Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...21113112s&link_type=abstract
American Astronomical Society, AAS Meeting #211, #131.12; Bulletin of the American Astronomical Society, Vol. 39, p.961
Astronomy and Astrophysics
Astrophysics
Scientific paper
Stars significantly deficient in metals relative to the Sun are presumed to be remnants of the earliest stellar populations and represent the oldest stars in the Galaxy. It is estimated that 14 - 25% of metal-poor stars with metallicities of [Fe/H] < -2.0 are enhanced in carbon ([C/Fe] > 1.0), and studies suggest that the percentage of these Carbon-Enhanced Metal-Poor (CEMP) stars increases with decreasing metallicity, reaching 40% of stars with [Fe/H] < -3.5 and 100% of stars with [Fe/H] < -4.0. Thus, determining the origin of the carbon and other metals in CEMP stars is clearly important to our understanding of the chemical evolution of the early Galaxy. To this end, we present the results of our analysis of 19F in the CEMP star HE 1305+0132. Asymptotic giant branch (AGB) stars and massive, rapidly-rotating metal-poor stars are the predicted sources of the enhanced carbon in CEMP stars, and recent theoretical models predict that the 19F production of these two sites differs by about four orders of magnitude, with AGB stars being the more prodigious producers. Using spectral synthesis we derive for HE 1305+0132 a super-solar 19F abundance of A(19F) = 4.96 ± 0.21, corresponding to a relative abundance of [F/Fe] = +2.90. This result suggests that the atmosphere of HE 1305+0132 has been polluted via mass transfer by a companion AGB star and that AGB star nucleosynthesis is highly efficient at low metallicities.
Support for S.C.S. has been provided by the NOAO Leo Goldberg Fellowship; NOAO is operated by AURA, Inc., under a cooperative agreement with the NSF. K.C. and V.V.S. acknowledge support from the NSF under grant AST 06-46790. T.S., T.C.B., and Y.S.L. acknowledge partial support from the NSF under grants AST 04-06784, AST 07-07776, and PHY 02-16783; Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA).
Beers Timothy C.
Cunha Katia
Lee Yeonbae
Schuler Simon C.
Sivarani Thirupathi
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