Stellar aspects of habitability--characterizing target stars for terrestrial planet-finding missions.
We present results of a reconnaissance for stellar companions to all 131 radialvelocity-detected candidate extrasolar planetary systems known as of July 1, 2005. Common proper motion companions were investigated using the multiepoch STScI Digitized Sky Surveys, and confirmed by matching the trigonometric parallax distances of the primaries to companion distances estimated photometrically. We also attempt to confirm or refute companions listed in the Washington Double Star Catalog, the Catalogs of Nearby Stars Series by Gliese and Jahreiß, in Hipparcos results, and in Duquennoy & Mayor (1991). Our findings indicate that a lower limit of 30 (23%) of the 131 exoplanet systems have stellar companions. We report new stellar companions to HD 38529 and HD 188015, and a new candidate companion to HD 169830. We confirm many previously reported stellar companions, including six stars in five systems, that are recognized for the first time as companions to exoplanet hosts. We have found evidence that 20 entries in the Washington Double Star Catalog