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astro-ph.HE2026

Revisiting EBL Constraints from Gamma-Ray Observations: A Critical Assessment and Methodological Improvements

K. Abe, S. Abe, J. Abhir +185

The extragalactic background light (EBL), ranging from the infrared to the ultraviolet bands, is the second most intense photon field in the universe, surpassed only by the cosmic…

astro-ph.HE2026

Radio Constraints on the Circumstellar Environment of the Type IIb Supernova SN 2024iss

Yuhei Iwata, Tomoki Matsuoka, Masanori Akimoto +6

Type~IIb supernovae exhibit diverse progenitor properties, and radio observations offer a unique probe of their mass-loss histories shortly before the explosion. We present Japanes…

astro-ph.HE2026

Constraints on the VHE counterpart of two binary black hole mergers observed by the MAGIC and CTAO LST-1 telescopes

K. Abe, S. Abe, J. Abhir +358

We present very-high-energy gamma-ray observations of two binary black hole merger candidates, GW240615_113620 and GW241125_010116, performed with the Major Atmospheric Gamma Imagi…

astro-ph.HE2026

Chandra X-Ray Imaging and Spatially Resolved Spectroscopy of SN 1987A: Energy-Dependent Morphology of the Equatorial Ring

Yusuke Sakai, Shinya Yamada, Koji Mori +8

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 d…

astro-ph.HE2026

Late-time evolution of the interacting stripped-envelope supernova 2017dio

C. Humina, C. P. Gutiérrez, H. Kuncarayakti +14

The discovery of stripped-envelope supernovae (SNe) interacting with dense circumstellar medium (CSM) challenges our current understanding of massive star evolution. We present lat…

astro-ph.HE2026

Discovery of CO Clouds Associated with the X-ray Jets of SS 433: Evidence for Shock-Cloud Interaction Enhancing Nonthermal X-ray Emission

Haruka Sakemi, Hidetoshi Sano, Yasuo Fukui +7

We report the first identification of molecular clumps directly associated with the re-brightening regions of the large-scale X-ray jets of SS 433, based on CO ( = 1--0)…

astro-ph.HE2026

Mass and Spin Growth of Very Massive Stars in Star Clusters Potentially Associated with Little Red Dots

Ataru Tanikawa, Masaru Shibata, Kunihito Ioka

Using gravitational -body simulations, we investigate the evolution of mass and spin for very massive stars (VMSs) in dense star clusters, which could subsequently evolve into L…

astro-ph.HE2026

From supernovae to neutron stars: crust formation time

Yudai Suwa, Ken'ichiro Nakazato

A neutron star is born as a hot, lepton-rich protoneutron star (PNS) and cools via neutrino emission, eventually allowing heavy ions in the outer layers to crystallize into a solid…

astro-ph.HE2026

Anisotropic Thermal Conduction as a Driver of Jet Collimation and Magnetic Field Amplification on Cold Fronts

Nana Matsuno, Takaaki Yokoyama, Mami Machida

Galaxy clusters contain a hot, diffuse, and weakly magnetized plasma known as the intracluster medium (ICM). In this environment, how thermal conduction influences plasma dynamics…

astro-ph.HE2026

Long-term study of the gamma-ray emission of Cygnus X-3 with MAGIC and Fermi-LAT

K. Abe, S. Abe, J. Abhir +185

Cygnus X-3 is a microquasar composed of a compact object of unknown nature closely orbiting around a Wolf-Rayet star. The particularities of this source make it a unique case among…

astro-ph.HE2026

The line modulations of H-like Fe, Ca, Ar, and S observed with /Resolve in Cyg X-3

Tomohiro Hakamata, Hirokazu Odaka, Ryota Tomaru +13

Cygnus X-3, hosting a Wolf-Rayet (WR) star whose dense wind produces various spectral lines due to photoionization by X-rays from a compact object, provides an ideal laboratory for…

astro-ph.HE2026

A XRISM Study of Highly Ionized Iron Emission Lines from the Low-Eddington-ratio AGN in NGC 7213

Kaito Murakami, Taiki Kawamuro, Ryota Tomaru +10

We present an analysis of XRISM and NuSTAR data obtained for the nearby low-Eddington active galactic nucleus NGC 7213. Our goal is to examine whether its He-like and H-like iron e…

astro-ph.HE2026★ 1 cited

Accurate Determination of Chemical Abundances near a Supermassive Black Hole

The XRISM collaboration

The metal abundances in galactic nuclei carry key information on the history of star formation and mass transfer in central regions of galaxies. X-ray fluorescence analysis is a un…

astro-ph.HE2026

Diversity of Type Ia supernova optical light curves among different spectroscopic subclasses

