AM CVn Stars: Status and Challenges
AM CVn Stars: Status and Challenges
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DOI：
10.1086/656680
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发表时间：
2010-09
影响因子：
3.5
通讯作者：
J. Solheim
中科院分区：
文献类型：
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作者：
J. Solheim
AMCVn恒星是微调双星演化路径的产物。它们富含氦，它们的双轨道周期不到65分钟。它们通过一个或两个公共包络(CE)事件演变，这些事件很难建模。对AM-CVN恒星的观测对于理解CE相是很重要的。由于密集的观测活动，在过去的15年里，AM CVN恒星的数量从5颗增加到了25颗。我们见证了长时间的光度运动、时间分辨光谱、紫外线和X射线观测，以及在模拟施主和吸积星的内部结构、盘结构、盘大气层及其演化方面的进展。AM CVn家族的两个可能的新成员的轨道周期不到10分钟。对于这些，已经提出了四种不同的模型，其中一种没有质量传递，由在主星磁场中运动的次星产生的电力驱动。短周期的AM CVN恒星是第一批可能探测到的低频引力波(GW)辐射源之一。它们也可能是Ia型超新星(SN Ia)和亚光爆炸的前身，它们可以在演化过程中产生氦新星。从斯隆数字天空调查的系统搜索中，已经有可能估计出可以根据人口合成模型进行测试的人口密度。需要研究的一个重要问题是三种分娩途径的相对重要性：低质量白矮星捐献者、氦星捐赠者或高度进化的激变变星(CV)捐赠者。对近15年来AM CVN星的研究进行了综述，并对未来的研究进行了展望。
AM CVn stars are the outcome of a fine-tuned binary star evolution pathway. They are helium-rich and their binary orbital periods are less than 65 minutes. They evolve through one or two common envelope (CE) events, which are difficult to model. Observations of AM CVn stars are important to understand the CE phase. Thanks to intensive observing campaigns, the number of AM CVn stars has increased from 5 to 25 during the last 15 yr. We have witnessed long photometric campaigns, time-resolved spectroscopy, UV and X-ray observations, and progress in modeling of the internal structure of donor and accretor stars, disk structure, disk atmosphere, and their evolution. Two possible new members of the AM CVn family have orbital periods of less than 10 minutes. For these, four different models have been proposed, including one without mass transfer, driven by electricity generated by the secondary star moving in the magnetic field of the primary. Short-period AM CVn stars are among the first possible detectable sources of low-frequency gravitational wave (GW) radiation. They are also possible progenitors of a Type Ia supernova (SN Ia) and subluminous explosions, and they can produce helium novae during their evolution. From systematic searches in the Sloan Digital Sky Survey, it has been possible to estimate population densities that can be tested against population synthesis models. One important question to investigate is the relative importance of the three proposed birth channels: a low-mass white dwarf donor, a helium-star donor, or a highly evolved cataclysmic variable (CV) as a donor. A review of the research on AM CVn stars covering the last 15 yr is given, and the outlook for future research is discussed.