Polarimetric interferometry : concept and applications

Adding a polarimetric device at the combined focus of a stellar interferometer opens new prospects for studying stellar polarization phenomena. Thanks to spatial resolution of long baseline interferometer local polarized structures should become observable unless otherwise undetectable by classical polarimetric techniques. In this paper we present the principles, the observables and the instrumental requirements of polarimetric interferometry. After a short description of earlier attempts to detect polarization effects with optical long baseline interferometry we review the potential applications of this technique once implemented on future optical arrays. We examine the case of scattering phenomena in the extended atmospheres of hot stars (O, B, A) or magnetism of chemically peculiar stars as targets for polarimetric interferometry or its extension SPIN (Spectro-Polarimetric INterferometry). Finally, based on the design of a polarimetric device of GI2T-REGAIN, we currently initiate an observing program which aims at scientific targets such as bright magnetic Ap and Be stars.