A theoretical and observational spectroscopic study of white dwarf stars

白矮星的理论和观测光谱研究

• 批准号: 261483-2008
• 负责人: Bergeron, Pierre
• 金额: $ 3.93万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=426625
• 关键词: theoretical; observational; spectroscopic; study; white

White dwarf stars represent the endpoint of stellar evolution for more than 95% of the stars in our galaxy, including our Sun. Having exhausted their nuclear fuel at their center, white dwarf stars simply cool off quietly over periods of billions of years. While their mass is comparable to that of the Sun, their volume is closer to that of Earth, which makes them extremely compact objects (about a million times the density of the Sun). The study of these dying stars and the determination of their fundamental parameters such as temperature, mass, and chemical composition, provide us with crucial information not only about the nature of these stars, but also on the evolutionary link with their immediate progenitors. The most accurate method used for measuring the fundamental parameters of white dwarf stars is the so-called spectroscopic technique where spectroscopic observations, i.e. the distribution of the stellar flux with wavelength, are compared with the predictions of detailed stellar atmospheres, a method originally developed and continuously being improved at the Université de Montréal. A stellar atmosphere corresponds to this thin superficial layer surrounding the star where all the radiation comes from. The goal of our project is to improve our understanding of white dwarf stars by measuring the fundamental parameters of a large sample of objects with the help of improved calculations of synthetic spectra appropriate for these stars. From an observational point of view, we will secure spectroscopic observations of white dwarf stars with surface abundances composed of hydrogen (DA type) and helium (DB type) using spectrographs located at Steward Observatory in Arizona as well as at Mont Mégantic Observatory in Québec. From a theoretical point of view, we will calculate a new generation of model atmospheres and synthetic spectra, including several improvements in the constitutive physics such as line broadening, opacities, and convective energy transport. The comparison between observed and theoretical spectra will provide us with improved parameters for a large sample of white dwarf stars, which in turn will shed some light on their global properties as well as on their evolution.

白色矮星代表了银河系中95%以上恒星演化的终点，包括我们的太阳。白色矮星耗尽了中心的核燃料，在数十亿年的时间里安静地冷却下来。虽然它们的质量与太阳相当，但它们的体积更接近地球，这使它们成为非常紧凑的物体（大约是太阳密度的一百万倍）。对这些垂死恒星的研究以及它们的基本参数（如温度、质量和化学成分）的测定，不仅为我们提供了关于这些恒星性质的重要信息，而且还提供了关于它们与直接祖先的进化联系的重要信息。测量白色矮星基本参数的最精确方法是所谓的光谱技术，其中光谱观测，即恒星通量随波长的分布，与详细恒星大气的预测进行比较，这是蒙特利尔大学最初开发并不断改进的方法。 恒星大气层相当于围绕在星星周围的薄薄的表层，所有的辐射都来自于此。我们的项目的目标是通过测量大样本物体的基本参数，并借助适合这些恒星的合成光谱的改进计算，提高我们对白色矮星的理解。从观测的角度来看，我们将使用位于亚利桑那州斯图尔特天文台和魁北克省Mont Mégantic天文台的摄谱仪对表面丰度由氢（DA型）和氦（DB型）组成的白色矮星进行光谱观测。从理论的角度来看，我们将计算新一代的模型大气和合成光谱，包括本构物理学的几个改进，如线加宽，不透明度和对流能量传输。观测光谱和理论光谱的比较将为我们提供一个大样本的白色矮星的改进参数，这反过来又将揭示它们的整体性质以及它们的演化。