Monte-Carlo Simulations of Thermal Comptonization Process in a Two Component Accretion Flow Around a Black Hole

TL;DR

This paper uses Monte Carlo simulations to study how thermal Comptonization in a two-component accretion flow around a black hole explains spectral state transitions, emphasizing the roles of the CENBOL boundary and flow density.

Contribution

It provides a detailed simulation-based analysis of spectral state transitions in black hole accretion flows, highlighting the influence of the CENBOL boundary and flow density.

Findings

Spectral state transitions can be explained by changes in the CENBOL boundary or density.

The interplay between soft photon intensity and Compton cloud properties drives state changes.

Simulation results support previous theoretical conclusions about accretion flow behavior.

Abstract

We compute the effects of thermal Comptonization of soft photons emitted from a Kep- lerian disk around a black hole by the post-shock region of a sub-Keplerian flow, known as the CENtrifugal pressure dominated BOundary Layer (CENBOL). We show that the spectral state transitions of black hole candidates could be explained either by varying the outer boundary of the CENBOL, which also happens to be the inner edge of the Keplerian disk, or by changing the central density of the CENBOL which is governed by the rate of the sub-Keplerian flow. We confirm the conclusions of the previous the- oretical studies that the interplay between the intensity of the soft photons emitted by the Keplerian flow and the optical depth and electron temperature of the Comptonizing cloud is responsible for the state transitions in a black hole.