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Astron. Astrophys. 337, 216-222 (1998)

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The chemical composition of HD 196944: a carbon and s-process rich, very metal-poor star *

Laimons Zas 1, Poul E. Nissen 2 and William J. Schuster 3

1 Ventspils International Radio Astronomy Center, Akadmijas laukums 1, LV-1050 Riga, Latvia (zacs@latnet.lv)
2 Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark (pen@obs.aau.dk)
3 Observatorio Astronomico Nacional, UNAM, Apartado Postal 877, C.P. 22800 Ensenada, B.C., Mexico (schuster@bufadora.astrosen.unam.mx)

Received 25 February 1998 / Accepted 19 May 1998

Abstract

An LTE abundance analysis of the post-AGB candidate star HD 196944 is presented based on high resolution, high S/N spectra. The radial velocity of HD 196944 is found to be -174 km s-1 indicating that it belongs to the halo population. The spectroscopic analysis provides the atmospheric parameters [FORMULA] = 5250 K, [FORMULA] = 1.7 (cgs), [FORMULA] = 1.9 km s-1 corresponding to those for G2-5 (bright) giants. A low iron abundance, [Fe/H] = -2.45, is derived confirming the old, low mass nature of the star. With [C/Fe] = +1.4 and a mean s-process overabundance of [s/Fe] = +1.1 the peculiar atmospheric composition of HD 196944 is confirmed. Possible evolutionary stages of HD 196944, that can explain its atmospheric parameters and composition, are discussed.

Key words: stars: evolution – stars: abundances – stars: chemically peculiar – stars: AGB and post-AGB – stars: individual: HD 196944

* Based on observations carried out at the European Southern Observatory, La Silla, Chile

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© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998
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