AstroSat view of IGR J17091-3624 and GRS 1915+105: decoding the 'pulse' in the 'Heartbeat State'

Abstract

IGR J17091--3624 is a transient galactic black hole which has a distinct quasi-periodic variability known as `heartbeat', similar to the one observed in GRS 1915+105. In this paper, we report the results of $\sim 125$ ks \textit{AstroSat} observations of this source during the 2016 outburst. For the first time a double peaked QPO (DPQ) is detected in a few time segments of this source with a difference of $\delta f\sim 12$ mHz between the two peaks. The nature of the DPQ was studied based on hardness ratios and using the static as well as the dynamic power spectrum. Additionally, a low frequency (25--48 mHz) `heartbeat' single peak QPO (SPQ) was observed at different intervals of time along with harmonics ($50-95$ mHz). Broadband spectra in the range $0.7-23$ keV, obtained with \textit{SXT} and \textit{LAXPC}, could be fitted well with combination of a thermal Comptonisation and a multicolour disc component model. During \textit{AstroSat} observation, the source was in the Soft-Intermediate State (SIMS) as observed with \textit{Swift/XRT}. We present a comparative study of the `heartbeat' state variability in IGR J17091--3624 with GRS 1915+105. Significant difference in the timing properties is observed although spectral parameters ($\Gamma \sim 2.1-2.4$ and $T_{\max }\sim 0.6-0.8$ keV) in the broad energy band remain similar. Spectral properties of segments exhibiting SPQ and DPQ are further studied using simple phase resolved spectroscopy which does not show a significant difference. Based on the model parameters, we obtain the maximum ratio of mass accretion rate in GRS 1915+105 to that in IGR J17091--3624 as $\sim 25:1$. We discuss the implications of our findings and comment on the physical origin of these exotic variabilities.

17 pages, 13 Figures, 6 Tables; Accepted for publication in MNRAS

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Cited by in corpus (9)

• Large Area X-ray Proportional Counter (LAXPC) in Orbit Performance : Calibration, background, analysis software
• Wide-band view of High Frequency QPOs of GRS 1915+105 in 'softer' variability classes observed with AstroSat
• Unraveling the foretime of GRS 1915+105 using AstroSat observations: Wide-band spectral and temporal characteristics
• Wideband Study of the Brightest Black Hole X-ray Binary 4U 1543-47 in the 2021 Outburst: Signature of Disk-Wind Regulated Accretion
• Accretion Scenario of MAXI J1820+070 during 2018 Outbursts with Multi-mission Observations
• Low Frequency Quasi Periodic Oscillations and Shocks in Accretion onto Black Hole
• Broadband X-ray properties of black holes GRS 1758-258 and 1E 1740.7-2942: AstroSat and NuSTAR results
• NICER Spectral and Timing Analysis of 4U 1630$-$47 and its Heartbeat State
• Multi-mission view of extragalactic black hole X-ray binaries LMC X-1 and LMC X-3: evolution of broadband spectral features