Current date: 2026-04-22
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Datestamp limit: 2026-04-22 (0 days ago)
Created/updated limit: 2026-04-15 (7 days ago)
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Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics
Setting default set: physics
OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2026-04-22&until=2026-04-22&set=physics&metadataPrefix=arXiv
Scoring abstracts
Number of records retrieved: 383
Keyword score statistics
score 6 -- 1 abstracts
score 5 -- 2 abstracts
score 4 -- 1 abstracts
score 3 -- 4 abstracts
score 2 -- 5 abstracts
in total -- 13 abstracts
Articles that appeared on 2026-04-22
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[abstract 1 / 13] Yes (score: 6)
- Title: Simulating the late stages of WD-BH/NS mergers: an origin for fast X-ray transients and GRBs with periodic modulationsAuthors: Jun-Ping Chen, Rong-Feng Shen, Jin-Hong Chen, Wei-Hua Lei,Comments: 17 pages, 11 figures, submitted to ApJ, revised version after the reviewer's reportSubjects: astro-ph.HE astro-ph.GACreated: 2026-04-21; Updated: 2026-04-22; Datestamp: 2026-04-22
Recent studies indicate that mergers of a white dwarf (WD) with a neutron star (NS) or a stellar-mass BLACK HOLE (BH) may be a potential progenitor channel for certain merger-kind, but long-duration $γ$-ray bursts (GRBs), e.g., GRBs 230307A and 211211A. The relatively large tidal disruption radius of the WD can result in non-negligible residual orbital eccentricity ($0 \lesssim e \lesssim 0.2$), causing episodic mass transfer, i.e., repeated tidal disruptions (RPDs) of the WD. We perform smoothed-particle-hydrodynamics simulations of RPDs in sixteen WD-BH/NS systems, capturing the subsequent mass transfer and accretion. The WD undergoes RPDs near the orbital periastron, modulating the ensuing accretion process, leading to variations of the accretion rate on the orbital period. Across all simulations, the peak accretion rates range from $4 \times10^{-4}$ to 0.2 $M_{\odot} \rm \ s^{-1}$, while the RPD duration spans from $\sim$ 10 s to an hour. More compact systems, i.e., those with a higher mass ratio (higher WD mass and lower accretor mass), tend to undergo fewer RPD cycles, resulting in shorter durations and higher accretion rates. If such events can launch RELATIVISTIC JETs, three categories of non-thermal X/$γ$-ray transients are predicted, in decreasing order of their mean accretion rates: (1) an X-ray transient with a simultaneous GRB, both lasting for $10^{1-2}$ s; (2) a longer X-ray transient lasting up to $10^{2-3}$ s that has a GRB appearing only at its later phase ; (3) an ultra-long X-ray transient lasting for $\sim 10^{3}$ s without a GRB. A generic feature of these transients is that their prompt emission light curves are probably periodically modulated with periods of a few to tens of seconds.
[abstract 2 / 13] Yes (score: 5) - Title: Very Long Baseline Interferometry Search for Nuclear Radio Continuum Emission in the Barred Spiral Galaxy NGC 7479Authors: Seppo Laine, Emmanuel Momjian, Emilia Järvelä, Thomas P. Krichbaum, S. Komossa, Travis C. Fischer, Thomas G. Pannuti,Comments: 20 pages, 6 figures, 2 tables. Accepted for publication in AJSubjects: astro-ph.GACreated: 2026-04-21; Updated: 2026-04-22; Datestamp: 2026-04-22
We have obtained very high angular resolution (a few milliarcseconds or sub-parsec scale) Very Long Baseline Array (VLBA) and European Very Long Baseline Interferometry (VLBI) Network (EVN) radio continuum images of the nucleus in the barred spiral galaxy NGC 7479, to search for possible nuclear emission on parsec scales. The observations were taken using phase referencing. Previous Karl G. Jansky Very Large Array (VLA) and Multi-Element Radio Linked Interferometer Network (MERLIN) observations revealed a large JET-like structure, apparently emanating from the nucleus, and unresolved nuclear emission at 0.1 arcsecond (about 15 pc at the assumed distance of 32 Mpc) scale, respectively. Our sensitive new VLBA and EVN images resolve the previously unresolved nuclear source and reveal two distinct emission regions (VLBI components) that are separated by about 30 milliarcseconds. We also report an apparent change in separation of the two main emission regions over the ten years between EVN and VLBA observations, implying RELATIVISTIC radio JET motion or changes in shock illumination of gas by a nuclear wind. We measure the spectral indices and brightness temperatures of the VLBI components, and discuss possible physical causes of the observed emission.
