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