Close binary evolution

密近联星的演化有三个主要的未知数：（a）共同包络相在减少联星分离方面的效率如何？(b)磁制动引起的轨道角动量损失有多强？(c)如果次级星星完全对流，磁制动是否消失？这些问题可以通过对白矮星/主序星双星的彻底观测研究来回答，这些双星在其演化过程中已经通过了共同的包络阶段。这些天体数量丰富，虽然还不为人所知，但它们足够明亮，双星成分的演化也得到了合理的理解，它们的光也没有被吸积辐射所污染。基于档案SDSS数据和自己的SEGUE光谱，我们正在生成一个大型数据库的白矮星/主序列的二进制文件，其中包含约25%的后共同信封类型的密切的二进制文件。我们正在进行一个大规模的协调光学后续计划，以确定密切的双星，确定其轨道周期，并进行彻底的统计研究，以观测约束磁制动定律和约束共同的包络效率。

The evolution of close binary stars has three major unknowns: (a) How efficient is the common envelope phase in reducing the binary separation? (b) How strong is orbital angular momentum loss due to magnetic braking? (c) Does magnetic braking vanish if the secondary star is fully convective? Those questions can be answered by a thorough observationally study of white-dwarf/main-sequence binaries which have passed the common envelope phase in their binary evolution. The objects are abundant, although not yet known, they are sufficiently bright, the evolution of the binary components is reasonably well understood, and their light is not contaminated by accretion radiation. Based on archival SDSS data and own SEGUE spectroscopy we are generating a large data base of white-dwarf/main-sequence binaries, which harbour some 25% of close binaries of post-common envelope type. We are conducting a large-scale coordinated optical follow-up program to identify the close binaries, determine their orbital periods and perform a thorough statistical study to observationally constrain the magnetic braking law and to constrain the common envelope efficiency.