Two New Candidate Planets in Eccentric Orbits

Doppler measurements of two G-type main-sequence stars, HD 210277 and HD 168443, reveal Keplerian variations that imply the presence of companions with masses (Msini) of 1.28 and 5.04 M_J (where M_J is the mass of Jupiter) and orbital periods of 437 and 58 days, respectively. The orbits have large eccentricities of e=0.45 and e=0.54, respectively. All nine known extrasolar planet candidates with a=0.2-2.5 AU have orbital eccentricities greater than 0.1, higher than that of Jupiter (e=0.05). Eccentric orbits may result from gravitational perturbations imposed by other orbiting planets or stars, by passing stars in the dense star-forming cluster, or by the protoplanetary disk. Based on published studies and our near-IR adaptive optics images, HD 210277 appears to be a single star. However, HD 168443 exhibits a long-term velocity trend consistent with a close stellar companion, as yet undetected directly.

Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology, and based on observations obtained at Lick Observatory, which is operated by the University of California.