Atmospheric Chemistry in Brown Dwarfs and Low Mass Stars

棕矮星和低质量恒星的大气化学

• 批准号: 0707377
• 负责人: M. Bruce Fegley
• 金额: $ 16.33万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0707377&HistoricalAwards=false
• 关键词: Atmospheric; Chemistry; Brown; Dwarfs; Low

Dr. Lodders will investigate the gas and condensation chemistry as a function of temperature, total pressure, and metallicity in the cool atmospheres of low-mass stars and brown (L and T) dwarfs. It is motivated by the need to understand molecular gas and cloud condensation chemistry in order to interpret the spectroscopic observations of these objects. A second major objective is to provide reliable abundance grids of gaseous, liquid, and solid compounds for such atmospheres derived from thermochemical equilibrium, and where necessary, thermochemical kinetic computations. This will provide the required chemistry inputs for atmospheric and spectral models of cool and low mass stars. The work is essential to address key questions about low-mass objects, including the following: What are the effective temperature scales of L and T dwarfs? What are their atmospheric compositions? How common are departures from chemical equilibrium due to vertical transport processes? How do clouds and weather affect the spectra of brown dwarfs? Dr. Lodders will also apply these results as part of a collaborative work to generate atmospheric models and high-resolution synthetic spectra of low-mass objects to determine spectral diagnostics of effective temperature, gravity, and composition as functions of mass and age. The project is complementary to observational studies of low-mass objects and provides a guide to interpret future observations from instruments such as HST, ISO, SIRTF, and SOFIA and from the ground-based observatories Gemini, Keck, Magellan, 2MASS, SDSS, and the LBT.The results of this work will be disseminated through refereed publications and meetings, with more popular/appealing results being presented to the public through press releases. The project will also benefit the existing interdisciplinary collaboration with other research groups working on spectral and evolutionary models. Undergraduates (to be supported here) and graduate students will be trained in this multidisciplinary field through participation in these projects.

Lodders博士将研究低质量恒星和棕矮星（L和T）冷大气中的气体和冷凝化学与温度、总压和金属丰度的关系。它的动机是需要了解分子气体和云凝结化学，以解释这些对象的光谱观测。第二个主要目标是提供可靠的丰度网格的气体，液体和固体的化合物，这种气氛来自热化学平衡，并在必要时，热化学动力学计算。这将为冷和低质量恒星的大气和光谱模型提供所需的化学输入。这项工作对于解决低质量天体的关键问题至关重要，包括以下问题：L和T矮星的有效温标是什么？它们的大气成分是什么？由于垂直迁移过程而偏离化学平衡的情况有多普遍？云和天气如何影响褐矮星的光谱？Lodders博士还将把这些结果作为协作工作的一部分，以生成低质量物体的大气模型和高分辨率合成光谱，以确定有效温度、重力和成分随质量和年龄变化的光谱诊断。该项目是对低质量天体观测研究的补充，并为解释未来来自HST、ISO、SIRTF和索菲亚等仪器以及来自Gemini、Keck、Magellan、2 MASS、SDSS和LBT等地面观测站的观测提供了指南。通过新闻稿向公众呈现更受欢迎/吸引人的结果。该项目还将有利于与其他研究小组在光谱和进化模型方面的现有跨学科合作。本科生（将在这里得到支持）和研究生将通过参加这些项目在这一多学科领域接受培训。