Hostname: page-component-78c5997874-mlc7c Total loading time: 0 Render date: 2024-11-11T11:33:43.076Z Has data issue: false hasContentIssue false

Helium abundances in HgMn and normal stars

Published online by Cambridge University Press:  02 March 2005

M.M. Dworetsky
Affiliation:
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK email: mmd@star.ucl.ac.uk
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The parameter-free model of diffusion in the atmospheres of HgMn stars (Michaud 1986, Michaud et al. 1979) predicts that helium should sink below the $\hbox{He\,{\sc ii}}$ ionization zone that the diffusion of other elements may take place, and that all HgMn stars should have deficits of helium in their photospheres, with a minimum deficit of 0.3 dex. In this study, the Smith & Dworetsky (1993) sample of HgMn stars and normal comparison stars is examined, and the helium abundances determined by spectrum synthesis using échelle spectra taken at Lick Observatory and the AAT. The prediction is confirmed. All HgMn stars are deficient in He by as much as 1.5 dex. Also, two HgMn stars, HR 7361 and HR 7664, show clear evidence of helium stratification.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Type
Contributed Papers
Copyright
© 2004 International Astronomical Union