TY - JOUR
T1 - The correlation between mixing length and metallicity on the giant branch
T2 - implications for ages in the Gaia era
AU - Tayar, J.
AU - Somers, G.
AU - Pinsonneault, M.~H.
AU - Stello, D.
AU - Mints, A.
AU - Johnson, J.~A.
AU - Zamora, O.
AU - García-Hernández, D.~A.
AU - Maraston, C.
AU - Serenelli, A.
AU - Allende Prieto, C.
AU - Bastien, F.~A.
AU - Basu, S.
AU - Bird, J.~C.
AU - Cohen, R.~E.
AU - Cunha, K.
AU - Elsworth, Y.
AU - García, R.~A.
AU - Girardi, L.
AU - Hekker, S.
AU - Holtzman, J.
AU - Huber, D.
AU - Mathur, S.
AU - Mészáros, S.
AU - Mosser, B.
AU - Shetrone, M.
AU - Silva Aguirre, V.
AU - Stassun, K.
AU - Stringfellow, G.~S.
AU - Zasowski, G.
AU - Roman-Lopes, A.
PY - 2017/5/1
Y1 - 2017/5/1
N2 - 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 ∆αML,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).
AB - 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 ∆αML,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).
KW - Astrophysics - Solar and Stellar Astrophysics
KW - stars
KW - evolution – stars
KW - fundamental parameters
UR - https://arxiv.org/abs/1704.01164
U2 - 10.3847/1538-4357/aa6a1e
DO - 10.3847/1538-4357/aa6a1e
M3 - Article
SN - 0004-637X
VL - 840
JO - The Astrophysical Journal
JF - The Astrophysical Journal
IS - 1
M1 - 17
ER -