A Candidate Substellar Companion to CD −33°7795 (TWA 5)

We present the discovery of a candidate substellar object in a survey of young stars in the solar vicinity using the sensitivity and spatial resolution afforded by the NICMOS coronagraph on the Hubble Space Telescope . The H = 12.1 mag object was discovered approximately 2'' from the TW Hydrae association member CD -33°7795 (TWA 5), and the photometry implies a spectral type M8-M8.5, with a temperature of ~2600 K. We estimate that the probability of a chance alignment with a background object of this nature is less than 2 × 10 -5 and therefore postulate that the object (TWA 5B) is physically associated at a projected separation of 100 AU. Given the likely youth of the primary (~10 Myr), current brown dwarf cooling models predict a mass of ≈20 M Jup for TWA 5B.