Current date: 2026-05-25
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Scoring abstracts
Number of records retrieved: 565
Keyword score statistics
score 12 -- 1 abstracts
score 10 -- 1 abstracts
score 8 -- 1 abstracts
score 7 -- 1 abstracts
score 6 -- 1 abstracts
score 4 -- 3 abstracts
score 3 -- 11 abstracts
score 2 -- 16 abstracts
in total -- 35 abstracts
Articles that appeared on 2026-05-25
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[abstract 1 / 35] Wow! (score: 12)
- Title: Maximum Energy of Particles Accelerated in Gamma-Ray Burst Afterglow ShocksAuthors: Zhao-Feng Wu, Sofía Guevara-Montoya, Paz Beniamini, Dimitrios Giannios, Daniel Grošelj, Lorenzo Sironi,Comments: 12 pages, 5 figures, published in ApJSubjects: astro-ph.HE physics.plasm-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
Particle acceleration in RELATIVISTIC collisionless shocks remains an open problem in high-energy astrophysics. Particle-in-cell (PIC) simulations predict that electron acceleration in weakly MAGNETized shocks proceeds via small-angle scattering, leading to a maximum electron energy significantly below the Bohm limit. This upper bound on electron energy manifests observationally as a characteristic SYNCHROTRON cutoff, providing a direct probe of the underlying acceleration physics. Gamma-ray burst (GRB) afterglows offer an exceptional laboratory for testing these predictions. Here, we model the spectral evolution of GRB afterglows during the RELATIVISTIC deceleration phase, incorporating PIC-motivated acceleration prescriptions and self-consistently computing SYNCHROTRON and SYNCHROTRON self-Compton emission. We find that low-energy bursts in low-density environments, typical of short GRBs, exhibit a pronounced SYNCHROTRON cutoff in the GeV band within minutes to hours after the trigger. Applying our framework to GRB 190114C and GRB 130427A, we find that current observations are insufficient to discriminate between PIC-motivated acceleration and the Bohm limit, primarily due to poor photon statistics in the FERMI-LAT band. Nevertheless, future MeV-TeV afterglow observations can break model degeneracies and place substantially tighter constraints on the mechanisms responsible for particle acceleration in RELATIVISTIC shocks. To this end, we simulate a fiducial nearby short GRB as a promising probe of the cutoff location, for which the two acceleration scenarios are cleanly distinguishable and the detection of such an event in the near future remains feasible.
[abstract 2 / 35] Wow! (score: 10) - Title: Detectability of Polarized Gamma-ray Emission from Blazar Flares with COSIAuthors: Garrett A. Latiolais, Jorge Otero-Santos, Michela Negro, Lea Marcotulli, Mohammad Ali Boroumand, Savitri Gallego, Christopher M. Karwin, Israel Martinez-Castellanos, Daniel Kocevski, Marco Ajello, Sara Capecchiacci, Ioannis Liodakis, Srinadh R. Bhavanam, Steven E. Boggs, Dieter H. Hartmann, Carolyn A. Kierans, Tiffany R. Lewis, Alberto Sciaccaluga, John A. Tomsick, Haocheng Zhang, Andreas Zoglauer,Comments: Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
We investigate the detectability of polarized gamma-ray emission from BLAZAR flares with the Compton Spectrometer and Imager (COSI). Using 17 years of FERMI Large Area Telescope observations, we analyze light curves for 1413 BLAZARs and identify a maximum of 787 sources with flaring episodes through Bayesian block analysis. For each flare, we estimate the minimum detectable POLARIZATION MDP99 in the COSI energy band (0.2-5 MeV) using instrument response functions under a range of spectral assumptions and background conditions. Under baseline background levels (1 counts/s), and assuming that BLAZAR flare statistics in the MeV band are comparable to those observed at GeV energies, we find that COSI can realistically detect POLARIZATION in up to ~6 flares with MDP99<50% over its two-year prime mission depending on different spectral and flare identification assumptions, with only a few most powerful ones reaching MDP99<20%. These expectations are shown to improve when shorter intervals around bright peaks within long flares are considered. We provide a ranked list of the most promising targets, finding that flat-spectrum radio QUASARs dominate the population of POLARIZATION-detectable events. Through its continuous all-sky monitoring in the largely unexplored MeV band, COSI will open a new observational window on BLAZAR variability and deliver the first direct measurements of MeV POLARIZATION, offering unique insights into JET geometry and high-energy emission processes.
[abstract 3 / 35] Wow! (score: 8) - Title: Strong X-ray Variability of I Zwicky 1: Obscuration from Clumpy Accretion-Disk WindsAuthors: Jian Huang, Bin Luo, W. N. Brandt, Luis C. Ho, Qingling Ni,Comments: 24 pages, 11 figures, accepted for publication in the Astrophysical JournalSubjects: astro-ph.HE astro-ph.GACreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
Obscuration from clumpy accretion-disk winds has been invoked to explain the extreme X-ray weakness and X-ray variability observed in a substantial fraction of super-Eddington accreting QUASARs. We present a comprehensive study of the strong X-ray variability of the super-Eddington accreting ACTIVE GALACTIC NUCLEus (AGN) I Zwicky 1 (I Zw 1), a prototypical narrow-line} Seyfert 1 galaxy (NLS1), to test the disk-wind obscuration scenario as the underlying mechanism and characterizing the disk-wind absorber properties. We focus on spectral and temporal analyses of simultaneous XMM-Newton and NUSTAR observations in 2020, and a 100-day NICER monitoring campaign in 2022. Despite strong X-ray variability by factors of $\approx3$ and $\approx6$ on short-term and long-term timescales, respectively, the XMM-Newton Optical Monitor observations do not show contemporaneous significant UV variability, and archival data reveal only mild long-term optical/infrared variability ($\approx30\%$), indicating a stable accretion process in I Zw 1. The strong X-ray variability thus likely arises from variable absorption of relatively stable coronal emission. We perform time-resolved X-ray spectroscopy utilizing a partial-covering absorption model with a stable corona and varying ionized absorbers. We identify three distinct absorbers whose variations in the column density and covering factor successfully explain the observed X-ray ``flares'' in 2020 and the longer-term spectral evolution in 2022. Our results support a unified scenario in which obscuration from clumpy disk winds produces the strong X-ray variability observed in super-Eddington accreting AGNs. This scenario may be applicable to other NLS1s exhibiting strong X-ray variability to better characterize the disk winds driven by super-Eddington accretion.
[abstract 4 / 35] Wow! (score: 7) - Title: Hydrodynamic model of nonthermal emission from the FERMI bubblesAuthors: V. A. Dogiel, D. O. Chernyshov, T. S. Fatekhov, A. M. Kiselev, C. M. Ko,Comments: 26 pages, 5 figures. Accepted to Astroparticle PhysicsSubjects: astro-ph.HE astro-ph.GACreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
We suggest a model of FERMI Bubbles (FBs) in the Galactic halo of the altitude about 7-8 kpc, which is seen in non-thermal microwave and gamma-ray ranges. It was assumed that this emission is generated by RELATIVISTIC electrons of COSMIC RAYs whose origin is still under debate. It has been assumed that the FB shell is generated in the halo by the release of energy, generated by the routine capture of stars at the central BLACK HOLE of the Galactic Centre (GC). In this case COSMIC RAY electrons (CR) in the shells of the FBs of sufficiently high energies are generated by the standard shock acceleration. However, one of the problems of this model is that the Mach number of the FB shock is not high enough to generate the observed non-thermal radiation from the halo. We propose an alternative model of stochastic CR acceleration by Rayleigh-Taylor (RT) instabilities in the shell of the FB at the late stages of the evolution of the shell in the halo. Unlike the shock model of CR acceleration, the RT model of in-situ acceleration in the FBs does not require strong shock fronts. In our model, we derived the spectrum of RT instabilities and estimate the spectra of kinetic equations for MHD-fluctuations needed for acceleration of CRs. We assessed the time of CR electron acceleration up to TeV energies that needed to interpret the observed data of gamma-ray and microwave emission from the envelope of FBs.
