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Astron. Astrophys. 354, 595-604 (2000)

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Spectro-polarimetric interferometry (SPIN) of magnetic stars

K. Rousselet-Perraut 1, O. Chesneau 2, Ph. Berio 2 and F. Vakili 2

1 Laboratoire d'Astrophysique UMR UJF/CNRS 5571, Observatoire de Grenoble, B.P. 53, 38041 Grenoble cedex 9, France
2 Observatoire de la Côte d'Azur, Département Fresnel, CNRS UMR 6528, 06460 Saint Vallier de Thiey, France

Received 8 February 1999 / Accepted 18 November 1999

Abstract

Stellar magnetic fields are usually studied by spectropolarimetric analysis of the Zeeman effect across spectral lines. Such studies are often limited by the net detectable polarization after averaging the small scale magnetic structures over the photospheric disk of the star. In this paper we examine the possibility to use optical long baseline interferometry to overcome this limitation for a partially or fully resolved star which, in the case of the brightest Ap and Bp stars, demands milliarcsecond resolutions achievable at 50 m baselines at least in the visible. We develop a simple geometrical model of magnetic stars from which we derive the intensity maps and their corresponding interferometric observables across Zeeman-split lines. The accuracy of the interferometric signal phase must be better than 0.5o (hence a relative accuracy of 0.1[FORMULA]), which limits the technique to brightest magnetic stars ([FORMULA] [FORMULA] 2) for operating interferometers. Nevertheless, this limiting magnitude can reach [FORMULA] [FORMULA] 8-10 for 8-m class planned interferometers. These foreseeable possibilities open new areas for studying slowly rotating magnetic stars or those sources possessing complex structures over their visible disk, otherwise undetectable by classical spectropolarimetry.

Key words: instrumentation: interferometers – techniques: polarimetric – techniques: spectroscopic – stars: magnetic fields

Send offprint requests to: K. Rousselet-Perraut

Correspondence to: perraut@obs.ujf-grenoble.fr

This article contains no SIMBAD objects.

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© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000
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