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## The correlation between mixing length and metallicity on the giant branch: implications for ages in the Gaia era

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Jamie Tayar
Garrett Somers
• Function : Author
Marc H. Pinsonneault
• Function : Author
Dennis Stello
Alexey Mints
• Function : Author
Jennifer A. Johnson
• Function : Author
O. Zamora
• Function : Author
D.A. García-Hernandez
• Function : Author
Claudia Maraston
• Function : Author
Aldo Serenelli
• Function : Author
Carlos Allende Prieto
• Function : Author
Fabienne A. Bastien
• Function : Author
Sarbani Basu
• Function : Author
J.C. Bird
• Function : Author
R.E. Cohen
• Function : Author
Katia Cunha
• Function : Author
Yvonne Elsworth
• Function : Author
Leo Girardi
• Function : Author
John Holtzman
• Function : Author
Daniel Huber
Savita Mathur
• Function : Author
Szabolcs S Mészáros
• Function : Author
B. Mosser
• Function : Author
Matthew S Shetrone
• Function : Author
Victor Silva Aguirre
• Function : Author
Keivan Stassun
Guy S Stringfellow
• Function : Author
Gail Zasowski
• Function : Author
A. Roman-Lopes
Rafael A. Garcia
• Function : Author

#### Abstract

In the updated APOGEE-Kepler catalog, we have asteroseismic and spectroscopic data for over 3000 first ascent red giants. Given the size and accuracy of this sample, these data offer an unprecedented test of the accuracy of stellar models on the post-main-sequence. When we compare these data to theoretical predictions, we find a metallicity dependent temperature offset with a slope of around 100 K per dex in metallicity. We find that this effect is present in all model grids tested and that theoretical uncertainties in the models, correlated spectroscopic errors, and shifts in the asteroseismic mass scale are insufficient to explain this effect. Stellar models can be brought into agreement with the data if a metallicity dependent convective mixing length is used, with $\Delta_{\alpha_{ML,YREC}}$ ∼ 0.2 per dex in metallicity, a trend inconsistent with the predictions of three dimensional stellar convection simulations. If this effect is not taken into account, isochrone ages for red giants from the Gaia data will be off by as much as a factor of 2 even at modest deviations from solar metallicity ([Fe/H]=−0.5).

#### Domains

Sciences of the Universe [physics]

### Dates and versions

cea-01502408 , version 1 (05-04-2017)

### Identifiers

• HAL Id : cea-01502408 , version 1

### Cite

Jamie Tayar, Garrett Somers, Marc H. Pinsonneault, Dennis Stello, Alexey Mints, et al.. The correlation between mixing length and metallicity on the giant branch: implications for ages in the Gaia era. 2017. ⟨cea-01502408⟩

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