Quasi-Periodic Oscillations due to radiative feedback mechanism between the disc and corona

TL;DR

This paper presents a physical radiative feedback model between the accretion disc and corona that naturally explains observed quasi-periodic oscillations in black hole systems, fitting real observational data.

Contribution

It introduces the first physical model linking disc-corona feedback to QPOs and successfully fits observed power spectra from AstroSat data.

Findings

The model reproduces observed QPO frequencies and harmonics.

It fits the broadband spectral components of the power spectra.

The primary QPO frequency matches the inverse of the feedback delay.

Abstract

Compact object systems exhibit Quasi-Periodic Oscillations (QPOs) as revealed by peaked features in their power density spectra. It has been known that stochastic variations in the accretion disc will propagate to the corona after a time delay and that the hard X-rays from the corona impinge back on the disc, giving reflection spectral features. Here, we show that the combination of these two effects makes a simple radiative feedback system between the corona and the disc, which naturally produces the observed QPOs whose primary frequency corresponds to the inverse of the time delay. The analytical form of the expected power spectra can be statistically compared with the observed ones. Hence, for the first time, a physical model is used to describe and fit the AstroSat observed power spectra of the black hole systems MAXI J1535-571 and GRS 1915+105, including the QPO, its harmonics, as well as the broadband components.