Occurrence of giant planets around stars with dusty debris disks
Monday 2 July, 17:40
Debris disks may be the signposts of recent planet formation. The dust, which is generated in collisional cascades of asteroids and comets, is enhanced by the gravitational stirring of gas giant planets. Thus bright debris disk systems are natural targets for imaging searches for planets, as it indicates that the host star may possess some kind of planetary system. In this work, we describe a joint high contrast imaging survey for planetary mass companions at Keck and VLT of the last significant sample of debris disks identified by the Spitzer Space Telescope. No new substellar companions were discovered in our survey of Spitzer-selected targets. We combine these observations with from four published surveys, to put constraints on the frequency of planets around debris disk stars in the largest sample to date. We also obtained published data on stars that do not show infrared excesses for a control sample. We assume a double power law distribution of the form f(m,a) = Cm^alpha a^beta for this population of companions. We find that the frequency of giant planets with masses 5-20 MJup and separations 10-1000 au around stars with debris disks is 6.3% (68% confidence interval 3.7-9.8%), compared to 0.7% (68% confidence interval 0.2-1.8%) for the control sample of stars without disks. For the first time, we show that the occurrence of young giant planets around stars with debris disks is higher than those without debris disks at the 88% confidence level, tentatively suggesting that these distributions are distinct.