干旱区生态环境知识资源中心

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 (similar to 50-500 AU) companions to solar-type stars in Upper Scorpius. We report one new discovery of a similar to 14 M-J companion around GSC 06214-00210 and confirm that the candidate planetary-mass companion 1RXS J160929.1-210524 detected by Lafreniere et al. is in fact comoving with its primary star. In our survey, these two detections correspond to similar to 4% of solar-type stars having companions in the 6-20 M-J mass and similar to 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.