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The capability of optical long baseline interferometry for measuring the angular diameter of stars or binary separation is now well established. However, for the imaging of photospheric disk structures one needs very long baseline interferometers operated in the multi-telescope phase-closure technique. In this paper we will stress the capability of spectro-interferometric measurements to constrain the physics of hot stars. We will report our study of the interacting binary, β Lyrae, and the mass-losing Be star γ Cassiopeiae. We will look at the interpretation of both the modulus and phase data recorded by the long baseline interferometer GI2T in the southern France. The performances and limitations of spectro-interferometric techniques will also be discussed through some of the most exciting prospects within the reach of current interferometers.

Although stellar interferometers are capable of measuring the angular diameters of stars, with longer baselines they may also be used to measure brightness variations across a star's surface and to provide constraints on models of stellar envelopes. In this paper we will look at the interpretation of visibility data and some of the more exciting prospects within the reach of current interferometers.

We present theoretical line profiles and intensity maps from an axi-symmetric radiative wind model from a fast rotating Be star (Araújo & Freitas Pacheco, 1989; Araújo et al, 1993). The introduction of a viscosity parameter in the latitude dependent hydrodynamic code enables us to consider the effects of the viscous force in the azimuthal component of momentum equations. The line force is the same as Friend and Abbott (1986), but it is introduced a varying contribution of thin and thick lines from pole to equator by adopting latitude-dependent radiative parameters. The numerical calculation for parameters characteristic of early Be stars gives a density contrast between equator and pole of the order of 100. The total mass loss rates range from 10-8 to 10-7 solar mass per year. Furthermore, the “opening-angle” usually adopted in had-hoc models (Lamers and Waters, 1987; Waters et al., 1991) arises naturally as a result of our model. The velocity fields and density laws derived from the hydrodynamic equations have been used for solving the statistical equilibrium equations. By adopting the Sobolev approximation, we could easily obtain a good estimate of both electronic density and hydrogen level populations throughout the envelope (Stee and Araújo, 1994).

B[e] supergiants constitute one group of stars in the upper left part of the HR diagram. On the basis of their hybrid spectrum and their intrinsic polarization a two components envelope was suggested (Zickgraf & Schulte-Ladbeck, 1989): a “polar wind” and a denser “equatorial disc”.