The Hobby-Eberly Telescope Chemical Abundances of Stars in the Halo CASH Project II. The Li-, r- and s-Enhanced Metal-Poor Giant ligiant
Abstract
We present the first detailed abundance analysis of the metal-poor giant ligiant. This star was observed as part of the University of Texas Long-Term Chemical Abundances of Stars in the Halo (CASH) Project. We find that this metal-poor ([Fe/H] =-2.2) star has an unusually high lithium abundance (log ɛ (Li)= +2.1), mild carbon ([C/Fe] =+0.7) and sodium ([Na/Fe] =+0.6) enhancement, as well as enhancement of both spro ([Ba/Fe] =+0.8) and rpro ([Eu/Fe] =+0.5) material. The high Li abundance can be explained by self-enrichment through extra mixing mechanisms. If so, ligiant is the most metal-poor star in which this short-lived phase of Li enrichment has been observed. The r- and spro material was not produced in this star but was either present in the gas from which ligiant formed or was transferred to it from a more massive binary companion. Despite the current non-detection of radial velocity variations (over a time span of ∼180 days), it is possible that ligiant is in a long-period binary system, similar to other stars with both r and s enrichment.
- Publication:
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New Horizons in Astronomy
- Pub Date:
- August 2008
- Bibcode:
- 2008ASPC..393..207F