[abstract 5 / 35] Yes (score: 6) - Title: An extremely bright slow-rising afterglow from an off-axis JET in GRB 260310AAuthors: Yu-Han Yang, Roberto Ricci, Eleonora Troja, Muskan Yadav, Yi-Han Iris Yin, Rubén Sánchez-Ramírez, Brendan O'Connor, Niccoló Passaleva, Alberto J. Castro-Tirado, Hendrik van Eerten, Simone Dichiara, Vincenzo Galluzzi, Narjes Shahamat Dehsorkh, Iván Agudo, Jesús Aceituno, Malte Busmann, María D. Caballero-García, Emilio Fernández-García, Daniel Gruen, Maria Gritsevich, Sergiy Guziy, David Hiriart, You-Dong Hu, Martin Jelínek, Alexander Kutyrev, Alzbeta Malenakova, Filip Novotny, Ignacio Pérez-García, Shashi B. Pandey, Jorma Ryske, Alfredo Sota, Jan Strobl, Hira Waseem, Siyu Wu,Comments: 26 pages, 11 figures, 1 table; comments welcomeSubjects: astro-ph.HECreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
We present a multi-wavelength study of GRB 260310A, a nearby long-duration GAMMA-RAY BURST at $z\simeq0.153$ associated with a broad-lined Type Ic SUPERNOVA. Despite its modest prompt gamma-ray output, $E_{γ,\rm iso}\simeq3.5\times10^{50}$ erg, GRB\,260310A exhibits one of the brightest afterglows ever observed in the X-ray, optical, and radio bands. Its apparent brightness is not its only remarkable feature. The optical afterglow displays a delayed onset, characterized by a slow rising phase, with slope $α\approx-1$, and a late peak at $\approx$0.1 d. We argue that the combination of weak prompt emission, hard peak energy, and late afterglow onset is naturally explained by a GRB JET viewed off-axis. The radio spectral energy distributions are consistent with SYNCHROTRON radiation and indicate the presence of both reverse- and forward-shock components, thus providing a first test of reverse-shock models in an off-axis geometry. The X-ray afterglow displays a prominent rebrightening, monitored for up to $\approx$68 d with no evidence of spectral evolution. A low level of linear POLARIZATION, $Π\approx1.7\%$, is measured at 15 GHz at $T_0+55$ d and suggests that, at these late times, the forward-shock is the dominant emission component from radio to X-rays. This late-time rebrightening represents a critical test for the two-component JET model. If interpreted as the emergence of a narrow JET core viewed further off-axis, it would imply extreme luminosities and energetics for an on-axis observer.
[abstract 6 / 35] Yes (score: 4) - Title: Probing spectral variability in NGC 4490 ULX-8 over 24 years of XMM-Newton, Chandra and SWIFT-XRT observationsAuthors: Tarang Vashisht, Aru Beri, Tanuman Ghosh, Aman Upadhyay, Vikram Rana,Comments: Accepted by MNRASSubjects: astro-ph.HECreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
We present a spectral variability study of the ultraluminous X-ray source NGC 4490 ULX-8 based on 14 Chandra, 6 XMM-Newton and 19 SWIFT-XRT observations obtained between 2000 and 2024. The X-ray spectra are modelled using absorbed power-law and absorbed multicolour disc blackbody models. The best-fit photon indices span 0.9-2.7, while the inferred inner disc temperatures lie in the range 1.0-1.6 keV. We detect pronounced long-term variability in the unabsorbed X-ray luminosity on multi-year timescales, while variability within individual observations is comparatively modest. A Hardness-Intensity Diagram of the source shows no clear transition between hard and soft states; however, two recent observations taken on 2022 December 1 and 2024 May 4 show a sharp increase in brightness. The spectra across all observations are dominated by smooth, single-component curvature in the 0.3-10 keV band, consistent with the broadened-disc regime of ultraluminous X-ray sources. A correlation analysis reveals a weak positive X-ray luminosity-photon index trend that remains statistically supported after controlling for related degeneracies, indicating that it is not driven solely by fitting covariance. The luminosity-inner disc temperature relation is only weakly constrained, but remains compatible, within uncertainties, with both thin-disc and slim-disc scalings. Using disc parameters derived from higher-quality XMM-Newton spectra, we obtain model-dependent estimates of the characteristic inner disc radius and compact-object mass as functions of inclination and spin. The reported results are consistent with a stellar-mass BLACK HOLE accretor operating at or near the Eddington limit.
[abstract 7 / 35] Yes (score: 4) - Title: Constraining the Photon Intensity of Extragalactic Background Light with the HAWC Observatory for the Blazar Mrk 421Authors: R. Alfaro, C. Alvarez, A. Andrés, E. Anita-Rangel, M. Araya, J. C. Arteaga-Velázquez, D. Avila Rojas, R. Babu, P. Bangale, E. Belmont-Moreno, A. Bernal, T. Capistrán, A. Carramiñana, F. Carreón, A. L. Colmenero-Cesar, U. Cotti, J. Cotzomi, S. Coutiño de León, N. Di Lalla, R. Diaz Hernandez, B. L. Dingus, M. A. DuVernois, T. Ergin, C. Espinoza, N. Fraija, S. Fraija, J. A. García-González, F. Garfias, J. A. González, N. Ghosh, A. Gonzalez Muñoz, M. M. González, J. A. Goodman, S. Groetsch, J. Gyeong, S. Hernández-Cadena, I. Herzog, F. Hueyotl-Zahuantitla, D. Huang, A. Iriarte, S. Kaufmann, D. Kieda, H. León Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, H. Martínez-Huerta, P. Miranda-Romagnoli, P. E. Mirón-Enriquez, E. Moreno, M. Mostafá, M. Najafi, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, M. Osorio-Archila, E. Ponce, Y. Pérez Araujo, E. G. Pérez-Pérez, A. Pratts, C. D. Rho, D. Rosa-González, M. Roth, A. Sandoval, M. Shin, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, I. Torres, R. Torres-Escobedo, E. Varela, L. Villaseñor, X. Wang, I. J. Watson, H. Wu, S. Yu, X. Zhang, H. Zhou, C. de León,Comments: 16 pages, 2 Tables, 8 figuresSubjects: astro-ph.HECreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
The BLAZAR Mrk 421 exhibits rapid variability over a wide range of timescales. Spectral differences have been observed during the different emission states of Mrk 421. During the high emission states, tests to constraint the Hubble constant and the photon intensity of Extragalactic Background Light (EBL) can be performed. The HAWC observatory provides an exceptionally long term monitoring of the source at TeV energies. We selected periods of high emission state and low emission state in data with total observation time of 2460 transits from the HAWC observatory using the All-sky Root around in an Unbiased way methodology. We report on evidence of a cutoff in the spectrum of Mrk 421 during high emission states. An Exponential Cutoff Power Law is preferred over a Simple Power Law at a $3.8\,σ$ level. In the Exponential Cutoff Power Law, the cutoff is found at $13\pm3~\text{TeV}$. Using this result, we provide upper limits on the specific intensity of EBL photons. Moreover, the value of the energy cutoff found in our analysis is different from the cutoff expected by the interaction of gamma-rays with EBL photons. This result indicates that the cutoff is intrinsic to the source.
