On the accretion flow and mass accretion rates/fluctuations in black hole candidate; MAXI J1535–571

MAXI J1535–571 underwent dramatic and transient outbursts accompanied by accretion flow. Hard X-radiations are produced due to thermal–and inverse–comptonization of soft photons by high-temperature electrons. The variations/fluctuations of components of the accretion flow rates and their fractional X-ray emissions/flux variability contributions at different epochs infer the spectral states. In this study, we utilized MAXI J1535–571 data observed by the three X-ray missions/detectors (MAXI/GSC, NuSTAR, and SWIFT/BAT) on the same and/or close-in epochs. Each detector's data were separately reduced and analyzed using HEASoft v6.28 and its software packages alongside the standard pipeline product software of each detector. Thereafter, the MAXI J1535–571 data were simultaneously fitted in XSPEC version 12.10.1f and modelled using selected analytical and phenomenological models (AP-model) to examine the photon index–N_BMC saturation effect and variations of components of the accretion flow rates. Moreover, the TCAF model was used on MAXI J1535–571 data to determine the correlation of components of the accretion flow rates. The AP– and TCAF–models gave a statistically acceptable fit with a reduced Chi-squared value of ≤ 1.2, and their spectral results were compared. The best-fit photon index of ∼ 2.0–2.20 affirms that MAXI J1535–571 is in its rising phase; the hard-intermediate state. The correlation of mass accretion rates suggests that their variations/fluctuations could be responsible for the dynamics and geometry of the accretion flow.