Speaker
Description
GS 1354-64 is a transient black hole X-ray binary that has been studied during its past outbursts, which primarily exhibited hard-state behavior. In this work, we present a detailed broadband spectral analysis of its 2025-2026 outburst using data from Insight-HXMT and NuSTAR, providing wide energy coverage from soft to hard X-rays.
The spectra are modeled using diskbb+powerlaw, thcomp*diskbb, and diskbb+relxill, allowing a comprehensive comparison between phenomenological and physical descriptions of Comptonization and relativistic reflection. We estimate key spectral parameters and perform flux decomposition to track the contributions of the accretion disk and the high-energy component.
Our results show that the non-thermal emission dominates throughout the outburst; however, clear spectral evolution towards the softer state is observed during the two short-duration X-ray flares. The inner disk temperature increases toward the flux peaks, accompanied by a rise in the disk flux, indicating enhanced accretion of high-viscosity Keplerian matter and disk heating due to the reflection of hard photons from the corona. The photon index shows softening during the peaks.
These results provide strong evidence for the emergence of the accretion disk and indicate a transition from the hard state toward an intermediate state. This behavior distinguishes the 2025-2026 outburst from the previously reported hard-state-dominated events during the 1997-1998 and 2015 `failed' outbursts, highlighting the importance of broadband modeling in constraining disk-corona components in black hole X-ray binaries.
| Participate the oral/poster presentation award competition | Yes |
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