Deep Imaging Search for Planets Forming in the TW Hya Protoplanetary Disk with the Keck/NIRC2 Vortex Coronagraph
Distinct gap features in the nearest protoplanetary disk, TW Hya (distance of 59.5 ± 0.9 pc), may be signposts of ongoing planet formation. We performed long-exposure thermal infrared coronagraphic imaging observations to search for accreting planets, especially within dust gaps previously detected in scattered light and submillimeter-wave thermal emission. Three nights of observations with the Keck/NIRC2 vortex coronagraph in L' (3.4–4.1 μm) did not reveal any statistically significant point sources. We thereby set strict upper limits on the masses of non-accreting planets. In the four most prominent disk gaps at 24, 41, 47, and 88 au, we obtain upper mass limits of 1.6–2.3, 1.1–1.6, 1.1–1.5, and 1.0–1.2 Jupiter masses (M_J), assuming an age range of 7–10 Myr for TW Hya. These limits correspond to the contrast at 95% completeness (true positive fraction of 0.95) with a 1% chance of a false positive within 1'' of the star. We also approximate an upper limit on the product of the planet mass and planetary accretion rate of M_pM ≾ 10^(-8) M^2_j yr^(-1) implying that any putative ~0.1 M J planet, which could be responsible for opening the 24 au gap, is presently accreting at rates insufficient to build up a Jupiter mass within TW Hya's pre-main-sequence lifetime.
Additional Information© 2017 The American Astronomical Society. Received 2017 May 19; revised 2017 June 19; accepted 2017 June 22; published 2017 July 27. G.R. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1602444. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration (NASA). 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 Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. J.H.K. acknowledges support from NASA Exoplanets program grant NNX16AB43G to RIT. Part of this work was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under contract with NASA. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (ERC Grant Agreement No. 337569), and from the French Community of Belgium through an ARC grant for Concerted Research Action. E.C. acknowledges support from NASA through Hubble Fellowship grant HF2-51355 awarded by STScI, which is operated by AURA, Inc. for NASA under contract NAS5-26555, for research carried out at the Jet Propulsion Laboratory, California Institute of Technology. Facility: Keck:II (NIRC2) - .
Published - Ruane_2017_AJ_154_73.pdf
Submitted - 1706.07489.pdf