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Photometric observations of the X-ray nova 0748-676 show that optical eclipses occur in phase with the X-ray eclipses. In addition, the light curve shows considerable modulation throughout the 3.8 hr orbital period. Spectra show emission lines of H and He II which vary in velocity, intensity, and profile throughout the orbital cycle. The phasing of the velocity variations suggests that the emission lines are formed in the vicinity of the compact star. However the lines are very weak, and accurate velocities cannot be determined from the data. Curiously, the emission lines have maximum flux near phase 0 (eclipse), indicating they cannot arise principally in the region which is eclipsed.
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Crampton et al. (1986) studied this question.
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