A New Route to Phase-Resolved Spectroscopy of Pulsations and QPOs in X-ray Binaries
The accretion disks in neutron star and stellar-mass black hole X-ray binaries provide an opportunity to study matter in strong gravitational fields. In particular, using spectral-timing measurements of X-ray emission, we can analyze the inner parts of the accretion disk and corona. Here we present the application of a new spectral-timing technique to carry out phase-resolved spectroscopy of rapid periodic and quasi-periodic signals from X-ray binaries. This technique measures relative phase and does not require ephemerides or exactly periodic signals, so it is applicable to a wide range of data, from X-ray millisecond pulsations to kHz and low-frequency QPOs. The method gives new insight into the physical mechanisms underlying these signals as well as the geometry of the emitting regions.