{
  "id": "1605.03732",
  "version": "v1",
  "published": "2016-05-12T09:00:01.000Z",
  "updated": "2016-05-12T09:00:01.000Z",
  "title": "Examining the relationships between colour, $T_{\\rm eff}$, and [M/H] for APOGEE K and M dwarfs",
  "authors": [
    "Sarah J. Schmidt",
    "Erika L. Wagoner",
    "Jennifer A. Johnson",
    "James R. A. Davenport",
    "Keivan G. Stassun",
    "Diogo Souto",
    "Jian Ge"
  ],
  "comment": "14 pages, 6 tables, 5 figures, accepted for publication in MNRAS",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "We present the effective temperatures ($T_{\\rm eff}$), metallicities, and colours in SDSS, 2MASS, and WISE filters, of a sample of 3834 late-K and early-M dwarfs selected from the Sloan Digital Sky Survey APOGEE spectroscopic survey ASPCAP catalog. We confirm that ASPCAP $T_{\\rm eff}$ values between 3550 K$<T_{\\rm eff}<$4200 K are accurate to $\\sim$100 K compared to interferometric $T_{\\rm eff}$ values. In that same $T_{\\rm eff}$ range, ASPCAP metallicities are accurate to 0.18 dex between $-1.0<$[M/H]$<0.2$. For these cool dwarfs, nearly every colour is sensitive to both $T_{\\rm eff}$ and metallicity. Notably, we find that $g-r$ is not a good indicator of metallicity for near-solar metallicity early-M dwarfs. We confirm that $J-K_S$ colour is strongly dependent on metallicity, and find that $W1-W2$ colour is a promising metallicity indicator. Comparison of the late-K and early-M dwarf colours, metallicities, and $T_{\\rm eff}$ to those from three different model grids shows reasonable agreement in $r-z$ and $J-K_S$ colours, but poor agreement in $u-g$, $g-r$, and $W1-W2$. Comparison of the metallicities of the KM dwarf sample to those from previous colour-metallicity relations reveals a lack of consensus in photometric metallicity indicators for late-K and early-M dwarfs. We also present empirical relations for $T_{\\rm eff}$ as a function of $r-z$ colour combined with either [M/H] or $W1-W2$ colour, and for [M/H] as a function of $r-z$ and $W1-W2$ colour. These relations yield $T_{\\rm eff}$ to $\\sim$100 K and [M/H] to $\\sim$0.18 dex precision with colours alone, for $T_{\\rm eff}$ in the range of 3550-4200 K and [M/H] in the range of $-$0.5-0.2.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-05-12T09:00:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "metallicity",
      "apogee spectroscopic survey aspcap",
      "spectroscopic survey aspcap catalog",
      "sky survey apogee spectroscopic",
      "early-m dwarf"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}