The big dipper to learn about accretion disks and their ionized atmosphere

With the discovery of FeXXV and FeXXVI absorption lines in the dipping systems(viewed close to the disk plane), XMM has revealed the existence of ahighlyionized atmosphere above the accretion disk in lowmass Xray binaries.We have further demonstrated that the spectral changes during dips, both in thelines and in the continuum could be explained by a decrease in the ionizationlevel of this plasma. We want to investigate the structure of the disk and ofits ionized atmosphere through timeresolved spectroscopy of the dips in X1624490. Using the orbital ephemeris, we propose to trigger 4 observations,each one centered on one dip, for a total exposure of 104 ks. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]