Accretion Flow Evolution of a New Black Hole Candidate MAXI J1348-630 During the 2019 Outburst
Abstract
Galactic black hole candidate MAXI~J1348-630 was recently discovered by MAXI and Swift/BAT satellites during its first outburst in 2019 January which continued for 4 months. We study the spectral and timing properties of the source in detail. The combined 1-150 keV Swift/XRT, Swift/BAT and MAXI/GSC spectra are investigated with the two component advective flow (TCAF) solution. Physical flow parameters of TCAF, such as the Keplerian disk accretion rate, the sub-Keplerian halo accretion rate, the shock location and the shock compression ratio are estimated from our spectral fits. Based on the variation of flux in soft and hard X-ray ranges, the hardness ratio, TCAF model fitted accretion rates and accretion rate ratio (ARR), we show how the sources evolved through four spectral states viz. hard, hard-intermediate, soft-intermediate and soft states in rising and declining states. Low-frequency quasi-periodic oscillations (QPO) are observed in two observations during the rising phase of the outburst. From the spectral analysis, we estimate the mass of the black hole to be 9.1+1.6-1.2 M. We also find that the viscous timescale in this outburst is 3.5 days. The distance of the source is also estimated as 5-10 kpc from state transition luminosity.