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Issue A&A Volume 432, Number 1, March II 2005 Page(s) L21 - L24 Section Letters DOI 10.1051/0004-6361:200500013

A&A 432, L21-L24 (2005)
DOI: 10.1051/0004-6361:200500013

Letter

The calcium isotopic anomaly in magnetic CP stars

C. R. Cowley¹ and S. Hubrig<sup>2

1</sup>  Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090, USA
    e-mail: cowley@umich.edu
²  European Southern Observatory, Casilla 19001, Santiago 19, Chile
    e-mail: shubrig@eso.org

(Received 20 December 2004 / Accepted 26 January 2005)

Abstract
Chemically peculiar stars in the magnetic sequence can show the same isotopic anomaly in calcium previously discovered for mercury-manganese stars in the non-magnetic sequence. In extreme cases, the dominant isotope is the exotic  ⁴⁸Ca. Measurements of lines arising from 3d-4p transitions reveal the anomaly by showing shifts up to 0.2 Å for the extreme cases - too large to be measurement errors. We report measurements of miscellaneous objects, including two metal-poor stars, two apparently normal F-stars, an Am-star, and the N-star U Ant. Demonstrable anomalies are apparent only for the Ap stars. The largest shifts are found in rapidly oscillating Ap stars and in one weakly magnetic Ap star, HD 133792. We note the possible relevance of these shifts for the GAIA mission.

Key words: stars: abundances -- stars: atmospheres -- stars: chemically peculiar -- stars: atomic data -- stars

SIMBAD Objects

© ESO 2005

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