Current date: 2026-07-08
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Number of records retrieved: 752
Keyword score statistics
score 8 -- 1 abstracts
score 7 -- 1 abstracts
score 5 -- 3 abstracts
score 4 -- 2 abstracts
score 3 -- 13 abstracts
score 2 -- 25 abstracts
in total -- 45 abstracts
Articles that appeared on 2026-07-08
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[abstract 1 / 45] Wow! (score: 8)
- Title: Dependence of Particle Acceleration Efficiency on Shock Velocity in Weakly Magnetized Electron-Ion ShocksAuthors: Taiki Jikei, Daniel Groselj, Lorenzo Sironi,Comments: 13 pages, 6 figuresSubjects: astro-ph.HE physics.plasm-phCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Using unprecedentedly long 2D particle-in-cell simulations, we study electron and ion acceleration in weakly MAGNETized quasi-parallel shocks, propagating at velocities ranging from transRELATIVISTIC to subRELATIVISTIC. At a fixed upstream MAGNETic field strength, low-velocity quasi-parallel shocks are dominated by the Bell instability, whereas high-velocity shocks are dominated by the Weibel instability. Both regimes accelerate ions with similar efficiency, with the Bell-dominated regime exhibiting faster growth in the maximum particle energy. The electron acceleration efficiency is strongly dependent on shock velocity. Weibel-dominated shocks have $\sim15\,\%$ of shock energy in nonthermal electrons, whereas in the Bell-dominated regime we attribute less than $\sim2\,\%$ of shock energy to nonthermal electrons. We discuss applications of our results to the bright X-ray emission from the late-stage afterglows of GAMMA-RAY BURSTs, the radio emission from fast blue optical transients, and the X-ray variability in microQUASARs.
[abstract 2 / 45] Wow! (score: 7) - Title: Minimum Energies and Magnetic Field Strengths of Edge-brightened Compact Symmetric ObjectsAuthors: Tirth D. Surti, Martijn S. S. L. Oei, Anthony C. S. Readhead, Andrew G. Sullivan,Comments: Published to ApJSubjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Compact symmetric objects (CSOs) are subkiloparsec radio sources with two-sided emission about a core resulting from JETs that are not RELATIVISTICally beamed towards the observer. This relative simplicity makes them attractive targets to study the launching and evolution of RELATIVISTIC JETs. We use radio surveys and spatially resolved VLBA observations to estimate the minimum energies and MAGNETic field strengths of a subset of edge-brightened CSOs (CSO-2s). These are necessary to test models of CSO-2 formation via stellar capture and evolution via SYNCHROTRON cooling. By treating the observed X-ray emission of CSO-2s as inverse Compton emission from SYNCHROTRON and external photon fields, we estimate a mean departure from the minimum energy MAGNETic field strengths of ${\sim}2\times$, suggesting that CSO-2 lobes are close to minimum energy. Typical lobal minimum energy MAGNETic field strengths of $20$ mG suggest that once the JETs shut off, luminous CSO-2s should fade at GHz frequencies within ${\sim}10^{3}$ years. We find that CSO-2 minimum energies are systematically larger than previously estimated. If luminous CSO-2s result from tidal disruption events, a majority would require the capture of massive stars $>1 \ M_{\odot}$ assuming JET launching efficiencies less than $100\%$.
[abstract 3 / 45] Yes (score: 5) - Title: The X-ray Variability of the Ultraluminous X-ray Sources in the NGC 4631 galaxyAuthors: Jiashun Chen, Jianfeng Wu, Zikun Lin,Comments:Subjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
We perform a systematic study on the long-term X-ray variability for the five ultraluminous X-ray sources (ULXs) in the NGC 4631 galaxy (X1-X5), using Chandra, XMM-Newton, and SWIFT observations covering a 24-year span. Light curves for the five ULXs are presented, while X-ray spectra were modeled for observations with sufficient counts. The normalized excess variance and structure function are utilized to study the X-ray variability behavior of the ULXs. The normalized excess variance is anti-correlated with average X-ray luminosity for three ULXs, indicating that objects with higher average luminosity tend to exhibit relatively lower amplitude of variability. The structure function values increases with time interval in two sources, showing that flux variations become more significant for longer timescales. These trends are also found in the X-ray variability of ACTIVE GALACTIC NUCLEi (AGNs). The similarity between ULXs and AGNs, if confirmed for a larger sample of sources, possibly indicates similar underlying physical mechanisms for their X-ray variability.
[abstract 4 / 45] Yes (score: 5) - Title: An intrinsic decline of accretion activity in GRS 1915+105Authors: Poshak Gandhi, Peter G. Boorman,Comments: Submitted 2026 July 06. Comments welcomeSubjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The canonical microQUASAR GRS 1915+105 is exhibiting unprecedented changes in its multiwavelength properties since 2018. Recent pointed observations with NUSTAR in November 2025 have failed to detect the source at flux limits several orders of magnitude deeper than historical X-ray levels. Under an enhanced obscuration scenario, the absence of hard X-rays requires that any obscuring cocoon must be deeply Compton-thick and fully sky covering, with a stringent limit on scattering fractions being less than 1 part in >~10^4, if intrinsic accretion activity continues unabated. An ionised cocoon could also account for a deep radio non-detection in June 2026. But such an interpretation is in conflict with mid-infrared fading of the source observed with SPHEREx in September 2025 and then again in April/May 2026. These facts, together with the source location in the infrared vs. X-ray plane, are consistent with an intrinsic weakening of accretion activity around November 2025 or earlier. We propose that outflows witnessed during intense multiwavelength flaring in 2023-2024 have progressively expelled fueling material from the inner disc, resulting in a significant drop in accretion activity. If correct, the current state gives unique insight into ongoing dramatic secular accretion changes on human timescales. High-frequency resolved radio observations and sensitive infrared or sub-mm observations could test this scenario, and characterise any gaseous cocoon still veiling the source.
[abstract 5 / 45] Yes (score: 5) - Title: Unravelling Turbulence and Magnetic Fields in Galaxy Clusters with SKA and XRISMAuthors: Kohei Kurahara, Takuya Akahori, Amit Seta, Kosuke Nishiwaki, Kazuhiro Nakazawa, Yuki Omiya, Daisuke Ito, Kosei Sakai,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Kurahara01Subjects: astro-ph.HE astro-ph.GACreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
This chapter proposes a research framework to quantitatively investigate non-thermal components in the Intracluster Medium (ICM) of galaxy clusters, which are critical ingredients for governing energy transport, structure formation, and particle acceleration. Turbulence, primarily driven by cluster mergers, is the leading mechanism for re-accelerating COSMIC RAY electrons (forming radio halos) and amplifying MAGNETic fields (via the turbulent dynamo). Observational understanding of both the turbulence and MAGNETic fields is rapidly evolving: the high-resolution X-ray spectrometer XRISM is directly measuring the velocity properties of the thermal ICM, providing insights into the kinetic energy of turbulence. Concurrently, high-sensitivity low-frequency radio observations, including SKA pathfinders, are mapping non-thermal components and MAGNETic structures through diffuse SYNCHROTRON emission and high-density Faraday Rotation Measure (RM) grids. The synergy between XRISM and SKA offers a decisive paradigm shift. XRISM's velocity maps, with its high energy resolution (<7 eV FWHM), combined with SKA-Mid's capability to deliver high-resolution RM grids ($\sim 100$--$200~\rm deg^{-2}$) and high-dynamic-range imaging, will allow for the first direct, multi-wavelength comparison of the turbulent energy properties (from X-ray) and the MAGNETic field properties (from radio). This joint analysis will validate Magnetohydrodynamic (MHD) simulation predictions, clarify the process of turbulent energy cascade and decay, and ultimately lead to a comprehensive understanding of the co-evolution of turbulence, MAGNETic fields, and COSMIC RAYs in the largest laboratories of the Universe.
[abstract 6 / 45] Yes (score: 4) - Title: Properties of BLACK HOLE mergers in disks of ACTIVE GALACTIC NUCLEiAuthors: Hiromichi Tagawa, Zoltán Haiman, Bence Kocsis,Comments: 23 pages, 20 figures, accepted for publication in ApJSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Ground-based gravitational wave (GW) observatories have detected approximately 200 binary BLACK HOLE (BH) mergers. The astrophysical origin of these events are debated, with evidence suggesting that at least a subset originated from dynamic environments characterized by frequent close encounters. Accretion disks in ACTIVE GALACTIC NUCLEi (AGNs) are of particular interest, as certain observed features could be more readily produced within such environments. In this paper, we investigate the expected properties of mergers in these environments, and their dependence on various parameters, using one-dimensional $N$-body simulations combined with a comprehensive semi-analytical model. In our fiducial model, the distributions of masses and mass ratios ($q$) are similar to those observed. However, they depend strongly on the lifetime and density of the AGN disk and on the number and accretion efficiency of BHs, with higher masses predicted as these quantities increase. The most massive mergers, such as GW231123, can be produced either by efficient gas accretion or by hierarchical mergers among $\geq 3$ generations of BHs. The observed negative correlation between $q$ and the average effective spin ($χ_{\rm eff}$), along with the positive correlation between $χ_{\rm eff}$ and the chirp mass ($M_{\rm chirp}$), can be explained by a combination of efficient gas accretion, which promotes spin alignment, and hierarchical mergers, which produce high-$|χ_{\rm eff}|$ and low-$q$ binaries. Hierarchical mergers can also explain the negative correlation between $q$ and the dispersion of $χ_{\rm eff}$, as well as the positive correlation between $|χ_{\rm eff}|$ and $M_{\rm chirp}$. We present a comprehensive study on how the expected distribution of each of these quantities depends on model parameters and assumptions, which will aid the interpretation of observed GW population properties.
