Probing long-period companions to planetary hosts

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Abstract
Aims.We present the results of a deep imaging survey of stars surrounded by planets detected with the radial velocity technique. The purpose is to search for and to characterize long-period stellar and substellar companions. The sample contains a total of 26 stars, among which 6 exhibit additional radial velocity drifts. Methods.We used NACO, at the ESO Very Large Telescope, and PUEO-KIR, at the Candian French Hawaiian Telescope, to conduct a near-infrared coronographic survey with adaptive optics of the faint circumstellar environment of the planetary hosts. The domain investigated ranges between 0.1'' to (i.e. about 3 to 500 AU, according to the mean distance of the sample). The survey is sensitive to companions within the stellar and the substellar domains, depending on the distance to the central stars and on the star properties.Results.The images of 14 stars do not reveal any companions once the field objects are removed. 8 stars have close potential companions that need to be re-observed within 1–2 years to check for physical companionship. 4 stars are surrounded by faint objects which are confirmed or very probable companions. The companion to HD 13445 (Gl 86) is already known. The HD 196885 star is a new close visual binary system with a high probability of being bound. The 2 newly discovered companions, HD 1237 B and HD 27442 B, share common proper motions with the central stars. Orbital motion is detected for HD 1237 B. HD 1237 B is likely a low-mass M star, located at 70 AU (projected distance) from the primary. HD 27442 B is most probably a white dwarf companion located at about 240 AU (projected distance).

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