Three Wide Planetary-mass Companions to FW Tau, ROXs 12, and ROXs 42B

Creators: Kraus, Adam L.; Ireland, Michael J.; Cieza, Lucas A.; Hinkley, Sasha; Dupuy, Trent J.; Bowler, Brendan P.; Liu, Michael C.

Abstract

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.

Additional Information

© 2014 American Astronomical Society. Received 2012 December 21; accepted 2013 November 28; published 2013 December 31. We thank the referee for providing a thorough and helpful critique of this paper. A.L.K. was supported in part by a Clay Fellowship and by NASA through Hubble Fellowship grant 51257.01 awarded by STScI, which is operated by AURA, Inc., for NASA, under contract NAS 5-26555. M.J.I. acknowledges support from the Australian Research Council's Discovery program (DP1094977) and a Macquarie University Research Development Grant. T.D. was supported by NASA through Hubble Fellowship grant 51271.01 awarded by STScI, which is operated by AURA, Inc., for NASA, under contract NAS 5-26555. S.H. and L.C. were supported by NASA through the Sagan Fellowship program, and L.C. was supported by the ALMA-CONICYT fund allocated to the project number 31120009. M.L. acknowledges support from NSF grant AST09-09222. Finally, this work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Some of the data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to NASA through the agency's scientific partnership with Caltech and the University of California. 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. Note added in proof. The comovement of ROXs4213 b was also confirmed by Currie et al. (2014) based on an independent analysis of archival data including the 2011 observations we describe in Section 3.

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