[abstract 7 / 45] Yes (score: 4) - Title: Extreme particle acceleration in X-ray binaries is linked to their JETsAuthors: Laura Olivera-Nieto, Fraser J. Cowie, Sera Markoff, Rob Fender, Justine Crook-Mansour,Comments: submitted to A&ASubjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The detection of multi-TeV radiation from a handful of black-hole X-ray binaries (BHXRBs) has positioned the source class as promising candidate to explain the cosmic-ray flux in the PeV energy range. To determine what distinguishes the systems detected in the gamma-ray range from the rest of the population, we build on existing catalogues of BHXRBs by including information on the radio and gamma-ray emission from these systems. We then compare the $>100$ TeV gamma-ray luminosity to different properties of the systems and evaluate the strength of the (rank) correlation between them. Additionally, we compare the distribution of BHXRBs with the positions of unassociated gamma-ray sources in the 1LHAASO and 1HGPS catalogues. We find no correlation with the mass of the compact object, the companion mass or the inclination angle. Instead, we find evidence for a strong correlation between the gamma-ray luminosity and the radio and hard-state X-ray luminosities in our sample. The limited number of gamma-ray detections means that this correlation cannot yet be claimed as statistically significant. We find indications that a high (>20\%) duty cycle (defined as fraction of time spent in outburst) might be a requirement for $>100$ TeV gamma-ray loudness. We find significant evidence ($>3σ$) that BHXRBs are located near unassociated gamma-ray sources in the region of the sky not covered by LHAASO. This evidence is only significant when comparing to BHXRBs detected in the radio band. We conclude that radio-bright BHXRBs with a high duty cycle are more likely to be detected as gamma-ray sources than sources which are not detected in the radio band or those with low duty cycles. This result indicates that the particles responsible for the gamma-ray emission are associated with the JETs, either accelerated within them or via their interaction with their surroundings.
[abstract 8 / 45] (score: 3) - Title: Kinetic route to helicity-constrained decayAuthors: Dion Li,Comments: Proof-reviewed version accepted for publication in APS Open Science; main conclusions unchanged. 25 pages, 9 figures, 1 tableSubjects: physics.plasm-ph astro-ph.HE astro-ph.SR physics.space-phCreated: 2026-07-02; Updated: 2026-07-08; Datestamp: 2026-07-08
Through two-dimensional, three-velocity-component particle-in-cell simulations of freely decaying subion turbulence, intermittent localized regions with $\mathbf{E} \cdot \mathbf{B} \neq 0$ are found, in the early electron-scale interaction phase, to be statistically associated with decreases in $|H_{V_s}|$, the fixed-gauge structure-integrated MAGNETic-helicity diagnostic. This structure-level behavior coincides with a decline of the Saffman helicity-variance plateau value $I_H$. Motivated by these observations, we propose a source-compensated, history-dependent helicity density that satisfies an exact local balance identity by construction, enabling Saffman-type two-point correlation integrals, which, under standard flux-decorrelation assumptions, can exhibit intermediate-scale plateaus that are roughly time independent. In the simulations, such plateaus are observed to remain approximately invariant over the measured kinetic interval even as $I_H$ evolves during the early kinetic stage. Under approximate single-scale self-similarity, the plateau behavior of the MAGNETic integral is consistent with the two-dimensional decay constraint $BL \sim \text{const}$. For initially net-helical configurations, we observe rapid development of mixed-signed MAGNETic-helicity patches and a decrease of the global fractional helicity, such that the decay over the kinetic interval is again most consistent with the cancellation-dominated scaling constraint.
[abstract 9 / 45] (score: 3) - Title: Simultaneous TRACERS and THEMIS Observations of Reversed Cusp Ion Dispersions and Dual-Lobe ReconnectionAuthors: M. Øieroset, S. A. Fuselier, J. B. Bonnell, R. A. Roglans, J. S. Halekas, R. J. Strangeway, T. D. Phan, R. G. Gomez, S. M. Petrinec, K. J. Trattner, S. R. Shaver, K. A. Goodrich, S. A. Henderson, S. L. Soni, V. Angelopoulos, B. L. Burkholder, H. Cao, L-J. Chen, H. K. Connor, D. M. Miles, A. Moore, J. Ng, Y. Shen,Comments:Subjects: physics.space-phCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
We present observations from two consecutive TRACERS-2 orbits through the northern low-altitude cusp. During the first crossing, TRACERS-2 observed reversed cusp ion dispersion and sunward convection, consistent with MAGNETopause RECONNECTion tailward of the cusp during this northward IMF interval. Simultaneous THEMIS-D observations at the equatorial MAGNETopause show heated MAGNETosheath plasma captured on closed field lines, with similar particle spectra as in in the low-altitude cusp, indicating that RECONNECTion indeed occurred tailward of the cusp and in both hemispheres. When TRACERS-2 traversed the northern cusp again, 95 minutes later, the IMF was dominated by a negative BX component. Despite the different IMF conditions, TRACERS-2 recorded nearly the same cusp signatures as before, i.e., reversed ion dispersion and sunward convection. The observations indicate that tailward-of-cusp RECONNECTion can occur for both northward and BX-dominated IMF and that these distinct IMF geometries can produce remarkably similar plasma and field signatures in the low-altitude cusp.
[abstract 10 / 45] (score: 3) - Title: A narrow Comptonization locus in Seyfert slab coronae: implications for dominant coronal dissipation and reduced feedbackAuthors: Haichao Xu,Comments: Substantially revised version after peer-review feedback. The manuscript has been reorganized and updated for MNRAS submissionSubjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The thermal state of ACTIVE GALACTIC NUCLEus (AGN) coronae is commonly described by the electron temperature $kT_{\rm e}$, the Thomson optical depth $τ_{\rm T}$, and the geometry of the Comptonizing medium. We compile a literature sample of radio-quiet Seyfert galaxies with direct slab-geometry thermal Comptonization measurements of $kT_{\rm e}$ and $τ_{\rm T}$. For bottom-illuminated slab coronae, we adopt a geometry-motivated effective Comptonization parameter, $y=4θτ_{\rm T}\,{K_3(1/θ)} / {K_2(1/θ)}$, where $θ=kT_{\rm e}/m_{\rm e}c^2$ and $K_n$ is the modified Bessel function of the second kind. We find that the compiled slab-corona measurements are distributed along a narrow anti-correlated ridge in the $kT_{\rm e}-τ_{\rm T}$ plane. For the cleaned primary \texttt{compTT} sample, this ridge corresponds to $\langle y\rangle=0.770$ with a logarithmic dispersion of only 0.086 dex. We then compare the observed ridge with reduced-feedback slab-equilibrium calculations and find that the locus favours a corona-dominated local energy budget, $f\simeq1$, together with a feedback factor well below the full-covering value, $g\ll1$. We interpret the constant-$y$ locus as implications for dominant local coronal dissipation and reduced disc-corona radiative feedback, consistent with a patchy corona. Supplementary pair-balance calculations indicate that the low-temperature, high-optical-depth part of the sample is unlikely to be sustained by a purely thermal pair plasma alone, suggesting that the fitted optical depths are more plausibly dominated by electron--ion plasma.
[abstract 11 / 45] (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 figures, v2 with revisions and updated resultsSubjects: astro-ph.HE gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
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 $90\%$ 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 12 / 45] (score: 3) - Title: The Information Content of Quasar Variability Light Curves: How Well Can we Infer Stochastic Model Parameters?Authors: Brendon J. Brewer, Geraint F. Lewis, Xiang Yu, Yuan Li,Comments: Published in the Open Journal of Astrophysics. 18 pages, 7 figures, 3 tablesSubjects: astro-ph.GA physics.data-an stat.APCreated: 2026-07-03; Updated: 2026-07-08; Datestamp: 2026-07-08
Quasar variability, driven by multi-scale physical processing within a RELATIVISTIC accretion disk, is commonly modelled with stochastic time series models. The simplest of these is the Damped Random Walk (DRW), also known as the Ornstein-Uhlenbeck (OU) process. Here, we demonstrate that, when fitting such a model to QUASAR light curve data, the mean of the light curve, $μ$, should not be fixed (which is the typical approach), as this leads to overconfident inferences about the variability timescale $τ$, with substantially underestimated uncertainties. However, the short term volatility parameter $η$ is typically very well constrained from short light curves. Through simulations, we compute information theoretic quantities such as the conditional entropy and the mutual information, confirming that light curves provide much more information about $η$ than about $τ$. As a result, we recommend that future QUASAR variability studies focus on $η$ rather than $τ$. To demonstrate this approach, we fit a hierarchical Bayesian regression model for $η$ as a function of bolometric luminosity and rest wavelength to a dataset of 570 light curves measured over decades. We perform the fit using a likelihood function that uses the light curves directly, rather than using intermediate $η$ values from individual light curve fits. We find that volatility decreases as a function of both bolometric luminosity and rest wavelength. The volatility also decreases more steeply with redshift than time dilation alone would suggest, pointing to an increase in intrinsic volatility as QUASARs evolve over cosmic time.
