A method for selecting M dwarfs with an increased likelihood of unresolved ultracool companionship

April 2016 • 2016MNRAS.457.2192C

Authors • Cook, N. J. • Pinfield, D. J. • Marocco, F. • Burningham, B. • Jones, H. R. A. • Frith, J. • Zhong, J. • Luo, A. L. • Qi, Z. X. • Lucas, P. W. • Gromadzki, M. • Day-Jones, A. C. • Kurtev, R. G. • Guo, Y. X. • Wang, Y. F. • Bai, Y. • Yi, Z. P. • Smart, R. L.

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.


IPAC Authors

Federico Marocco

Assistant Scientist