Abstract:
We present the X-ray spectral and temporal analysis of the black hole X-ray transient Swift J1658.2–4242 observed by AstroSat.
Three epochs of data have been analysed using the JeTCAF model to estimate the mass accretion rates and to understand
the geometry of the flow. The best-fitting disc mass accretion rate (m˙ d) varies between 0.90+0.02 −0.01 and 1.09+0.04 −0.03 M˙ Edd in these
observations, while the halo mass accretion rate changes from 0.15+0.01 −0.01 to 0.25+0.02 −0.01 M˙ Edd. We estimate the size of the dynamic
corona that varies substantially from 64.9+3.9 −3.1 to 34.5+2.0
−1.5 rg and a moderately high jet/outflow collimation factor stipulates
isotropic outflow. The inferred high disc mass accretion rate and bigger corona size indicate that the source might be in the
intermediate to soft spectral state of black hole X-ray binaries. The mass of the black hole estimated from different model
combinations is ∼14 M⊙. In addition, we compute the quasi-periodic oscillation (QPO) frequencies from the model-fitted
parameters, which match the observed QPOs. We further calculate the binary parameters of the system from the decay profile of
the light curve and the spectral parameters. The estimated orbital period of the system is 4.0 ± 0.4 h by assuming the companion
as a mid or late K-type star. Our analysis using the JeTCAF model sheds light on the physical origin of the spectrotemporal
behaviour of the source, and the observed properties are mainly due to the change in both the mass accretion rates and absorbing
column density.
