On the inner envelope of the Be star Cassiopeiae

We report the first spectrally-resolved observations of the Be star Cas in the Hei �6678 and Hemission lines using the Grand Interf´ erom` ` ´ in the south- ern France. Milliarcsecond angular resolution measurements were carried in both lines and their neighbouring continuum during October and November 1993. The Hei �6678 and H� maximum emissions correspond respectively to 1.05 and 1.5 of the local continuum level. The interferometric baselines ranged from 15m to 51m on the sky which correspond to angular res- olutions of 9 to 3 mas at Hei �6678 and 6.5 to 2 mas at H� wavelengths. We compare these values to predicted extents of Hand Hei �6678 components of the circumstellar gas from models of radiative transfer in these lines. We conclude that the emitting region must be smaller than 8.5 stellar radius in H� and close to 2.3 stellar radius in Hei �6678 which is, for Hei �6678, smaller than the nearby continuum extent. These results confirm Cas basic parameters for this star obtained by Stee et al. on 1993 from their model constrained by GI2T observations in Hline.