Observations of eight close binaries with the Einstein Observatory

Eight close binaries were observed with the Imaging Proportional Counter aboard the Einstein Observatory. The binaries R Ara, Zeta Aur, RZ Cas, 31 Cyg, Delta Lib, U Sge, RZ Sct, and RW Tau all show strong indications of active mass flow in their ground-based and/or ultraviolet spectra. The systems R Ara, RZ Cas, 31 Cyg, Delta Lib, and U Sge were detected as X-ray sources while only upper limits on the X-ray luminosities of Zeta Aur, RZ Sct, and RW Tau could be determined. Nondetection of the latter three is probably attributable to their distance. With the exception of 31 Cyg which has an X-ray luminosity of about 10 to the 32nd erg/s, the detected sources have X-ray luminosities in the range 10 to the 30th-31st erg/s. These luminosities are approximately equal to those observed for single stars of similar spectral types. It appears that the X-ray luminosity of 31 Cyg is at least 60 times higher than that of Zeta Aur.