解体岩石行星的彩色transit光变曲线
Chromatic transit light curves of disintegrating rocky planets
摘要：
上下文开普勒的观测揭示了一类短周期系外行星，其中开普勒-1520 b是原型，它们具有彗星状的尘埃尾巴，被认为是小型岩石行星失去质量的结果。凌日的形状和色度限制了来自行星表面的尘埃颗粒的性质，为探测岩石系外行星的成分和物理性质提供了独特的机会。目的。我们的目标是近似的开普勒-1520 b的平均开普勒长节奏的光变曲线，并研究如何的光学厚度和过境横截面的一般尘埃尾巴可以影响所观察到的波长依赖性和深度的过境光变曲线。方法.我们开发了一个新的3D模型，从行星表面蒸发升华粒子，建立一个尘埃尾巴，假设它是光学薄，并使用3D辐射转移计算，充分处理散射使用空心球分布（DHS）的方法，产生过境光变曲线之间的0.45和2.5 $μ$ m。结果我们发现，过境深度是波长无关的光学厚尾巴，可能解释为什么只有一些观测表明波长依赖性。从我们的模拟尾巴的3D性质，我们表明，他们的过境截面与垂直于行星的轨道平面的粒子喷射速度的分量有关，并使用此导出最小喷射速度为1.2公里$^{-1}$。为了适应开普勒-1520 b的平均过境深度为0.87%，我们需要一个高的尘埃质量损失率为7 $-$ 80 M $_\oplus$ Gyr $^{-1}$，这意味着行星的寿命可能与观察到的样本不一致。因此，这些质量损失率应被视为上限。
英文摘要：
Context. Kepler observations have revealed a class of short period exoplanets, of which Kepler-1520 b is the prototype, which have comet-like dust tails thought to be the result of small, rocky planets losing mass. The shape and chromaticity of the transits constrain the properties of the dust particles originating from the planet's surface, offering a unique opportunity to probe the composition and geophysics of rocky exoplanets. Aims. We aim to approximate the average Kepler long-cadence light curve of Kepler-1520 b and investigate how the optical thickness and transit cross-section of a general dust tail can affect the observed wavelength dependence and depth of transit light curves. Methods. We developed a new 3D model that ejects sublimating particles from the planet surface to build up a dust tail, assuming it to be optically thin, and used 3D radiative transfer computations that fully treat scattering using the distribution of hollow spheres (DHS) method, to generate transit light curves between 0.45 and 2.5 $μ$m. Results. We show that the transit depth is wavelength independent for optically thick tails, potentially explaining why only some observations indicate a wavelength dependence. From the 3D nature of our simulated tails, we show that their transit cross-sections are related to the component of particle ejection velocity perpendicular to the planet's orbital plane and use this to derive a minimum ejection velocity of 1.2 kms$^{-1}$. To fit the average transit depth of Kepler-1520 b of 0.87%, we require a high dust mas-loss rate of 7 $-$ 80 M$_\oplus$ Gyr$^{-1}$ which implies planet lifetimes that may be inconsistent with the observed sample. Therefore, these mass-loss rates should be considered to be upper limits.
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