A new phase of activity of the Herbig Be star HD 200775 in 2001: Evidence for binarity

Abstract

The results of high-resolution spectroscopy of the Herbig Be star HD 200775 obtained within the framework of a cooperative observing programme in 2000-2002 are presented. A new high-activity phase of the object's Hα line occurred in the middle of 2001 in full agreement with a 3.68-year periodicity predicted by Miroshnichenko et al. (1998). A complicated picture of the Hα line profile variability near the activity maximum phase turned out to be very similar to that observed during the previous one in 1997. Variations of the radial velocity with the activity phase are detected in He I, Si II, and S II photospheric lines. The observed phenomena are interpreted in the framework of a model in which the star, together with its gaseous envelope, is a component of an eccentric binary system. A preliminary orbital solution is derived, and the system's parameters are estimated from the radial velocity curves of the Hα emission line. We find that the orbital eccentricity is e ∼ 0.3, the mean companion separation is ∼1000 R⊙, and the secondary companion is most likely to be a ∼3.5 Ṁ pre-main sequence object. We emphasize the importance of coordinated spectroscopic and interferometric observations at different phases of the object's activity for further understanding the properties of the system.