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arXiv · 2203.11884

Probing the shot behaviour in Cygnus X-1 using simultaneous AstroSat-NICER observation

Yash Bhargava·Nandini Hazra·A. R. Rao·Ranjeev Misra·Dipankar Bhattacharya·Jayashree Roy·Md. Shah Alam
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Abstract

We analyse the aperiodic flaring features, also known as shots, observed in Cyg X-1 in the 0.1-80 keV energy band using a 6.39 ks simultaneous observation with AstroSat and NICER. We detect 49 simultaneous shots in the soft and hard X-ray bands with NICER and AstroSat-LAXPC, respectively. We observe the shot profile for the first time in soft X-rays (0.1-3 keV), which shows a spectral peak at $\sim$2 keV. Using time-averaged spectroscopy, we measured the truncation of the inner accretion disk at $6.7\pm0.2$ gravitational radii. The shot-phase resolved spectroscopy allowed us to identify the origin of some of the brightest aperiodic peaks in the soft X-rays. We find that the accretion rate is consistent with a constant during the shots while the inner edge of the accretion disk moves inwards/outwards as these shots rise/decay. We discuss the possible mechanisms causing the swing in the inner radius.

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Yash Bhargava, Nandini Hazra, A. R. Rao, Ranjeev Misra, Dipankar Bhattacharya, Jayashree Roy, Md. Shah Alam. 2022-03-22. Probing the shot behaviour in Cygnus X-1 using simultaneous AstroSat-NICER observation. https://doi.org/10.1093/mnras%2Fstac853

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