LESIA - Observatoire de Paris

Searching for planets forming in transitional disks with the Keck/NIRC2 vortex coronagraph

mercredi 4 octobre 2017, par Garreth Ruane (Caltech)

Vendredi 13 octobre 2017 à 14h00 , Lieu : Salle de conférence du bâtiment 17

Perhaps one of the key signposts of planet formation is the presence of gaps, cavities, and spirals in transitional disks. I will describe a Keck/NIRC2 program that seeks to test this hypothesis by searching for accreting planets within such gaps and cavities via deep direct imaging observations in the infrared. This program makes use of a new observing strategy consisting of a combination of angular and reference star differential imaging, improved wavefront control algorithms, and a small inner working angle coronagraph to push the high-contrast imaging performance of NIRC2.

In an initial case study of TW Hya, the nearest protoplanetary disk (distance of 60 pc), we searched for accreting planets within dust gaps previously detected in scattered light and submm-wave thermal emission. Three nights of observations with the Keck/NIRC2 vortex coronagraph mode in L’ (3.4-4.1 um) 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 assuming an age range of 7-10 Myr for TW Hya. Our non-detection also implies that any putative 0.1 Jupiter mass 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.