New Interferometric Constraints on the Physics of Active OB-Stars


Paper:	New Interferometric Constraints on the Physics of Active OB-Stars
Volume:	361, Active OB-Stars: Laboratories For Stellar and Circumstellar Physics
Page:	57
Authors:	Jankov, S.; Domiciano de Souza, A.; Vakili, F.; Petrov, R.G.; Robbe-Dubois, S.
Abstract:	In the recent years the optical interferometry proved its ability to provide important observational constraints on the physics of active OB stars by spatially resolving not only circumstellar environments but also central stars. Particularly, an increasingly rich image information obtained by a modern generation of interferometers provided an evidence of extremely oblate shape of the Be star Achernar (Domiciano de Souza et al. 2003). We present this result and discuss it with respect to the most recent discovery of similar oblateness of Regulus (McAlister et al. 2005) in the context of the Circum-Stellar Envelope formation of Be stars in combination with their fundamental property of rapid rotation. We also discuss new interferometric observational constraints from direct measures of Be star photospheres which should prove whether these objects rotate close, to a few percent, of their critical velocity or not, with a profound impact on the dynamical models of Be stars disk formation from rapid rotation combined to mechanisms like non-radial pulsation, radiation pressure of photospheric hot spots or expelled plasma by magnetic flares. Optical interferometry is currently rapidly evolving, and stronger constraints for more stars can be expected using new interferometers that allow spectral resolution, for instance the VLTI with the AMBER instrument as well as the next generation VLTI instrumentation. In this contribution we review a selection of outstanding problems in physics of OB stars (the study of gravity darkening, non-radial pulsations, surface brightness distribution, differential rotation and magnetic fields) that can be resolved using new interferometric constraints. We show the potential of dedicated Interferometric-Doppler Imaging methods (Jankov et al. 2001) which provide a qualitatively new informations that cannot be obtained with classical techniques as photometry and spectroscopy.