[abstract 13 / 45] (score: 3) - Title: Understanding Pulsar Magnetospheres with the SKAOAuthors: L. S. Oswald, A. Basu, M. Chakraborty, B. C. Joshi, N. Lewandowska, K. Liu, M. E. Lower, A. Philippov, X. Song, P. Tarafdar, J. van Leeuwen, A. L. Watts, P. Weltevrede, G. Wright, J. Benáček, A. Beri, S. Cao, P. Esposito, F. Jankowski, J. C. Jiang, A. Karastergiou, K. J. Lee, N. Rea, D. Vohl,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Oswald01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes. N.B. a version of this article was previously published as part of a Special Issue, linked at arxiv:2512.16157Subjects: astro-ph.HECreated: 2026-07-03; Updated: 2026-07-08; Datestamp: 2026-07-08
The SKA telescopes will bring unparalleled sensitivity across a broad radio band, a wide field of view across the Southern sky, and the capacity for sub-arraying, all of which make them the ideal instruments for studying the pulsar MAGNETosphere. This chapter describes the advances that have been made in pulsar MAGNETosphere physics over the last decade, and details how these have been made possible through the advances of modern radio telescopes, particularly SKA precursors and pathfinders. It explains how the SKA telescopes would transform the field of pulsar MAGNETosphere physics through a combination of large-scale monitoring surveys and in-depth follow-up observations of unique sources and new discoveries. Finally, it describes how the specific observing opportunities available with the AA* and AA4 configurations will achieve the advances necessary to solve the problem of pulsar radio emission physics in the coming years.
[abstract 14 / 45] (score: 3) - Title: Radio and X-ray Observations of the Transitional Supernova 2019yvr: Insights into the Progenitor Mass-Loss HistoryAuthors: Raphael Baer-way, Poonam Chandra, Maryam Modjaz, A. J. Nayana, Keiichi Maeda, Katie Auchettl, Maria R. Drout, Charles D. Kilpatrick, Alak K. Ray, Stuart D. Ryder,Comments: 19 pages,9 Figures, submitted to ApJSubjects: astro-ph.HE astro-ph.SRCreated: 2026-07-06; Updated: 2026-07-08; Datestamp: 2026-07-08
The final life stages of the massive star progenitors of stripped-envelope SUPERNOVAe (SESNe) are still an open question, especially when it comes to the timing and magnitude of the progenitor stripping. Observing SESNe across the electroMAGNETic spectrum allows for the most direct constraints on mass loss in the final stages of progenitor evolution. In this work, we present radio (GMRT+VLA) and X-ray (SWIFT+Chandra) observations of SN 2019yvr obtained from 18-1784 days post-explosion. SN 2019yvr was a type Ib SUPERNOVA (SN Ib, with strong helium but no or little optical hydrogen features) that transitioned into a type IIn SUPERNOVA (SN IIn, with shock-driven hydrogen features) at $\sim$ 100 days post-explosion. The radio evolution is best-fit by a SYNCHROTRON self-absorbed model with a $ρ\propto r^{-1.65 \pm 0.25}$ CSM density profile, suggesting a decreasing mass-loss rate from the progenitor in the years leading up to the explosion. The radio-derived shock speed is high, more than 30,000 km/s at early times, suggesting a compact progenitor star. The combined radio and X-ray data probe CSM that extends from less than $10^{16}$ cm up to $\sim$ 20$\times10^{16}$ cm and was created by mass-loss from $\sim 1-3 \times10^{-5} \rm{M_{\odot} yr^{-1}} $ (assuming a CSM speed of 100 km/s). The combined dataset rules out any dramatic jump in CSM density (which was seen in the optical analog SN 2014C) associated with the emergence of optical hydrogen emission in SN 2019yvr. We place SN 2019yvr in context with similar transitional SNe and discuss implications for the progenitor.
[abstract 15 / 45] (score: 3) - Title: Analyzing Cosmic Ray Spectral Features: A Numerical InvestigationAuthors: Yuca C. Chen, Zachary M. Dorris, Eun-Suk Seo, Vladimir S. Ptuskin,Comments: 23 pages, 12 figures. Published in the Special Issue "Astrophysics of cosmic rays in the multi-messenger era"Subjects: astro-ph.HECreated: 2026-07-06; Updated: 2026-07-08; Datestamp: 2026-07-08
Recent COSMIC RAY space-based and balloon-borne experiments have revealed various spectral features. Spectral hardening around ~200 GV has been seen in primary nuclei as well as secondaries produced during propagation. Proton spectrum softening at ~10 TV and helium spectrum softening at a few tens TV has also been seen. Additionally, a positron excess has been observed above ~25 GeV. The COSMIC RAY propagation code, GALPROP v57, was utilized to investigate the cause behind these features. A diffusion model with reacceleration and convection effects was used as a baseline. To find the best fit to the experimental data, GALPROP v57's parameter optimization module, utilizing the external numerical minimization software MINUIT2, was used. For the hardening, three scenarios were studied: (1) a diffusion coefficient break, (2) injection spectra breaks, and (3) a combination of both breaks. An additional injection spectrum break was considered to fit the softening of the proton and helium spectra. An additional positron source was introduced for the positron excess. The resulting elemental spectra and ratios, along with the all-particle spectrum, are compared to compiled COSMIC RAY data. Implications of these spectral features are also discussed.
[abstract 16 / 45] (score: 3) - Title: Mega-Gauss Plasma Jet Creation Using a Ring of Laser BeamsAuthors: L. Gao, E. Liang, Y. Lu, R. K. Follet, H. Sio, P. Tzeferacos, D. H. Froula, A. Birkel, C. Li, D. Lamb, R. Petrasso, W. Fu, M. Wei, H. Ji,Comments:Subjects: physics.plasm-phCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Using 20 OMEGA LASER beams at the Laboratory for Laser Energetics, University of Rochester, to irradiate a flat plastic target in a hollow ring configuration, we created supersonic cylindrical stable plasma JETs with self-generated megagauss MAGNETic fields extending out to > 4 mm. These well-collimated MAGNETized JETs possess a number of distinct and novel properties that will allow us to study the dynamics, physical processes and scaling properties of astrophysical JETs not feasible with other laboratory settings. The dimensionless parameters of these laboratory JETs fall in the same regime as those of YSO JETs. They will also provide new versatile LASER-based platforms to study MAGNETized shocks, shear flows and other plasma processes under controllable conditions.
[abstract 17 / 45] (score: 3) - Title: Multi-messenger View of White Dwarf Tidal Disruption Events by Intermediate-Mass Black Holes: I. Gravitational Waves and Disk Photon and Neutrino EmissionsAuthors: Jin-Hong Chen, Lixin Dai, Bing Zhang,Comments: 25 pages, 22 figures, submitted to ApJSubjects: astro-ph.HE astro-ph.GACreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
White dwarf (WD) tidal disruption events (TDEs) provide a unique window onto intermediate-mass BLACK HOLEs (IMBHs). We present a multi-messenger view of these systems in two papers. In this paper, we develop an accretion-disk model for WD--TDEs in which the bound debris accretes at extremely super-Eddington rates, $\sim 10^5$--$10^9$ times higher than in typical (main-sequence) TDEs. The model includes MAGNETic pressure, nuclear-burning heating, wind mass loss, and neutrino production via $e^{\pm}$ pair annihilation. At such high accretion rates, the gas and radiation temperatures of the inner flow can reach $T\gtrsim 10^9\,\mathrm{K}$, enabling prolific pair production and MeV neutrino emission. We find that the disk is predominantly advection dominated over a broad range of accretion rates, while disk winds can partially cool the flow and reduce the inner temperature. The predicted thermal EM emission is nearly insensitive to the fallback rate in the super-Eddington regime: the luminosity only mildly exceeds the IMBH Eddington luminosity and the spectrum peaks at $\sim 0.1$--$1\,\mathrm{keV}$, implying detectability with current X-ray facilities such as Einstein Probe. For low-mass IMBHs ($\sim 10^3\,M_{\odot}$), the disk can also produce a burst of MeV neutrinos with luminosities up to $\sim 10^{47}\,\mathrm{erg\,s^{-1}}$ for ONeMg WD--TDEs, although detectability with current neutrino detectors (e.g., Super-Kamiokande and JUNO) is limited to Galactic distances. Finally, we estimate the GW burst produced during the final passage prior to disruption, which peaks at $\sim 0.1$--$1\,\mathrm{Hz}$, placing WD--TDEs in the target band of proposed decihertz detectors and motivating coordinated GW+EM+neutrino searches. We also present a first exploration of GWs from a precessing WD--TDE disk; this signal is much weaker, with a detection horizon $\lesssim 1\,\mathrm{Mpc}$ for these missions.
[abstract 18 / 45] (score: 3) - Title: Unveiling the Local Environment of FRB 20220912A: Sub-arcsecond $4-26$ GHz Radio Continuum MappingAuthors: Yash Bhusare, Yogesh Maan, Mohit Bhardwaj, Thomas C. Abbott, Yuxin Dong, Danté M. Hewitt, Afrokk Khan,Comments: 16 pages, 6 figures, 4 tablesSubjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The local environments of repeating fast radio bursts (FRBs) provide critical clues to their progenitors. While some active repeaters (e.g., FRB~20121102A, FRB~20190520B) are embedded in compact persistent radio sources (PRS), others appear to reside in cleaner environments. We present a high-resolution, multi-frequency (4$-$26 GHz) continuum study of the hyperactive repeater FRB 20220912A using the Karl G. Jansky Very Large Array (VLA). We report the discovery of a previously unknown radio source distinct from the compact PRSs seen in other FRBs, spatially coincident with the FRB position and offset by $\approx 300$~mas ($\approx 450$~pc) from the host galaxy's center. The absence of continuum emission in archival milliarcsecond-resolution VLBI observations indicates that the source is resolved out, ruling out a hyper-compact ($< 1$~pc) central-engine-powered origin. We constrain the physical diameter of the emitting region between 75~pc and 190~pc. We further demonstrate that the source is characterized by a steep non-thermal spectral index ($α\approx -0.73$) and a remarkably high star-formation rate surface density $Σ_{\text{SFR}} \gtrsim 13~M_{\odot}~\text{yr}^{-1}~\text{kpc}^{-2}$. We argue that this emission is best explained as a compact star-forming region within the host galaxy. This association with a site of ongoing STAR FORMATION provides strong observational support for the hypothesis that young MAGNETars, formed after the deaths of massive stars, are the progenitors of at least some repeating FRBs.
