1997A&AS..123..173R

We report on the results of an observing run of γ Cassiopeiae using the optical long baseline interferometer Grand Interferometre a 2 Telescopes (GI2T) in the southern France equipped with film-sheet polarizers. Four interferometric baselines ranging from 20 to 40m were obtained on this star during 1994 on September 5th and 6th, with α Cephei as a calibrator. We aimed at detecting possible variations of the angular diameter of γ Cas as a function of polarization directions parallel and orthogonal to the north-south baseline of the GI2T. We do not detect any variation of the visibility as a function of Hour Angle on α Cephei, neither on γ Cas. We find an upper limit of 1.3 on the ratio of the angular diameters of the envelope of γ Cas seen through polarizers parallel and perpendicular to the North-South direction of the GI2T's baseline. We discuss how this limit could constrain density laws in the wind of this Be star. We clearly resolve γ Cas for increasing baselines in the red continuum whatever the polarization. Assuming the continuum flux originating from a photosphere surrounded by an elliptical gaussian envelope we estimate the extent of the latter as (2.9±0.5)mas. This diameter agrees well with the Hα emitting envelope as obtained by other interferometers.