Mapping abundance inhomogeneities and magnetic fields of chemically peculiar (CP) stars with optical aperture synthesis arrays

Karine Rousselet-Perraut; Chantal Stehle; Thierry Lanz; Thomas Boudoyen; Slobodan Jankov; Farrokh Vakili; Martin Kilbinger; Jean-Baptiste Lebouquin; Oleg Kochukhov

doi:10.1117/12.458590

21 February 2003 Mapping abundance inhomogeneities and magnetic fields of chemically peculiar (CP) stars with optical aperture synthesis arrays

Karine Rousselet-Perraut, Chantal Stehle, Thierry Lanz, Thomas Boudoyen, Slobodan Jankov, Farrokh Vakili, Martin Kilbinger, Jean-Baptiste Lebouquin, Oleg Kochukhov

Author Affiliations +

Proceedings Volume 4838, Interferometry for Optical Astronomy II; (2003) https://doi.org/10.1117/12.458590
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

Simultaneously mapping the abundance inhomogeneities and the magnetic fields of chemically peculiar (CP) stars is essential to improve our understanding of stellar magnetism and its key role in structuring stellar atmospheres, in particular relative to ion migration and chemical stratification. However, magnetic fields and chemical inhomogenities tend to have similar effects on classical observables. Magnetic and abundance maps have therefore to be reconstructed most often either independently or in making a priori assumptions. To overcome these difficulties, we propose to take benefit of optical aperture synthesis arrays to resolve local magnetic structures and patchy stellar surfaces. This requires ability to resolve polarimetrically magnetically-sensitive spectral lines, and thus to add a polarimetric device at the combined focus of an interferometric array. Within this instrumental context, it becomes possible to map magnetic fields with visibility and phase measurements in circularly polarized light and to map the chemical inhomogeneities thanks to "classical" interferometric measurements (i.e. without the polarimeter). In this paper, we show that the interference fringe phase is the suitable observable for polarimetric measurements and for mapping patchy surfaces (see also Jankov et al. in these proceedings). We present some illustrative cases of different magnetic topologies and abundance distributions. We focus on two well-known CP stars, βCrB and α²CVn, and we show observational predictions with different instruments currently in operation (GI2T, VLTI).

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Karine Rousselet-Perraut, Chantal Stehle, Thierry Lanz, Thomas Boudoyen, Slobodan Jankov, Farrokh Vakili, Martin Kilbinger, Jean-Baptiste Lebouquin, and Oleg Kochukhov "Mapping abundance inhomogeneities and magnetic fields of chemically peculiar (CP) stars with optical aperture synthesis arrays", Proc. SPIE 4838, Interferometry for Optical Astronomy II, (21 February 2003); https://doi.org/10.1117/12.458590

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KEYWORDS

Magnetism

Stars

Phase measurement

Polarimetry

Interferometry

Visibility

Optical arrays

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