THREE WIDE PLANETARY-MASS COMPANIONS TO FW TAU, ROXs 12, AND ROXs 42B

We report the discovery of three planetary-mass companions (M = 6-20 M_(Jup)) in wide orbits (ρ ~ 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 >10 yr. We therefore obtained followup observations that demonstrate that each candidate is comoving with its host star. Based on the absolute M_K' magnitudes, we infer masses (from hot-start evolutionary models) and projected separations of 10 ± 4 M_(Jup) and 330 ± 30 AU for FW Tau b, 16 ± 4 M_(Jup) and 210 ± 20 AU for ROXs 12, and 10 ± 4 M_(Jup) and 140 ± 10 AU for ROXs 42B b. We also present similar observations for 10 other candidates that 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 near-infrared 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, five of the seven objects with M < 30 M_(Jup) are redder in K' – L' than the distribution of young free-floating counterparts of similar J – K' color. We speculate that this distinction could indicate a structural difference in circumplanetary 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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