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Astron. Astrophys. 348, 924-932 (1999)

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Multi element Doppler imaging of Ap stars

I. He, Mg, Si, Cr and Fe surface distribution for CU Virginis *

R. Kuschnig 1, T.A. Ryabchikova 2, N.E. Piskunov 3, W.W. Weiss 1 and M.J. Gelbmann 1

1 Institute of Astronomy, University Vienna, Türkenschanzstrasse 17, A-1180 Vienna, Austria (last_name@galileo.astro.univie.ac.at)
2 Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 109017 Moscow, Russia (ryabchik@inasan.rssi.ru)
3 Uppsala Astronomical Observatory, Box 515, S-751 20, Uppsala, Sweden (piskunov@astro.uu.se)

Received 2 February 1999 / Accepted 16 June 1999

Abstract

We present the distribution of helium, magnesium, silicon, chromium and iron on the surface of the fast rotating magnetic B9p Si star CU Virginis, obtained with a Doppler Imaging inversion code. A clearly defined helium spot coincides with the position of one magnetic pole whereas silicon, chromium and iron accumulate in regions where the magnetic field lines are dominantly horizontal in the stellar atmosphere. The distribution of magnesium is significantly different compared to the other elements. The H[FORMULA] line varies in phase with the helium spot and the magnetic pole and the line profiles can be fitted within the observational errors with model atmospheres of constant [FORMULA] of 12500 K, but different surface gravity.

We compare our observations with current concepts for diffusion in magnetic chemically peculiar stars and find good agreement.

Key words: methods: data analysis – stars: abundances – stars: chemically peculiar – stars: individual: CU Vir – stars: magnetic fields

* Based on observation obtained at the Observatoire d'Haute-Provence

Send offprint requests to: Rainer Kuschnig (kuschnig@geop.ubc.ca)

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© European Southern Observatory (ESO) 1999

Online publication: August 13, 199
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