[abstract 8 / 35] Yes (score: 4) - Title: A comparison between Galactic MAGNETic field models and polarized SYNCHROTRON emission with C-BASS at 4.76 GHz and S-PASS at 2.3 GHzAuthors: Vasundhara Shaw, S. E. Harper, C. Dickinson, J. P. Leahy, Gabriel A. Hoerning, R. Cepeda-Arroita, Gilles Weymann-Despres, Mike Peel, Angela C. Taylor, T. J. Pearson, Jamie Leech, Michael Jones,Comments: accepted in MNRASSubjects: astro-ph.GA astro-ph.HECreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
We compare a set of contemporary Galactic MAGNETic field (GMF) models with polarized SYNCHROTRON observations from the S-PASS and C-BASS radio surveys and combine them to create a reconstructed 4.76~GHz full sky map. Pixels that potentially have a large Faraday rotation are excluded while small ($< 80\degree$) Faraday corrections derived at the respective frequencies of the two surveys are applied to the rest of the map. Using a template-fitting approach, we evaluate the ability of each model to reproduce the observed POLARIZATION amplitudes and POLARIZATION angles. We find that while most GMF models match the POLARIZATION angles reasonably well, they often fail to reproduce the morphology of the polarized intensity. We find that for most models there is a clear correlation between the data and models in POLARIZATION angles on large scales, but this does not hold true for polarized intensity. Our results show that a large portion of the polarized sky is shaped by local ``foreground'' features such as the North Polar Spur/Loop\,I and the Fan region. We conclude that incorporating such local structures is essential for accurately modelling the polarized SYNCHROTRON emission at microwave frequencies.
[abstract 9 / 35] (score: 3) - Title: Asymptotic-preserving semi-implicit finite volume scheme for Extended MagnetohydrodynamicsAuthors: Yi Han Toh, Joshua Dolence, Karthik Duraisamy,Comments: 48 pages, 16 figuresSubjects: physics.plasm-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
A Finite Volume (FV) scheme is developed for solving the extended MAGNETohydrodynamic (XMHD) equations, yielding accurate results in the ideal, resistive, and Hall MHD limits. This is accomplished by first re-writing the XMHD equations such that it allows the algorithm to retain the use of ideal MHD Riemann solvers and the constrained transport method to preserve divergence-free MAGNETic fields. Incorporation of electron inertia and displacement current introduces additional numerical stiffness which motivates a semi-implicit FV scheme that re-formulates the XMHD model as a relaxation system. The equations are then advanced in time using an explicit 2nd-order Runge-Kutta scheme with operator splitting applied to the implicit source term updates at each sub-stage. For additional numerical stability, a density-dependent slope limiter is implemented to increase flux diffusivity at low density regions where non-ideal effects become significant. The algorithm is subsequently implemented in a scalable adaptive mesh refinement (AMR) framework. As the new algorithm retains many aspects of the ideal MHD formulations, it asymptotes naturally to the ideal MHD limit. Moreover, it shows promising results at the resistive and Hall MHD limits. This is verified against reference test problems for ideal, resistive and Hall MHD.
[abstract 10 / 35] (score: 3) - Title: Compressible Turbulence as a Source of Particle Beams and Ion Bernstein Waves in Collisionless PlasmasAuthors: Chuanpeng Hou, Huirong Yan, Siqi Zhao,Comments: 10 pages, 6 figures, Accepted for publication in The Astrophysical JournalSubjects: physics.plasm-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
Unraveling the origin of proton beams and ion Bernstein waves is important to understanding kinetic dissipation in the solar wind. Here we focus on their generation mechanisms, rather than their well-studied roles in instabilities and particle heating. We investigate their formation in collisionless plasmas using high-resolution particle-in-cell simulations of compressible turbulence. At MAGNETohydrodynamic (MHD) scales, compressive fluctuations are damped via transit-time damping (TTD), naturally producing suprathermal electrons and proton beams. At sub-ion scales, quasi-perpendicular fast modes excite multiple branches of ion Bernstein waves, whose properties agree with predictions from the plasma dispersion relation solver. Under solar wind conditions, TTD remains efficient and provides a natural explanation for the super-Alfvénic proton beams measured in situ. Our results demonstrate that compressive fluctuations play a central role in driving cross-scale energy transfer and kinetic dissipation in collisionless plasma turbulence.
[abstract 11 / 35] (score: 3) - Title: Little Red Dot $-$ Host Galaxy $=$ Black Hole Star: A Gas-Enshrouded Heart at the Center of Every Little Red DotAuthors: Wendy Q. Sun, Rohan P. Naidu, Jorryt Matthee, Anna de Graaff, John Chisholm, Jenny E. Greene, Pascal A. Oesch, Alberto Torralba, Raphael E. Hviding, Gabriel Brammer, Robert A. Simcoe, Sownak Bose, Rychard Bouwens, Pratika Dayal, Anna-Christina Eilers, Qinyue Fei, Lukas J. Furtak, Rashmi Gottumukkala, Andy Goulding, Kasper E. Heintz, Michaela Hirschmann, Vasily Kokorev, Joel Leja, Zhaoran Liu, Priyamvada Natarajan, Andrew D. Santarelli, David J. Setton, Aaron Smith, Sandro Tacchella, Marta Volonteri, Fabian Walter, Andrea Weibel, Christina C. Williams,Comments: Published in the Open Journal of Astrophysics. Main results in Figs. 5 (BH* stack), 12 (explanation of the LRD SED), and 15 (hidden BH*s in blue galaxies). Comments warmly welcomed!Subjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
The central engines of Little Red Dots (LRDs) may be ``BLACK HOLE stars" (BH*s), early stages of BLACK HOLE growth characterized by dense gas envelopes. So far, the most direct evidence for BH*s comes from a handful of sources where the host galaxy is completely outshone as suggested by their remarkably steep Balmer breaks. Here we present a novel scheme to disentangle BH*s from their host galaxies assuming that the [OIII]5008Å line arises exclusively from the host. Using a sample of 98 LRDs ($z$~$2-9$) with high quality NIRSpec/PRISM spectra, we demonstrate that the host-subtracted median stack displays a Balmer break $>2\times$ stronger than massive quiescent galaxies, with the rest-optical continuum resembling a blackbody-like SED ($T_{\rm{eff}}$~$4050$ K, $\log(L_{\rm{bol}})$~$43.9$ erg s$^{-1}$, $R_{\rm{eff}}$~$1300$ au). We measure a steep Balmer decrement (H$α$/H$β>10$) and numerous density-sensitive features (e.g., FeII, HeI, OI). These are hallmark signatures of dense gas envelopes, providing population-level evidence that BH*s indeed power LRDs. In the median LRD, BH*s account for $\sim20\%$ of the UV emission, $\sim50\%$ at the Balmer break, and $\sim90\%$ at wavelengths longer than H$α$ with the remainder arising from the host. BH*s preferentially reside in low-mass galaxies ($M_{\rm{\star}}$~$10^{8}\,{\rm M}_{\rm{\odot}}$) undergoing recent starbursts, as evidenced by extreme emission line EWs (e.g., [OIII]5008Å~$1100$Å, CIII]~$12$Å), thereby favoring BH* origins linked to star-formation. We show V-shaped LRD selections are biased to high BH*/host fractions ($\gtrsim60\%$ at 5500Å) -- less dominant BH*s may be powering JWST's blue broad-line AGN. We find BH*s are so commonplace and transient (duty cycle $\sim1\%$, lifetime $\sim10$ Myrs) that every massive BLACK HOLE may have once shone as a BH*.
[abstract 12 / 35] (score: 3) - Title: Implications of a Cosmogenic Origin of KM3-230213A for Ultra-High-Energy ProtonsAuthors: A. R. Alhebsi, Arjen van Vliet, Domenik Ehlert, Satyendra Thoudam,Comments: 12 pages, 3 figures, 1 table. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
A significant neutrino event with an estimated energy between $72\,\mathrm{PeV}$ and $2.6\,\mathrm{EeV}$ was recently observed by the KM3NeT experiment (KM3-230213A). When interpreted as cosmogenic in origin, this event can provide constraints on several phenomenological parameters of UHE proton sources. In this study, we present the best fit to the spectrum and composition of UHECRs that is consistent with multi-messenger constraints, including the detection of a single neutrino event by the KM3NeT detector in the energy range of KM3-230213A. From the best fit, we obtain the 68\% CL constraints on the parameters of a two-population model of UHECRs, comprising a mixed-composition population and a subdominant UHE proton population. Our results indicate that the detection of a single neutrino event in the energy range of KM3-230213A solely with the KM3NeT exposure requires strongly evolving UHE proton sources, consistent with high-luminosity ACTIVE GALACTIC NUCLEi. On the other hand, including the null observations from the Pierre Auger and IceCube observatories disfavors such strong evolution. In both cases, the observed proton fraction of UHECRs is primarily constrained by the composition data to be $\sim 20\%$ at $20\,\mathrm{EeV}$.
