Simulations of flux variability of oscillating accretion fluid tori around Kerr black holes

TL;DR

This paper models flux variability in oscillating accretion tori around Kerr black holes, linking fluid oscillations to observed high-frequency QPOs in X-ray binaries, and explores resonance and precession mode combinations.

Contribution

It introduces a detailed simulation of flux variations caused by oscillating accretion tori, comparing resonance and precession models for QPOs near Kerr black holes.

Findings

Flux variation can be significantly caused by combined radial and vertical oscillations.

Different mode combinations correspond to distinct QPO models.

Simulation results support the relevance of mode resonance in QPO phenomena.

Abstract

High frequency quasi-periodic oscillations (HF QPOs) are observed in the X-ray power-density spectra (PDS) of several microquasars and low mass X-ray binaries. Many proposed QPO models are based on oscillations of accretion toroidal fluid structures orbiting in the vicinity of a compact object. We study oscillating accretion tori orbiting in the vicinity of a Kerr black hole. We demonstrate that significant variation of the observed flux can be caused by the combination of radial and vertical oscillation modes of a slender, polytropic, perfect fluid, non-self-graviting torus with constant specific angular momentum. We investigate two combinations of the oscillating modes corresponding to the direct resonance QPO model and the modified relativistic precession QPO model.