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AstroSat view of IGR J17091−3624 and GRS 1915 + 105: decoding the 'pulse' in the 'Heartbeat State'.
- Source :
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Monthly Notices of the Royal Astronomical Society . 3/11/2021, Vol. 501 Issue 4, p6123-6138. 16p. - Publication Year :
- 2021
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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 ∼125 ks 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 δ f   ∼ 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). Broad-band spectra in the range 0.7–23 keV, obtained with Soft X-ray Telescope and Large Area X-ray Proportional Counter , could be fitted well with combination of a thermal Comptonization and a multicolour disc component model. During AstroSat observation, the source was in the soft-intermediate state (SIMS) as observed with 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 (Γ ∼ 2.1–2.4 and T max ∼ 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 ∼25: 1. We discuss the implications of our findings and comment on the physical origin of these exotic variabilities. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 501
- Issue :
- 4
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 148573288
- Full Text :
- https://doi.org/10.1093/mnras/staa3756