[abstract 13 / 35] (score: 3) - Title: A Precise Measurement of the FERMI-LAT Galactic Center Excess Morphology and SpectrumAuthors: Mattia Di Mauro,Comments: 18 pages and 10 figures. Comments are welcome!Subjects: astro-ph.HE hep-phCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
We present a new FERMI-LAT analysis of the Galactic-center excess (GCE) designed to substantially reduce the dominant systematic uncertainties associated with interstellar-emission and source modeling in the inner Galaxy. Using an optimized multi-step fitting procedure together with an iterative source-finding pipeline, we achieve a markedly improved agreement between data and model, reducing fractional residuals to $\lesssim 10\%$ over a $40^\circ\times 40^\circ$ region centered on the Galactic center. We analyze a suite of GALPROP-based interstellar-emission models (IEMs) and complementary analysis variants (Galactic-plane masking, fits restricted to $1$-$10$ GeV, and weighted-likelihood fits) to quantify robustness. The reconstructed surface-brightness profile is strongly centrally concentrated and is well described by an approximately spherical generalized Navarro-Frenk-White morphology with inner slope $γ\simeq 1.15$. Bulge-tracing templates (nuclear bulge plus boxy bulge) fail to reproduce the full radial morphology, most notably for line-of-sight angles around $θ\simeq 1^\circ$-$2^\circ$ and at $θ\gtrsim 8^\circ$, whereas the DM-motivated component provides a good description over the full angular range. Moreover, the DM component remains highly significant across all IEMs and analysis choices, including fits that simultaneously include the bulge templates. We also provide an updated measurement of the GCE spectrum from $0.5$ to $1000$ GeV, confirming a peak at a few GeV and setting stringent constraints above tens of GeV, where we obtain only upper limits at the level $E^2Φ\lesssim 10^{-8}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$. These results deliver a sharpened and systematically controlled characterization of the GCE morphology and spectrum, enabling more incisive tests of astrophysical and dark-matter interpretations.
[abstract 14 / 35] (score: 3) - Title: Magnetic field dynamics in isolated neutron stars with an external dipole fieldAuthors: Aurora Capobianco, William Cook, Sebastiano Bernuzzi, Brynmor Haskell, Jacob Fields,Comments: 12 pages, 11 figuresSubjects: astro-ph.HE gr-qcCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
Neutron stars can harbor extremely strong MAGNETic fields, yet the structure and stability of their MAGNETic field configuration remain poorly understood. Observations of pulsars indicate that the large-scale external field is predominantly dipolar far from the star, while the internal MAGNETic configurations are largely unconstrained. We investigate the dynamical stability of MAGNETized neutron stars through long-term numerical-relativity simulations. We explore a range of models with an initial external dipole field and mixed poloidal-toroidal internal field where the energy of the toroidal component varies up to $80\%$ of the MAGNETic energy. We find that the internal MAGNETic field relaxes toward a dynamically stable mixed poloidal-toroidal geometry, in which the toroidal component contributes to $\lesssim10\%$ of the total MAGNETic energy both in the exterior and in the interior. This configuration emerges within one Alfvén time following the saturation of the Tayler instabilities and also aided by gravitational-wave emission. These results suggest that long-lived neutron star MAGNETic fields are strongly constrained toward stable mixed configurations, with important implications for pulsar emission models, MAGNETar evolution, and the interpretation of gravitational-wave signals from MAGNETized remnants.
[abstract 15 / 35] (score: 3) - Title: Star-planet interaction in the Proxima systemAuthors: M. R. Zapatero Osorio, V. J. S. Béjar, A. Suárez Mascareño, R. Rebolo, S. Cristiani, G. Micela, P. A. Miles-Páez, N. C. Santos, E. Pallé, J. I. González Hernández, M. Damasso, A. Castro-González, C. J. A. P. Martins, F. Pepe, A. Sozzetti, B. Lavie, J. Rodrigues,Comments: Accepted for publication in A&A. The quality of some figures was reduced to comply with arXiv requirementsSubjects: astro-ph.EP astro-ph.SRCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
(Abridged) We search for evidence of star-planet MAGNETic interactions in the nearby Proxima Centauri planetary system using high-quality, high-spectral-resolution optical observations. We measure a photospheric stellar rotation period of 84.9 +/- 0.6 d and a half-rotation period of 44.3 +/- 0.2 d, consistent with previous studies. Using FeI absorption and emission lines, we find that Proxima Centauri was flaring during 4.8 +/- 4.7 % of the observing time, with significant statistical evidence (>99.8 %) of flare events likely phase-locked to the inner Mars-mass planet Proxima d. Modeling the star-planet interaction via the helicity-driven RECONNECTion mechanism with the Poynting flux formalism, we estimate a likely polar MAGNETic field of -16 G for Proxima d (assuming a Mars-sized radius), with a plausible range of 3-280 G accounting for radial and dipolar stellar MAGNETic field configurations, planetary radii comparable to Mars and Earth, and the observed range of stellar flare intensities. This represents the first such estimate for a terrestrial exoplanet. Evidence for a potential star-planet interaction with the outer, Earth-mass Proxima b arises not from phase-locked flare clustering, but from modulation of flare intensities. Applying a prewhitening analysis to the full time series of combined chromospheric Halpha, NaI D1 and D2, and CaII H &K lines reveals peaks, in order, at half the stellar rotation period, Proxima b's orbital period, the full stellar rotation, and Proxima d's orbital period. All evidence suggests that both planets show MAGNETic interaction with their host star. Focusing on flaring epochs only, the periodogram of these chromospheric lines shows a peak consistent with the synodic period between half the stellar rotation and the mutual synodic period of Proxima b and d, implying prograde stellar rotation and planetary orbits.
[abstract 16 / 35] (score: 3) - Title: NIMROD-to-IMAS workflow for extended-MAGNETohydrodynamic data with reusable datasets and implications for IMAS schema developmentAuthors: Alexei Y. Pankin, Fatima Ebrahimi, Qian Gong, Jacob King, Andreas Kleiner, Jesus Dominguez-Palacios, Norbert Podhorszki, Eric Suchyta,Comments:Subjects: physics.plasm-ph physics.comp-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
Extended MAGNETohydrodynamic (MHD) simulations of tokamak plasmas regularly produce outputs in multi-dimensional, multiple-field formats; these code-specific formats make it difficult to do cross-code validation/coupling and analyze at a database scale. In this paper, a workflow that converts NIMROD code inputs and outputs to records compatible with version 4 of the ITER IMAS Data Dictionary is presented. The scope of the workflow includes preprocessing of NIMROD code inputs, conversion of hierarchical NIMROD code HDF5 dumps, COCOS-consistent treatment of the coordinate system and sign convention, and encoding finite-element poloidal meshes and toroidal Fourier components through IMAS General Grid Description. Furthermore, the workflow allows for provenance and integrity metadata to be included while providing optimal I/O operations for large array structures. An example conversion based on an NIMROD code simulation of edge harmonic oscillations performed for the DIII-D discharge 163518 [A.Y. Pankin, et al., Nuclear Fusion 60.9 (2020), p. 092004] is used to validate the conservation of essential equilibrium, profile, perturbation, and grid data in the resulting IMAS records. Finally, this implementation exposes gaps in the current IMAS framework that need to be addressed to accommodate extended MHD data, and it highlights the metadata, provenance, and governance needs of the downstream use cases in the form of dataset validation, integration, and machine learning.
