Distinguishing between spot and torus models of high-frequency quasiperiodic oscillations

Abstract

In the context of high-frequency quasi-periodic oscillation (HF QPOs) we further explore the appearance of an observable signal generated by hot spots moving along quasi-elliptic trajectories close to the innermost stable circular orbit in the Schwarzschild spacetime. The aim of our investigation is to reveal whether observable characteristics of the Fourier power-spectral density can help us to distinguish between the two competing models, namely, the idea of bright spots orbiting on the surface of an accretion torus versus the scenario of intrinsic oscillations of the torus itself. We take the capabilities of the present observatories (represented by the Rossi X-ray Timing Explorer, RXTE) into account, and we also consider the proposed future instruments (represented here by the Large Observatory for X-ray Timing, LOFT).

6 pages, 5 figures; based on a talk given at 10th IBWS workshop, some of findings presented in Bakala et al. (2014, MNRAS, eprint arXiv:1401.4468) are discussed in a broader context; to appear in Proceedings of the 10th INTEGRAL/BART Workshop in Karlovy Vary (Czech Republic, 22-25 April 2013), Acta Polytechnica, 2014