Two New Candidate Planets in Eccentric Orbits

Abstract

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 (M sin i) 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.