Properties and nature of Be stars - 28. Implications of systematic observations for the nature of the multiple system with the Be star o?Cassiope??and its circumstellar environment

摘要

The analysis of radial velocities of the Be star oCas fromspectra taken between 1992 and 2008 at the Ondrejov Observatory and the DominionAstrophysical Observatory allowed us to reconfirm the binary nature ofthis object, first suggested by Abt and Levy in 1978, but later refutedby several authors. The orbital parameters of this SB1 system implya very high mass function of about one solar mass. This in turn leadsto a very high mass of the secondary, possibly higher than that of theprimary. In order to look for such a massive secondary,o Cas was observed with the Navy Prototype Optical Interferometer,which allowed the binary components to be spatially resolved for thefirst time. The interferometric observations lead to the detection of asecondary, about 3 mag fainter than the primary. The possible propertiesof this peculiar binary system and the reasons why the massive secondarydoes not dominate the optical spectrum are discussed.Key words: binaries: close - binaries: spectroscopic - stars: emission-line, Be - stars: fundamental parameters - stars: individual: oCas