2000AJ....120.1106B

With fourteen epochs of fringe-tracking data spanning 1.7 yr from Fine Guidance Sensor 3 we have obtained a parallax (π_abs=113.1±0.3 mas) and perturbation orbit for Gl 791.2A. Contemporaneous fringe-scanning observations yield only three clear detections of the secondary on both interferometer axes. They provide a mean component magnitude difference, ΔV=3.27±0.10. The period (P=1.4731 yr), from the perturbation orbit, and the semimajor axis (a=0.963±0.007 AU), from the measured component separations with our parallax, provide a total system mass M_A+M_B=0.412±0.009 M_☉. Component masses are M_A=0.286±0.006 M_☉ and M_B=0.126±0.003 M_☉. Gl 791.2A and Gl 791.2B are placed in a sparsely populated region of the lower main-sequence mass-luminosity relation where they help define the relation because the masses have been determined to high accuracy, with errors of only 2%.