Discovery of the widest very low mass field binary

Abstract

We present the discovery of the widest (6700 AU) very low mass (VLM) field binary to date, found in a proper motion cross-match of the Sloan Digital Sky Survey and the Two Micron All Sky Survey. Our follow-up J-band imaging provides a 10 year baseline for measuring proper motions. Consequently, we are able to confirm the common proper motion of the pair to within 10 mas, implying a 99.5% probability of their physical association. Near-infrared spectra of the components indicate spectral types of M6 1 and M7 1. The system resides at a spectroscopic distance of 105 13 pc and has an angular separation of 6338 005. We have used evolutionary models to infer component masses of 0.105 +0.029-0.017 M and 0.091+0.010-0.007 M. The large separation and low binding energy of this system can provide constraints for formation models of VLM stars. © 2009. The American Astronomical Society.