We present optical and ultraviolet spectra , lightcurves , and Doppler tomograms of the low-mass X-ray binary EXO 0748–676 .
Using an extensive set of 15 emission line tomograms , we show that , along with the usual emission from the stream and “ hot spot ” , there is extended non-axisymmetric emission from the disk rim .
Some of the emission and H \alpha and \beta absorption features lend weight to the hypothesis that part of the stream overflows the disk rim and forms a two phase medium .
The data are consistent with a 1.35M _ { \odot } neutron star with a main sequence companion and hence a mass ratio q \approx 0.34 .