[abstract 3 / 13] Yes (score: 5) - Title: VLTI-GRAVITY observations of BLAZARsAuthors: Talvikki Hovatta, Elina Lindfors, Heidi Korhonen, Preeti Kharb, Markus Wittkowski, Aaron Labdon, Tapio Pursimo, Kaj Wiik,Comments: Accepted for publication in A&A. 6 pages of main text with 4 figuresSubjects: astro-ph.GA astro-ph.HECreated: 2026-04-21; Updated: 2026-04-22; Datestamp: 2026-04-22
Parsec-scale JETs of BLAZARs have so far been spatially resolved only in mm- and submm wavelengths, where very long baseline interferometry can be used to obtain milliarcsecond-scale images of the JETs. We have attempted to spatially resolve the near-infrared emission in JET-dominated BLAZARs for the first time. We used the VLTI-GRAVITY instrument to obtain milliarcsecond-scale near-infrared interferometric observations of a flaring BLAZAR Ton 599. Additionally, we observed four non-flaring BLAZARs using the GRAVITY-wide mode, where a nearby bright star is used as a fringe tracker. We modeled the squared visibilities of Ton 599, and find that they are incompatible with a single unresolved point source unless there is a significant amount of additional unknown coherence loss in the instrument. With the present data, we cannot distinguish between a model with an unresolved point source and extended emission or coherence loss and a model with a single Gaussian component. This suggests that we are seeing the unresolved or only partially resolved JET-base in near-infrared wavelengths. The wide-field mode of GRAVITY was challenging for the additional relatively faint targets resulting in either non detections or poor quality data that could not be modeled. Our observations demonstrate that it is possible to detect the compact JET emission in BLAZARs with near-infrared interferometry, suggesting that with the improved GRAVITY+ instrument it will be possible to spatially resolve and image the near-infrared emission of BLAZAR JETs.
[abstract 4 / 13] Yes (score: 4) - Title: System Size Dependence of Collisionless Reconnection RateAuthors: Yi-Min Huang, Naoki Bessho, Li-Jen Chen, Judith T. Karpen, Amitava Bhattacharjee,Comments:Subjects: physics.plasm-ph astro-ph.SR physics.space-phCreated: 2026-04-20; Updated: 2026-04-22; Datestamp: 2026-04-22
It is a widely accepted paradigm that collisionless MAGNETic RECONNECTion proceeds at a universal fast rate of $\sim0.1$ when normalized to a properly defined RECONNECTing MAGNETic field and Alfvén speed, effectively independent of the macroscopic system size. This conclusion, derived primarily from kinetic simulations of classical Harris current sheets with kinetic-scale thickness, stands in contrast to results from forced RECONNECTion and island coalescence, where the rate significantly depends on the system size. Here, we reconcile this disparity by performing a rigorous scaling study using both particle-in-cell and Hall MAGNETohydrodynamic simulations. We demonstrate that when the global MAGNETic configuration is self-consistently preserved by scaling the initial current sheet thickness proportionally with the system size, the ``universal'' fast rate disappears. Instead, the RECONNECTion rate decreases as the system size increases. These results indicate that dependence on macroscopic scales is not peculiar to specific geometries but is a fundamental property of collisionless RECONNECTion, effectively unifying the Harris sheet with other configurations exhibiting size-dependence.
[abstract 5 / 13] (score: 3) - Title: High-Frequency Gravitational Waves from the Galactic Pulsar PopulationAuthors: Anne S. Freise, Jamie I. McDonald, Kirill Riabtsev, Samuel J. Witte,Comments: This manuscript was submitted without knowledge or consent of ASF, JIM, or SJW. In addition, content of manuscript was plagarised from draft of ASF, JIM, and SJWSubjects: astro-ph.HECreated: 2026-04-20; Updated: 2026-04-22; Datestamp: 2026-04-22
The high-frequency gravitational-wave band is often discussed primarily in the context of new physics, but realistic Standard-Model foregrounds remain incompletely characterized. We investigate pulsar polar caps as a physically motivated astrophysical source of high-frequency gravitational waves, generated by repeated discharge cycles in compact near-surface plasma gaps. Our baseline result is population-level: we construct the signal from the Galactic normal-pulsar population rather than from a single especially favorable object. To do so, we calibrate the source dynamics with particle-in-cell simulations performed at real physical scales, with physical pulsar parameters mapped directly onto numerical scales, and then lift the resolved longitudinal discharge to a cap-scale emission model. The gravitational-wave signal is computed in a full Fourier-space framework, retaining finite-source, geometric, and POLARIZATION effects explicitly. Within this treatment, the dominant contribution is not the purely electric channel emphasized in some earlier simplified approaches, but a source channel involving the large background MAGNETic field and discharge-induced transverse fluctuations of MAGNETic field. Integrating this description over a normal-pulsar population, we find an astrophysical foreground in the MHz-scale high-frequency band that can overlap with and partially obscure the thermal gravitational-wave signal sourced by the plasma of the early Universe. At the same time, the normalization remains sensitive to the modeled assumptions. Although the predicted strain remains far below current experimental sensitivity, pulsar polar caps provide a concrete Standard-Model foreground benchmark in a band often treated as nearly background-free. Alternative source configurations further broaden the plausible signal range around this baseline.
