2002ApJ...564L..27M

Doppler spectroscopy of ρ¹ Cnc has detected evidence of a companion with an orbital period of 14.65 days and a minimum mass of 0.88 Jupiter masses. Astrometric observations performed with the Hubble Space Telescope Fine Guidance Sensor 1r using a novel observing technique have placed an upper limit on the astrometric reflex motion of ρ¹ Cnc in a time period of only 1 month. These observations detected no reflex motion induced by the 14.65 day period radial velocity companion, allowing us to place a 3 σ upper limit of ∼0.3 mas on the semimajor axis of this motion, ruling out the preliminary Hipparcos value of 1.15 mas. The corresponding upper limit on the true mass of the companion is ∼30 M_J, confirming that it is a substellar object.