A Test of Pre-Main-Sequence Lithium Depletion Models - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate

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Abstract: Despite the extensive study of lithium depletion during pre-main-sequencecontraction, studies of individual stars show discrepancies between agesdetermined from the HR diagram and ages determined from lithium depletion Songet al. 2002, White and Hillenbrand 2005 indicating open questions in thepre-main-sequence evolutionary models. To further test these models, we presenthigh resolution spectra for members of the Beta Pictoris Moving Group BPMG,which is young and nearby. We measure equivalent widths of the 6707.8 AngstromLi I line in these stars and use them to determine lithium abundances. Wecombine the lithium abundance with the predictions of pre-main-sequenceevolutionary models in order to calculate a lithium depletion age for eachstar. We compare this age to the age predicted by the HR diagram of the samemodel. We find that the evolutionary models under-predict the amount of lithiumdepletion for the BPMG given its nominal HR diagram age of ~12 Myr Zuckermanet al. 2001, particularly for the mid-M stars, which have no observable Li Iline. This results in systematically older ages calculated from lithiumdepletion isochrones than from the HR diagram. We suggest that this discrepancymay be related to the discrepancy between measured M-dwarf radii and thesmaller radii predicted by evolutionary models.

Author: Jennifer C. Yee Ohio State University, Eric L. N. Jensen Swarthmore College

Source: https://arxiv.org/

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