HIPPARCOS distances and mass limits for the planetary candidates: 47 Ursae Majoris, 70 Virginis, and 51 Pegasi

Distances to the recently-discovered planetary system candidates, 47 UMa, 70 Vir and 51 Peg, are presented, based on absolute trigonometric parallaxes from the global reduction of the ESA Hipparcos astrometry satellite data. Standard errors of the parallaxes are in the range 0.66-0.76mas (milliarcsec), with resulting distances accurate to around 1 percent. For 70 Vir, the Hipparcos parallax (55.22+/-0.73mas) resolves a discrepancy of almost a factor of three in published trigonometric and photometric parallaxes. The residuals of the astrometric parameters are used in combination with the radial velocity data for these orbital systems to place upper limits on the companion masses of between 7-22 and 38-65 Jupiter masses (M_J_) for 47 UMa and 70 Vir respectively, with less stringent limits for 51 Peg. The Hipparcos data therefore provide confirmation of the existence of sub-stellar masses significantly below the brown dwarf limit (of about 0.08M_sun_) surrounding other stars.