[abstract 17 / 35] (score: 3) - Title: Imaging spectroscopy reveals spike-like repeating radio burst pairs in the solar coronaAuthors: Suli Ma, Eduard P. Kontar, Daniel L. Clarkson, Huadong Chen, Yihua Yan,Comments: This manuscript has been accepted for publication in Nature Communications. (35 pages, 10 main figures, 3 supplement figures, 1 table, 1 movie)Subjects: astro-ph.SR physics.space-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
Solar radio bursts exhibit complex fine structures that reveal intricate coronal plasma dynamics. Here, we report detection of spike-like repeating burst pairs, characterized by two short-lived (0.1-2 s), narrowband components separated by about 4 s at frequencies 30-50 MHz. Using high-resolution dynamic spectra and spectroscopic imaging, we analyzed 613 burst pairs, measuring their durations, bandwidths, drift rates, flux densities, and spatial characteristics. Imaging links sources to an active region, with earlier components spatially concentrated above the region while delayed components are displaced and exhibit reduced drift rates. Radio-wave propagation simulations support the delayed bursts as turbulent echoes of harmonic emission in anisotropic coronal plasma. The location of the burst sources high in the corona suggests ongoing MAGNETic RECONNECTion and electron acceleration well above typical flare heights. Our findings offer new insights into coronal turbulence effects while advancing diagnostics of coronal plasma and the elusive nature of solar radio echoes from ground-based transmitters.
[abstract 18 / 35] (score: 3) - Title: Probing the environments of FRI and FRII RADIO GALAXies in LoTSS DR2 with galaxy clustersAuthors: Tong Pan, Yuming Fu, H. J. A. Rottgering, J. M. G. H. J. de Jong, M. J. Hardcastle, B. Mingo, L. Clews, M. Magliocchetti, J. W. Petley, Bohan Yue,Comments: 12 pages, 13 figures, 3 tables. Accepted for publication by A&ASubjects: astro-ph.GACreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
The origin of the Fanaroff--Riley Class I/II (FRI/FRII) morphological dichotomy remains uncertain. We investigate whether cluster-scale environment contributes to this distinction using a morphologically classified LoTSS DR2 catalogue at \(z<0.4\). We construct a volume-limited sample with \(L_{144}>4\times10^{24}\,\mathrm{W\,Hz^{-1}}\) and a luminosity--redshift paired sample, and cross-match them with DESI Legacy Imaging Survey galaxy clusters. A RADIO GALAXy is associated with a cluster if \(|Δz|<0.01\), projected separation \(<2R_{500}\). In the volume-limited sample, \(48.6\%\) of FRIs and \(30.6\%\) of FRIIs are cluster-associated; in the paired sample, the corresponding fractions are \(45.6\%\) and \(32.6\%\). The difference is stronger at \(L_{144}>10^{26}\,\mathrm{W\,Hz^{-1}}\), where the fractions are \(55.6\%\) versus \(19.0\%\) in the volume-limited sample and \(50.0\%\) versus \(6.7\%\) in the paired sample. However, cluster-associated FRIs and FRIIs occupy similar environments: their radio luminosities and stellar masses show similar trends with cluster richness and \(M_{500}\), and their radial distributions both peak near \(0.5R_{500}\) and decline beyond \(R_{500}\). Most cluster-associated sources are brightest cluster galaxies (BCGs), with fractions of \(74.8\%\) for FRIs and \(61.9\%\) for FRIIs in the volume-limited sample, and \(78.1\%\) and \(65.9\%\) in the paired sample. These results show that FRIIs are less frequently found in clusters, especially at high radio luminosity, consistent with dense intracluster gas disrupting or decelerating JETs and suppressing stable FRII structures. Nevertheless, once inside clusters, FRIs and FRIIs inhabit similar large-scale environments, implying that cluster-scale properties alone are unlikely to be the primary driver of the FRI/FRII dichotomy.
[abstract 19 / 35] (score: 3) - Title: Minor Merger, Major Growth: An Overmassive, Highly Accreting Black Hole Powering a Secondary AGN In a Cosmic Noon Minor MergerAuthors: Marko Mićić,Comments: 6 pages, 2 figures. Accepted for publication in ApJSubjects: astro-ph.HECreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
We report the discovery of a spectroscopically confirmed z = 1.824 minor merger with a mass ratio of ~35:1 in which the secondary (smaller) galaxy hosts a luminous AGN. The system is identified in the 3D-HST survey and exhibits clear tidal features in James Webb Space Telescope imaging, confirming an ongoing interaction. Using archival Chandra X-ray observations, we detect 121 +/- 11 X-ray counts associated with the secondary galaxy, corresponding to a rest-frame 2-10 keV luminosity of L_X ~ (9 +/- 0.1) x 10^43 erg/s and a photon index of Gamma ~ 2.0-2.3. Analysis of the HST/WFC3 G141 grism spectrum yields an [O III] lambda5007 luminosity of (2 +/- 0.5) x 10^42 erg/s. Independent bolometric luminosity estimates from X-ray and [O III] emission are consistent, implying L_bol ~ (3-7) x 10^45 erg/s. Assuming standard BLACK HOLE-galaxy scaling relations, the expected BLACK HOLE mass is ~2 x 10^6 M_sun, which would require extreme super-Eddington accretion to explain the observed luminosity. On the other hand, assuming Eddington-limited or moderately sub-Eddington accretion implies a BLACK HOLE mass more than an order of magnitude above expectations. The observed X-ray spectral slope disfavors low accretion rates, restricting the allowed parameter space to high lambda_Edd and elevated BLACK HOLE masses. We conclude that the secondary AGN must be powered by an overmassive, highly accreting BLACK HOLE, providing direct observational support for theoretical predictions that minor mergers can drive rapid BLACK HOLE growth in secondary, smaller companions.
[abstract 20 / 35] (score: 2) - Title: Critical phenomenon inside asymptotically flat BLACK HOLEs with spontaneous scalarizationAuthors: Li Li, Ze Sun, Fu-Guo Yang,Comments: Major revision, to appear in PRLSubjects: gr-qcCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
We study the interior dynamics of spontaneously scalarized BLACK HOLEs in Einstein-Maxwell-Scalar theory with zero cosmological constant, revealing novel critical phenomena. We demonstrate that, for a wide range of scalar-electroMAGNETic couplings, scalarized BLACK HOLEs possess no smooth inner Cauchy horizon and instead evolve into a spacelike Kasner singularity. The scalar hair triggers a rapid collapse of the Einstein-Rosen bridge at the would-be Cauchy horizon. Near the critical point where scalarized BLACK HOLEs bifurcate from the Reissner-Nordstrom solution, we establish a robust scaling relation between the Kasner parameter and the charge-to-mass ratio of the hairy BLACK HOLE, opening a new window into the remarkable simplicity underlying BLACK HOLE interiors.
[abstract 21 / 35] (score: 2) - Title: Anisotropic Diffusion in Pulsar Halos: Interpreting the asymmetric morphology of Geminga and Monogem halos measured by HAWCAuthors: Si-Zhe Wu, Chao-Ming Li, Ruo-Yu Liu,Comments: 11 pages, 8 figures, 2 table. Matches the published version in ApJ, except that Fig.1 is fully displayed here (the figure was unfortunately truncated in the ApJ production process)Subjects: astro-ph.HECreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
Pulsar halos are produced by electrons and positrons diffusing in the interstellar medium around their parent pulsar wind nebulae. Recent observations by HAWC and LHAASO have revealed asymmetric morphologies in the halos surrounding Geminga and Monogem. The anisotropic diffusion model provides a natural explanation for such asymmetries, where the morphology is determined by the viewing angle of the mean MAGNETic field, the Alfvénic Mach number ($M_{\rm A}$), and the pulsar distance. In this work, we model the measured morphologies based on this framework and constrain the properties of interstellar MAGNETic turbulence. We find that the mean MAGNETic field orientations within the two halos are different, implying that they reside in different MAGNETic coherence regions, whereas the Alfvénic Mach numbers are relatively close ($M_{\rm A}\sim 0.2$). The results suggest a local MAGNETic field coherence length of approximately 100pc. Our study demonstrates that the morphology of pulsar halos serves as a powerful diagnostic tool for the properties of interstellar MAGNETic fields, highlighting the need for more accurate morphological measurements and sophisticated diffusion modeling in future studies.
