Resonance Condition and Low Frequency Quasi Periodic Oscillations of the Outbursting Source H 1743-322

TL;DR

This paper investigates how resonance between infall and cooling time scales in black hole accretion flows can explain low frequency QPOs, with explicit calculations during H 1743-322's 2010 outburst confirming the resonance condition.

Contribution

It provides a detailed computation of infall and cooling time scales and demonstrates their resonance as a mechanism for LFQPOs during black hole outbursts.

Findings

Resonance between cooling and infall time scales correlates with LFQPOs.

Higher Q-factor QPOs have a ratio of time scales close to 1.

Resonance condition is satisfied within ~50% during outburst periods.

Abstract

It has long been proposed that low frequency QPOs in stellar mass black holes or their equivalents in super massive black holes are results of resonances between infall and cooling time scales. We explicitly compute these two time scales in a generic situation to show that resonances are easily achieved. During an outburst of a transient black hole candidate (BHC), the accretion rate of the Keplerian disk as well as the geometry of the Comptonizing cloud change very rapidly. During some period, resonance condition between the cooling time scale (predominantly by Comptonization) and the infall time scale of the Comptonizing cloud is roughly satisfied. This leads to low frequency quasi-periodic oscillations (LFQPOs) of the Compton cloud and the consequent oscillation of hard X-rays. In this paper, we explicitly follow the BHC H 1743-322 during its 2010 outburst. We compute Compton cooling time and infall time on several days and show that QPOs take place when these two roughly agree within ~50%, i.e., the resonance condition is generally satisfied. We also confirm that for the sharper LFQPOs (i.e., higher Q-factors) the ratio of two time scales is very close to 1.