Ronald E. Cohen

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

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

Target Selection for the SDSS-IV APOGEE-2 Survey

Delta_{alpha_{ML,YREC}}

The APOGEE-2 survey: \textit{H}-band discovery of additional Second-Generation stars in the Galactic Bulge Globular Cluster NGC 6522.

∼ 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).

H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522

Barry M. Lasker Data Science Research Fellowship - Space Telescope Science Institute in Baltimore, MD, USA; Gemini-CONICYT [32140007]; National Science Foundation (NSF) [AST-1517592]; NSF [AST-1311835, AST-1715662]; Ramon y Cajal fellowship [RYC-2013-14182]; Spanish Ministry of Economy and Competitiveness (MINECO) [AYA-2014-58082-P]; Premium Postdoctoral Research Program of the Hungarian Academy of Sciences; Hungarian NKFI grants of the Hungarian National Research, Development and Innovation Office [K-119517]; Alfred P. Sloan Foundation; U.S. Department of Energy Office of Science; Center for High-Performance Computing at the University of Utah; Brazilian Participation Group; Carnegie Institution for Science; Carnegie Mellon University; Chilean Participation Group; French Participation Group; Harvard-Smithsonian Center for Astrophysics; Instituto de Astroisica de Canarias; Johns Hopkins University; Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo; Lawrence Berkeley National Laboratory; Leibniz Institut fur Astrophysik Potsdam (AIP); Max-Planck-Institut fur Astronomie (MPIA Heidelberg); Max-Planck-Institut fur Astrophysik (MPA Garching); Max-Planck-Institut fur Extraterrestrische Physik (MPE); National Astronomical Observatory of China; New Mexico State University; New York University; University of Notre Dame; Observatorio Nacional/MCTI; Ohio State University; Pennsylvania State University; Shanghai Astronomical Observatory; United Kingdom Participation Group; Universidad Nacional Autonoma de Mexico; University of Arizona; University of Colorado Boulder; University of Oxford; University of Portsmouth; University of Utah; University of Virginia; University of Washington; University of Wisconsin; Vanderbilt University; Yale University; National Aeronautics and Space Administration; National Science Foundation