R. B. Koshi, M. Doi, S. Sako +3

Attempts to reveal the spectroscopic diversity of Type Ia supernovae (SNe Ia) have led to subclassification schemes such as the Branch system, which classifies SNe Ia into four cat…

astro-ph.HE2026

Comprehensive neutrino light curves and spectra: from pre-supernova evolution to early supernova phase

Chinami Kato, Hiroki Nagakura, Akira Ito +4

We present the first systematic study of neutrino emissions from massive stars, continuously tracking the late evolutionary stages through the early core-collapse supernova phase.…

astro-ph.HE2026

Interpreting Swift and NuSTAR Observations of the Low-Luminosity Active Galactic Nucleus NGC 4278 with Radiatively Inefficient Accretion Flows and Implications for Neutrino Emission

Abhishek Das, Qi Feng, Eleanor Young +3

We report the first NuSTAR hard X-ray observations of the low-luminosity active galactic nucleus NGC 4278. The source is clearly detected beyond 10 keV with a hard X-ray spectrum c…

astro-ph.HE2026

An investigation on the FWHM of absorption features of type Ia supernovae

Xulin Zhao, Keiichi Maeda, Xiaofeng Wang

We present an investigation of the full width at half maximum (FWHM, or γ) of absorption features of Type Ia supernova (SNe Ia). We found that, the average value of FWHM can be wel…

astro-ph.HE2026★ 2 cited

High Spectral Resolution X-ray Observations of the Evolved Supermassive Stellar Binary System Carinae - Iron K Band Profile Revealed with XRISM

XRISM Collaboration, Marc Audard, Hisamitsu Awaki +138

The supermassive binary system, Carinae, is experiencing enormous wind-driven mass loss at a rate unparalleled in the rest of the Galaxy. Their wind-wind collision (WWC) contin…

astro-ph.HE2026★ 4 cited

Spectral and photometric variability of SS 433 observed with XRISM and simultaneous optical and near-infrared telescopes

Yusuke Sakai, Shinya Yamada, Yuta Okada +36

We present results from coordinated multiwavelength observations of the SS 433, obtained with XRISM, optical telescopes, and near-infrared camera during 2024 April and 2025 March.…

astro-ph.HE2026

A Faint Progenitor System for the Faint Supernova 2024vjm

Erez A. Zimmerman, Avishay Gal-Yam, Paul J. Groot +68

Type Ia Supernovae (SNe Ia) are well known for their role as standardizable cosmological candles. Their uniformity is credited to their single origin as thermonuclear explosions of…

astro-ph.HE2026★ 4 cited

The hydrodynamics of stratified ultra-relativistic outflows and the origin of GRB X-ray plateaus

Gilad Sadeh, Kenta Hotokezaka, Masaru Shibata

The origin of the X-ray plateau phase observed in a large fraction of gamma-ray burst afterglows remains debated. We present a novel analytic framework for the hydrodynamics of ult…

astro-ph.HE2026★ 1 cited

Probing the Diversity of Type Ia Supernova Remnants in 3-D Hydrodynamic Simulations with X-ray Spectral Synthesis

Yusei Fujimaru, Shiu-Hang Lee, Gilles Ferrand +7

Type Ia supernovae (SNe), thermonuclear explosions of white dwarfs in binary systems, are widely used as standard candles owing to the empirical width-luminosity relation of their…

astro-ph.HE2026

The Supernova Remnant G284.31.8 and Its Relation to the Gamma-ray Binary 1FGL J1018.65856

Natsuki Terano, Takaaki Tanaka, Hiromasa Suzuki +6

G284.31.8 is a supernova remnant with a radio shell and thermal X-ray emission. Located near its center is the gamma-ray binary 1FGL J1018.65856, although the physical associ…

astro-ph.HE2026★ 2 cited

GRB 180728A and SN 2018fip: the nearest high-energy cosmological gamma-ray burst with an associated supernova

A. Rossi, L. Izzo, K. Maeda +29

The long GRB 180728A, at a redshift of , stands out due to its high isotropic energy of erg, in contrast with most events at redshif…