THE LOWEST MASS STARS IN THE HYADES

In Bryja et al., [ApJ, 388, L23 (1992)], we presented proper motions and photometry of 12 very low mass star and brown dwarf candidates in the Hyades cluster, selected on the basis of colors and proper motions measured from three epochs of plate material. We here present new observations of some of these candidates, including seven low resolution spectra, plus motions and photometry of 17 fainter additional candidates. Most of the candidates have JHK colors typical of M5-M8 dwarfs, while their optical colors are consistent with earlier M spectral types. The available spectra consist of late M dwarfs with Ha emission features indicative of Hyades membership, earlier M dwarf background stars, and two anomalous objects with early M dwarf features but unusually red continua. We find that the proper motion distribution of faint red field stars in the region is irregular, and it is not possible to determine if the anomalous objects are Hyades members or background field stars. In the most conservative view, only five of our 29 candidates are Hyads. These five stars have optical and infrared colors consistent with the bottom of the Hyades main sequence, with four of them also shown to have late M dwarf spectra. It follows that these are the lowest mass stars known in the Hyades (M approximately 0.1 M.).