Kepler-408 is one of the 33 planet-hosting 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 0.86R ⊕ , 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 = - + i 42 4 5 degrees. Kepler-408b is, by far, the smallest planet known to have a significantly misaligned orbit.
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机译：开普勒408是33个托管开普勒行星的恒星之一，已使用星震学研究了恒星旋转轴相对于行星轨道平面的定向。过渡中的热地球Kepler-408b的轨道周期为2.5天，半径为0.86R⊕，使其比使用Rossiter-McLaughlin效应研究自旋轨道对准的行星小得多。由于文献中已经报道了矛盾的地震结果，因此我们对该系统进行了全面的重新评估，并对一致性和鲁棒性进行了大量检查。我们发现冲突的结果是由于功率谱中低频噪声的模型不同所致。仔细处理背景噪声可解决这些冲突，并显示恒星倾角为=-+ i 42 4 5度。到目前为止，开普勒408b是已知轨道明显未对准的最小行星。
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