Publication Date:
2016-06-17
Description:
We present the effective temperatures ( T eff ), metallicities, and colours in Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer filters, of a sample of 3834 late-K and early-M dwarfs selected from the SDSS Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectroscopic survey ASPCAP (APOGEE Stellar Parameters and Chemical Abundances Pipeline) catalogue. We confirm that ASPCAP T eff values between 3550 〈 T eff 〈 4200 K are accurate to ~100 K compared to interferometric T eff values. In that same T 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 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 W 1 – W 2 colour is a promising metallicity indicator. Comparison of the late-K and early-M dwarf colours, metallicities, and T 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 W 1 – W 2. 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 eff as a function of r – z colour combined with either [M/H] or W 1 – W 2 colour, and for [M/H] as a function of r – z and W 1 – W 2 colour. These relations yield T eff to ~100 K and [M/H] to ~0.18 dex precision with colours alone, for T eff in the range of 3550–4200 K and [M/H] in the range of –0.5–0.2.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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