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Astron. Astrophys. 326, L29-L32 (1997)

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Letter to the Editor

On the evolutionary status of [FORMULA] Bootis stars using Hipparcos data *

Ernst Paunzen

Institut für Astronomie der Universität Wien, Türkenschanzstr. 17, A-1180 Wien, Austria (paunzen@galileo.ast.univie.ac.at)

Received 24 June 1997 / Accepted 5 August 1997

Abstract

We have used the Hipparcos data to derive absolute magnitudes and thus the evolutionary status for the group of [FORMULA] Bootis stars. The origin for this small group of nonmagnetic, chemically peculiar stars, still remains a matter of debate. Using new evolutionary tracks, we are able to provide an age determination to distinguish between the two proposed theories - the diffusion/mass-loss and the accretion theory.

Our results establish the member of this group as objects which are very close to the Main Sequence. This is also supported by Pre-Main Sequence evolutionary tracks as well as by observational results. We therefore contradict prior conclusions that most of these stars are in the middle of their Main Sequence lifetime. The new results strongly support the predictions of the accretion theory.

Key words: stars – Bootis ; stars – chemically peculiar; stars – early type; stars – fundamental parameters; stars – pre-main sequence

* Based on observations obtained with the Hipparcos satellite

Send offprint requests to: E. Paunzen

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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