[abstract 19 / 45] (score: 3) - Title: Pulsars in Globular Clusters With the SKAOAuthors: M. Bagchi, F. Abbate, V. Balakrishnan, M. C. i Bernadich, B. Bhattacharyya, A. Dutta, P. C. C. Freire, K. Halley, J. W. T. Hessels, S. Kumari, D. R. Lorimer, A. Possenti, R. Nag, S. M. Ransom, A. Ridolfi, V. Venkatraman Krishnan, W. W. Zhu,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no: AASKAII/Bagchi01. A slightly different version was published in The Open Journal of Astrophysics with arXiv id arXiv:2512:16154Subjects: astro-ph.HE astro-ph.GA astro-ph.SRCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Globular clusters (GCs) are highly efficient factories of radio pulsars: per unit of stellar mass, they contain about 1000 times more pulsars than in the Galactic field. Thus far, 345 radio pulsars have been found in GCs. These can be used as precision probes of the structure, gas content, MAGNETic field, and dynamic history of their host clusters; some of them are also highly interesting in their own right because they probe exotic stellar evolution scenarios, the physics of dense matter, accretion, gravity, etc. One of them (PSR~J0514$-$4002E) might even be the first pulsar - BLACK HOLE system known. Deep searches with SKA telescopes will only require one to a few tied-array beams, and can be done during early commissioning of the telescopes, before an all-sky pulsar survey using hundreds to thousands of tied-array beams is feasible. Even a conservative approach predicts discoveries only with the core of SKA-MID AA*. Eventually, SKA-MID AA4 is expected to increase the number of discoveries even more, leading to more than doubling the current known population. Thus, a dedicated search for pulsars in GCs will fully utilise the best possible natural laboratories to study various branches of physics and astrophysics, including the properties of dense matter, stellar evolution, and the dynamical history of these GCs.
[abstract 20 / 45] (score: 3) - Title: Exact 1D Nonlinear Solutions for Proton-Driven Plasma Wakefields: Benchmarking Against AWAKE Data EnvelopesAuthors: D. Tsiklauri,Comments: submitted for publicationSubjects: physics.plasm-ph astro-ph.HE astro-ph.SR physics.acc-ph physics.space-phCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The analytical modeling of a plasma wakefield driven by a RELATIVISTIC proton beam is an element in optimizing advanced plasma-based acceleration schemes. In this work, we present a 1D nonlinear fluid framework under the quasi-static approximation to describe the wake potential excited by a positively charged proton driver. We examine our model using a two-bunch pump-probe configuration, demonstrating close agreement between the analytical invariants and adaptive numerical integrations. The distinct geometric curvature changes observed at the micro-bunch boundaries are shown to be physical consequences of step-discontinuities in the second derivative of the wake potential across the beam interfaces. Furthermore, by scaling this numerical framework to a train of $N=100$ micro-bunches undergoing seeded self-modulation (SSM), we model the physical parameters of the CERN AWAKE facility ($n_0 = 7.0 \times 10^{14}\text{ cm}^{-3}$). Our model replicates the characteristic linear growth envelope and matches the calibrated field envelope boundaries of approximately $\pm 0.75\text{ GV/m}$ inferred from the experiment. This piece-wise framework provides a computationally efficient foundation for investigating customized, asymmetric micro-bunch profiles designed to optimize the transformer ratio beyond the fundamental symmetric limit of 2.
[abstract 21 / 45] (score: 2) - Title: Black Hole Solutions with Electric and Magnetic Charges in Nonlinear ElectrodynamicAuthors: Shu Luo,Comments: 35 pagesSubjects: gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
This review article provides a comprehensive and self-contained overview of BLACK HOLE solutions coupled to nonlinear electrodynamics (NLED) with both electric and MAGNETic charges. We systematically discuss the theoretical foundations, including the general action principle, the Hamiltonian P-framework for constructing exact solutions, and the classification of NLED theories (Born-Infeld, Euler-Heisenberg, power-law, logarithmic, exponential, and regular models). Detailed derivations are presented for dyonic BLACK HOLE solutions in each theory, including explicit metric functions, asymptotic expansions, and horizon structures. The thermodynamic properties are examined in depth, including the first law, Smarr relations, heat capacities, extended phase space thermodynamics with p-V criticality, and the effect of MAGNETic charge on phase transitions. The geodesic structure is analyzed with complete calculations of null and timelike geodesics, photon spheres, BLACK HOLE shadows, and gravitational lensing. Regular BLACK HOLE solutions that resolve the central singularity are discussed with detailed analysis of energy conditions. Holographic applications via the AdS/CFT correspondence are explored, including holographic superconductors, entanglement entropy, and conductivity. Connections to quantum gravity through the weak gravity conjecture, swampland criteria, and string theory embeddings are examined.
[abstract 22 / 45] (score: 2) - Title: Revisiting the limits on DARK MATTER annihilation cross-section and decay lifetime in light of electron and positron fluxesAuthors: Nagisa Hiroshima, Kazunori Kohri, Partha Kumar Paul, Narendra Sahu,Comments: v2: 1+18 pages, 12 captioned figures, 4 tables, version accepted for publication in JCAPSubjects: hep-ph astro-ph.CO astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
We revisit the upper bound on the annihilation cross-section, $\langleσv\rangle$ of a stable DARK MATTER (DM) of mass $500-10^{14}$ GeV by considering five different channels: $W^+W^-$, $b\bar{b}$, $μ^+μ^-$, $τ^+τ^-$, and $e^+e^-$. We use the observed electron and positron fluxes from CALET, DAMPE, HESS, positron flux from AMS-02, and gamma-ray flux from HAWC, GRAPES-3, CASA-MIA to constrain the annihilation cross-section. We also consider unstable DM of mass $10^3-10^{16}$~GeV decaying to $W^+W^-$, $b\bar{b}$, $μ^+μ^-$, $τ^+τ^-$, and $e^+e^-$ and derive the corresponding lower bound on the DM lifetime, $τ_{\rm DM}$. We find that the latest AMS-02 data provide the most stringent constraints on $\langleσv\rangle$ for DM masses below 2 TeV, while HESS yields the strongest limits for $M_{\rm DM}\gtrsim2$ TeV. The HESS gives a much more stringent limit on the DM lifetime, excluding $τ_{\rm DM\rightarrowμ^+μ^-}\lesssim\mathcal{O}(10^{30})$ s for a 10 TeV mass of DM. The limits on $\langleσv\rangle$ derived from the $e^+e^-$ flux are competitive with those from $γ$-ray and neutrino observations for DM masses in the range $10^5$--$10^{11}$ GeV, and become the most stringent beyond this range. For decaying DM, the $e^+e^-$ flux provides the strongest constraints on the DM lifetime over the mass range $10^3$--$10^9$ GeV.
[abstract 23 / 45] (score: 2) - Title: The impact of precession and higher-order multipoles for gravitational wave cosmological inferenceAuthors: Charlie Hoy, Konstantin Leyde,Comments: 32 pages, 10 figures, 2 appendicesSubjects: astro-ph.CO astro-ph.HE gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Gravitational-wave astronomy presents an exciting opportunity to provide an independent measurement of the expansion rate of the Universe. By combining inferences for the binary component masses and luminosity distances from individual observations, it is possible to infer $H_0$ without direct electroMAGNETic counterparts or galaxy catalogs. However, this relies on theoretical gravitational-wave models, which are known to be incomplete descriptions of the full predictions of general relativity. Although the accuracy of our models are improving, they are also becoming increasingly expensive as additional phenomena are incorporated. In this work, we demonstrate that there is no significant advantage in including spin-precession and higher-order multipole moments when inferring $H_0$ via the mass spectrum method for current and near-future gravitational-wave event numbers. Even when simulating a population of highly precessing and preferentially asymmetric-mass-ratio binaries, we show that the inferred $H_0$ posterior changes minimally. Using a simpler, less accurate model, achieves comparable $H_0$ estimates with six times less computational cost (on average). Using computationally cheaper models for single event inference may become crucial as thousands of gravitational-wave observations are expected to be detected in the near future.
[abstract 24 / 45] (score: 2) - Title: On the Astrophysical Origin of Binary Black Hole Subpopulations: A Tale of Three Channels?Authors: Anarya Ray, Shirsha Mukherjee, Michael Zevin, Vicky Kalogera,Comments: Journal-accepted versionSubjects: astro-ph.HE astro-ph.GA gr-qcCreated: 2026-07-06; Updated: 2026-07-08; Datestamp: 2026-07-08
There is increasing evidence for multiple binary BLACK HOLE~(BBH) subpopulations in the cumulative gravitational wave catalog by the LIGO-Virgo-KAGRA Collaboration. The astrophysical interpretation of this complex underlying population is subject to theoretical uncertainties in treatments of binary stellar evolution, core collapse, and host environments. In this \textit{Letter}, using parametrized mixture models, we show that the BBH detection sample comprises three astrophysical subpopulations that are likely dominated by specific formation channels. In particular, we show that the $10M_{\odot}$ peak and the $35M_{\odot}$ feature in the BBH mass spectrum correspond to distinct mass-ratio, spin alignment, spin precession, and redshift evolution properties. We show that mass-based transitions reported in the distribution of BBH parameters naturally emerge from our inferred distributions without explicit modeling. Our results are consistent with the current observed population arising from specific relative abundances of isolated binary evolution, dynamical formation in globular clusters, and higher-generation BBH mergers. Under this interpretation, we constrain the relative underlying fraction of these channels to be $79.0^{+11.5}_{-10.9}\%$, $14.5^{+11.6}_{-8.0}\%$, and, $2.5^{+5.5}_{-1.8}\%$, respectively, and find these relative fractions to be evolving over cosmic time with more than $1σ$ confidence. Our interpretation relies on simple theoretical predictions that are mostly robust against uncertainties in BBH formation, with more definite conclusions expected in the near future.
