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arXiv · 1902.02057

The misaligned orbit of the Earth-sized planet Kepler-408b

Shoya Kamiaka·Othman Benomar·Yasushi Suto·Fei Dai·Kento Masuda·Joshua N. Winn
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Abstract

Kepler-408 is one of the 33 planet-hosting {\it Kepler} stars for which asteroseismology has been used to investigate the orientation of the stellar rotation axis relative to the planetary orbital plane. The transiting "hot Earth," Kepler-408b, has an orbital period of 2.5 days and a radius of $0.86$~$R_\oplus$, making it much smaller than the planets for which spin-orbit alignment has been studied using the Rossiter-McLaughlin effect. Because conflicting asteroseismic results have been reported in the literature, we undertake a thorough re-appraisal of this system and perform numerous checks for consistency and robustness. We find that the conflicting results are due to the different models for the low-frequency noise in the power spectrum. A careful treatment of the background noise resolves these conflicts, and shows that the stellar inclination is $\is=42^{+5}_{-4}$ degrees. Kepler-408b is, by far, the smallest planet known to have a significantly misaligned orbit.

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Shoya Kamiaka, Othman Benomar, Yasushi Suto, Fei Dai, Kento Masuda, Joshua N. Winn. 2019-02-09. The misaligned orbit of the Earth-sized planet Kepler-408b. https://doi.org/10.3847/1538-3881%2Fab04a9

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