High Resolution Spectroscopy of the ADC Source 2S0921-630

We propose to observe the high inclination low mass Xray binary 2S0921630in order to test the hypothesis that the residual Xrays seen during eclipse are due to reprocessing and scatttering in an accretion disk corona. By observing atomic emission features from elements such as Ne, Mg, Si, and S athigh resolution using RGS1, we can determine the ionization state and emissionmeasure, and thereby infer the density and size of the corona. We can alsoconstrain the elemental abundances. Using the EPIC detectors we can test forvariability in the spectrum during the eclipse, and constrain the geometricalextent of the corona. This source is ideal for such a study owing to itsdemonstrated strong line emission and its long eclipse. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]