ItemArticle

Probing the Origin of X-Ray Flares in the Low-hard State of GRS 1915+105 Using AstroSat and NuSTAR

Title
Probing the Origin of X-Ray Flares in the Low-hard State of GRS 1915+105 Using AstroSat and NuSTAR
Creator
Akhter, Shahzada; Boked, Sajad; Maqbool, Bari; Misra, Ranjeev; Jithesh, V.
Description
We performed a detailed time-resolved spectral study of GRS 1915+105 during its low-flux rebrightening phase using the broadband capabilities of AstroSat and NuSTAR in 2019 MayJune. The AstroSat light curves revealed erratic X-ray flares with count rates rising by a factor of ?5. Flares with simultaneous LAXPC and SXT coverage were segmented and fitted using two degenerate but physically motivated spectral models: a reflection-dominated model (hereafter model A) and an absorption-dominated model (hereafter model B). In model A, the inner disk radius (Rin) shows a broken power-law dependence on flux, indicating rapid inward motion of the disk at higher flux levels. In contrast, model B shows variable column density in the range of 10231024 cm?2, displaying a strong anticorrelation with flux. Both models exhibit significant variation in the ionization parameter between low- and high-flux segments. The total unabsorbed luminosity in the 0.730 keV energy range ranged from 6.64 1036 to 6.33 1038 erg s?1Across both models, several spectral parameters exhibited step-function-like behavior around flux thresholds of 510 10?9 erg cm?2 s?1, indicating multiple spectral regimes. The disk flux contribution, more evident in model B, increased with total flux, supporting an intrinsic origin for the variability. These findings point to a complex interplay between intrinsic disk emission, structured winds, and variable local absorption in driving the flare activity. 2025. The Author(s).
Source
Astrophysical Journal;Volume;994;Issue;2;Article No.;223;
Date
01-01-2025
Publisher
American Astronomical Society
Coverage
Akhter S., Islamic University of Science and Technology, Pulwama, Awantipora, 192122, India; Boked S., Department of Physics, University of Kashmir, Srinagar, 190006, India, Government Degree College, Anantnag, Bijbehara, 192124, India; Maqbool B., Islamic University of Science and Technology, Pulwama, Awantipora, 192122, India, Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune, 411007, India; Misra R., Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune, 411007, India; Jithesh V., Department of Physics and Electronics, Christ University, Hosur Main Road, Bengaluru, 560029, India
Rights
All Open Access; Gold Open Access; Green Open Access
Relation
ISSN: 0004637X;
Format
online
Language
English
Type
Article

Citation

Akhter, Shahzada; Boked, Sajad; Maqbool, Bari; Misra, Ranjeev; Jithesh, V., “Probing the Origin of X-Ray Flares in the Low-hard State of GRS 1915+105 Using AstroSat and NuSTAR,” CHRIST (Deemed To Be University) Institutional Repository, accessed June 19, 2026, https://archives.christuniversity.in/items/show/23587.

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