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

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 $6.7\pm 0.2$ 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.

12 pages, 7 figures, Accepted for publication in MNRAS

References in corpus (5)

• Modelling the behaviour of accretion flows in X-ray binaries
• Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds
• Spectral and temporal properties of Compton scattering by mildly relativistic thermal electrons
• Re-condensation from an ADAF into an inner disk - the intermediate state of black hole accretion?
• A stochastic propagation model to the energy dependent rapid temporal behaviour of Cygnus X-1 as observed by AstroSat in the hard state

Cited by in corpus (7)

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• Polarized X-rays Correlated with Short--Timescale Variability of Cygnus X-1
• Probing the soft state evolution of 4U 1543-47 during its 2021 outburst using AstroSat
• Searching for similarities in the accretion flow of Seyfert 1 galaxies and cataclysmic variables based on flare profiles of IRAS 13224-3809, 1H 0707-495, Mrk 766 and MV Lyr
• Evolution of X-ray and optical rapid variability during the low/hard state in the 2018 outburst of MAXI J1820+070 = ASASSN-18ey
• A new algorithm for detecting X-ray shots in Cyg X-1
• Unprecedentedly bright X-ray flaring in Cygnus X-1 observed by INTEGRAL