부산대학교 도서관

The rather elusive High-Frequency Quasi-Periodic Oscillations(HFQPO) observed in the X-ray lightcurve of black holes have been seen in a wide range of frequencies, even within one source. It is also notable to have been detected in "pairs" of HFQPOs with a close to integer ratio between the frequencies. The aim of this paper is to investigate some of the possible observable that we could obtain from having the Rossby Wave Instability (RWI) active in the accretion disc surrounding the compact object. Using the newly developed GR-AMRVAC code able to follow the evolution of the RWI in a full general relativistic framework, we explore how RWI can reproduce observed HFQPO frequencies ratios and if it is compatible with the observations. In order to model the emission coming from the disc we have linked our general relativistic simulations to the general relativistic ray-tracing GYOTO code and delivered synthetic observables that can be confronted to actual data from binary systems hosting HFQPOs.}{We have demonstrated in our study that some changes in the physical conditions prevailing in the part of the disc where RWI can be triggered leads to various dominant RWI modes whose ratio recovers frequency ratios observed in various X-ray binary systems. In addition, we have also highlighted that when RWI is triggered near the last stable orbit of a spinning black hole, the amplitude of the X-ray modulation increases with the spin of the black hole. Revisiting published data on X-ray binary systems, we show that this type of relationship actually exists in the five systems where an indirect measure of the spin of the black hole is available.
Comment: accepted by A&A