Time-resolved spectroscopy on the heartbeat state of GRS 1915+105 using AstroSat

Abstract

AstroSat spectra of the black hole system GRS 1915+105 during the heartbeat state (with a varying oscillation period from 150 to 100 secs) were analysed using a truncated relativistic disc model along with a Comptonization component. Spectra were fitted for segments of length ~ 24 secs. The oscillation can be described as coordinated variations of the accretion rate, Comptonised flux, and the inner disc radius, with the latter ranging from 1.235-5 gravitational radii. Comparison with results from the $\chi$ and Intermediate states shows that while the accretion rate and the high energy photon index were similar, the inner disc radius and the fraction of Comptonised photons were larger for these states than for the heartbeat one. The coronal efficiency $\eta \equiv L_{ac}/\dot{M}{c}^2$, where $L_{ac}$ is the radiative luminosity generated in the corona is found to be approximately $\propto {\dot{M}}^{-2/3}$ for all the observations. The efficiency decreases with inner radii for the heartbeat state but has similar values for the $\chi$ and Intermediate states where the inner radii is larger. The implications of these results are discussed.

7 pages, 5 figures, Accepted for publication in MNRAS

References in corpus (9)

• A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass
• Black hole-like hysteresis and accretion states in neutron star low mass X-ray binaries
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• Testing the dynamic origin of Quasi-periodic Oscillations in MAXI J1535-571 and H 1743-322
• Evolution of QPOs in GX 339-4 and EXO 1846-031 with Insight-HXMT and NICER
• Probing the soft state evolution of 4U 1543-47 during its 2021 outburst using AstroSat
• Spectral characteristics of the black hole binary 4U 1957+115: A multi-mission perspective
• NICER Spectral and Timing Analysis of 4U 1630$-$47 and its Heartbeat State