摘要：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 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.
