2000AJ....120..935S

New simultaneous photometric and spectroscopic observations of the supersoft X-ray binary RX J0925.7-4758 (MR Vel) have been obtained. These confirm the unusually long orbital period near 3.8 days. An accurate period is determined based on several years of photometric observations. Short-term photometric variability (∼0.25 days) is also present, but it does not appear to be strictly periodic. The spectroscopic behavior reveals large-amplitude He II and H velocity curves, indicating that the system is viewed from a moderately high inclination angle. Masses for the component stars are derived. Evidence of a high-velocity jet (outflow velocity of 5350 km.s^–1) is present at Hα. Its radial velocity curve is very similar to the disk emission lines, suggesting the jet is formed near the compact star. A new model for the system is presented.