Spectroscopically confirmed brown dwarf members of Coma Berenices and the Hyades

We have obtained low- and medium-resolution spectra of nine brown dwarf candidate members of Coma Berenices and the Hyades using SpEX on the NASA InfraRed Telescope Facility and Long Slit Intermediate Resolution Infrared Spectrograph on the William Herschel Telescope. We conclude that seven 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 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 53MJup, close to the hydrogen-burning boundary for these clusters; however, only an optical detection of lithium can confirm if they are truly substellar.