A&A 434, 1117-1124 (2005)
DOI: 10.1051/0004-6361:20042082

Analysis of the carbon-rich very metal-poor dwarf G77-61

B. Plez¹ and J. G. Cohen<sup>2

1</sup>  GRAAL, CNRS UMR 5024, Université Montpellier II, 34095 Montpellier Cedex 5, France
    e-mail: plez@graal.univ-montp2.fr
²  Palomar Observatory, Mail Stop 105-24, California Institute of Technology, Pasadena, Ca 91125, USA

(Received 28 September 2004 / Accepted 5 January 2005)

Abstract
We present an analysis of the carbon dwarf G77-61, a known binary, based on high resolution Keck spectra. G77-61 has a very-low metallicity, although not as extreme as what was previously conjectured. This star is very carbon-enhanced, the spectra showing very strong CH, CN, and C₂ bands of both ¹³C and ¹²C isotopes. Atomic lines are sparse, and often blended, but we were able to derive abundances for Na, Mg, Ca, Cr, Mn, and Fe. Its [Fe/H] of -4.03  0.1 places it among the lowest metallicity stars known, and its very high [C/Fe] = +2.6 , and [N/Fe] = +2.6 among the most C and N-rich metal-poor stars. The carbon isotopic ratio is ¹²C/¹³C = 5  1. No overabundance of s- or r-process elements is detectable, but the upper limits that can be set on these overabundances are not very constraining.

Key words: stars: abundances -- stars: carbon -- stars: Population II -- stars: individual: G77-61

SIMBAD Objects

© ESO 2005