The Asymmetric Envelope of gamma Cassiopeiae Observed with the MK III Optical Interferometer

Abstract

We present interferometric observations of the Be star γ Cas in the light of the Hα emission line. Northsouth baselines ranging from 4.2 to 23.6 m have been used over a large range of hour angles. With the resulting coverage of the u-v plane, we have been able for the first time to measure the asymmetry of the Hα emitting region directly. The brightness distribution on the sky can be fit by an elliptical Gaussian model with an axial ratio of 0.74 and an angular diameter (FWHM of the major axis) of 3.2 milliarcsec (mas). The radial brightness distribution is not well-constrained by our data; elliptical uniform disk or ring models also give acceptable fits