FREQUENCY MODULATION OF DIRECTLY IMAGED EXOPLANETS: GEOMETRIC EFFECT AS A PROBE OF PLANETARY OBLIQUITY
FREQUENCY MODULATION OF DIRECTLY IMAGED EXOPLANETS: GEOMETRIC EFFECT AS A PROBE OF PLANETARY OBLIQUITY
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直接成像系外行星的频率调制：几何效应作为行星倾角探测器
DOI：
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发表时间：
2016
期刊：
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通讯作者：
H. Kawahara
中科院分区：
文献类型：
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作者：
H. Kawahara
我们考虑对直接成像的系外行星的散射光曲线进行时频分析。我们表明，行星倾角和轨道倾角引起的几何效应会引起视昼周期的频率调制。我们构建了频率调制模型，并将其与从无云地球的模拟光变曲线的伪维格纳分布中提取的瞬时频率进行比较。该模型与模拟调制因子具有良好的一致性，即使对于具有与信号可比的高斯噪声的光曲线也是如此。值得注意的是，瞬时频率的形状对顺行、逆行和极上旋转之间的差异敏感。虽然我们的技术要求反照率图是静态的，但它不需要求解行星的反照率图。时频分析是对其他利用幅度调制的方法的补充。本文论证了光度变异性的频域对于未来研究中直接成像系外行星表征的重要性。
We consider the time–frequency analysis of a scattered light curve of a directly imaged exoplanet. We show that the geometric effect due to planetary obliquity and orbital inclination induce the frequency modulation of the apparent diurnal periodicity. We construct a model of the frequency modulation and compare it with the instantaneous frequency extracted from the pseudo-Wigner distribution of simulated light curves of a cloudless Earth. The model provides good agreement with the simulated modulation factor, even for the light curve with Gaussian noise comparable to the signal. Notably, the shape of the instantaneous frequency is sensitive to the difference between the prograde, retrograde, and pole-on spin rotations. While our technique requires the albedo map to be static, it does not need to solve the albedo map of the planet. The time–frequency analysis is complementary to other methods which utilize the amplitude modulation. This paper demonstrates the importance of the frequency domain of the photometric variability for the characterization of directly imaged exoplanets in future research.