Galactic transient black hole candidate ( BHC ) MAXI J1535-571 was discovered on 2017 September 02 simultaneously by MAXI /GSC and Swift /BAT instruments .
It has also been observed by India ’ s first multi-wavelength astronomy-mission satellite 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 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 fits file .
From the nature of the variation of the TCAF model fitted physical flow parameters , we conclude and confirm that during our analysis period source was in the soft-intermediate spectral state .
We observe sharp type-C quasi-periodic oscillations ( QPOs ) in the frequency range of \sim 1.74 - 2.81 Hz , which are not common in the soft-intermediate spectral state .
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 as is expected in the soft-Intermediate spectral states , non-satisfaction of Rankine-Hugoniot conditions for non-dissipative shocks and not their resonance oscillations may be the cause of the origin of type-C QPOs .