ON THE KINEMATICS OF THE ENVELOPE OF GAMMA-CASSIOPEIAE

We study the rotational component of the wind in the envelope of the B e star gamma Gas. We have computed scenarios based on the axi-symmetri c radiative wind model that we have developed for this star. We obtain line profiles and predicted interferometric observables from long bas eline Michelson interferometry. It turns out that the models with cons tant and solid body rotation can be ruled out. It is also shown that c lassical technics as spectroscopy as well as interferometry can not di stinguish between the angular momentum conservation (beta = 1.0), the Keplerian motion (beta = 0.5) and beta = 0.25 models. Besides, we have computed theoretical photocenter displacement as a fuction of wavelen gth in the North-South and East-West directions and also in the sky pl ane. We conclude that only technics which are able to follow the photo center displacement with wavelength, as Michelson spectro-interferomet ry or differential speckle interferometry would be able to infer the a ctual rotational law in the envelope of gamma Cas.