Three New ``51 Pegasi-Type'' Planets

We report Keplerian Doppler velocity variations, consistent with orbiting ``51 Pegasi-type'' planets, for the three stars HR 3522 (G8V), HR 5185 (F7V), and HR 458 (F8V). HR 3522 exhibits a velocity semiamplitude of 77 m s^-1 and a period of 14.65 days, implying a semimajor axis of 0.11 AU and a minimum mass for the companion of M₂ sin i = 0.84M_JUP. For HR 5185, the semiamplitude is 469 m s^-1, and the period is 3.3128 days, implying an orbital radius of 0.0462 AU and a minimum mass of 3.87M_JUP. For HR 458, the semiamplitude is 74 m s^-1, and the period is 4.61 days, implying an orbital radius of 0.057 AU and a minimum mass of 0.68M_JUP. These three companions, along with 51 Peg b, may constitute a heretofore unrecognized class of planets, defined by circular orbits, Jupiter-like masses, and orbital radii less than ~0.2 AU. The relatively large orbital radius for HR 3522 (0.11 AU) precludes tidal circularization, suggesting that the circular orbits are primordial. During the past 9 years, the velocity residuals to the Keplerian fit of HR 3522 exhibit a long-term systematic trend, suggestive of an additional companion. HR 5185 exhibits velocity residuals that fluctuate erratically by ~70 m s^-1, which are as yet unaccounted for. HR 5185 has a rotation period very close to the orbital period of the planet, suggesting that the companion may have tidally locked the primary.

Based on observations obtained at Lick Observatory, which is operated by the University of California.