[abstract 25 / 45] (score: 2) - Title: Eccentricity constraints disfavor single-single capture in nuclear star clusters as the origin of all LIGO-Virgo-KAGRA binary BLACK HOLEsAuthors: Nihar Gupte, M. Coleman Miller, Rhiannon Udall, Sophie Bini, Alexandre Toubiana, Alessandra Buonanno, Jonathan Gair, Aldo Gamboa, Lorenzo Pompili, Antoni Ramos-Buades, Maximilian Dax, Stephen R. Green, Annalena Kofler, Jakob Macke, Bernhard Schölkopf,Comments: 24 pages, 9 figures, 4 tablesSubjects: astro-ph.HE gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Multiple formation pathways have been proposed for the origin of binary BLACK HOLEs (BBHs). These include isolated binary evolution and dynamical assembly in dense stellar environments such as nuclear or globular star clusters. Yet, the fraction of BBHs originating from each channel remains uncertain. One way to constrain this fraction is by investigating the orbital eccentricities of the BH coalescences detected by the LIGO-Virgo-KAGRA (LVK) Collaboration. We analyze 84 BBHs from the first part of the fourth LVK observing run (O4a) using a multipolar, eccentric, aligned-spin effective-one-body waveform model. We perform parameter inference with neural posterior estimation and nested sampling. After incorporating astrophysical prior odds and comparing to the quasicircular precessing-spin hypothesis, we find that no candidates reach a high enough significance to claim a confident detection of eccentricity. We use these upper limits to explore a model, in which all O4a BBHs originate from single-single gravitational wave (GW) captures. We perform hierarchical inference on the velocity dispersion of the host environment of the BBHs and find $σ$ < 19.7 km/s (95% credible upper bound). This disfavors single-single capture in nuclear star clusters (approximately 20-200 km/s) as the dominant source of all observed BBH mergers. Our analysis also jointly infers the mass, spin and redshift distributions and takes into account selection effects due to using quasi-circular templates for BBH detection. Our results place improved constraints on the number of eccentric BBHs and highlight the importance of eccentricity measurements in disentangling compact-binary formation channels in current and future GW detectors.
[abstract 26 / 45] (score: 2) - Title: Chaos bound for spinning particles in Kerr-Newman-AdS BLACK HOLEsAuthors: Deyou Chen, Chuang Yang, Kangqiao Liu,Comments: 24 pages, 11 figuresSubjects: gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
In this paper, we employ spinning test particles as probes to investigate the regulatory effects of particle and BLACK HOLE parameters on the violation of the chaos bound in Kerr-Newman-AdS spacetime. Our results demonstrate that the chaos bound violation is governed by the interplay of spacetime geometry, electroMAGNETic forces, and particle dynamics. The particle spin modulates the direction dependence and parameter thresholds of the violation through its coupling with the orbital angular momentum, which contributes to the total angular momentum. The negative cosmological constant acts as a potential well, with a larger magnitude of the cosmological constant leading to stronger chaotic behavior. A competitive coupling exists between the BLACK HOLE rotation and charge -- its prograde rotation exerts a stabilizing effect that can suppress or even completely quench charge-driven violations, while the charge serves as a condition for triggering the violation, with its effect modulated by the spin stabilization. In the Kerr-AdS limit, the violation occurs only when the BLACK HOLE rotates opposite to the $z$-axis with a sufficiently large rotation parameter and a sufficiently small cosmological constant. In the RN-AdS limit, the violation condition is jointly determined by the charge and the cosmological constant, with electroMAGNETic repulsion more readily inducing the violation than electroMAGNETic attraction.
[abstract 27 / 45] (score: 2) - Title: Dark matter energy exchange in stars orbiting supermassive BLACK HOLEsAuthors: Stephan A. Meighen-Berger, R. Andrew Gustafson, Nicole F. Bell, Jayden L. Newstead, Sandra Robles, Ian M. Shoemaker,Comments: 6 figures, 6 pages, v2 references added, comments welcomeSubjects: hep-ph astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Stars on tight orbits around the supermassive BLACK HOLE at the Galactic Center pass through regions where the DARK MATTER~(DM) density may be strongly enhanced. We compute the orbit-averaged DM-induced energy exchange for S4714 as an example. It is a star on an exceptionally close and RELATIVISTIC orbit around Sagittarius~A*. For a spiked DARK MATTER profile, the exchange reaches the stellar luminosity at $σ_{χp} \sim 10^{-36}~\mathrm{cm}^2$ for MeV-GeV masses and $σ_{χe} \sim 5\times10^{-38}~\mathrm{cm}^2$ for sub-MeV masses, opening a new annihilation-free route toward dark-star phases. These cross sections lie within the range predicted by freeze-in scenarios and are consistent with cosmic-ray--boosted and solar-reflection DARK MATTER constraints.
[abstract 28 / 45] (score: 2) - Title: Hubble constant measurement with 13 bright standard sirens from binary BLACK HOLE mergers inside ACTIVE GALACTIC NUCLEiAuthors: Dhruv Kumar, Alejandro Torres-Orjuela,Comments: 4 pages, 2 figures, 1 tableSubjects: astro-ph.CO gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
We measure the Hubble constant $H_0$ using 13 gravitational-wave binary BLACK HOLE mergers associated with ACTIVE GALACTIC NUCLEus hosts. We find $H_0=70.50^{+3.37}_{-2.89}\,({\rm stat})\pm1.56\,({\rm cal})$\,km\,s$^{-1}$\,Mpc$^{-1}$ ($4.4\%$ precision), consistent with both Planck\,2018 ($0.98σ$) and SH0ES\,2024 ($0.76σ$), with no significant preference between the two. Combining with the bright siren GW170817 sharpens the constraint to $H_0=70.31^{+3.00}_{-2.85}\,({\rm stat})\pm1.55\,({\rm cal})$\,km\,s$^{-1}$\,Mpc$^{-1}$ ($4.2\%$ precision), and further combining with an independent dark-and-bright-siren sample tightens it to $H_0=69.71^{+2.55}_{-2.40}\,({\rm stat})\pm1.54\,({\rm cal})$\,km\,s$^{-1}$\,Mpc$^{-1}$ ($3.5\%$ precision). Assuming a luminosity-distance prior centered around the value related to a fixed cosmology in turn, recovers $H_0=67.62\pm0.72$ (Planck-anchored) and $H_0=72.91\pm0.72$\,km\,s$^{-1}$\,Mpc$^{-1}$ (SH0ES-anchored). We show that under such an assumption, a rejection of $\gtrsim4σ$ to the opposing anchor is obtained.
[abstract 29 / 45] (score: 2) - Title: Star Planet InteractionsAuthors: Arghyadeep Paul, Kristina Kislyakova, Manuel Güdel, Rim Fares, Judy Chebly, Sergio Joya, Miljenko Čemeljić, Katja Poppenhäger, Julian Alvarado-Gomez, Silva Järvinen, Cesar Bertucci, Dibyendu Nandy, Antonio García Muñoz, Antoine Strugarek, Mayank Narang, Shyama Narendranath,Comments: Submitted to Space Science ReviewsSubjects: astro-ph.SR astro-ph.EPCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
Star-planet interactions (SPIs) describe the continuous exchange of energy, momentum, and mass between exoplanets and their host stars through radiative, tidal, MAGNETic, and particle-driven processes. Together, these interactions shape the structure, evolution, and observable properties of exoplanetary systems. In this review, we bring together current theoretical and observational understanding of SPIs, highlighting how stellar radiation, winds, and MAGNETic activity influence planetary atmospheres, interiors, and orbital evolution, while using the Solar System as a valuable reference for interpreting these processes. High-energy stellar radiation, particularly in the far- and extreme-ultraviolet and X-ray bands, drives atmospheric heating, photochemistry, ionisation, and escape. These effects are further influenced by stellar winds and MAGNETic interactions, which can either protect planetary atmospheres or accelerate their loss over time. Tidal interactions redistribute energy and angular momentum, producing internal heating and driving orbital migration and circularisation. Magnetic star-planet coupling provides additional pathways for energy transfer through RECONNECTion and current systems, potentially enhancing atmospheric escape, heating planetary ionospheres and interiors, and generating observable signatures such as radio emission and enhanced stellar activity. We discuss how these processes work together, emphasising that their long-term impact depends on stellar evolution, planetary properties, atmospheric structure, and MAGNETic field strength. By presenting radiative, tidal, and MAGNETic interactions within a unified framework, this review highlights the physical mechanisms that shape planetary environments and identifies the key observational signatures that will complement future studies of exoplanet evolution and habitability.
