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arXiv2020

AstroSat Observation of Non-Resonant Type-C QPOs in MAXI J1535-571

Galactic transient black hole candidate (BHC) MAXI J1535-571 was discovered on 2017 September 02 simultaneously by {\it MAXI}/GSC and {\it Swift}/BAT instruments. It has also been observed by India's first multi-wavelength astronomy-mission satellite {\it AstroSat}, during the rising phase of its 2017-18 outburst. We make both the spectral and the temporal analysis of the source during 2017 September 12-17 using data of {\it AstroSat}'s Large Area X-ray Proportional Counter (LAXPC) in the energy range of $3-40$~keV to infer the accretion flow properties of the source. Spectral analysis is done with the physical two-component advective flow (TCAF) solution-based {\it fits} file. From the nature of the variation of the TCAF model fitted physical flow parameters, we conclude and confirm that the source was in the intermediate spectral state during our analysis period. We observe sharp type-C quasi-periodic oscillations (QPOs) in the frequency range of $\sim 1.75-2.81$~Hz. For a better understanding of the nature and evolution of these type-C QPOs, a dynamic study of the power density spectra is done. We also investigate the origin of these QPOs from the shock oscillation model. We find that non-satisfaction of Rankine-Hugoniot conditions for non-dissipative shocks and not their resonance oscillations is the cause of the observed type-C QPOs.

astro-ph.HE↗

arXiv2018

Evolution of X-Ray Properties of MAXI J1535-571: Analysis with the TCAF Solution

We present spectral and timing properties of the newly discovered X-ray transient source, MAXI J1535-571, which is believed to be a Galactic X-ray binary containing a black hole candidate (BHC) as the primary object. After its discovery on 2017 Sep. 2, it has been monitored regularly in multi-wavelength bands by several satellites. We use archival data of Swift (XRT and BAT) and MAXI (GSC) satellite instruments to study accretion flow dynamics of the source during the outburst. During its outburst, the source became very bright in the sky with a maximum observed flux of $5$~Crab in the $2-10$~keV GSC band. Similar to other transient BHCs, it also shows signatures of low frequency quasi-periodic oscillations (QPOs) during the outburst. Spectral data of different instruments are fitted with the transonic flow solution based two-component advective flow (TCAF) model fits file to find the direct accretion flow parameters. Evolution of spectral states and their transitions are understood from the model fitted physical flow parameters and nature of QPOs. We also estimate probable mass of the black hole from our spectral analysis as $7.9-9.9~M_\odot$ or $8.9\pm1.0~M_\odot$.

astro-ph.HE↗