A method for selecting M dwarfs with an increased likelihood of unresolved ultracool companionship
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Author
Cook, Neil
Pinfield, D.J.
Marocco, F.
Burningham, B.
Jones, H.R.A.
Frith, James
Zhong, J.
Luo, A.
Qi, Z.
Lucas, P.W.
Gromadzki, Mariusz
Day-Jones, Avril
Kurtev, Radostin
Guo, Y.
Wang, Y.
Bai, Y.
Yi, Z.
Smart, R.
Attention
2299/17133
Abstract
Locating ultracool companions to M dwarfs is important for constraining low-mass formation models, the measurement of substellar dynamical masses and radii, and for testing ultracool evolutionary models. We present an optimized method for identifying M dwarfs which may have unresolved ultracool companions. We construct a catalogue of 440 694 M dwarf candidates, from Wide-Field Infrared Survey Explorer, Two Micron All-Sky Survey and Sloan Digital Sky Survey, based on optical- and near-infrared colours and reduced proper motion. With strict reddening, photometric and quality constraints we isolate a subsample of 36 898 M dwarfs and search for possible mid-infrared M dwarf + ultracool dwarf candidates by comparing M dwarfs which have similar optical/near-infrared colours (chosen for their sensitivity to effective temperature and metallicity). We present 1082 M dwarf + ultracool dwarf candidates for follow-up. Using simulated ultracool dwarf companions to M dwarfs, we estimate that the occurrence of unresolved ultracool companions amongst our M dwarf + ultracool dwarf candidates should be at least four times the average for our full M dwarf catalogue. We discuss possible contamination and bias and predict yields of candidates based on our simulations.