[abstract 22 / 35] (score: 2) - Title: Correlation between Ultrahigh-Energy Neutrino KM3-230213A and Gamma-Ray BurstsAuthors: Ruiqi Wang, Bo-Qiang Ma,Comments: 15 pages, 2 figures, 3 tables, final version for publicationSubjects: astro-ph.HE gr-qc hep-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
The KM3NeT Collaboration reported the detection of a neutrino, designated as KM3-230213A, with a reconstructed energy peaking at 220 PeV and equatorial coordinates (J2000) of RA=$94.3\degree$ and Dec=$-7.8\degree$. As the highest-energy neutrino event documented to date, its astrophysical origin remains unascertained. Prior preliminary investigations have probed potential associations between this neutrino event and GAMMA-RAY BURSTs (GRBs), factoring in the possibility of Lorentz invariance violation (LV). In this study, we perform a comprehensive analysis to explore correlations between KM3-230213A and all viable GRBs. We explicitly account for the angular uncertainties intrinsic to both the neutrino event and the respective GRBs. Our analysis identifies a larger set of correlated GRBs. For each associated GRB, we compute the LV scale, integrating uncertainties from redshift measurements and neutrino energy determinations to enhance the robustness of our findings.
[abstract 23 / 35] (score: 2) - Title: The NUV transit of XO-3 bAuthors: Raven Cilley, Lia Corrales, George W. King, Jiayin Dong, Robert Frazier, Kohei Miyakawa, Akihiko Fukui, Teruyuki Hirano, Juliette Becker, James T. Sikora, Lisa Dang,Comments: Accepted for publication in AAS JournalsSubjects: astro-ph.EPCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
Near-UV (NUV) measurements of exoplanet transits offer a means to probe atmospheric escape, cloud formation, and planetary MAGNETic fields. We examine a 2024 XMM-Newton Optical Monitor NUV observation of the transit of XO-3~b, a massive hot Jupiter on an eccentric orbit with a previously observed abnormally large NUV-absorbing atmosphere. We analyze this NUV data jointly with a concurrent ground-based optical observation and all TESS transit observations, and find a NUV transit depth of $R_{p,NUV}/R_{\star} = 0.1371^{+0.016}_{-0.019}$, which is 30-70% deeper than the optical transit. Although the optical transits do not show signs of transit timing variations, the transit center in the NUV is $22^{+13}_{-11}$ minutes late compared to the optical ephemeris. We investigate atmospheric escape as a potential explanation of the properties of this NUV transit by examining X-ray data from XMM-Newton, characterizing the X-ray luminosity of XO-3 for the first time and estimating an extremely small mass-loss rate of $\sim10^4$ g/s ($\sim10^{-19}$ M$_{\text{jup}}$/yr). Finally, we investigate the likelihood of an NUV-absorbent bow-shock by estimating the MAGNETic field of the planet. While such a mechanism is capable of producing NUV transit offsets on the order of tens of minutes, our analytic approximations predict an early rather than late transit, indicating a need for further MAGNETohydrodynamic simulations.
[abstract 24 / 35] (score: 2) - Title: Mg II h&k spectral line properties computed using 3D radiative transfer in an enhanced network region simulated with the MURaM-ChE codeAuthors: P. Ondratschek, D. Przybylski, H. N. Smitha, J. Leenaarts, R. Cameron, S. K. Solanki,Comments: Accepted for publication in A&ASubjects: astro-ph.SRCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
The Mg II h&k lines form in the middle to upper chromosphere and are well-suited to study the structure of the chromosphere. However, the details of their formation in the solar chromosphere are not fully understood. We aim to study the effects of 3D radiative transfer (RT) on the Mg II h&k line properties and to verify known correlations between the underlying atmosphere and spectral line features in a new model of the chromosphere. We forward model the Mg II h&k lines in 3D RT with partial frequency redistribution (PRD) in a self-consistent 3D radiative MAGNETohydrodynamics (rMHD) simulation with non-local-thermodynamic-equilibrium (NLTE) energy transport and non-equilibrium (NE) hydrogen ionization of an enhanced network (EN) region simulated with the chromospheric extension of MURaM (MURaM-ChE). The spatially averaged Mg II h&k spectral lines computed with 3D RT match approximately a typical IRIS observation. The peak separation is still slightly lower in the simulation. In the MURaM-ChE model, the qualitative difference between 1.5D and 3D RT results is even more pronounced than in the public Bifrost snapshot, as given in the literature. We found that this large discrepancy might partly be attributed to the horizontal velocities that are naturally included in the full 3D RT synthesis but not in typical 1.5D RT computations. We confirm that correlations between spectral line properties and the underlying atmosphere from the MURaM-ChE simulation are similar to those obtained from Bifrost, but show more scatter due to the more dynamic atmosphere. The Mg II h&k lines computed with 3D RT match the observations better in the core intensities and their distribution on the Sun compared to 1.5D computations. This underlines the importance of 3D RT in the forward modeling of Mg II h&k.
[abstract 25 / 35] (score: 2) - Title: Gyrokinetic Simulations for Spherical Tokamak Divertor DesignAuthors: Akash Shukla,Comments: The University of Texas at Austin PhD thesisSubjects: physics.plasm-phCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
Nuclear fusion is an attractive source of energy because the fuel is abundant and it produces low levels of carbon emissions. The tokamak, which confines a plasma using MAGNETic fields, is the most mature nuclear fusion reactor concept. Maximizing energy confinement by minimizing turbulent heat loss while also minimizing damage to the reactor is essential for producing efficient, commercially viable fusion reactors. Heat exhaust methods used in the scrape-off layer (SOL) of the tokamak greatly influence performance. Conventional heat exhaust methods focus on minimizing reactor damage rather than maximizing confinement. The low-recycling regime, a newer approach, focuses on maximizing energy confinement. Studying the low-recycling regime, which features a high temperature and low density SOL, requires new modeling tools. We have developed the gyrokinetic code Gkeyll into an appropriate tool, and we use it to demonstrate the viability of the low-recycling regime with simulations of the Spherical Tokamak for Energy Production (STEP). Our work addresses several key issues with low recycling. Our simulation results indicate that a high SOL temperature and low SOL density could be achieved without using a lithium divertor plate. This is an important step because lithium divertor plates evaporate when exposed to large heat fluxes, which lowers the SOL temperature, counteracting the desired regime. Our simulation results also indicate that kinetic effects can lower the peak heat flux on the divertor plate, which would improve reactor survivability, and confine sputtered impurities to the divertor region, which would prevent core contamination and performance degradation.
