Spectroscopically confirmed brown dwarf members of Coma Berenices and the Hyades

Abstract

We have obtained low and medium resolution spectra of 9 brown dwarf candidate members of Coma Berenices and the Hyades using SpEX on the NASA InfaRed Telescope Facility and LIRIS on the William Herschel Telescope. We conclude that 7 of these objects are indeed late M or early L dwarfs, and that two are likely members of Coma Berenices, and four of the Hyades. Two objects, cbd40 and Hy3 are suggested to be a field L dwarfs, although there is also a possibility that Hy3 is an unresolved binary belonging to the cluster. These objects have masses between 71 and 53 M$_{\rm Jup}$, close to the hydrogen burning boundary for these clusters, however only an optical detection of Lithium can confirm if they are truly substellar.