction at the first wall. In the plasma boundary, turbulence is typically investigated through three-dimensional two-fluid flux-driven turbulence simulations. In this work, the GBS boundary turbulence code is extended to enable turbulence simulations in reversed field pinch configurations, encompassing the reversal surface and an arbitrary level of MAGNETic chaos. The differential operators implemented in the code are modified to avoid the approximations of large-aspect ratio and weak poloidal MAGNETic field. Three-dimensional Poisson and Ampere solvers are implemented to allow for turbulence simulations in conditions of partially or fully disrupted MAGNETic flux surfaces. This modified version of the GBS code is then applied to simulate turbulence in the boundary of RFX-mod reversed field pinch plasmas. Turbulent eddies across the reversal surface show properties similar to those typically found in tokamak boundary turbulence simulations. Despite the good agreement found with experimental measurements, these simulations reveal a significant limitation of the fluid-based turbulence modeling of the edge region in reversed field pinch plasmas, which arises from the intrinsically short parallel connection length. This conclusion is also supported by a linear gyrokinetic analysis that identifies trapped electron modes as the dominant microinstability in this region.
[abstract 48 / 52] (score: 2) - Title: Spatially resolved thermal dust emission in the L1157 outflow reveals grain-driven molecular enrichmentAuthors: Siyi Feng, Hauyu Baobab Liu, Yang Lu, Qiancheng Yang, Sheng-Yuan Liu, Paola Caselli, Zhi-Yu Zhang, Shuting Lin, Xuejian Jiang, Sihan Jiao, Linjing Feng, Donghui Quan, Fujun Du, Yuanzhen Xiong,Comments: 11 pages, 5 figures, accepted by Astronomy & AstrophysicsSubjects: astro-ph.GACreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
Protostellar outflow shocks reshape local dust properties and molecular chemistry. The L1157 outflow is an archetypal chemically rich shocked region, but the thermal dust associated with its successive shocks has remained unresolved because molecular-line contamination obscures the broadband continuum. We obtained new James Clerk Maxwell Telescope (825--906 $μ$m) spectral-line observations and Submillimeter Array (1.1--1.4 mm) continuum observations toward L1157 B0-B1-B2, probing spatial scales from 0.4 pc to 1200 au. After removing molecular-line contamination on a pixel-by-pixel basis, we derived the dust temperature, column density, and dust opacity index from continuum data spanning 70 $μ$m to 1.3 mm. The line-corrected continuum maps reveal the dust distribution across successive shocks. The dust opacity index ($β\approx1.8$--2.3) indicates that grains have not grown to millimeter sizes throughout the shocked regions. Combined with previous $\rm NH_3$ observations, we find that the dust emission resolves into compact clumps along the precessing JET, whereas gaseous $\rm NH_3$ peaks at the shock fronts, reaching abundances of $\sim10^{-5}$ relative to $\rm H_2$, even where the 0.85 and 1.3 mm dust emission is detected at only 3--5$σ$. Our newly developed physicochemical shock model shows that $\rm NH_3$ forms predominantly on grain surfaces and is released by shock-induced sputtering, with the highest abundances occurring where post-shock re-adsorption remains inefficient. These results establish spatially resolved dust continuum imaging as a direct observational probe of grain evolution and provide new observational constraints on dust-gas interactions in protostellar shocks.
[abstract 49 / 52] (score: 2) - Title: Deformation of the CME and CME-driven shock due to interaction with the ambient solar wind: I. Modelling with Cone ModelAuthors: A. Niemela, A. Valentino, J. Magdalenic,Comments:Subjects: astro-ph.SRCreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
Context. The near-Earth environment is continuously impacted by the solar wind and the transients embedded in it. The largest eruptions of plasma and MAGNETic field at the Sun are Coronal Mass Ejections (CMEs), which, upon reaching Earth, can induce geoMAGNETic storms and disrupt our technologically advanced societies. Aims. We aim to improve our understanding of how CMEs and CME-driven shock waves interact with the ambient solar wind, and how the resulting deformations in time and space affect the accuracy of space weather forecasting. Methods. We studied two Earth-directed CMEs, observed on December 7, 2020 and October 28, 2021. To model the solar wind and CME propagation in the inner heliosphere, we used the state-of-the-art 3D MHD model EUHFORIA with the cone CME model, focusing on the regions along the main direction of propagation (MDP) and along the Sun-Earth line. Results. The deformations of the CME and the CME-driven shock can be significant. Both CMEs propagate in a variable background wind and are structured differently even at very close angular distances. The first, in a mildly structured wind, shows its stronger deformation predominantly away from the MDP; the second, in a more complex environment, develops a strongly structured shock at very different locations, including regions close to the MDP. Conclusions. These interactions also affect the characteristics of the CME-driven shock, such as the gas compression ratio across it. CMEs observed as flank encounters at Earth can be strongly affected by the ambient solar wind, with the expected differences in the arrival time at Earth reaching up to 16 hours.
