Is the Be star theta CrB an eclipsing binary

The analysis of 19 published radial velocity measurements of the broad H I and He I lines covering the time span 1904 to 1979 indicates that theta CrB may be a long-periodic spectroscopic binary with an orbital period of 510.87 days. The predicted time of a hypothetical primary eclipse from the orbital solution coincides remarkably well with the 0.7/sup m/ deep photometric minimum observed by Roark (1971, Astron. J. 76, 634). It is argued that the proposal by Roark et al. (1972, Astrophys. Lett. 10, 55), i.e. that the visual companion to theta CrB, discovered by Couteau (1971, IAU Circ. 2339), is responsible for this light variation, is untenable. It may also be significant that the unusual disappearance of the C IV lines in the UV spectrum of theta CrB, reported by Doazan et al. (1983, preprint) occurred around the time of the predicted primary eclipse. Highly speculative conclusions, which should be subjected to critical tests by future observations and quantitative analyses of archival data, are: 1. theta CrB is a triple system, consisting of a spectroscopic eclipsing binary with P=510.87 days, and a distant visual companion with P>45 years. 2. Light variations observed by Roark (1971, Astron. J. 76, 634) are interpreted as a superimposition of an (atmospheric) eclipse of the primary, and of rapid physical variations of the spectroscopic secondary, detectable only during eclipses. 3. The next primary eclipse is expected to occur on May 25 to June 15, 1984. (author)