starry: Analytic Occultation Light Curves
starry: Analytic Occultation Light Curves
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繁星点点：分析掩星光曲线
DOI：
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发表时间：
2018
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通讯作者：
R. Deitrick
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作者：
R. Luger;E. Agol;D. Foreman;David P. Fleming;J. Lustig;R. Deitrick
如果天体的特定强度图表示为球面谐波之和，则我们推导出掩星期间从球形行星、月球或恒星接收到的总通量的解析、封闭形式、数值稳定的解。我们的表达式在任意程度上都是有效的，并且可以递归地计算速度。我们在这里发展的形式适用于计算恒星凌日光曲线、行星次日食光曲线、行星-行星/行星-月球掩星光曲线以及热（旋转）相位曲线。在本文中，我们还介绍了starry，这是一个用c++编写并用Python封装的开源包，用于计算这些光曲线。该算法比直接数值积分算法快6个数量级，精度提高几个数量级。starry还计算所有输入参数的光曲线的解析导数，用于基于梯度的优化和推理，如哈密顿蒙特卡罗（HMC），允许用户快速有效地拟合观测到的光曲线，以推断天体表面地图的属性。（请参阅https://github.com/rodluger/starry、https://rodluger.github.io/starry/和https://doi.org/10.5281/zenodo.1312286）。
We derive analytic, closed form, numerically stable solutions for the total flux received from a spherical planet, moon, or star during an occultation if the specific intensity map of the body is expressed as a sum of spherical harmonics. Our expressions are valid to arbitrary degree and may be computed recursively for speed. The formalism we develop here applies to the computation of stellar transit light curves, planetary secondary eclipse light curves, and planet–planet/planet–moon occultation light curves, as well as thermal (rotational) phase curves. In this paper, we also introduce starry, an open-source package written in C++ and wrapped in Python that computes these light curves. The algorithm in starry is six orders of magnitude faster than direct numerical integration and several orders of magnitude more precise. starry also computes analytic derivatives of the light curves with respect to all input parameters for use in gradient-based optimization and inference, such as Hamiltonian Monte Carlo (HMC), allowing users to quickly and efficiently fit observed light curves to infer properties of a celestial body’s surface map. (Please see https://github.com/rodluger/starry, https://rodluger.github.io/starry/, and https://doi.org/10.5281/zenodo.1312286).