演講資訊

摘要：

Black hole and neutron star X-ray binaries show variability on time-scales ranging from milliseconds to years. While variability on the time scale of years is related to the accretion rate of matter, the origin of variability on short time scales is still under debate. In the last two decades a detailed phenomenological picture of short-term variability in low-mass X-ray binaries has emerged. This picture comprises periodic and quasi-periodic variability, seen as spikes or humps in power density spectra, that are superposed on broad noise components. The overall shape of the noise components as well as the occurrence of quasi-periodic oscillations is known to vary with the state of the X-ray binary. Quasi-periodic oscillations can be related to the relativistic precession of the accretion flow, instabilities in the accretion disc, or to nuclear burning on the neutron star surface. Here I present the results of a comprehensive variability study of a sample of black hole X-ray binaries based on XMM-Newton observations, including a discussion of the energy dependence of the variability. I will discuss the implications of these findings for the picture of the accretion geometry in black hole X-ray binaries. Regarding neutron star binaries, we performed a variability study of archival XMM-Newton data of 4U 1636-536 and investigated the energy dependence of the low frequency variability. Here I present the results of our waveform analysis and phase resolved spectral investigations of the low frequency variability in this source and discuss implications on the thermonuclear burning mode, neutron star size and equation of state.