AAS 207th Meeting, 8-12 January 2006
Session 68 Extra-Solar Planets II: Current Searches, Properties and Analysis
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[68.04] Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems

D. Raghavan, T.J. Henry (Georgia State University), B.D. Mason (USNO), J.P. Subasavage, W.C. Jao, T.D. Beaulieu (Georgia State University), N.C. Hambly (University of Edinburgh)

We present results of a reconnaissance for stellar companions to all 131 radial-velocity-detected candidate extrasolar planetary systems known as of July 1, 2005. Common proper motion (CPM) companions were investigated using the multi-epoch STScI Digitized Sky Surveys (DSS), and confirmed by matching the trigonometric parallax distances of the primaries to companion distances estimated photometrically using SuperCOSMOS plate, CCD optical and 2MASS infrared photometry. We evaluate whether the ``companions" listed in the Washington Double Star Catalog (WDS) are gravitationally bound to the primary or coincidental alignments in the sky. We also attempt to confirm or refute companions listed in the Catalog of Nearby Stars (CNS), Hipparcos, and Duquennoy & Mayor, 1991.

Our findings indicate that a lower limit of 29 (22%) of the 131 exoplanet systems have stellar companions, and an additional 7 (5%) have candidate companions. We report a previously unknown stellar companion to planet host HD 38529, and identify a companion candidate to HD 188015. We confirm 16 previously reported stellar companions to exoplanet hosts, and report 8 additional companions --- these are known stellar companions, but previously not recognized to be in exoplanet systems. In addition, we have confirmed the gravitational connection for a WDS entry for HD 222582. We have also found evidence for 20 entries in WDS that are not gravitationally bound companions --- they do not show any related proper motion in the DSS plates. At least three, and possibly five of the exoplanet systems are contained within triple star systems, and of these, HD 38529 may have a fourth stellar companion as well. Two of the exoplanet systems contain white dwarf companions. These results indicate that solar systems are found in a variety of stellar multiplicity environments -- singles, binaries, triples, and possibly quadruples; and that planets survive post-main-sequence evolution of companion stars.

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