http://arxiv.org/abs/1911.11399
Kepler-13Ab (KOI-13) is an exoplanet orbiting a rapidly rotating A-type star. The system shows a significant spin-orbit misalignment and a changing transit duration most probably caused by the precession of the orbit. Here we present a self-consistent analysis of the system combining {\it Kepler} and TESS observations. We model the light curves asssuming a planet transits a rotating oblate star which has a strong surface temperature gradient due to rotation-induced gravity darkening. The transit chord moves slowly as an emergent feature of orbital precession excited by the oblate star with a decline rate in the impact parameter of ${\rm d}b/{\rm d}t = -0.011/{\rm yr}$, and with an actual value of $b=0.19$ for the latest TESS measurements. The changing transit duration that was measured from {\it Kepler} Q2 and Q17 quarters and the TESS measurements indicates a linear drift of the impact parameter. The solutions for the stellar spin axis suggest a nearly orthogonal aspect, with inclination around $100^\circ$.
G. Gyula, M. Szabó, T. Theodor, et. al.
Wed, 27 Nov 19
4/59
Comments: 5 pages, 4 figures, 1 table; accepted by MNRAS
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