Retired A Stars and Their Companions. VII. 18 New Jovian Planets

We report the detection of 18 Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 <= M _sstarf/M _⊙ <= 1.95, radii 2.5 <= R _sstarf/R _⊙ <= 8.7, and metallicities -0.46 <= [Fe/H] <=+0.30. The planets have minimum masses 0.9 M _Jup <= M_P sin i <~ 13 M _Jup and semimajor axes a >= 0.76 AU. These detections represent a 50% increase in the number of planets known to orbit stars more massive than 1.5 M _⊙ and provide valuable additional information about the properties of planets around stars more massive than the Sun.

Based on observations obtained at the W. M. Keck Observatory and with the Hobby-Ebberly Telescope at the McDonald Observatory. Keck is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by Caltech, the University of Hawaii, NASA, and the University of California.