1998PASP..110...31S

The low mass binary system \w424 (GJ∼473∼AB) was spatially resolved in an image obtained on 1996 April 16 with the imaging mode of the HST Faint Object Spectrograph. The separation was measured to be 0\farcs 42~±0\farcs 03 at a position angle of 353\degpoint 2~±2\degpoint 5. The new measurement was combined with previously published orbital positions to update the orbital elements and obtain an estimate of the total mass. Spectroscopy and photometry of these objects suggest they are nearly equal in mass. The derived orbital solution, using all of the observations since 1938 appropriately weighted, yields a total mass of m_{1}+m{2} of 0.143∼M\subsun, and component masses of ∼0.07∼M\subsun, just under the theoretical limit for a brown dwarf. An alternate orbital solution derived solely from speckle observations since 1986 and the FOS image yields a total mass of 0.232∼M\subsun, placing both components well above the brown dwarf limit. The mass depends on the value for the semi-major axis, which is controlled in the latter solution by an optical speckle observation made near the last period of maximum separation. Further high-resolution observations during the upcoming maximum separation, and through the next secondary maximum, are needed to constrain the orbit.(c) Astronomical Society of the Pacific