$^7$Li Abundances in Halo Stars: Testing Stellar Evolution Models and the Primordial $^7$Li Abundance

Brian Chaboyer; P. Demarque

doi:10.1086/174662

paper

$^{7}$ Li Abundances in Halo Stars: Testing Stellar Evolution Models and the Primordial $^{7}$ Li Abundance

arXiv:astro-ph/9403043 · doi:10.1086/174662

Abstract

A large number of stellar evolution models with [Fe/H] = -2.3 and -3.3 have been calculated in order to determine the primordial $^{7}$ Li abundance and to test current stellar evolution models by a comparison to the extensive database of Li abundances in extremely metal poor halo stars observed by Thorburn (1994). Standard models do a good job of fitting the observed Li abundances in stars hotter than 5600 K. They predict a primordial $^{7}$ Li abundance of Log N(Li) = 2.24\pm 0.03 $. M o d e l s w hi c hin c l u d e mi cr osco p i c d i f f u s i o n p r e d i c t a d o w n w a r d c u r v a t u r e in t h e$ ^7 $L i d es t r u c t i o ni soc h r o n es a t h o tt e m p er a t u r es w hi c hi s n o tp r ese n t in t h eo b ser v a t i o n s . T h u s, t h eo b ser v a t i o n sc l e a r l y r u l eo u t m o d e l s w hi c hin c l u d e u ninhibi t e d mi cr osco p i c d i f f u s i o n o f$ ^7 $L i f r o m t h es u r f a ceo f t h es t a r . T h e [F e / H] = - 2.3 s t e l l a r m o d e l s w hi c hin c l u d e b o t h d i f f u s i o nan d r o t a t i o na l mi x in g p r o v i d e an e x ce l l e n t ma t c h t o t h eo b ser v a t i o n s . B o t h t h e pl a t e a u s t a r s an d t h e h e a v i l y d e pl e t e d coo l s t a r s a r e w e l l f i t b y t h ese m o d e l s . T h er o t a t i o na l mi x in g l e a d s t oco n s i d er ab l e$ ^7 $L i d e pl e t i o nin t h ese m o d e l s an d t h e p r im or d ia l$ ^7 $L iab u n d an ce in f er r e df r o m t h ese m o d e l s i s L o g N (L i) =$ 3.08\pm 0.1$.

27 pages, AAS LaTeX, complete postscript file (with figures) available via anonymous ftp from: ftp.cita.utoronto.ca in /cita/brian/papers/pop2.ps

7Li Abundances in Halo Stars: Testing Stellar Evolution Models and the Primordial 7Li Abundance

Abstract

$^{7}$ Li Abundances in Halo Stars: Testing Stellar Evolution Models and the Primordial $^{7}$ Li Abundance