Retired A Stars and Their Companions. II. Jovian planets orbiting κ CrB and HD 167042

Abstract

We report precise Doppler measurements of two stars, obtained at Lick Observatory as part of our search for planets orbiting intermediate-mass subgiants. Periodic variations in the radial velocities of both stars reveal the presence of substellar orbital companions. These two stars are notably massive with stellar masses of 1.80 and 1.64 Msolar, respectively, indicating that they are former A-type dwarfs that have evolved off of the main sequence and are now K-type subgiants. The planet orbiting κ CrB has a minimum mass MPsini=1.8 MJup, eccentricity e=0.146 and a 1208 day period, corresponding to a semimajor axis a=2.7 AU. The planet around HD 167042 has a minimum mass MPsini=1.7 MJup and a 412.6 day orbit, corresponding to a semimajor axis a=1.3 AU. The eccentricity of HD 167042b is consistent with circular (e=0.027+/-0.04), adding to the rare class of known exoplanets in long-period, circular orbits similar to the solar system gas giants. Like all of the planets previously discovered around evolved A stars, κ CrBb and HD 167042b orbit beyond 0.8 AU. Based on observations obtained at the Lick Observatory, which is operated by the University of California.