Bibcode
Roederer, Ian U.; Frebel, Anna; Shetrone, Matthew; Allende Prieto, Carlos; Rhee, Jaehyon; Gallino, Roberto; Bisterzo, Sara; Sneden, Christopher; Beers, Timothy C.; Cowan, John J.
Referencia bibliográfica
IXTH TORINO WORKSHOP ON EVOLUTION AND NUCLEOSYNTHESIS IN AGB STARS AND THE IIND PERUGIA WORKSHOP ON NUCLEAR ASTROPHYSICS. AIP Conference Proceedings, Volume 1001, pp. 169-176 (2008).
Fecha de publicación:
4
2008
Número de citas
0
Número de citas referidas
0
Descripción
We present the first detailed abundance analysis of the metal-poor giant
HK-II 17435-00532. This star was observed as part of the University of
Texas Long-Term Chemical Abundances of Stars in the Halo (CASH) Project.
A spectrum was obtained with the High Resolution Spectrograph (HRS) on
the Hobby-Eberly Telescope with a resolving power of R~15000. Our
analysis reveals that this star may be located on the red giant branch,
red horizontal branch, or early asymptotic giant branch. We find that
this metal-poor ([Fe/H] = -2.2) star has an unusually high lithium
abundance (logɛ(Li) = +2.1), mild carbon ([C/Fe] = +0.7) and
sodium ([Na/Fe] = +0.6) enhancement, as well as enhancement of both
s-process ([Ba/Fe] = +0.8) and r-process ([Eu/Fe] = +0.5) material. The
high Li abundance can be explained by self-enrichment through extra
mixing mechanisms that connect the convective envelope with the outer
regions of the H-burning shell. If so, HK-II 17435-00532 is the most
metal-poor starin which this short-lived phase of Li enrichment has been
observed. The r- and s-process material was not produced in this star
but was either present in the gas from which HK-II 17435-00532 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 HK-II 17435-00532 is in a long-period
binary system, similar to other stars with both r and s enrichment.