Radial Velocity Search for Extrasolar Planets in Visual Binary Systems

摘要

We searched for extrasolar planets in visual binary systems using precise Doppler-shift measurements taken overa period of 4 yr. Using the HIgh Dispersion Echelle Spectrograph (HIDES) equipped on the Okayama AstrophysicalObservatory (OAO) 188 cm reflector, we achieved a radial-velocity precision of about 10 m s~-I.We monitored bothprimary and secondary stars of six visual binary systems, and primary stars of three visual binaries. Among them,three objects show large radial-velocity variations. ADS 7311 A exhibits a decreasing trend in radial velocity witha best-fit slope of -30 m s~-Iyr~-1, while 31 Dra A shows an increasing trend with a best-fit slope of +220 m s~-1yr~-1.These long-term trends in radial velocity may be attributable to unseen companions. BDS 10966 A shows a periodicvariation in radial velocity with a period of 840 d and a semiamplitude of about 120m s~-1, implying an associationof a planetary-mass companion, rotational modulation, or nonradial oscillation of the photosphere. In any case, weshould mention the nonassociation between BDS 10966 A and B, suggested by the different proper motions, radialvelocities, and Hipparcos parallaxes.