SIMBAD references

The Hubble Space Telescope Faint Object Spectrograph has been used to acquire separate spectra of each of the component stars in the binaries Ross 614A,B (Gl 234A,B) and L722-22A,B (GJ 1005). Spectral types have been determined for each: M4.0 V, M5.5 V, M3.5 V, and M5.0 V, respectively, relative to a series of ground-based CCD spectra, in the 6500-8000 Å region. The four members of the two binaries form a narrow locus in the spectral type-mass plane, from 0.18 to 0.08 M_☉ and reaching 0.08 M_☉ near spectral type M6.0. Both binaries are believed to be members of a relatively young disk population. Their masses and newly determined spectra imply that the apparently single M dwarf stars, of a similar population and with spectral types of M6, are likely to be near, or less massive than, 0.08 M_☉. Presumably, dwarf M7, M8, and M9 stars of a similar age and population are in a declining mass sequence and thus should reach well below the theoretical main-sequence mass limit of 0.08 M_☉ and by current theory are substellar or ``brown dwarf'' objects.