[abstract 26 / 35] (score: 2) - Title: Continuous coherent spin-frequency metrology in storage rings via resonant beam-driven detectionAuthors: Younggeun Kim, Themis Bowcock, Dmitry Budker, Giovanni Cantatore, Hooman Davoudiasl, Dmitry Denisov, Abhay Deshbande, Wolfram Fischer, Selcuk Haciomeroglu, Haixin Huang, David Kawall, on Kim, Ivan Koop, Valeri Lebedev, Jonathan Lee, William M. Morse, Cenap Ozben, Vincent Schoefer, Yannis K. Semertzidis, Eleftherios Skordis, Edward Stephenson, Vladimir Tishchenko, Nicholaos Tsoupas, Graziano Venanzoni, Joost Vossebeld, Peter Winter,Comments:Subjects: hep-exCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
Precision measurements in storage rings are increasingly limited by the ability to monitor collective spin dynamics coherently over long time scales. Existing polarimetry techniques rely on destructive scattering processes that preclude continuous, non-intercepting tracking of spin evolution and constrain both statistical sensitivity and systematic control. Here we introduce a non-destructive, phase-coherent polarimetry method in which the stored beam POLARIZATION is treated as a continuous dynamical observable rather than a quantity inferred from scattering events. Spin-dependent electroMAGNETic fields generated by a polarized RELATIVISTIC beam establish a symmetry-selected differential signal on pickup electrodes. This signal is transduced into a narrowband phase modulation of a high-Q resonator interrogated with a coherent probe, while dominant charge-induced backgrounds are rejected through geometric symmetry, helicity reversal, and synchronous demodulation. Controlled spin precession (spin-wheel operation) provides a stable phase reference enabling phase-coherent detection of slow spin evolution. Combined with optimized lattice symmetry and beam cooling, this approach can substantially extend the usable spin coherence time, with values approaching 10^5 s appearing realistic within existing accelerator technology. The resulting readout supports optimal slope-based estimation with T^{-3/2} statistical scaling while eliminating the efficiency penalties inherent to scattering-based polarimetry. For storage-ring EDM experiments, this combination enables sensitivity approaching the level expected within the Standard Model. More broadly, the method establishes a general phase-coherent architecture for collective spin measurements in storage rings, adapting resonant sensing concepts from axion dark-matter searches to charged-particle precision experiments.
[abstract 27 / 35] (score: 2) - Title: Pre L-H Transition Radial Electric Field and Transport Validations of Edge and Scrape-off Layer Gyrokinetic Simulations at ASDEX UpgradeAuthors: B. J. Frei, C. Angioni, G. Lo-Cascio, W. Zholobenko, P. Ulbl, R. Bilato, F. Jenko, the ASDEX Upgrade Team,Comments:Subjects: physics.plasm-phCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
This work presents a stepwise validation of the evolution of the radial electric field (Er) and heat transport during the pre L-H transition phase using full-f gyrokinetic simulations of the edge and scrape-off layer in the ASDEX Upgrade (AUG) tokamak, including X-point geometry. Several L-mode time slices up to the L-H transition from a dedicated hydrogen discharge, featuring stepwise increases in ECRH input power, are selected [N. Bonanomi \textit{et al.}, Phys. Plasmas 31, 072302 (2024)] and simulated with the \texttt{GENE-X} code. As the edge boundary conditions are progressively increased between the time slices, particle and heat fluxes rise, and the radial electric field Er well deepens. A detailed validation of the Er profiles and of the Er well depth shows excellent agreement with experimental measurements at the successive time slices approaching the L-H transition. A force balance decomposition identifies turbulence-driven poloidal flows as the dominant contribution within the Er well. Edge turbulence is governed by a competition between electron drift waves and trapped-electron modes. The introduction of an edge density source, modeling neutral gas ionization, is shown to be essential to reproduce experimentally relevant density profiles, Er, and edge ion heat fluxes, which are dominated by both turbulent and diaMAGNETic contributions. This stepwise validation constitutes an important milestone toward predictive, first-principles gyrokinetic simulations of the L-H transition power threshold.
[abstract 28 / 35] (score: 2) - Title: A Strongly Parametrized Mass Ratio Model for the Stable Mass Transfer Channel: a Case Study of the $10 \, \rm{M}_{\odot}$ PeakAuthors: Jaxen Godfrey, Lieke van Son, Ben Farr,Comments:Subjects: astro-ph.HE astro-ph.SRCreated: 2026-05-21; Updated: 2026-05-25; Datestamp: 2026-05-25
The mass ratio of merging binary BLACK HOLEs (BBHs) carries information about their formation history, yet has received less attention than masses, spins and eccentricities as a channel discriminator. We derive a strongly parametrized analytical model for the mass-ratio distribution expected from the stable mass transfer (SMT) channel. The model maps mass-transfer stability and accretion efficiency onto the observed mass-ratio distribution, and naturally produces two qualitatively distinct subpopulations: a non-mass-ratio-reversed and a mass-ratio-reversed subpopulation whose distinct shapes depend on the binary-evolution parameters in a traceable way. We embed this model in a hierarchical population analysis and apply it to the $\sim 10\, \rm{M}_{\odot}$ peak in the GWTC-4 BBH catalog. We find that the data favor little to no mass-ratio reversal in this peak, and infer SMT parameters in an astrophysically plausible range. This work demonstrates how data-driven models can be used in mixtures to study singular features in BBH population data and serves as a proof of concept for how a measurement of the BBH mass-ratio distribution within a subpopulation can be translated into direct constraints on the binary-evolution physics that produced it.
[abstract 29 / 35] (score: 2) - Title: General Expressions for Measurable Parameters in Curved SpacetimeAuthors: Dmitri Lebedev, Kayll Lake,Comments:Subjects: gr-qcCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
General covariant expressions for measurable angles, distances, velocities, and accelerations are provided in terms of fundamental parameters that can be applied in any setup. The RELATIVISTIC aberration of light relationship is presented in full generality, which is applicable to any orientation of observers and light rays. An expansion for the geometrical exponential map is established and used to form an expression for the physical distance between an observer and a nearby object within its extended local frame. Curvature effects on measurable distances, velocities, and accelerations are made explicit and appear in general tensorial form. The concepts of FERMI frames on timelike worldlines and the FERMI-Walker derivative are discussed in detail and used throughout; and in examining the meaning of relative stationarity between timelike observers, the FERMI-Walker derivative is established from first principles through physically meaningful consideration. A generalized type of Taylor expansion is provided for tensors of any rank in a covariant form. Expressions for the optically based angular diameter distance and luminosity distance are provided in general forms, and the reciprocity theorem is discussed and verified. A generalized version of the geodesic deviation equation, applicable to extreme relative motion, is provided as well.
[abstract 30 / 35] (score: 2) - Title: The two-stream instability generation around Moon: Effect of Interplanetary Magnetic Field during Solar Wind - Lunar Plasma InteractionAuthors: Vipin K. Yadav, Abhinav Singh, Rajneesh Kumar,Comments:Subjects: physics.plasm-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
The relative motion of two interpenetrating streams of charged particles usually leads to the generation of two stream instability (TSI) and eventually result in the onset of non-linear plasma processes such as the turbulence or the plasma waves. A natural example of such an event is the solar wind interaction with the lunar electron plasma where the interplanetary MAGNETic field (IMF) is embedded within the solar wind. The inclusion of IMF in the solar wind lunar plasma interaction modifies the dispersion relation of the TSI and an angular cyclotron frequency term appears in the denominator of the leading term and hence leads to the change in the parameters such as the instability growth rate as now it depends on the solar wind electron velocity, solar wind and the lunar electron plasma density, and the IMF magnitude. It is observed that the growth rate increases fast with the increase in the MAGNETic field initially but the increase slows down on further increasing the MAGNETic field thereby smoothening the top. From the particle in cell (PIC) simulations, it is observed that during the solar wind IMF interaction with lunar plasma, the non-energetic background electrons make a shield around the solar wind electrons in the vortices formed. It is further observed that those lunar electrons which are not participating either in the vortices formation or in the shielding of solar wind electrons, start moving in the direction of the incoming solar wind. These observations indicate this interaction is capable in getting converted into a non-linear physical process in the lunar plasma environment.
