New rotational velocities for eclipsing binaries, and a comparison of spectroscopic and photometric rotations

Rotational velocities are determined spectroscopically for 38 eclipsing binaries, including many long-period, nominally semidetached, systems. We note that spectroscopic rotations may differ from rotations derived from light-curve modeling using the Wilson-Devinney program. In 'direct-impact' mass-transferring systems, or in most systems with periods smaller than about 7 days, observations suggest that the two rotations are usually about the same. In cases where the stream misses the gainer and an accretion disk forms, however, photometric rotation estimates often exceed spectroscopic determinations. The possible physical significance of this situation is briefly discussed. Doubt is cast on the likelihood that the rotation of the hot component of U Sge has changed detectably in the last 30 years.