Stellar activity and magnetism studied by optical interferometry

¹ Laboratoire d'Astrophysique de l'Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
² Laboratoire de l'Univers et de ses THéories, UMR 8102, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France
³ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
⁴ NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA
⁵ Institut für Astrophysik und Extraterrestrische Forschung, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
⁶ Uppsala Astronomical Observatory, Box 515, 751 20, Uppsala, Sweden
⁷ Observatoire de la Côte d'Azur, Département Fresnel, CNRS UMR 6528, 06460 Saint Vallier de Thiey, France

Corresponding author: K. Rousselet-Perraut, karine.perraut@obs.ujf-grenoble.fr

Received: 31 March 2003
Accepted: 23 March 2004

Abstract

By means of numerical simulations, we investigate the ability of optical interferometry, via the fringe phase observable, to address stellar activity and magnetism. To derive abundance maps and stellar rotation axes, we use color differential interferometry which couples high angular resolution to high spectral resolution. To constrain magnetic field topologies, we add to this spectro-interferometer a polarimetric mode. Two cases of well-known Chemically Peculiar (CP) stars (βCrB and CVn) are simulated to derive instrumental requirements to obtain 2D-maps of abundance inhomogeneities and magnetic fields. We conclude that the near-infrared instrument AMBER of the VLTI will allow us to locate abundance inhomogeneities of CP stars larger than a fraction of milliarcsecond whereas the polarimetric mode of the French GI2T/REGAIN interferometer would permit one to disentangle various magnetic field topologies on CP stars. We emphasize the crucial need for developing and validating inversion algorithms so that future instruments on optical aperture synthesis arrays can be optimally used.