U.S.-U.K. Cooperative Research: Spectroscopy of Faint Cataclysmic Variables

该奖项将支持亚利桑那州图森市行星科学研究所的Steven Howell博士和伦敦大学学院Mullard空间科学实验室的Keith Mason博士在天文学方面的合作研究。该计划的目标是调查一组以前未被研究过的变星，这些变星可能是银河晕的成员。灾难性变星（CV）的标准图像是一个紧密的双星系统，由一颗晚期主序星组成，它将质量转移给一颗白矮星伴星。离开次级恒星的物质在主星周围形成了一个圆盘。这束光与圆盘的交点产生了一个“热点”，它可以提供大部分的系统光。如果白矮星有足够强的磁场，转移的物质就会受到干扰，甚至可以延缓盘的形成。找到这些灾难性变量的真实位置的唯一直接方法是通过距离测定。研究人员正在分析光谱数据，使用他们在穆拉德空间科学实验室共同开发的软件，对不同系统组件对数据的贡献进行建模和反卷积。这一过程将使他们能够推算出这些恒星的距离。如果这些双星系统真的位于银晕中，那么它们的性质应该与位于盘中的双星系统有很大的不同。这项研究的结果将对理解灾难性变量的真实性质以及这些种群的差异，以及理解我们银河系的结构和演化做出重要贡献。该项目将受益于两位研究人员在双星理论解释领域的互补专业知识。

This award will support collaborative research in astronomy between Dr. Steven Howell, Planetary Science Institute, Tucson, Arizona and Dr. Keith Mason, Mullard Space Science Laboratory, University College London. The objective of the proposed project is to investigate a previously unstudied group of cataclysmic variable stars which may be members of the Galactic halo. The standard picture of a cataclysmic variable (CV) is a close binary system consisting of a late type main sequence star which transfers mass to a white dwarf companion. The material that leaves the secondary forms a disk around the primary star. The intersection of this stream and the disk gives rise to a "hot spot", which can provide a large fraction of the system light. If the white dwarf has a sufficiently strong magnetic field, the transferred material will be disturbed and even the formation of the disk can be retarded. The only direct method of finding the true location of these cataclysmic variables is through distance determination. The investigators are analyzing spectroscopic data, using software which they developed jointly at the Mullard Space Science Laboratory, to model and deconvolve the contributions to the data from the various systems components. This procedure will allow them to derive a distance for these stars. If these binary systems are really located in the Galactic halo, they should have very different properties from their well studied counterparts located in the disk. The results of this study will make an important contribution to understanding the true nature of cataclysmic variables and how these populations differ, as well as to understanding the structure and evolution of our Galaxy in general. The project will benefit from the complementary expertise of the two investigators in the area of theoretical interpretations of binary stars.