http://arxiv.org/abs/1901.01974
Currently, we have only limited means to probe the presence of planets at large orbital separations. Foreman-Mackey et al. (2016, FM16) searched for long-period transiting planets in the Kepler light curves using an automated pipeline. Here, we apply their pipeline, with minor modifications, to a larger sample and use the updated stellar parameters from Gaia DR2. The latter boosts the sizes for the majority of the planet candidates found by FM16, invalidating a number of them as false positives. We identify 12 good candidates, including 2 new ones. All but one have periods from 2 to 10 years, and sizes from 0.4 to 1.26 $R_{\rm J}$. We report two main findings. First, we find a total occurrence rate of $0.43_{-0.11}^{+0.13}$ planets per Sun-like star in the outer region, consistent with results from radial-velocity and microlensing surveys. Neptune-sized planets are a few times more common than Jupiter-sized ones, as is also derived by microlensing studies. Second, 5 out of our 12 candidates orbit stars with known transiting planets at shorter periods, including one with 5 inner planets. We interpret this high incidence rate as: (1) almost all our candidates should be genuine; (2) across a large orbital range (from $\sim 0.05$ AU to a few AUs), mutual inclinations in these systems are at most a few degrees; (3) cold giant planets exist exclusively in systems with inner small planets.
M. Herman, W. Zhu and Y. Wu
Tue, 8 Jan 19
32/99
Comments: Submitted to AJ. 14 pages, 11 figures
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