[abstract 6 / 13] (score: 3) - Title: Magnetic properties of the Abell 3391-3395 system revealed using wide-field MeerKAT polarimetryAuthors: V. Gustafsson, M. Brüggen, C. Tasse, S. P. O'Sullivan,Comments:Subjects: astro-ph.GA astro-ph.COCreated: 2026-04-20; Updated: 2026-04-22; Datestamp: 2026-04-22
Magnetic fields in cluster outskirts and the intercluster medium are poorly constrained because diffuse SYNCHROTRON emission is hard to detect at low surface brightness. Faraday rotation measures (RMs) of polarized background sources can probe foreground large-scale structure. The nearby interacting Abell 3391-3395 system hosts a well-established X-ray bridge, making it an excellent target for studying MAGNETization in the intercluster environment. We characterize the MAGNETized environment of Abell 3391/95 and its surroundings by constructing a dense RM grid from wide-field polarimetry. We observed Abell 3391/95 with MeerKAT in full POLARIZATION using a three-pointing mosaic. The data were calibrated with direction-independent and direction-dependent techniques and imaged using visibility-plane mosaicing for a large field of view at high sensitivity. Using Faraday synthesis, we formed Faraday cubes and measured RMs for polarized background sources. We defined on- and off-target regions using contours from a wavelet-filtered eROSITA image. We identified 434 polarized sources within the field, with a polarized source density ranging from about 30 sources per square degree in the outer regions to about 110 sources per square degree in the central field, and a field-averaged density of 73 sources per square degree. The clusters show a statistically significant enhancement of RM scatter relative to the off-target region. In contrast, the bridge shows comparatively low RM scatter, while an RM structure-function analysis on matched angular scales yields a tentative indication of larger RM differences in the bridge than off-target. Combined with low per-source dePOLARIZATION, this suggests a bridge MAGNETic field relatively ordered on ~10 kpc scales, but less ordered on larger scales. The non-detection of diffuse SYNCHROTRON emission in the bridge yields improved upper limits on the emissivity.
[abstract 7 / 13] (score: 3) - Title: The Gamma-Ray Monitor onboard the SVOM satelliteAuthors: Jian-Chao Sun, Yong-Wei Dong, Jiang He, Jiang-Tao Liu, Lu Li, Rui-Jie Wang, Xin Liu, Li Zhang, Min Gao, Yue Huang, Hao-Li Shi, Li-Ming Song, Wen-Jun Tan, Chen-Wei Wang, Jin Wang, Jin-Zhou Wang, Ping Wang, Xing Wen, Bo-Bing Wu, Shao-Lin Xiong, Juan Zhang, Shuang-Nan Zhang, Xiao-Yun Zhao, Shi-Jie Zheng,Comments: 13 pages, 15 figures, 4 tables, SVOM special issue (RAA), accepted by RAASubjects: astro-ph.IM astro-ph.HECreated: 2026-04-21; Updated: 2026-04-22; Datestamp: 2026-04-22
The Gamma-Ray Monitor (GRM) is a key scientific payload onboard the Space-based Multi-band Variable Object Monitor (SVOM) satellite, designed specifically for the detection and study of GAMMA-RAY BURSTs (GRBs). Launched into a 625 km low-Earth orbit on 22 June 2024, GRM serves as a large-area, wide-field-of-view instrument capable of observing the hard X-ray and soft gamma-ray emissions in the energy range of 15 keV to 5 MeV. Its primary scientific objectives include: promptly triggering and localizing GRBs (with particular sensitivity to short-hard GRBs), measuring spectral and temporal properties of bursts, monitoring charged particle fluxes in orbit. GRM successfully detected its first GRB (GRB 240627B) on 27 June 2024, and has since maintained a detection rate of more than 100 GRBs per year. Cross-instrument comparisons with detectors such as GECAM and FERMI/GBM have validated the performance and data quality of GRM. This paper provides a comprehensive overview of GRM instrument design, reliability verification through ground testing, in-orbit triggering and localization algorithms, performance calibration, and preliminary in-orbit results, demonstrating its capability as a versatile gamma-ray all-sky monitor.
