Constraining the interiors of exoplanets by measuring the Love number k_2

通过测量 Love 数 k_2 来约束系外行星的内部

• 批准号: 329666757
• 负责人: Professorin Dr. Heike Rauer
• 金额: --
• 依托单位: Institut für Planetenforschung
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/329666757?language=en
• 关键词: Constraining; interiors; exoplanets; measuring; Love

We will develop a new software package to model transit light curves of exoplanets with tidally and rotationally distorted components. This work is starting from an already existing code based on the Roche-model (which consists of a massless, but emitting and/or reflecting, tidally and rotationally distorted envelope, and a core in the center of the celestial object that contains the entire mass of the object). Such a model was found to be appropriate for main sequence stars. The code will be modified to make it appropriate for exoplanets. Therefore, it will be extended by non-homogeneous internalmass distribution components and it will take into account the radiation pressure caused by the host star because this is important for close-in exoplanets with extended, dense atmospheres. Since gravitational microlensing in the binary system of the planet (lense) and star (source) is thought to contribute to the observed light curve distortions, we plan to add this effect into the code. Limb darkening will be an adjustable parameter independent of existing stellar atmosphere models, but we plan to allow the user the possibility to modify this for a given stellar atmosphere model. We will improve our existing code to include stellar variability phenomena by developing and adding a red-noise (autoregressive and/or Gaussian Process) model. Then the code will be able to determine the ratio of the polar and the equatorial radii of the transiting exoplanet from a measured transit light curve.In addition, we will perform studies on applicability of multicolour photometry. Observations obtained at different wavelengths may help to resolve the degeneracy between different parametersFinally, the measured polar flattening values will be linked to the internal structure of the exoplanet. This requires knowledge of the rotational period of the exoplanet. To first approximation, we assume that the closest exoplanets are tidally locked. A more sophisticated estimate can be based on the shape-distortion, because the centrifugal force is axially symmetric while tidal forces have a characteristic orientation. The code will be able to separate these effects.The expected result of SP6 is an estimate of the polar flattening of several exoplanets and constraints for the rotational period, gravitational quadrupole moment J_2 and Lovenumber k_{2,f}. These numbers can be compared to theoretical expectations and thus can be used for further refinement of our knowledge on exoplanets' interiors.The interior models of SP4 and SP5 based on EoS data obtained by SP1-3 and SP7-9 can be used as initial estimates in our work. Then we can make predictions concerning which kind of light curve distortions can be observed. A comparison of the observed data and our model calculations may allow us to refine the k_{2,f} Love-number values and giving a feedback about the observability of polar flattening as well as the code will be able to constrain this interior structure parameter.

我们将开发一个新的软件包，以用潮汐和旋转扭曲的组件建模系外行星的过境光曲线。这项工作是从基于Roche模型的已经存在的代码开始的（该代码由无质量但散发和/或反射，潮汐和旋转扭曲的信封，以及包含整个对象质量的天体中心的核心）。发现这种模型适用于主序列恒星。该代码将进行修改以使其适合外行星。因此，它将通过非均匀的内部质量分布组件扩展，并考虑到宿主星引起的辐射压力，因为这对于具有延伸，密度大气的近距离外行星很重要。由于行星二进制系统（晶状体）和恒星（源）的重力微透明被认为会导致观察到的光曲线扭曲，因此我们计划将此效果添加到代码中。肢体变暗将是一个独立于现有恒星大气模型的可调节参数，但我们计划使用户有可能为给定的恒星大气模型修改它。我们将通过开发和添加红色噪声（自回归和/或高斯过程）模型来改进现有代码，以包括出色的可变性现象。然后，该代码将能够从测量的过境光曲线确定过渡系外行星的极性和赤道半径的比率。此外，我们将对多色光度法的适用性进行研究。在不同波长下获得的观察结果可能有助于解决不同参数之间的变性，测得的极性平坦值将与外部球星的内部结构相关。这需要了解系外行星的旋转期。首先近似，我们假设最接近的系外行星是潮汐锁定的。更复杂的估计值可以基于形状渗透率，因为离心力在轴向对称性上是对称的，而潮汐力具有特征方向。该代码将能够分开这些效果。SP6的预期结果是旋转期间几个系外行星的极性扁平和约束，重力四极力矩J_2和Lovenumber K_ {2，f}的限制。可以将这些数字与理论期望进行比较，因此可以用于进一步完善我们对系外行星内部的知识。基于SP1-3和SP7-9获得的EOS数据的SP4和SP5的内部模型可以用作我们工作的初始估计。然后，我们可以预测可以观察到哪种光曲线扭曲。对观察到的数据和我们的模型计算的比较可能使我们能够完善k_ {2，f} love-number值，并给出有关极性平坦的可观察性以及代码的反馈，并且代码将能够限制此内部结构参数。