Collaborative Research: Using Brown Dwarfs to Understand Exoplanetary Atmospheres: Spectral Inversions of an Analog Population

天文学家开始直接对系外行星进行成像并获取光谱数据。解释数据的主要障碍之一是对凝析云的全面理解。通常情况下，来自系外行星大气层的数据不够好（样本量太小），无法直接确定云的性质。标准技术包括使用网格技术从第一原理对行星大气进行“前向建模”。这项工作将使用孤立的年轻棕矮星作为巨大系外行星大气的类似物。该团队将使用光谱反演技术对来自这一群体的数据进行直接解释。这些褐矮星通常具有与成像的系外行星非常相似的特性：温度，光度，年龄，颜色，光谱特征。然而，它们缺少一颗模糊的母星星。这使得光谱更容易收集，并允许更大的样本量。该团队将检查一组26颗年轻（5- 1.3亿年）孤立的棕矮星，这些棕矮星来自已发现和成像的大型系外行星的同一恒星协会。他们将使用团队合作者之一开发的布鲁斯特代码进行光谱反演。这些反演，沿着经验光谱能量拟合和使用BT SETTL代码的前向建模，将用于（1）推导和比较基本参数，（2）评估云动力学对源物体的环境、颜色和光谱特征的依赖性，（3）研究直接-该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Astronomers are beginning to directly image exoplanets and obtain spectroscopic data. One of the chief barriers in interpreting the data is a complete understanding of condensate clouds. Typically, the data from exoplanet atmospheres are not good enough (and the sample size is too small) for direct determination of cloud properties. The standard technique involves 'forward-modeling' of planetary atmospheres from first principles using a grid technique. This work will use isolated, young brown dwarfs as analogs for massive exoplanet atmospheres. The team will use spectral inversion techniques on data from this population to make direct interpretations of brown dwarf atmospheres. These brown dwarfs typically have properties very similar to imaged exoplanets: temperature, luminosity, age, color, spectral features. However, they lack an obscuring parent star. This makes the spectra greatly easier to collect and allows for a much larger sample size.The team will examine a set of 26 young (5-130 Myr) isolated brown dwarfs from the same stellar associations in which large exoplanets have been discovered and imaged. They will use the BREWSTER code, developed by one of the team collaborators, to conduct spectral inversions. These inversions, along with empirical spectral energy fits and forwarding modeling using the BT SETTL code, will be used to (1) derive and compare fundamental parameters, (2) assess the dependence of cloud dynamics on environment, color and spectral features of the source object, and (3) examine compositional variations among directly-imaged exoplanets and exoplanet analogs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.