[abstract 8 / 13] (score: 3) - Title: Identifying Merger-Driven and Collapsar-Driven Gamma-Ray Bursts with Precursor based Solely on Prompt EmissionAuthors: Si-Yuan Zhu, Pak-Hin Thomas Tam, Fu-Wen Zhang, Hui-Ying Deng, Bing Zhang,Comments: 13 pages, 6 figures, 1 table, Accepted for publication in the ApJSubjects: astro-ph.HECreated: 2026-04-21; Updated: 2026-04-22; Datestamp: 2026-04-22
Gamma-ray bursts (GRBs) are generally classified as Type~I GRBs, which originate from compact binary mergers, and Type~II GRBs, which originate from massive collapsars. The traditional correspondence between short--Type~I GRBs and long--Type~II GRBs, separated by a duration of 2 seconds, has been challenged by recent observations of long GRBs associated with kilonovae (i.e., Type~I-L GRBs) and a short GRB associated with a SUPERNOVA. In this paper, we focus on GRBs with precursor emission (PE) and compile 366 GRBs detected by FERMI/GBM. Applying the unsupervised machine learning methods t-SNE and UMAP, we are able to distinguish Type~I (including subclass Type~I-L) and Type~II GRBs for the first time and identify PE as a key feature for distinguishing GRBs of different origins. Inspired by results of machine learning, we propose a diagnostic parameter, the $E_{\rm p,ME}$-precursor index ($EPI$), defined as ${\rm log_{10}}(E_{\rm p,ME}^{2}/(T_{\rm 100,PE}T_{\rm 100,QE1}^{1/2}T_{\rm MVT,PE}))$, where most Type~I GRBs have $EPI > 6.2$ and most Type~II GRBs have $EPI < 6.2$. This parameter can help the community to diagnose the origin of any GRB with PE based solely on its prompt emission and rapidly plan for follow-up observations. The validation using SWIFT GRBs provides illustrative evidence that our method may also be applicable to GRBs observed by instruments other than FERMI.
[abstract 9 / 13] (score: 2) - Title: Enhanced performance in quasi-isodynamic max-$J$ stellarators with a turbulent particle pinchAuthors: G. G. Plunk, A. G. Goodman, P. Xanthopoulos, P. Costello, H. M. Smith, K. Aleynikova, C. D. Beidler, M. Drevlak, S. Stroteich, P. Helander,Comments:Subjects: physics.plasm-phCreated: 2026-04-21; Updated: 2026-04-22; Datestamp: 2026-04-22
Recent stellarator reactor designs demonstrate mostly outward turbulent particle transport, which, without advanced fueling technology, inhibits the formation of density gradients needed for confinement. We introduce ``SQuID-$τ$'', a self-fueling quasi-isodynamic stellarator capable of sustaining density peaking through inward particle transport caused by turbulence. Temperature and density profile predictions based on high-fidelity gyrokinetic simulations demonstrate enhanced performance, significantly relaxing constraints on the size and MAGNETic field strength for reactor designs.
[abstract 10 / 13] (score: 2) - Title: Visual Characteristics of a Rotating Black Hole in $4$D Einstein-Gauss-Bonnet Gravity with Thin Accretion Disk Under EHT ConstraintsAuthors: Muhammad Israr Aslam, Manahil Ali, Abdul Malik Sultan, Xiao-Xiong Zeng, Sultan Hussain,Comments: This article contains 32 pages, 25 equations, 13 figures and 82 referencesSubjects: astro-ph.HE gr-qcCreated: 2026-04-18; Updated: 2026-04-22; Datestamp: 2026-04-22
This study investigates the visual characteristics of a rotating BLACK HOLE (BH) within the fabric of $4$D Einstein-Gauss-Bonnet gravity illuminated with two illumination models, such as a celestial light sphere and a thin accretion disk. To visualize the BH shadow images, we use a recent fisheye camera model and ray-tracing method. And then, we focus on investigating the impact of the coupling parameter $α$ and the spin parameter $a$ on the shadow images. The results exhibit that the shadow radius decreases, while the shadow deviation increases with the aid of $α$. However, with respect to $a$, the shadow radius is slightly increased compared to the corresponding shadow deviation. For a celestial light sphere, the increasing values of $α$, lead to a decrease in the corresponding photon ring, while the space-dragging effect becomes more prominent with increasing $a$. For a thin accretion disk, we enhance its inner edge to the BH event horizon, and the particle motion is different in the regions inside and outside the innermost stable circular orbit. The result demonstrates that the shadow becomes progressively asymmetric with $a$, while the overall size of the inner shadow gradually decreases with the variations of $α$. Subsequently, we also investigated the distinct features of red-shift configurations on the disk for both direct and lensed images. Additionally, we used the latest observational data from M87* and Sgr A* to impose certain parameter constraints on $α$; the results depict the consistency of our considering the BH model.
