Precise Masses for Wolf 1062 AB from [ITAL]HUBBLE SPACE TELESCOPE[/ITAL][ITAL]Hubble Space Telescope[/ITAL] Interferometric Astrometry and M[CLC]c[/CLC]Donald Observatory Radial Velocities

We present an analysis of astrometric data from FGS 3, a white-light interferometer on {it HST}, and of radial velocity data from two ground-based campaigns. We model the astrometric and radial velocity measurements simultaneously to obtain parallax, proper motion and component masses for Wolf 1062 = Gl 748 AB (M3.5V). To derive the mass fraction, we relate FGS 3 fringe scanning observations of the science target to a reference frame provided by fringe tracking observations of a surrounding star field. We obtain an absolute parallax $pi_{abs} = 98.0 pm 0.4$ milliseconds of arc, yielding ${cal M}_A = 0.379 pm 0.005{cal M}_{sun}$ and ${cal M}_B= 0.192 pm 0.003 {cal M}_{sun}$, high quality component masses with errors of only 1.5%.Comment: 13 pages, 7 figures. To appear in AJ March 200