Two Wide Planetary-Mass Companions to Solar-Type Stars in Upper Scorpius

TL;DR

This study surveys wide planetary-mass companions to solar-type stars in Upper Scorpius, discovering two such companions and analyzing their frequency, which challenges existing formation models.

Contribution

It presents new adaptive optics observations identifying two wide planetary-mass companions and assesses their occurrence rate around solar-type stars.

Findings

Approximately 4% of solar-type stars have companions of 6-20 M_J at 200-500 AU.

The observed companion frequency exceeds expectations from binary mass function extrapolations.

Implications for formation mechanisms of wide planetary-mass companions are discussed.

Abstract

At wide separations, planetary-mass and brown dwarf companions to solar type stars occupy a curious region of parameters 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 06214-00210, and confirm that the candidate planetary mass companion 1RXS J160929.1-210524 detected by Lafreniere et al (2008) is in fact co-moving 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.