A deep look at accretion disks: Fe lines, kHz QPOs and spectral states.

Iron lines have now been detected in about half a dozen neutron-star accreting X-ray binaries. These lines can be used to set tight constrains on the accretion disk geometry and on the radius of the neutron star. We have recently shown that simultaneous XMM-Newton/RXTE and Chandra/RXTE observations appear to contradict previous works. Here we propose to observe a NS with XMM-Newton seven times for 25~ks, simultaneously with some of those RXTE observations. Our program will sample a wide range of inner disk radii. This program requires both XMM-Newton and RXTE observations. Since 2009 may be the last year of operations of RXTE, this program can only be done now.