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Astron. Astrophys. 356, 200-208 (2000)


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Abundance analysis of roAp stars

V. HD 166473 *

M. Gelbmann 1, T. Ryabchikova 1,2, W.W. Weiss 1, N. Piskunov 3, F. Kupka 1 and G. Mathys 4

1 Institute for Astronomy, University Vienna, Türkenschanzstrasse 17, 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, 751 20 Uppsala, Sweden (piskunov@astro.uu.se)
4 European Southern Observatory, Casilla 19001, Santiago 19, Chile (gmathys@eso.org)

Received 10 December 1999 / Accepted 20 January 2000

Abstract

This fifth paper in a sequence on abundance analyses of roAp stars features several improvements and complements over the previous investigations:
i. The new VALD-2 atomic data base was used which significantly improves the analysis of C, N, O, and rare earth elements (REE) and in particular includes also some doubly ionized REE species.
ii. An individual opacity distribution function table was generated for a successful synthesis of photometric indices of this very peculiar star.
iii. The influence of a (rather strong) magnetic field on abundance determinations is studied and presented for 30 elements.
iv. Our investigation of 33 elements (45 ions) is the hitherto most complete chemical analysis of a chemically peculiar star, using modern tools.

Similar to the four roAp stars analysed by us so far ([FORMULA] Cir: Kupka et al. 1996, HD 203932: Gelbmann et al. 1997, [FORMULA] Equ: Ryabchikova et al. 1997a, and HD 24712: Ryabchikova et al. 1997b) we find nearly solar abundances of Fe and Ni, and a definite overabundance of Cr and especially Co. Rare earth elements have large overabundances, whereas C and O are underabundant relative to the Sun. This pattern seems to be a common property of the chemically peculiar (CP2, Ap) stars.

A new and most striking result is the discovery of the anomalous line strengths of the second ions of REE resulting in an abundance increase of up to +1.5 dex, compared to values obtained from lines of the first ions. This anomaly is not found in non-roAp and "normal" stars.

Key words: stars: abundances – stars: atmospheres – stars: chemically peculiar – stars: fundamental parameters – stars: individual: HD166473

* Based on observations obtained at the European Southern Observatory (La Silla, Chile)

Send offprint requests to: Werner W. Weiss

© European Southern Observatory (ESO) 2000

Online publication: March 28, 2000

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