A Systematic Data Driven Characterization of the Atmospheres of Brown Dwarfs: At the Boundary Between Stars and Planets

棕矮星是银河系中不寻常的物体。它们横跨恒星和行星之间的边界——太大而不能被称为行星，又太小而不能被称为恒星。它们的质量不足以像恒星那样聚变氢。此外，它们的化学成分通常类似于木星这样的巨型气体行星。研究它们为了解恒星和行星的大气物理学提供了一个很好的机会。该奖项资助了利用公共档案数据研究数千颗褐矮星的工作。研究人员将更新他们的大气模型，并与他们的数据进行比较。他们的主要数据库将是美国宇航局红外望远镜设施获得的SpeX棱镜光谱库。他们还将根据对这些褐矮星的详细统计研究得出大气物理学的结论。这些结果也将有助于解释太阳系外行星的观测结果。一名研究生和几名本科生将参与这项研究，其中包括少数民族学生。PI将与奇卡诺人/西班牙裔美国人和土著美国人科学促进协会（SACNAS）合作，增加西班牙裔美国人和土著美国人从事科学的人数。该团队将把广泛应用于太阳系外行星群落的贝叶斯大气检索技术应用于大量棕矮星样本。这些工具将用于确定云的性质、热结构和化学物质在广泛的温度和重力范围内。特别是，他们将解决突出的褐矮星问题，如云在低质量L-T转变中的行为，不平衡化学随温度的演变，以及金属丰度和碳氧比随种群分布的第一次测量。首先，他们将升级他们的模型，以包括高温不透明和不同的热剖面。接下来，他们将在整个SpeX数据库中应用他们的分析，探索温度、云特性和分子丰度之间的关系，并公布结果。最终，他们将完成对所有SpeX对象的检索分析，并应用于其他可用的棕矮星数据集。

Brown dwarfs are unusual objects in the galaxy. They straddle the boundary between stars and planets - too large to be called planets and too small to be stars. They are not massive enough to fuse hydrogen like stars. Also, their chemical composition often resembles giant gas planets like Jupiter. Studying them presents a great opportunity to learn about atmospheric physics in both stars and planets. This award funds work to study thousands of brown dwarfs using data from public archives. The researchers will update their atmospheric models, and test them with comparisons with their data. Their main database will be the SpeX Prism Spectral Library obtained with the NASA Infrared Telescope Facility. They will also draw conclusions about atmospheric physics based on a detailed statistical study of these brown dwarfs. The results will also be useful to interpreting observations of extrasolar planets. A graduate student and several undergraduate students will participate in the research, including minorities. The PI will work with the Society for Advancement of Chicanos/Hispanics and Native Americans in Science (SACNAS) to increase the numbers of Hispanics and Native Americans in science. The team will apply Bayesian atmospheric retrieval techniques, widely employed in the extrasolar planet community, to a large sample of brown dwarfs. These tools will be used to determine cloud properties and thermal structures and chemistries across a broad range of temperatures and gravities. In particular, they will address outstanding brown dwarf issues such as the behavior of clouds across the low mass L-T transition, the evolution of disequilibrium chemistry with temperature, and the first measure of the distribution of metallicities and carbon-to-oxygen ratios with the populations. First, they will upgrade their models to include high-temperature opacities and different thermal profiles. Next, they will apply their analysis across the entire SpeX database and explore the relationships between temperature, cloud properties, and molecular abundances and publish results. Ultimately, they will finish retrieval analysis on all SpeX objects and apply to other available datasets for brown dwarfs.