Discovery of a new flaring class in GRS 1915+105 using AstroSat

Abstract

Highly variable Black Hole X-ray Binary (BHXB) GRS~1915+105 has shown many flaring classes when the source oscillates between the High Soft state (HS) and the Hard Intermediate state (HIMS) with a transition time of less than 10 s. The X-ray flux is anti-correlated with hardness ratio (HR2) during these X-ray flaring classes. We have analyzed Astrosat/LAXPC \& SXT data and report here a new X-ray flaring class named $\eta$ class when the source oscillates between two HS states (the power-law index is always greater than 4) with transition time around 50 s. The X-ray flux is correlated with hardness ratio. This class is quasi-regular, and we have detected High Frequency Quasi Periodic Oscillations (HFQPOs) around 70 Hz during this new flaring class. The accretion rate changes by a factor of three over the burst cycle. We report here the results of our extensive study of spectral and timing characteristics of this new class.

12 pages, 7 figures

References in corpus (11)

• X-ray Properties of Black-Hole Binaries
• A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass
• AstroSat/LAXPC reveals the high energy variability of GRS 1915+105 in the chi class
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• A timing view of the heartbeat state of GRS 1915+105
• Exploring the broadband spectral and timing characteristics of GRS 1915+105 with AstroSat and NICER observations