Spectro-timing origin of large amplitude X-ray variability in GRS 1915+105 using AstroSat/LAXPC and SXT
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arXiv
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| Autores principales: | , , , , |
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| Formato: | Preprint |
| Publicado: |
2026
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| _version_ | 1866918334243536896 |
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| author | Suman, Shree Khatua, Shuvajit Jadoliya, Vishal Gupta, Prathamesh Narayan Pahari, Mayukh |
| author_facet | Suman, Shree Khatua, Shuvajit Jadoliya, Vishal Gupta, Prathamesh Narayan Pahari, Mayukh |
| contents | The origin of the large-amplitude, quasi-periodic X-ray flux variations in several classes of the Galactic microquasar GRS~1915+105 remains unresolved. We address this issue through flux-resolved, broadband (0.8-20 keV) spectral modelling and simultaneous covariance spectral analysis during two $κ$ and two $ω$ class observations using \textit{AstroSat}/SXT and LAXPC. The lightcurves show strong, quasi-periodic oscillations involving rapid transitions between bright bursts and deep dips on timescales of a few tens of seconds. Flux-resolved spectroscopy indicates that high-flux intervals in both classes are dominated by a hot, optically thick accretion disc with steep Comptonized emission, whereas low-flux intervals correspond to a cooler or partially recessed disc and a harder coronal continuum. These transitions involve a systematic 1-2 keV drop in disc temperature and a pronounced hardening of the Comptonized component, with flux reductions of up to a factor of five. Using covariance spectra across 0.015-5 Hz, we show that the rapid coherent variability arises almost entirely from the disc, which exhibits strong energy-dependent variations, while the Comptonized component contributes minimally. The combined results suggest that radiation-pressure-driven structural changes in the disc, with a slower coronal response, produce the observed oscillations, consistent with cyclic disc evacuation and refilling in the $κ$ and $ω$ classes. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_11876 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Spectro-timing origin of large amplitude X-ray variability in GRS 1915+105 using AstroSat/LAXPC and SXT Suman, Shree Khatua, Shuvajit Jadoliya, Vishal Gupta, Prathamesh Narayan Pahari, Mayukh High Energy Astrophysical Phenomena The origin of the large-amplitude, quasi-periodic X-ray flux variations in several classes of the Galactic microquasar GRS~1915+105 remains unresolved. We address this issue through flux-resolved, broadband (0.8-20 keV) spectral modelling and simultaneous covariance spectral analysis during two $κ$ and two $ω$ class observations using \textit{AstroSat}/SXT and LAXPC. The lightcurves show strong, quasi-periodic oscillations involving rapid transitions between bright bursts and deep dips on timescales of a few tens of seconds. Flux-resolved spectroscopy indicates that high-flux intervals in both classes are dominated by a hot, optically thick accretion disc with steep Comptonized emission, whereas low-flux intervals correspond to a cooler or partially recessed disc and a harder coronal continuum. These transitions involve a systematic 1-2 keV drop in disc temperature and a pronounced hardening of the Comptonized component, with flux reductions of up to a factor of five. Using covariance spectra across 0.015-5 Hz, we show that the rapid coherent variability arises almost entirely from the disc, which exhibits strong energy-dependent variations, while the Comptonized component contributes minimally. The combined results suggest that radiation-pressure-driven structural changes in the disc, with a slower coronal response, produce the observed oscillations, consistent with cyclic disc evacuation and refilling in the $κ$ and $ω$ classes. |
| title | Spectro-timing origin of large amplitude X-ray variability in GRS 1915+105 using AstroSat/LAXPC and SXT |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2602.11876 |