Linking Lithium and Cheetos

DispersionIn Lithium

Lithium destroyed (2.5 MK) during PMS - probe of stellar interior

Lithium abundance dispersion at fixed mass, composition and age (IC2602, alpha Per, Pleiades)- why?

- not predicted by standard stellar models

- flaw in understanding of stellar structure/evolution

Li and K resonance line formation is similar

Scatter in Li eqw mirrored by K eqw scatter?

- K is not easily depleted

- Li scatter not depletion related - temperatures or line formation effects (i.e.

spots)?

•Updated Data shows no K scatter

•Lithium scatter still significant

•Not line-formation

effects

Analytic spot models - can reproduce Li EQW scatter w/o K EQW

scatter (80 % coverage)

2 Spectroscopic signatures discount analytic spot models:

- Li 6104 and 6707 syntheses differences

- CN too strong in spot models

A(Li) A(Li) Diff

HII250 3.09 3.03 0.06

HII263 2.96 2.97 -0.01

HII916 2.52 2.60 -0.08

Spot Model 3.32 2.90 0.423.62 3.02 0.60

CN Discounts Spot Models Dotted: Analytic Spot

Model with T=5225 K Solid: Synthetic

Spectrum with T=5225 K Spot CN 3-5 times

stronger than non-spot Non-spot CN strengths

consistent with observations

Real abundance dispersion

Signature of variable PMS depletion from radius differences?

M-dwarfs, rapid rotators and active stars are “puffy”- Spots inhibit convective energy transport,

and star puffs up - rapid rotating, active stars deplete less Li

Same mass stars have different PMS Li depletion

10 % Radius Increase= factor of 2.5 increase in surface lithium

Qualitatively consistent with Yee and Jensen

2010

- suggest a 10-20% radius increase can resolve Li depletion ages with HR diagram model ages

•Variable spot coverage can make stars of same mass, age and composition “puffy”

•“Puffy” stars deplete less lithium in the PMS

•Eventually stars settle down and lose “puffyness”

•Retain signature of PMS “puffyness” resulting in real Lithium abundance dispersions for stars of single mass, age and composition