[abstract 31 / 35] (score: 2) - Title: Ensemble asteroseismology: An ensemble approach to detecting signatures of solar-like oscillations in K-dwarfsAuthors: William J. Chaplin, Tiago L. Campante, Mikkel N. Lund, Martin B. Nielsen, Guy R. Davies, Emily Hatt, Rachel Howe, Amalie Stokholm,Comments: 13 pages, 8 figures, accepted for publication in Astronomy & AstrophysicsSubjects: astro-ph.SRCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
Solar-like oscillations have to date been observed in hundreds of main-sequence and sub-giant stars. However, only a handful of detections have been made in K-type dwarfs, using ground-based extreme precision radial velocity observations and space-based photometric observations made by the NASA \emph{Kepler} and TESS missions. Whilst the upcoming ESA PLATO Mission promises to add to these individual detections, it will do so only in a similar, modest number of stars. Here, we propose a new ensemble strategy to exploit the PLATO data, in which frequency power spectra on hundreds of K-dwarfs lying in constrained ranges of effective temperature are combined in a weighted manner to significantly improve the detectability of the oscillations. Whilst this approach means it is not possible to extract usable constraints on individual oscillation frequencies, it provides a way to detect and measure the characteristics of the composite envelope of oscillation power given by the ensemble, which in turn provides diagnostics of granulation and MAGNETo-convection and the impact of MAGNETic activity on the modes. We use data in the PLATO Input Catalogue (PIC) to make discrete numerical predictions of the detectability of the ensemble spectra. We also derive a simple analytical approximation of our method that obviates the need to perform numerical calculations over a discrete sample of targets, and which serves as a useful tool to make quick predictions for other future or planned missions. Our predictions indicate that PLATO has the potential to provide solid ensemble detections well into the K-dwarf regime. In summary, PLATO offers an ideal opportunity to exploit this new approach.
[abstract 32 / 35] (score: 2) - Title: A quasi-neutral electroMAGNETic hybrid model with drift-kinetic electrons and fully kinetic ionsAuthors: Guo Meng, Nishant Narechania, Eric Sonnendrücker,Comments: 25 pages, 14 figuresSubjects: physics.plasm-phCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
In this work, we propose a hybrid model that combines drift-kinetic electrons with fully kinetic ions under the quasi-neutrality assumption, discretized using a geometric particle-in-cell framework on dual-grids. The model advances the perturbed electroMAGNETic fields $E$ and $B$ directly, rather than the scalar and vector potentials. The parallel electric field $E_\parallel$ is obtained from Ohm's law. The perpendicular electric field $E_\perp$ is computed from Ampère's law by extracting the $E_\perp$-dependent component of the drift-kinetic electron current. The quasi-neutrality constraint eliminates high-frequency light waves and Langmuir waves from the system. Temporal discretization is performed using low-storage Runge--Kutta schemes. In this quasi-neutral hybrid model, the right-hand polarized wave branch exhibits a whistler-like dispersion relation, which imposes a stringent timestep constraint. To address this, we develop a novel implicit-explicit splitting scheme for Faraday's law that significantly relaxes the timestep stability restriction. The model is validated in slab geometry by reproducing cold plasma wave branches, ion Bernstein waves, compressional and shear Alfvén waves, and ion acoustic waves.
[abstract 33 / 35] (score: 2) - Title: Investigation of the Two-Dimensional Velocity Field of the Large-Scale Coronal Wave from September 6, 2011 using the SOLERwave ToolAuthors: Markus Baumgartner-Steinleitner, Astrid M. Veronig, Karin Dissauer, Jens Pomoell,Comments: 31 pages,16 figuresSubjects: astro-ph.SRCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
We investigate the two-dimensional velocity field of the fast and complex large-scale coronal wave observed on September 6, 2011. We use both a classical perturbation profile approach and the newly developed multi-sector method of the SOLERwave tool, using a Huygens-plotting-based approach. The multi-sector method utilizes perturbation profiles derived in multiple directions (sectors) to determine the location of the wavefront at a given time. The two-dimensional velocity vector at each point along the wavefront is derived by identifying the point closest to it along the wavefront observed one time step earlier and dividing the distance between the two points along the solar surface by the time difference between the observations. For the event under study the resulting two-dimensional velocity field shows a significant difference between the northward traveling and the northwest ward traveling part of the wave front of over 40%, in the range of 750 to 1500 km/s. To determine the cause of this difference in speed, we investigate the coronal structures, the photospheric MAGNETic field distribution and the Alfvén speed derived from a steady-state coronal MAGNETo hydro dynamic (MHD) solution along different propagation directions of the wave. We find the large difference in MAGNETosonic speed found in the investigated sector as the most likely explanation for the velocity difference.
[abstract 34 / 35] (score: 2) - Title: GMRT Survey of Radio Emission from Magnetic Massive Stars -- I: Emission from Single Stars at sub-GHz FrequenciesAuthors: Ayan Biswas, Gregg A. Wade, Barnali Das, Veronique Petit, Matthew E. Shultz,Comments: 26 pages, 12 figures, 3 tables; Accepted for publication in ApJSSubjects: astro-ph.SRCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
With the growing subset of MAGNETic massive stars, it is now possible to conduct a systematic survey of radio emission from MAGNETic hot stars to better understand the underlying emission mechanisms. Previous surveys of radio emission from hot star MAGNETospheres have focused on high frequencies ($>$2 GHz). At lower frequencies, additional emission and absorption mechanisms are expected, increasing the complexity of the observed emission. In this work, we survey towards lower frequencies while also increasing the sample size. We report the study of 28 MAGNETic hot stars with the Giant Metrewave Radio Telescope (GMRT) during cycles 27 and 28 of its operation. Among these, we found 11 detections and 17 non-detections. We also include 16 additional targets observed with GMRT from the literature. We investigated the dependence of low-frequency radio luminosity on different stellar parameters and searched for a scaling relationship at low frequencies. We further test the centrifugal breakout model for gyroSYNCHROTRON emission. The observed low-frequency radio luminosities show a clear dependence of radio emission on MAGNETic field strength and rotation period, consistent with high-frequency studies. We observe a trend in scaling relationships with frequency and comment on the statistical behavior of gyroSYNCHROTRON spectra. The observed low-frequency behavior likely reflects a combination of free-free absorption and the location of the low-frequency turnover in the gyroSYNCHROTRON spectrum, which may vary among stars depending on their MAGNETospheric properties and can suppress detectable sub-GHz emission. One of the detected stars, HD 37742, is the first MAGNETic O-type star detected at sub-GHz frequencies.
[abstract 35 / 35] (score: 2) - Title: Orbital Selective Dirac-like States in EuAgAs Revealed by Polarization Dependent ARPES and DFTAuthors: Mohit Mudgal, Suman Nandi, Mohamed El Gazzah, Masashi Arita, Shin-ichiro Ideta, Nirmal J. Ghimire, Kenya Shimada, Anup Pradhan Sakhya,Comments:Subjects: cond-mat.mes-hallCreated: 2026-05-22; Updated: 2026-05-25; Datestamp: 2026-05-25
Magnetic topological semimetals provide a promising platform for emergent quantum phenomena driven by the interplay between MAGNETism and RELATIVISTIC fermions, including anomalous transport effects and tunable topological phases. Here, we investigate the electronic structure and orbital character of EuAgAs, a MAGNETic topological Dirac semimetal candidate, using density functional theory (DFT) and POLARIZATION dependent angle resolved photoemission spectroscopy (ARPES). FERMI surface mapping and constant energy contours measured at 9 eV reveal ring like features that systematically expand with increasing binding energy, consistent with nearly linear low energy Dirac like dispersion. ARPES measurements at different photon energies hint at the presence of a van Hove singularity predicted by DFT calculations. Furthermore, this indicates that the photoemission matrix elements are highly sensitive to the excitation energy, allowing different photon energies to selectively probe distinct orbital characters. Polarization dependent ARPES measurements performed in s- and p-polarized geometries exhibit pronounced variations in spectral intensity, indicating symmetry selective orbital contributions to electronic states. These matrix element driven intensity modulations are well reproduced by DFT calculations. Furthermore, the observed Dirac like states remain nearly unchanged over the temperature range from 9 K to 30 K, suggesting that the MAGNETic ordering has minimal influence on the electronic structure. Our combined experimental and theoretical results provide detailed insight into the orbital selective electronic structure of EuAgAs and its implications for MAGNETic topological quantum states.
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