Spin-Orbit Misalignment and Precession in the Kepler-13Ab Planetary System

Abstract

Gravity darkening induced by rapid stellar rotation provides us with a unique opportunity to characterize the spin-orbit misalignment of a planetary system through analysis of its photometric transit. We use the gravity-darkened transit modeling code simuTrans to reproduce the transit light curve of Kepler-13Ab by separately analyzing phase-folded transits for 12 short-cadence Kepler quarters. We verify the temporal change in impact parameter indicative of spin-orbit precession identified by Szabó et al. (2012) and Masuda (2015), reporting a rate of change $db/dt=(-4.1\pm 0.2)\times 10^{-5}$ day${}^{-1}$. We further investigate the effect of light dilution on the fitted impact parameter and find that less than 1% of additional light is sufficient to explain the seasonal variation seen in the Kepler quarter data. We then extend our precession analysis to the phase curve data from which we report a rate of change $db/dt=(-3.2\pm 1.3)\times 10^{-5}$ day${}^{-1}$. This value is consistent with that of the transit data at a lower significance and provides the first evidence of spin-orbit precession based solely on the temporal variation of the secondary eclipse.

Accepted to AJ. 8 pages, 7 figures

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Cited by in corpus (2)

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