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Published January 10, 2011 | Published
Journal Article Open

Two Wide Planetary-mass Companions to Solar-type Stars in Upper Scorpius


At wide separations, planetary-mass and brown dwarf companions to solar-type stars occupy a curious region of parameter space not obviously linked to binary star formation or solar system scale planet formation. These companions provide insight into the extreme case of companion formation (either binary or planetary), and due to their relative ease of observation when compared to close companions, they offer a useful template for our expectations of more typical planets. We present the results from an adaptive optics imaging survey for wide (~50–500 AU) companions to solar-type stars in Upper Scorpius. We report one new discovery of a ~14 M_J companion around GSC 06214−00210and confirm that the candidate planetary-mass companion 1RXS J160929.1−210524 detected by Lafrenière et al. is in fact comoving with its primary star. In our survey, these two detections correspond to ~4% of solar-type stars having companions in the 6–20 M_J mass and ~200–500 AU separation range. This figure is higher than would be expected if brown dwarfs and planetary-mass companions were drawn from an extrapolation of the binary mass function. Finally, we discuss implications for the formation of these objects.

Additional Information

© 2011 The American Astronomical Society. Received 2010 July 23; accepted 2010 November 5; published 2010 December 21. M.I. acknowledges support from the Australian Research Council through an Australian Postdoctoral Fellowship. We thank undergraduate students Alison Hammond and Matthew Hill from the University of Sydney, who made a first-pass astrometric analysis of the data. We also thank Mike Liu, Brendan Bowler, and the anonymous referee for helpful detailed comments on the manuscript. A.L.K. was supported by a SIM Science Study and by NASA through Hubble Fellowship grant 51257.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. This work is based in part on data obtained as part of the UKIRT Infrared Deep Sky Survey. Some of these observations were obtained at the Hale Telescope at Palomar Observatory, as part of a collaborative agreement between the California Institute of Technology, JPL, and Cornell University. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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