http://arxiv.org/abs/1908.05833
Recent work has found that in the NASA Kepler multi-planet systems, the planets tend to have similar sizes to their neighbors and regular orbital spacing (Weiss et al. 2018, Millholland et al. 2017), and also the outer planet of a pair tends to be larger than the inner planet (Ciardi et al. 2013). In a new study, Zhu 2019 (Z19) claims that these patterns are the result of detection bias. In this rebuttal letter, we address several shortcomings of Z19. In the vast majority of planetary systems that have small planets ($R_P < 1.5 R_\oplus$), a planet and its neighbor are both small, even though larger planets could have been detected. This aspect of the Kepler multi-planet systems is not addressed in Z19. Furthermore, the Z19 hypothesis-testing technique used to resample the planet sizes is fundamentally flawed. We find that generating synthetic planet radii by drawing the signal-to-noise ratio (SNR) of the transit photometry at random induces correlated planet radii, rather than random radii, before any detection bias is applied. We also find that the Z19 sample of planet orbital spacings is prone to detection bias. We conclude that the radii of planets within planetary systems are indeed correlated, and their spacings are regular.
L. Weiss and E. Petigura
Mon, 19 Aug 19
18/46
Comments: Submitted to ApJL
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