Tracing the accretion disk using Fe lines and kHz QPOs

Fe K lines have now been detected in about half a dozen neutronstar accretingXray binaries. Under the commonly accepted interpretation, these lines can beused to set tight constrains on the accretion disk geometry and on the radius ofthe neutron star. Using simultaneous XMMNewton/RXTE observations of 4U 163653,we have recently shown that the inner disc radius deduced from thecharacteristic frequency of the timing features and from the Feline profiledoes not change consistently with time, contradicting the expected scenario. Itis intriguing that the Fe line appears to behave differently. Here we propose toobserve this system with XMMNewton three times for 30 ks, simultaneously withNuStar observations. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]