[abstract 30 / 45] (score: 2) - Title: Quasi mono-energetic, RELATIVISTIC electron acceleration in a femtosecond, high intensity LASER excited solid MAGNETAuthors: Trishul Dhalia, Anandam Choudhary, C. Aparajit, Amit D. Lad, Ankit Dulat, Yash M. Ved, Rohit Juneja, Amita Das, G Ravindra Kumar,Comments: 10 pages, 10 figures, 1 tableSubjects: physics.plasm-ph physics.acc-ph physics.comp-phCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The interaction of ultraintense LASERs with MAGNETized overdense plasmas reveals a fundamentally new regime of LASER-driven particle acceleration. Particle-in-cell simulations demonstrate the generation of directional, quasi-monoenergetic electrons in the MeV energy range superimposed on a broad thermal electron background with the estimated acceleration gradient of 3.6 MeV/μm, which is the highest till date. In contrast to conventional LASER-plasma accelerators, which rely on underdense plasmas and are therefore constrained to relatively low plasma densities and limited beam charge, the present scheme operates in plasmas with densities orders of magnitude higher, opening new possibilities for the generation of high-flux energetic electron beams. A central result of this work is the demonstration of the excitation of electron Bernstein waves during RELATIVISTIC LASER interaction with MAGNETized overdense plasmas. The subsequent Landau damping of these electrostatic warm-plasma modes selectively transfers energy to resonant electrons, leading to the emergence of quasi-monoenergetic spectral peaks at energies that can be tuned through the applied MAGNETic field. To support the simulation results, we experimentally demonstrate the directional emission of energetic electrons from a simple permanent-MAGNET target irradiated by an ultraintense LASER pulse, highlighting the practical feasibility of controlled electron-beam generation in dense plasma environments. These findings establish electron Bernstein waves as an efficient mediator of LASER energy coupling in overdense plasmas and introduce a new paradigm for controlled particle acceleration and energy deposition in high-energy-density plasma systems.
[abstract 31 / 45] (score: 2) - Title: Uncertainty-Aware Deep Learning for the Ly$α$ Forest: CNN-Based Absorber Detection and CharacterizationAuthors: Paryag Sharma, Vikram Khaire, Ting-Yun Cheng, Hum Chand, Prakash Gaikwad,Comments: Submitted to MNRAS. (Comments are welcome)Subjects: astro-ph.GACreated: 2026-07-06; Updated: 2026-07-08; Datestamp: 2026-07-08
The Ly$α$ forest is a powerful probe of the intergalactic medium and small-scale matter distribution, but deriving absorber properties traditionally requires computationally expensive Voigt-profile fitting. We present a convolutional neural network (CNN) that identifies and characterizes H I Ly$α$ absorbers directly from QUASAR spectra. The model is trained on synthetic spectra generated from the IllustrisTNG simulation and fitted with the VIPER Voigt-profile fitting code to provide training labels. The network simultaneously predicts absorber presence, column density ($N_{\rm HI}$), Doppler parameter ($b_{\rm HI}$), and line centroid. On simulated spectra, the CNN achieves an F1 score of $\sim$0.8, with mean absolute errors of $\sim$0.18 in $\log N_{\rm HI}$ and $\sim$0.10 in $\log b_{\rm HI}$. It accurately reproduces the H I column density distribution function (CDDF) and the $b_{\rm HI}$--$N_{\rm HI}$ relation, recovering CDDF slopes consistent with VIPER and a lower-envelope relation with an RMS difference of only 0.36 km s$^{-1}$. Applied to high-resolution UVES spectra, performance decreases to an F1 score of $\sim$0.5, with mean absolute errors of $\sim$0.34 in $\log N_{\rm HI}$ and $\sim$0.21 in $\log b_{\rm HI}$. Latent-space analysis reveals a significant domain shift between the simulated and observational spectra, contributing to the reduced performance. Nevertheless, the CNN preserves the observed CDDF and $b_{\rm HI}$--$N_{\rm HI}$ distributions, yielding CDDF slopes consistent with VIPER and a lower-envelope RMS difference of 2.96 km s$^{-1}$. Monte Carlo dropout is implemented during inference to quantify predictive uncertainties. Together with its computational efficiency, the method provides a scalable and uncertainty-aware framework for Ly$α$ forest analysis in upcoming spectroscopic surveys.
[abstract 32 / 45] (score: 2) - Title: Formation of rotating supergiants via stellar mergers in dense clusters: Implications for BLACK HOLE natal spinsAuthors: Ishaan Satish, Kyle Kremer, Fulya Kıroğlu, Daichi Tsuna, Shahed Shayan Aran,Comments: 14 pages, 10 figures, 1 table. Submitted to MNRAS. Comments welcome!Subjects: astro-ph.HE astro-ph.GACreated: 2026-07-06; Updated: 2026-07-08; Datestamp: 2026-07-08
We investigate how massive stellar mergers in young star clusters imprint on BLACK HOLE spin distributions and the broader implications for gravitational wave sources. The central hypothesis is that angular momentum transferred during stellar mergers substantially affects the spins of the merger products and resulting BLACK HOLEs, with some merger products evolving into collapsar-like objects that retain thick accretion disks that enable efficient spin up. This is in contrast to the more general expectation that BLACK HOLEs form with very small spins, having shed most of their envelope angular momentum via winds and expansion before core collapse. Using roughly 150 N-body models generated with the $\texttt{Cluster Monte Carlo}$ code, $\texttt{CMC}$, we analyze stellar mergers that lead to BLACK HOLE formation, prioritizing ``significant'' events with mass ratio $q>0.1$. After identifying optimal candidates from our $\texttt{CMC}$ models, we explore detailed stellar structure and post-merger evolution implications with MESA stellar evolution models to capture angular momentum injection and pre-collapse profiles most relevant for the BH natal spin. In our current dataset representative of Milky Way-like globular clusters, up to roughly half of BLACK HOLEs are formed from such mergers, including up to roughly $10\%$ from significant mergers with $q>0.1$. Preliminary angular momentum estimates indicate substantial spin-up during the merger, and trends with mass ratio and stellar properties suggest strong correlations with the final BLACK HOLE spin. In some cases, dimensionless spin parameters of $a\simeq 0.5$ or more are expected. This process has important implications for the dynamical formation and retention of gravitational wave sources in clusters.
[abstract 33 / 45] (score: 2) - Title: Radiation-hydrodynamics of star-disc collisions: From system parameters to outflows and lightcurvesAuthors: Taj Jankovič, Sergey Karpov, Michal Zajaček, Vladimír Karas, Marzena Śniegowska,Comments: Submitted to A&A, comments are welcome!Subjects: astro-ph.HE astro-ph.SRCreated: 2026-07-06; Updated: 2026-07-08; Datestamp: 2026-07-08
Quasi-periodic eruptions (QPEs) are nuclear transients producing bright, repeating soft X-ray flares superimposed on quiescent emission. A promising interpretation is that they are powered by star-disc collisions, in which a star crosses an accretion disc around a supermassive BLACK HOLE, drives shocks, and launches dense outflows from which radiation emerges. We present a systematic study of star-disc collisions, linking the physical parameters of the collision to the resulting outflows and emerging bolometric luminosities. We perform three-dimensional local radiation-hydrodynamics simulations, varying the disc surface density and vertical density profile, stellar velocity and radius, and local collision angle. We focus on the regime where the star remains unperturbed by the collision. We find that the variations of stellar velocity and disc surface density leave the bow shock and outflow morphology largely unchanged. However, faster stars produce brighter flares, while denser discs mainly increase the flare duration. Increasing the stellar radius increases the momentum of the forward outflow and produces brighter and longer flares. More centrally concentrated discs yield brighter and shorter flares because radiation escapes more efficiently through outer low-density layers. More oblique crossings reduce the momentum and luminosity asymmetry of two outflows and lengthen the flares. We provide empirical scalings of the peak luminosity and flare duration with the individual system parameters and apply them to GSN 069. The best candidate solutions favour a star with a radius $\sim R_\odot$ on a retrograde orbit, colliding with a dense post-TDE disc with a vertically concentrated density profile. Our findings suggest that specific combinations of system parameters can reproduce characteristic flare amplitudes, durations, duty cycles, and strong-weak flare patterns observed in QPE sources.
[abstract 34 / 45] (score: 2) - Title: BlackTHUNDER Reveals a Massive Filament around a Compact AGN at $z\simeq5.23$Authors: Giulia Tozzi, Hannah Übler, Eleonora Parlanti, Roberto Maiolino, Claudia Pulsoni, Rachel Somerville, Mirko Curti, Giovanni Mazzolari, Capucine Barfety, Elena Bertola, Andrew J. Bunker, Stefano Carniani, Giovanni Cresci, Richard Davies, Francesco D'Eugenio, Frank Eisenhauer, Natascha M. Förster Schreiber, Reinhard Genzel, Lucy R. Ivey, Ignas Juodžbalis, Dieter Lutz, Cosimo Marconcini, Thorsten Naab, Meghana Pannikkote, Stavros Pastras, Michele Perna, Letizia Scaloni, Raffaella Schneider, Linda J. Tacconi, Giacomo Venturi,Comments: 16 pages and 8 figures (main text). Submitted to A&A. Comments are welcomeSubjects: astro-ph.GACreated: 2026-07-06; Updated: 2026-07-08; Datestamp: 2026-07-08
Despite the growing number of compact ACTIVE GALACTIC NUCLEi (AGN) at $z>4$ discovered by JWST, their formation and evolution remain poorly understood. This paper investigates the large-scale environment of GN-77652, a compact AGN at $z=5.229$ observed as part of the JWST NIRSpec IFU Large Program BlackTHUNDER and complemented by deep multi-band NIRCam imaging. GN-77652 lies in close proximity to a 12 kpc-long filament composed of multiple sources at $z\simeq5.23$, spanning a remarkable range in stellar masses ($M_{\star}=0.7-13 \times 10^8$ ${M_\odot}$), gas phase metallicities (12$+$log(O/H) $=$ 7.6-8.5) and STAR FORMATION rates (SFR $=0.4-6$ ${M_\odot}$ yr$^{-1}$). The [OIII]$λ$5007 kinematics reveals a smooth large-scale velocity gradient centred on the central, massive ($M_{\star}\simeq1.1\times10^9$ ${M_\odot}$) and metal rich ($Z\sim0.6$ $Z_{\odot}$) system of the group. In this source, only 2.4 kpc (projected) from GN-77652, [OIII]$λ$4363 line diagnostics provide possible evidence for a second AGN. GN-77652 exhibits a shallow ($-30$ to $+20$ km s$^{-1}$) velocity gradient that is consistent with disk rotation according to dynamical modelling. The Lyman-Werner radiation field produced by the filament is too weak for the BLACK HOLE (BH) in GN-77652 to have formed recently via direct collapse. However, the required conditions may have existed at earlier epochs, or alternative scenarios (e.g. a recoiling BH ejected from the filament) could also be plausible. The whole system is expected to coalesce in $150-440$ Myr, also motivating an exploration of its future evolution through toy-model extrapolations and numerical simulations. Our analysis suggests that the compact AGN appearance of GN-77652 represents a transient evolutionary phase, consistent with the apparent decline with redshift in number density of compact AGN identified with JWST.
