Baraffe, I., Pratt, J., Goffrey, Thomas, Constantino, T., Folini, D., Popov, M. V., Walder, R. and Viallet, M. (2017) Lithium depletion in solar-like stars : effect of overshooting based on realistic multi-dimensional simulations. Astrophysical Journal, 845 (1). L6. doi:10.3847/2041-8213/aa82ff ISSN 0004-637X.

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Abstract

We study lithium depletion in low-mass and solar-like stars as a function of time, using a new diffusion coefficient describing extra-mixing taking place at the bottom of a convective envelope. This new form is motivated by multi-dimensional fully compressible, time-implicit hydrodynamic simulations performed with the MUSIC code. Intermittent convective mixing at the convective boundary in a star can be modeled using extreme value theory, a statistical analysis frequently used for finance, meteorology, and environmental science. In this Letter, we implement this statistical diffusion coefficient in a one-dimensional stellar evolution code, using parameters calibrated from multi-dimensional hydrodynamic simulations of a young low-mass star. We propose a new scenario that can explain observations of the surface abundance of lithium in the Sun and in clusters covering a wide range of ages, from ~50 Myr to ~4 Gyr. Because it relies on our physical model of convective penetration, this scenario has a limited number of assumptions. It can explain the observed trend between rotation and depletion, based on a single additional assumption, namely, that rotation affects the mixing efficiency at the convective boundary. We suggest the existence of a threshold in stellar rotation rate above which rotation strongly prevents the vertical penetration of plumes and below which rotation has small effects. In addition to providing a possible explanation for the long-standing problem of lithium depletion in pre-main-sequence and main-sequence stars, the strength of our scenario is that its basic assumptions can be tested by future hydrodynamic simulations.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Journal or Publication Title:	Astrophysical Journal
Publisher:	IOP Publishing
ISSN:	0004-637X
Official Date:	9 August 2017
Dates:	Date Event 9 August 2017 Available 29 July 2017 Valid 26 July 2017 Accepted 7 July 2017 Submitted
Volume:	845
Number:	1
Page Range:	L6
DOI:	10.3847/2041-8213/aa82ff
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Open Access Version:	Other ArXiv

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