白矮-主序双星的搜寻及研究进展

Research Progress on Searching for White Dwarf—Main Sequence Binaries

白矮-主序双星是银河系中最常见的致密双星系统,它包含一颗白矮星主星和一颗小质量主序星伴星,由主序双星演化而来。大约1/4的白矮-主序双星经历过一个公共包层演化阶段,其轨道间距较小,周期很短,被称为后共包层双星;而另外3/4的白矮-主序双星则从未经历过公共包层演化,其轨道间距几乎与其最初的主序双星的相同,被称为宽距白矮-主序双星。在光学波段,一般从白矮-主序双星的光谱上能明显地看出其有两个成分。随着大型巡天项目如SDSS、LAMOST巡天的开展,近年来搜寻到的白矮-主序双星的数目越来越多。通过对搜寻到的白矮-主序双星进行大量的后续观测,己从中发现并确认了一大批后共包层双星。利用观测到的白矮-主序双星及后共包层双星样本,有助于我们进一步理解密近双星的演化过程,尤其是公共包层演化的物理机制等重要的天体物理热点议题。介绍了白矮-主序双星的形成和演化,回顾了大型巡天项目中自矮-主序双星的系统搜寻,以及基于这些白矮-主序双星样本获得的研究成果,最后对白矮-主序双星的搜寻研究做了展望。

White dwarf-main sequence binaries （WDMS） are the most common compact binary ob jects in the Galaxy, each of which consists of a white dwarf and a main sequence star and is evolved from main sequence binary. About 25 percent of the WDMS binaries are close WDMS binaries that evolved through a common envelope phase, and are commonly referred to as post-common-envelope binaries （PCEBs）. The remaining 75 percent are wide WDMS binaries that did not evolve through a common envelope phase, with the orbital separation roughly the same as the orbital separation of the initial main sequence binary. Generally, the two components can be seen clearly from the WDMS binary spectra optically. 〈br〉 Thanks to the large spectroscopic survey like SDSS and LAMOST, the number of WDMS binaries has been increased dramatically recently. A large number of wide WDMS binaries and PCEBs have been identified by the follow-up observations of these WDMS bina-ries. Currently, more than 2000 WDMS binaries have been discovered spectroscopically and about 200 PCEBs have been confirmed. Upon the large sample of SDSS WDMS binaries and PCEBs identified, many important researches have been carried on, such as the com-mon envelope theory, the origin of low mass white dwarf, mass-radius relations of both white dwarfs and low mass main sequence stars, and the pairing properties of main sequence stars. However, as the SDSS WDMS binaries sample has serious selection effects, which is strongly biased against binary systems containing cool white dwarf and/or early type companions, we still need to search more WDMS binaries to enlarge the sample. The LAMOST sky survey began its five years regular survey from September 2012, which will observe a large number of targets in the Milky Way. From the recent data release （DR1） of LAMOST, more than 100 WDMS binaries have been found. With the ongoing SDSS and LAMOST survey, more WDMS binaries are hoped to be identified and extend the existing WDMS binary sample. 〈br〉 In this paper, we give a detailed review on WDMS binaries including the formation and evolution of WDMS PCEBs, the identification of WDMS binaries, and the recent research progresses and future prospects.