[abstract 35 / 45] (score: 2) - Title: Towards joint optimization of stellarator coils and support structuresAuthors: Lanke Fu, Alan A. Kaptanoglu,Comments:Subjects: physics.plasm-phCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The support structure is an integral part of the design of nuclear fusion reactors, especially 3D stellarator devices. A practical reactor's coils and support structures must have three competing qualities: an accurate MAGNETic field for good confinement, sufficient rigidity to protect the brittle high-temperature superconductor (HTS) from damage, and a simple geometry for low-cost construction. In existing devices, the coil geometry is often optimized without knowledge of the support structures' design and the coils' true stress and deformation. The support structures are then placed by hand through repeated finite element analyses (FEA) until engineering requirements are met. This makes the structural design of stellarator coil systems lengthy and labor-intensive. Using new developments in differentiable structural mechanics, we present coil-fem, an open-source software tool that integrates support differentiable FEA into the stellarator coil optimization loop. It enables the integrated optimization of coil geometry and support clamp locations to simultaneously reduce MAGNETic field errors and stresses in the coil body. We also present the first combined coil-support optimization in the stellarator literature. Using a penalty term based on coil-fem, we produced a coil set with 2.4x lower RMS von Mises stress and similar field error compared to an unoptimized baseline.
[abstract 36 / 45] (score: 2) - Title: Probing near-zone MAGNETic fields with extreme mass-ratio inspiralsAuthors: Jin-Lu Hu, Xin-Dong Du, Peng-Cheng Li, Tieguang Zi,Comments: 11 pages, 6 figuresSubjects: gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
We investigate whether weak near-zone MAGNETic fields can leave observable imprints on extreme-mass-ratio inspiral (EMRI) waveforms. The central massive BLACK HOLE is modeled by the MAGNETized Schwarzschild, or Ernst, solution, and the secondary compact object is treated as a neutral point particle on equatorial circular geodesics. We compute the MAGNETic corrections to the circular-orbit quantities and the innermost stable circular orbit, and then evolve the inspiral using a hybrid, source-corrected Regge--Wheeler--Zerilli approximation, in which the Schwarzschild wave-propagation potentials are kept fixed while the source is evaluated on the MAGNETized orbit. For a fiducial system with \(M=10^6M_\odot\) and \(μ=10M_\odot\), a field strength \(B\simeq 4\times10^{-5}M^{-1}\), corresponding to \(B_{\rm phys}\sim10^9\,{\rm G}\), produces a one-year dephasing of about \(1.3\) rad and reaches the adopted LISA-noise-weighted mismatch threshold. Our results suggest that EMRIs can in principle probe extremely strong near-zone MAGNETic fields, whereas ordinary MAGNETic environments around massive BLACK HOLEs are likely too weak to produce detectable effects within the present approximation.
[abstract 37 / 45] (score: 2) - Title: Identifying a circum-JET southern ring counterpart to the northern JET of the Crab NebulaAuthors: Noam Soker,Comments: Accepted for publication in Research Notes of the AASSubjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
I analyze images of the Crab Nebula core-collapse SUPERNOVA (CCSN) remnant in light of recent three-dimensional hydrodynamical simulations of the jittering-JETs explosion mechanism (JJEM) and identify a southern ring opposite to the northern JET, which I attribute to a counterJET. The Crab Nebula is known for its point-symmetric morphology of seven pairs of bays and a pair of two filaments, but no pairs of two JETs or their direct outcomes, like ears and rings, have been identified. I identify a ring in visible and infrared images of the Crab Nebula opposite to the prominent northern JET. Recent hydrodynamical simulations of the JJEM show that JETs that explode CCSNe can form such circum-JET rings. I, therefore, attribute the shaping of the southern ring to a southern JET, a counter JET to the northern JET, both of which participated in the explosion of the Crab Nebula in the framework of the JJEM.
[abstract 38 / 45] (score: 2) - Title: The problem of escape: a missing bit in the theory of the origin of COSMIC RAYsAuthors: P. Blasi, E. Amato,Comments: Short Review to appear in "Frontiers in Astronomy and Space Sciences"Subjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
The escape of COSMIC RAYs from their sources, as well as from the region surrounding a source, or from the galaxy hosting the sources, is a non-linear process that involves a complex chain of events, often overlooked. On the other hand, these phenomena are responsible for setting the maximum energy in accelerators, shaping the source spectra and determining the conditions for escape from the galaxy hosting the sources, a process that is usually modeled by imposing ad hoc boundary conditions in our equations. Here we discuss some of these phenomena and how they affect the spectra of COSMIC RAYs measured at the Earth.
[abstract 39 / 45] (score: 2) - Title: Exploring the Galactic plasma with pulsars in the SKA EraAuthors: Caterina Tiburzi, M. T. Lam, D. J. Reardon, N. K. Porayko, M. Mevius, S. K. Ocker, S. C. Susarla, J. R. Dawson, J. P. W. Verbiest, A. Deller, G. M. Shaifullah, N. D. R. Bhat, J. -M. Grießmeier, M. Walker, W. Jing, F. A. Iraci, M. Geyer, L. Levin, M. J. Keith, The SKA Pulsar Science Working Group,Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026. Report-no:AASKAII/Tiburzi01Subjects: astro-ph.HECreated: 2026-07-02; Updated: 2026-07-08; Datestamp: 2026-07-08
The ionised media that permeate the Milky Way have been active topics of research since the discovery of pulsars in 1967. In fact, pulsars allow one to study several aspects of said plasma, such as their column density, turbulence, scattering measures, and discrete, intervening structures between the neutron star and the observer, and aspects of the MAGNETic field throughout. Such sources of information allow us to characterise the electron distribution in the terrestrial ionosphere, the Solar Wind, and our Galaxy and have an important impact on other experiments involving pulsars such as Pulsar Timing Arrays. In this article, we review the state-of-the-art of plasma research using pulsars, the aspects that should be taken into consideration for optimal plasma studies, and we provide future perspectives on improvements to those enabled by the SKA.
[abstract 40 / 45] (score: 2) - Title: Chandra X-Ray Imaging and Spatially Resolved Spectroscopy of SN 1987A: Energy-Dependent Morphology of the Equatorial RingAuthors: Yusuke Sakai, Shinya Yamada, Koji Mori, Hiromasa Suzuki, Haruka Sakemi, Tsukasa Matsushima, Shintaro Kaneko, Kai Matsunaga, Shogo B. Kobayashi, Haruto Aoki, Toshiki Sato,Comments: Accepted for publication in ApJ. The paper is 16 pages long with 9 figuresSubjects: astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
We present a systematic imaging and spatially resolved spectral study of SN 1987A using Chandra observations obtained between 1999 and 2025. By combining multiepoch ACIS and HETG data, we investigate the long-term evolution of the remnant in both the soft and hard X-ray bands. To characterize the radial structure, we model the projected emission with a torus profile and derive its radius and width on the image plane. We find an energy dependence in the ring morphology: while the soft and hard bands exhibit similar structures at early epochs, the soft-band emission becomes systematically broader than the hard-band emission after the early 2010s. Furthermore, when considering the radius and width together, the soft-band emission shows an inward extension, suggesting an increasing contribution from interior and/or high-latitude emission components. The flux evolution of the Fe K line is consistent with previous XMM-Newton results, and we detect its presence already in earlier epochs (~2007-2009) using combined Chandra spectra. Spatially resolved analysis further indicates that the Fe K emission is enhanced in the eastern region. These results provide a unified view of the long-term morphological and spectral evolution of SN 1987A and highlight the emergence of energy-dependent radial structure as a key feature in its late-time evolution.