[abstract 11 / 13] (score: 2) - Title: Application of Metric-Based Mesh Adaptation to Hypersonic Aerothermal Simulations Using US3DAuthors: Dirk Ekelschot,Comments: 21 pagesSubjects: physics.flu-dynCreated: 2026-04-20; Updated: 2026-04-22; Datestamp: 2026-04-22
The main goal of this paper is to demonstrate the application of metric-based mesh adaptation to real gas problems and highlight the benefits particularly when complex geometries are considered. We use the Hessian of the temperature solution as an indicator to dictate where the mesh needs refinement or coarsening. In the context of hypersonic flow simulations, these methods are not widely adopted since unstructured meshes often result in poor surface heating predictions. The present work aims to demonstrate the great flexibility metric-based mesh adaptation provides when it comes to predicting complex flow features while still maintaining comparable surface heating predictions. We consider two test cases: (a) a supersonic flow over a hemisphere and show that comparable surface heating is obtained by applying mesh adaptation and by employing hexahedra instead of prisms in the boundary layer mesh; (b) we consider a more realistic test case of a hypersonic flow of a C02-N2 mixture past a 70 degree sphere cone atmospheric entry capsule. For the second test case, similar surface heating predictions are obtained compared to more conventional block structured DPLR simulations. Furthermore, for the adapted unstructured simulations, the geometries of the eight Reaction Control System (RCS) JET on the back shell were taken into account. This highlights the ability of these methods to deal with complex geometries that are typically out of reach for block structured approaches.
[abstract 12 / 13] (score: 2) - Title: Instability-Aware Steering of an Extreme Atmospheric River in an AI Weather Foundation ModelAuthors: Moyan Liu, Qin Huang, Upmanu Lall,Comments:Subjects: physics.ao-phCreated: 2026-04-20; Updated: 2026-04-22; Datestamp: 2026-04-22
Advances in deep learning methods for weather forecasting are creating opportunities to computationally explore the potential for steering or control of extreme weather trajectories for societal risk reduction. We present initial investigations into the feasibility of redirecting extreme atmospheric rivers (ARs) through small, instability-aware perturbations. Using the Aurora AI weather foundation model, we identify sensitive upstream locations using finite-time Lyapunov exponents and JET-eddy interaction criteria. We apply an idealized cloud-seeding operator that mimics latent heat release to assess whether these Lyapunov-guided interventions can influence downstream evolution. In a case study of a severe California AR, perturbations induce coherent downstream shifts in moisture transport, reducing intensity at landfall under favorable kinematic conditions. The response is nonlinear and contingent on the local flow geometry. These initial results suggest that the atmosphere's intrinsic chaotic sensitivity could be leveraged for dynamical control, offering a new research direction for extreme event risk mitigation.
[abstract 13 / 13] (score: 2) - Title: Numerical Studies of Accretion Flows onto a Neutron Star Engulfed in a Massive StarAuthors: Daiyu Sakurai, Ryuichiro Akaho, Shoichi Yamada,Comments: 20 pages, submitted to MNRAS, comments welcomeSubjects: astro-ph.HE astro-ph.SRCreated: 2026-04-21; Updated: 2026-04-22; Datestamp: 2026-04-22
Massive stars commonly form binaries that can evolve into compact systems via common envelope evolution (CEE), a critical but poorly understood phase -- especially when the companion is a neutron star. Understanding the drag force exerted on a neutron star during CEE is a key to the quantitative evaluation of orbital decay, merger timescale, and compactness of the resultant binary. In this paper, we conduct general-RELATIVISTIC hydrodynamical simulations under a novel strategy of multi-layer domain-decomposition to treat the vast disparity of $10^4$--$10^7$ between the neutron star radius and the accretion radius. Our 10-model survey spans diverse physical conditions that the neutron star encounters in the envelope of a massive star. We find that nested bow shocks with alternating orientations commonly form. This configuration is qualitatively different from those in the conventional picture and results in an enhancement of the drag force by one to two orders of magnitude from what the Bondi--Hoyle--Lyttleton formula predicts. Moreover, the direction of the net force can reverse depending on the envelope conditions, contrary to the standard picture in which the drag always decelerates the companion. These results will serve as a basis for improvements of the drag force prescription in CEE modeling, and have implications for binary evolution theory.
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