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Metal-Poor Lithium-Rich Giants in the RAVE Survey | | Gregory R. Ruchti
; Jon P. Fulbright
; Rosemary F. G. Wyse
; Gerard F. Gilmore
; Eva K. Grebel
; Olivier Bienayme
; Joss Bland-Hawthorn
; Ken C. Freeman
; Brad K. Gibson
; Ulisse Munari
; Julio F. Navarro
; Quentin A. Parker
; Warren Reid
; George M. Seabroke
; Arnaud Siebert
; Alessandro Siviero
; Matthias Steinmetz
; Fred G. Watson
; Mary Williams
; Tomaz Zwitter
; | | Date: |
7 Nov 2011 | | Abstract: | We report the discovery of eight lithium-rich field giants found in a high
resolution spectroscopic sample of over 700 metal-poor stars ([Fe/H]<-0.5)
selected from the RAVE survey. The majority of the Li-rich giants in our sample
are very metal-poor ([Fe/H]<-1.9), and have a Li abundance (in the form of
7Li), A(Li)=log(n(Li)/n(H))+12, between 2.30 and 3.63, well above the typical
upper red giant branch limit, A(Li)<0.5, while two stars, with A(Li)~1.7-1.8,
show similar lithium abundances to normal giants at the same gravity. We
further included two metal-poor, Li-rich globular cluster giants in our sample,
namely the previously discovered M3-IV101 and newly discovered (in this work)
M68-A96. This comprises the largest sample of metal-poor Li-rich giants to
date. We performed a detailed abundance analysis of all stars, finding that the
majority our sample stars have elemental abundances similar to that of
Li-normal halo giants. Although the evolutionary phase of each Li-rich giant
cannot be definitively determined, the Li-rich phase is likely connected to
extra mixing at the red giant branch bump or early asymptotic giant branch that
triggers cool bottom processing in which the bottom of the outer convective
envelope is connected to the H-burning shell in the star. The surface of a star
becomes Li-enhanced as 7Be (which burns to 7Li) is transported to the stellar
surface via the Cameron-Fowler mechanism. We discuss and discriminate among
several models for the extra mixing that can cause Li-production, given the
detailed abundances of the Li-rich giants in our sample. | | Source: | arXiv, 1111.1623 | | Services: | Forum | Review | PDF | Favorites | |
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