Blue Companions of Supergiants
Abstract
We would like to observe blue companions of supergiants in star clusters. For binaries in clusters we know the distance with some accuracy. IUE observations of blue companions of supergiants therefore tell their absolute magnitudes, so we can decide whether we are dealing with giants or main sequence stars. Because of the short evolution times along the giant branch the supergiants and evolved companions must have essentially the same mass. They then outline two points on an evolutionary track. For other apparently giant stars in the cluster we can never be sure about their membership. The luminosity difference between a supergiant and a giant of the same mass depends on the degree of mixing in the interior of the main sequence progenitor star, which can therefore be determined empirically by studying the luminosity difference between the supergiant and a giant companion. As all supergiants in a cluster must have essentially the same mass a dynamical mass determination for a supergiant in a cluster with Cepheids also determines the mass of the Cepheid.
- Publication:
-
IUE Proposal
- Pub Date:
- 1988
- Bibcode:
- 1988iue..prop.3054B