THREE WIDE PLANETARY-MASS COMPANIONS TO FW TAU, ROXS 12, AND ROXS 42B
Authors:
Kraus et al
Abstract:
We report the discovery of three planetary-mass companions (M = 6–20 MJup) in wide orbits ( ∼ 150–300 AU) around the young stars FW Tau (Taurus-Auriga), ROXs 12 (Ophiuchus), and ROXs 42B (Ophiuchus). All three wide planetary-mass companions (“PMCs”) were reported as candidate companions in previous binary survey programs, but then were neglected for greater than 10 years. We therefore obtained followup observations which demonstrate that each candidate is comoving with its host star. Based on the absolute MK′ magnitudes, we infer masses (from hot-start evolutionary models) and projected separations of 10 ± 4 MJup and 330 ± 30 AU for FW Tau b, 16 ± 4 MJup and 210 ± 20 AU for ROXs 12, and 10 ± 4 MJup and 140 ± 10 AU for ROXs 42B b. We also present similar observations for ten other candidates which show that they are unassociated field stars, as well as multicolor JHK′L′ near-infrared photometry for our new PMCs and for five previously-identified substellar or planetary-mass companions. The NIR photometry for our sample of eight known and new companions generally parallels the properties of free-floating low-mass brown dwarfs in these star-forming regions. However, 5 of the 7 objects with M less than 30MJup are redder in K′ − L′ than the distribution of young free-floating counterparts of similar J − K′. We speculate that this distinction could indicate a structural difference in circum-planetary disks, perhaps tied to higher disk mass since at least two of the objects in our sample are known to be accreting more vigorously than typical free-floating counterparts.
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