Be Stars as Interacting Binaries

At the last IAU Symposium on Be stars held in Bass River, MA in 1975, several of us (including P. Harmanec, M. Plavec, R.S. Polidan, and myself) suggested that Be stars are mass transfer binaries and represent the higher mass counterparts to the familiar Algol systems. Although a number of alternatives to the rotational hypothesis have been presented at this symposium (including “chromospheric” activity and non-radial pulsation) and some of these may well explain certain objects, I strongly believe that binary mass transfer is responsible (either directly or indirectly) for the circumstellar envelopes observed in a large percentage of Be stars.