[abstract 50 / 52] (score: 2) - Title: NEXUS: Spectral Variability of Little Red Dots and Blue Active Galactic Nuclei at $2 \lesssim z \lesssim 6$Authors: Zachary Stone, Yue Shen, Ming-Yang Zhuang, Junyao Li, Zhiwei Pan, Jenny E. Greene, Feige Wang,Comments: 24 pages, 10 figures, 2 tables. Submitted to ApJ. Key results are shown in Figures 8 & 9Subjects: astro-ph.GACreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
We present spectral measurements for 17 Little Red Dots (LRDs) and 14 blue broad-line ACTIVE GALACTIC NUCLEi (AGNs) at $2\lesssim z \lesssim 6$ using multi-epoch JWST NIRSpec MSA spectra from the NEXUS program, sampling rest-frame timescales of $\sim 1-3$ months. Overall, the LRD population shows significantly enhanced Balmer decrement compared with both blue JWST AGNs at similar redshifts and 56 low-redshift broad-line AGNs matched in H$\rmα$ luminosity. The rest-optical continua of LRDs show little ensemble variability (rms $\lesssim 3\%$), and the total H$\rmα$ emission also shows weaker ensemble variability compared with low-redshift AGNs matched in H$\rmα$ luminosity and rest-frame timescales. Based on the flux uncertainties, we constrain the intrinsic H$\rmα$ rms variability to be $\lesssim 4\%$ for the LRD population over these timescales. Combining our results with recent broad-line variability measurements of LRDs over yearly to decade timescales reveals a low-level white-noise pattern across all timescales, in stark contrast to the variability amplitude ($\sim 6\%$ over monthly timescales) and red-noise pattern observed in normal AGNs. These results add to the growing observational studies that suggest population-wise, LRDs have weak variability both in optical continuum and broad-line emission. Furthermore, the distinct white-noise broad-line variability pattern suggests different production mechanisms of broad-line emission in LRDs as opposed to normal AGNs, and/or different properties of the driving ionizing flux from the central engine.
[abstract 51 / 52] (score: 2) - Title: Alfvénic Motions in a Stratified Open Flux Tube: Transition from Propagating to Locally Standing Motions and Implications for the Kelvin-Helmholtz InstabilityAuthors: Mingzhe Guo, Bo Li, Yuhang Gao, Yao Chen,Comments: Accepted for publication in ApJ LettersSubjects: astro-ph.SRCreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
Standing transverse waves in closed coronal structures have been widely studied as a possible route to energy dissipation, with resonant absorption transferring kink wave energy to localized Alfvénic motions and the Kelvin-Helmholtz instability (KHI) accelerating the formation of small dissipative scales. However, it remains unclear whether the same mechanism applies to the open corona, given the long-standing consensus that the KHI tends to be prohibited for propagating Alfvénic waves. Within the framework of MAGNETohydrodynamics (MHD), we perform three-dimensional MHD simulations of boundary-driven kink waves in a gravitationally stratified open flux tube extending from the chromosphere into the corona. We find that propagating waves in open MAGNETic structures can also drive the system toward a turbulent state, with KH vortices clearly identifiable across the flux tube. This occurs because resonant absorption transfers energy from the propagating kink waves to azimuthal Alfvénic motions near the tube boundary, and wave reflection off the gradient of the Alfvén speed subsequently enables these boundary motions to acquire a locally standing character. Our results provide a possible answer to the long-standing question of whether and how propagating waves in open MAGNETic structures can generate nonlinear turbulent fine structures despite their globally propagating nature.
[abstract 52 / 52] (score: 2) - Title: Boosting the optical depth to Thomson scattering with primordial BLACK HOLE evaporation at high redshiftAuthors: Isaac Sierra, Gabriel P. Lynch, Lloyd Knox, Vivian Poulin, Lennart Balkenhol, Ali Rida Khalife,Comments: 17 pages, 6 figures. Comments welcomeSubjects: astro-ph.COCreated: 2026-08-03; Updated: 2026-08-04; Datestamp: 2026-08-04
BAO and CMB data are somewhat discrepant when interpreted in the context of $Λ$cdm, discrepancies that show up as a `matter density deficit' and as a `CMB lensing excess'. One possible resolution is an increased optical depth to scattering off of free electrons in the post-recombination universe, $τ$, a possibility raised by Sailer et al. 2025 and Jhaveri et al. 2025. Since Planck measurements of the low-$\ell$ POLARIZATION `reionization bump' already constrain $τ$ from standard stellar-driven reionization at $z<10$, we investigate additional optical depth sourced by transient or partial reionization at higher redshift from exotic processes. For specificity, we explore the impact of Hawking radiation from a monochromatic spectrum of primordial BLACK HOLEs, retaining the high-$\ell$ $TT/TE/EE$ data that constrain such histories and varying the reionization redshift jointly. We find that the CMB data do not significantly prefer these additional signals: the boost is at most $Δτ\simeq 0.008$, well short of the $Δτ\simeq 0.03$ that would completely eliminate the moderate discrepancy. The matter density deficit and the lensing excess are not significantly eased: we explain why, tracing it to compensation from the reionization redshift and the residual PBH signal at $\ell > 30$.
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