[abstract 41 / 45] (score: 2) - Title: Kinetic structure of the intracluster medium across nearby clusters observed with XRISMAuthors: Naomi Ota, Erwin T. Lau, Satoshi Yamada, Yuki Omiya, Hiroya Yamaguchi,Comments: 6 pages, 2 figures, submitted to PASJSubjects: astro-ph.CO astro-ph.GA astro-ph.HECreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
XRISM/Resolve is building a sample of galaxy clusters with directly measured ICM gas motions, revealing diverse projected dynamical states. We compile 45 XRISM/Resolve measurements in 19 nearby galaxy clusters and place them on a common, emission-weighted effective line-of-sight scale, $\ell_{\rm eff}$. We compare the line-of-sight velocity dispersion $σ_v$, bulk velocity amplitude $|v_{\rm bulk}|$, their ratio $R_v \equiv |v_{\rm bulk}|/σ_v$, and non-thermal pressure proxies. Disturbed non-cool-core systems are not simply higher-dispersion counterparts of relaxed cool-core regions. Instead, differences among cool-core centers, cool-core outer regions, and non-cool-core systems are driven mainly by coherent line-of-sight motion relative to unresolved line broadening: $R_v$ tends to remain below unity in cool-core regions but often exceeds unity in non-cool-core systems, with the mean $R_v$ rising from $0.45$ in cool-core centers to $1.6$ in non-cool-core systems. These diagnostics help separate local central line broadening, likely associated with AGN feedback in some cool cores, from larger-scale coherent motions associated with sloshing, mergers, and halo assembly. Comparison with forward-modeled TNG-Cluster predictions suggests that many cool-core measurements occupy the lower part of the predicted non-thermal pressure range, consistent with small hydrostatic-mass corrections in relaxed systems and larger corrections in disturbed ones. XRISM is thus beginning to resolve the projected kinetic structure of the ICM across cluster environments, rather than tracing a single sequence of increasing turbulence.
[abstract 42 / 45] (score: 2) - Title: Long-term performance of SiPMs in space environment measured by GRBAlpha, GRBBeta, and VZLUSAT-2 CubeSatsAuthors: Jakub Ripa, Filip Munz, Marianna Dafcikova, Andras Pal, Norbert Werner, Masanori Ohno, Laszlo Meszaros, Balazs Csak, Pavel Kosik, Michaela Duriskova, Lea Szakszonova, Martin Kolar, Tomas Vitek, Nikola Husarikova, Filip Hroch, Michal Pazderka, Yasushi Fukazawa, Hiromitsu Takahashi, Tsunefumi Mizuno, Jean-Paul Breuer, Masato Yokota, Kazuhiro Nakazawa, Hirokazu Odaka, Yuto Ichinohe, Tomas Urbanec, Ales Povalac, Miroslav Kasal, Miroslav Smelko, Peter Hanak, Gabor Galgoczi, Martin Topinka, Hsiang-Kuang Chang, Tsung-Che Liu, Chih-Hsun Lin, Chin-Ping Hu, Che-Chih Tsao, Kaustubha Sen, Chih-En Wu, Jakub Kapus, Jan Hudec, Marcel Frajt, Maksim Rezenov, Vladimir Daniel, Petr Svoboda, Juraj Dudas, Martin Sabol, Ivo Vertat, Robert Laszlo, Martin Koleda,Comments: 10 pages, 6 figures, submitted to the proceedings book of the conference: SPIE Astronomical Telescopes + Instrumentation 2026Subjects: astro-ph.IMCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
In this work, we report the successful application of silicon photomultipliers (SiPMs) in GAMMA-RAY BURST (GRB) detectors used in CubeSats operating in the low Earth orbit (LEO) radiation environment. It is known that SiPMs are susceptible to radiation damage, leading to an increase in the dark count rate. This results in an increase in the low-energy threshold in detectors combining SiPMs and scintillators. Despite this drawback, they became popular in gamma-ray detectors on CubeSats due to their low operating voltage, small size and fast response. Therefore, it is important to characterise their long-term performance in the space environment. Here, we describe the changes in the dark count rate and low-energy threshold of S13360-3050PE multi-pixel photon counters (MPPCs) by Hamamatsu Photonics K.K., using measurements from the GRBAlpha, GRBBeta, and VZLUSAT-2 CubeSats. In the case of GRBAlpha, the measurement of SiPM performance in space lasted over 4 years. GRBAlpha was a 1U CubeSat launched on 2021/03/22 to a 550 km altitude polar orbit carrying a CsI(Tl) scintillator GRB detector employing eight MPPCs and sensitive in the range of ~30-900 keV. GRBAlpha de-orbited on 2025/06/09. VZLUSAT-2 was a 3U CubeSat launched on 2022/01/13 to a 535 km altitude polar orbit and de-orbited on 2025/11/30. GRBBeta was launched on 2024/07/09 to a 580 km altitude, 62° inclination orbit. Both VZLUSAT-2 and GRBBeta carry detectors similar to the one on GRBAlpha. We have flight-proven the Hamamatsu MPPCs S13360-3050 PE and demonstrated that SiPMs, shielded by 2.5 mm of PbSb alloy, can be used in a LEO environment on a scientific mission lasting beyond 4 years. This shows the potential for SiPMs to be employed in future satellites.
[abstract 43 / 45] (score: 2) - Title: Polarization images of non-topological soliton Bardeen BOSON starsAuthors: Xiao-Xiong Zeng, Chen-Yu Yang, Ke-Jian He, Li-Fang Li,Comments: 19 pages, 7 figuresSubjects: gr-qcCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
In this study, we investigate the polarized images of non-topological soliton Bardeen BOSON stars by solving the coupled Einstein nonlinear electrodynamics complex scalar field equations, based on the thin accretion disk model surrounding these compact objects. We focus on the influence of key parameters, including the initial scalar field, MAGNETic charge, observer inclination angle, and MAGNETic field configuration, on the resulting POLARIZATION characteristics. The results show that the geometry of the MAGNETic field, particularly the relative strength between the radial \(B_r\) and angular \(B_θ\) components, plays a crucial role in determining the POLARIZATION pattern. Additionally, variations in the scalar field amplitude and MAGNETic charge significantly affect both the intensity and spatial distribution of the POLARIZATION. These results show that the POLARIZATION morphology is sensitive to the spacetime geometry and MAGNETic field configuration, and provide a qualitative basis for comparing BOSON stars with BLACK HOLEs.
[abstract 44 / 45] (score: 2) - Title: Suppressing wall modes in confined rotating turbulent convectionAuthors: Lázaro Martínez-Ortíz, Maarten Minartz, Youri H. Lemm, Xander M. de Wit, Herman J. H. Clercx, Rudie P. J. Kunnen,Comments:Subjects: physics.flu-dynCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
In confined turbulent rotating convection, the largest vertical velocities are found near the sidewalls in the form of wave-like structures known as wall modes. These structures persist deep into the turbulent regime, bias heat transport, and disrupt bulk flow organisation through radial JETs. Controlling or suppressing wall modes is, therefore, essential for accessing bulk dynamics free from wall-induced effects. Here, we combine experiments and direct numerical simulations to investigate wall modes control in cylindrical cells equipped with ring-shaped sidewall barriers. Barriers suppress vertical-velocity maxima near the sidewall and disrupt the characteristic wave-like pattern. Simulations further show that the barriers reduce the wall-mode-induced enhancement of heat transport, shifting it towards values characteristic of laterally periodic domains. The suppression efficiency is governed by the ratio of the barrier width to the wall-mode scale and is enhanced by the addition of a second barrier. In the horizontal plane, radial JET ejections are attenuated, while the time-averaged flow reveals suppression of the boundary zonal flow (BZF), a ring-shaped region of positive azimuthal velocity near the sidewall, provided measurements are taken away from the immediate vicinity of the barriers. In this region, isotherms bend toward the poorly conducting barrier, creating a local misalignment with the isobars and inducing a baroclinic flow adjacent to the barrier faces. This effect weakens with increasing barrier conductivity or smoother geometry. These results demonstrate that sidewall barriers provide a robust route for suppressing wall modes signatures in experimental turbulent rotating convection, while locally inducing secondary baroclinic flows near the barriers. Their use enables access to extreme rotating-convection regimes with reduced sidewall influence.
[abstract 45 / 45] (score: 2) - Title: Finite-Field QED Corrections to Vacuum Birefringence and Magnetar Polarization TransportAuthors: S. Abbassi, F. A. Chishtie, S. R. Valluri,Comments: e.g. 25 pages, 5 figuresSubjects: astro-ph.HE hep-phCreated: 2026-07-07; Updated: 2026-07-08; Datestamp: 2026-07-08
{We study low-energy photon propagation in a constant MAGNETic field within the one-loop Heisenberg--Euler theory, retaining the refractive-index normalization $γ_s$ without expansion. Here ``finite-field'' denotes exact dependence on $B/B_{\rm cr}$ within the one-loop, constant-field approximation. The resulting birefringence is propagated into MAGNETar POLARIZATION transport. In a centered-dipole model, the POLARIZATION-limiting radius is unchanged to better than $10^{-12}$ because mode decoupling occurs at $\sim10^2R_{\rm NS}$, where $B\ll B_{\rm cr}$. Near the surface, however, the weak-field Cotton--Mouton expression overestimates the accumulated birefringent phase by up to a factor $2.9$ at $10^{15}$~G. At the plasma--vacuum resonance, finite-field corrections reduce the resonance density by $32\%$ and raise the adiabatic conversion energy by $14\%$ for 1E~1547.0$-$5408; the corresponding changes are factors $2.6$ and $1.37$ for 1RXS~J1708$-$4009, and factors $9.7$ and $2.13$ for SGR~1806$-$20, the latter controlled by the strong-field asymptote. The resummed one-loop parallel-mode MAGNETic response remains positive and develops a broad maximum near $17B_{\rm cr}$. The strictly truncated $\mathcal O(α)$ response is monotonic; therefore the maximum is a structural prediction of the resummed one-loop constitutive model, while its detailed profile and precise location require higher-loop validation. These results identify vacuum-resonance observables as the most sensitive channel for testing finite-field QED in MAGNETars.
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