论文标题
白矮人二进制途径调查-IX。三个长时间白矮人加次二进制
The White Dwarf Binary Pathways Survey -- IX. Three long period white dwarf plus subgiant binaries
论文作者
论文摘要
几乎所有由白色矮人组成的二进制文件都可以归类为近距离交互后系统（轨道周期为几天或更短的时间），或者较宽的系统（比数十年的时间更长），其中两个组件在其中有效演变为单星星。具有这两个极端之间的时期的二进制文件可以帮助限制共同的包膜效率，或突出探索紧凑型二进制文件的替代途径。迄今为止，这样的二进制文件仍然难以捉摸。在这里，我们介绍了三个白色矮人的二进制室，其轨道周期为41、52和461 d。使用哈勃太空望远镜光谱，我们发现所有三个系统都包含低质量白色矮人（$ \ leq $ 0.4 m $ _ {\ odot} $）。一个系统，TYC 8394 $ - $ 1331 $ - $ 1，是一个层次三重的内部二进制，其中白矮人加上子级二进制是由更遥远的同伴星绕的。这些二进制文件可能是由稳定但非保守传质的阶段形成的，而不是共同的包膜进化。这三个系统将来都会经历一个共同的信封阶段，但是在此事件期间，预计两个较短的时期系统将合并，而最长的时期系统可能会生存并创建一个具有两个低质量白矮人的近距离二进制。
Virtually all binaries consisting of a white dwarf with a non-degenerate companion can be classified as either close post-interaction systems (with orbital periods of a few days or less), or wide systems (with periods longer than decades), in which both components have effectively evolved as single stars. Binaries with periods between these two extremes can help constrain common envelope efficiency, or highlight alternative pathways towards the creation of compact binaries. To date such binaries have remained mostly elusive. Here we present three white dwarfs in binaries with evolved subgiant stars with orbital periods of 41, 52 and 461 d. Using Hubble Space Telescope spectroscopy we find that all three systems contain low mass white dwarfs ($\leq$0.4 M$_{\odot}$). One system, TYC 8394$-$1331$-$1, is the inner binary of a hierarchical triple, where the white dwarf plus subgiant binary is orbited by a more distant companion star. These binaries were likely formed from a phase of stable but non-conservative mass transfer, as opposed to common envelope evolution. All three systems will undergo a common envelope phase in the future, but the two shorter period systems are expected to merge during this event, while the longest period system is likely to survive and create a close binary with two low mass white dwarfs.
