# Lithium Depletion in Solar-like Stars: Effect of Overshooting Based on Realistic Multi-dimensional Simulations

## 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 ofmore »

- Authors:

- Astrophysics Group, University of Exeter, Exeter EX4 4QL (United Kingdom)
- Ecole Normale Supérieure de Lyon, CRAL, UMR CNRS 5574, F-69364 Lyon Cedex 07 (France)

- Publication Date:

- OSTI Identifier:
- 22654414

- Resource Type:
- Journal Article

- Journal Name:
- Astrophysical Journal Letters

- Additional Journal Information:
- Journal Volume: 845; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CONVECTION; DIFFUSION; EFFICIENCY; HYDRODYNAMICS; LITHIUM; ONE-DIMENSIONAL CALCULATIONS; ROTATION; SIMULATION; STAR EVOLUTION; SURFACES; TIME DEPENDENCE

### Citation Formats

```
Baraffe, I., Pratt, J., Goffrey, T., Constantino, T., Viallet, M., Folini, D., Popov, M. V., and Walder, R., E-mail: i.baraffe@ex.ac.uk.
```*Lithium Depletion in Solar-like Stars: Effect of Overshooting Based on Realistic Multi-dimensional Simulations*. United States: N. p., 2017.
Web. doi:10.3847/2041-8213/AA82FF.

```
Baraffe, I., Pratt, J., Goffrey, T., Constantino, T., Viallet, M., Folini, D., Popov, M. V., & Walder, R., E-mail: i.baraffe@ex.ac.uk.
```*Lithium Depletion in Solar-like Stars: Effect of Overshooting Based on Realistic Multi-dimensional Simulations*. United States. doi:10.3847/2041-8213/AA82FF.

```
Baraffe, I., Pratt, J., Goffrey, T., Constantino, T., Viallet, M., Folini, D., Popov, M. V., and Walder, R., E-mail: i.baraffe@ex.ac.uk. Thu .
"Lithium Depletion in Solar-like Stars: Effect of Overshooting Based on Realistic Multi-dimensional Simulations". United States. doi:10.3847/2041-8213/AA82FF.
```

```
@article{osti_22654414,
```

title = {Lithium Depletion in Solar-like Stars: Effect of Overshooting Based on Realistic Multi-dimensional Simulations},

author = {Baraffe, I. and Pratt, J. and Goffrey, T. and Constantino, T. and Viallet, M. and Folini, D. and Popov, M. V. and Walder, R., E-mail: i.baraffe@ex.ac.uk},

abstractNote = {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.},

doi = {10.3847/2041-8213/AA82FF},

journal = {Astrophysical Journal Letters},

issn = {2041-8205},

number = 1,

volume = 845,

place = {United States},

year = {2017},

month = {8}

}