High-resolution spectroscopy of the low-mass X-ray binary EXO 0748-67

We present initial results from observations of the low-mass X-ray binary E XO 0748-67 with the Reflection Grating Spectrometer on board the XMM-Newton Observatory. The spectra exhibit discrete structure due to absorption and emission from ionized neon, oxygen, and nitrogen. We use the quantitative c onstraints imposed by the spectral features to develop an empirical model o f the circumsource material: This consists of a thickened accretion disk wi th emission and absorption in the plasma orbiting high above the binary pla ne. This model presents challenges to current theories of accretion in X-ra y binary systems.