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Lithium in the Upper Centaurus Lupus and Lower Centaurus Crux Subgroups of Scorpius-Centaurus

Bubar, Eric J. and Schaeuble, Marc and King, Jeremy R. and Mamajek, Eric E. and Stauffer, John R. (2011) Lithium in the Upper Centaurus Lupus and Lower Centaurus Crux Subgroups of Scorpius-Centaurus. Astronomical Journal, 142 (6). Art. No. 180. ISSN 0004-6256. https://resolver.caltech.edu/CaltechAUTHORS:20111219-115722279

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Abstract

We utilize spectroscopically derived model atmosphere parameters and the Li I λ6104 subordinate line and the λ6708 doublet to derive lithium abundances for 12 members of the Upper Centaurus Lupus and Lower Centaurus Crux subgroups of the Scorpius-Centaurus OB Association. The results indicate any intrinsic Li scatter in our 0.9-1.4 M_☉ stars is limited to ~0.15 dex, consistent with the lack of dispersion in ≥1.0 M_☉ stars in the 100 Myr Pleiades and 30-50 Myr IC 2391 and 2602 clusters. Both ab initio uncertainty estimates and the derived abundances themselves indicate that the λ6104 line yields abundances with equivalent or less scatter than is found from the λ6708 doublet as a result of lower uncertainties for the subordinate feature, a result of low sensitivity to broadening in the subordinate feature. Because non-local thermodynamic equilibrium (NLTE) corrections are less susceptible to changes in surface gravity and/or metallicity for the 6104 Å line, the subordinate Li feature is preferred for deriving lithium abundances in young Li-rich stellar association stars with T_(eff) ≥ 5200 K. At these temperatures, we find no difference between the Li abundances derived from the two Li I lines. For cooler stars, having temperatures at which main-sequence dwarfs show abundance patterns indicating overexcitation and overionization, the λ6104-based Li abundances are ~0.4 dex lower than those derived from the λ6708 doublet. The trends of the abundances from each feature with T eff suggest that this difference is due to (near)UV photoionization, which in NLTE preferentially ionizes Li atoms in the subordinate 2p state relative to the 2s resonance line state due to opacity effects. Consequently, this overionization of Li in the 2p state, apparently not adequately accounted for in NLTE corrections, weakens the λ6104 feature in cooler stars. Accordingly, the λ6708-based abundances may give more reliable estimates of the mean Li abundance in cool young stars. Our mean Li abundance, log N(Li) =3.50 ± 0.07 is ~0.2 dex larger than the meteoritic value. While stellar models suggest that Li depletion of at least 0.4 dex, and possibly much larger, should have occurred in our lowest mass star(s), our Li abundances show no decline with decreasing mass indicative of such depletion.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-6256/142/6/180 DOIArticle
http://iopscience.iop.org/1538-3881/142/6/180/PublisherArticle
ORCID:
AuthorORCID
Stauffer, John R.0000-0003-3595-7382
Additional Information:© 2011 The American Astronomical Society. Received 2011 July 31; accepted 2011 September 14; published 2011 October 20. E.J.B. and E.E.M. acknowledge support from NSF grant AST 10-08908 to E.E.M. and the University of Rochester School of Arts and Sciences. M.S. and J.R.K. gratefully acknowledge support for this work from NSF grant AST 09-08342 to J.R.K. We also acknowledge the referee whose comments helped to clarify the work.
Funders:
Funding AgencyGrant Number
NSFAST 10-08908
University of RochesterUNSPECIFIED
NSFAST 09-08342
Subject Keywords:stars: abundances; stars: late-type
Issue or Number:6
Record Number:CaltechAUTHORS:20111219-115722279
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20111219-115722279
Official Citation: Lithium in the Upper Centaurus Lupus and Lower Centaurus Crux Subgroups of Scorpius–Centaurus Eric J. Bubar et al. 2011 The Astronomical Journal 142 180
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28519
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:20 Dec 2011 17:05
Last Modified:03 Oct 2019 03:33

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