CS22964-161: A Double-Lined Carbon- and s-Process-Enhanced Metal-Poor Binary Star

Abstract

A detailed high-resolution spectroscopic analysis is presented for the carbon-rich low metallicity Galactic halo object CS 22964-161. We have discovered that CS 22964-161 is a double-lined spectroscopic binary, and have derived accurate orbital components for the system. From a model atmosphere analysis we show that both components are near the metal-poor main-sequence turnoff. Both stars are very enriched in carbon and in neutron-capture elements that can be created in the s-process, including lead. The primary star also possesses an abundance of lithium close to the value of the ``Spite-Plateau''. The simplest interpretation is that the binary members seen today were the recipients of these anomalous abundances from a third star that was losing mass as part of its AGB evolution. We compare the observed CS 22964-161 abundance set with nucleosynthesis predictions of AGB stars, and discuss issues of envelope stability in the observed stars under mass transfer conditions, and consider the dynamical stability of the alleged original triple star. Finally, we consider the circumstances that permit survival of lithium, whatever its origin, in the spectrum of this extraordinary system.

manuscript, 7 tables, 13 figures. ApJ, in press

References in corpus (6)

• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• Evolution of asymptotic giant branch stars I. Updated synthetic TP-AGB models and their basic calibration
• First stars VII. Lithium in extremely metal poor dwarfs
• The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
• Carbon Stars in the Hamburg/ESO Survey: Abundances
• First stars X. The nature of three unevolved Carbon-Enhanced Metal-Poor stars

Cited by in corpus (9)

• Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample
• Thermohaline mixing and gravitational settling in carbon-enhanced metal-poor stars
• Elemental abundances and classification of CEMP stars
• Lithium abundances in CEMP stars
• The Hobby-Eberly Telescope "Chemical Abundances of Stars in the Halo" (CASH) Project. I. The Lithium-, s-, and r-Enhanced Metal-Poor Giant HKII 17435-00532
• Fluorine in carbon-enhanced metal-poor stars: a binary scenario
• Light element abundances in carbon-enhanced metal-poor stars
• Abundances of neutron-capture elements in G 24-25. A halo-population CH subgiant
• The Clusters AgeS Experiment (CASE). III. Analysis of the Eccentric Eclipsing Binary V32 in the Globular Cluster NGC 6397