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### arXiv:2001.04962 [astro-ph.SR]AbstractReferencesReviewsResources

#### Temperatures and Metallicities of M dwarfs in the APOGEE Survey

Published 2020-01-14Version 1

M dwarfs have enormous potential for understanding structure and formation on both Galactic and exoplanetary scales through their properties and compositions. However, current atmosphere models have limited ability to reproduce spectral features in stars at the coolest temperatures ($T_{\rm eff} < 4200$K) and to fully exploit the information content of current and upcoming large-scale spectroscopic surveys. Here we present a catalog of spectroscopic temperatures, metallicities, and spectral types for 5,875 M dwarfs in the APOGEE + Gaia DR2 surveys using The Cannon: a flexible, data-driven spectral-modeling and parameter-inference framework demonstrated to estimate stellar-parameter labels ($T_{\rm eff}$, logg, [Fe/H], and detailed abundances) to high precision. Using a training sample of 87 M dwarfs with optically derived labels spanning $2860 < T_{\rm eff} < 4130$K calibrated with bolometric temperatures, and $-0.5 < [Fe/H] < 0.5$dex calibrated with FGK binary metallicities, we train a two-parameter model with predictive accuracy (in cross-validation) to 77K and 0.09dex respectively. We also train a one-dimensional spectral classification model using 51 M dwarfs with SDSS optical spectral types ranging from M0 to M6, to predictive accuracy of 0.7 types. We find Cannon temperatures to be in agreement to within 60K compared to a subsample of 1,702 sources with color-derived temperatures, and Cannon metallicites to be in agreement to within 0.08dex metallicity compared to a subsample of 15 FGK+M or M+M binaries. Finally, our comparison between Cannon and APOGEE pipeline (ASPCAP) labels finds that ASPCAP is systematically biased towards reporting higher temperatures and lower metallicities for M dwarfs.

Comments: 26 pages, 37 figures, ApJ under review
Categories: astro-ph.SR, astro-ph.GA
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