EVR-CB-001: An Evolving, Progenitor, White Dwarf Compact Binary Discovered with the Evryscope
EVR-CB-001: An Evolving, Progenitor, White Dwarf Compact Binary Discovered with the Evryscope
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DOI：
10.3847/1538-4357/ab3727
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发表时间：
2019-09
期刊：
影响因子：
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通讯作者：
J. Ratzloff;B. Barlow;T. Kupfer;Kyle A. Corcoran;S. Geier;E. Bauer;H. Corbett;W. Howard;
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文献类型：
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作者：
J. Ratzloff;B. Barlow;T. Kupfer;Kyle A. Corcoran;S. Geier;E. Bauer;H. Corbett;W. Howard;
EVR-CB-001是一颗致密的双星，它有一个极低质量（0.21 ± 0.05 M）的氦核白色矮星前身（前He WD）和一个看不见的低质量（0.32 ± 0.06 M）的氦白色矮星（He WD）伴星。WD被认为是从主序星的剩余富氦核心演变而来的，该核心在巨星阶段被一颗近伴星剥离。主序星星。低质量的He WDs是奇异天体（只有约0.2%的WDs被认为小于0.3 M），预计会在致密双星中发现。前He WD更为罕见，并且在核心被剥离之后，但在星星成为完全简并WD之前占据中间阶段，并且具有比典型WD更大的半径（10.2R）。EVR-CB-001（前He WD）的主要成分最初被认为是一颗热亚矮星（sdB）星星，因为它的颜色是蓝色的，亮度不足，是sdB的特征。这项工作的质量，温度（Teff = 18，500 ± 500 K）和表面重力（）的解决方案低于典型的热亚矮星的值。主要的可能是一个后红巨星分支，前He WD收缩成He WD，并在一个阶段，把它最接近sdBs的颜色星等和Teff-log（g）图。EVR-CB-001预计将演化成一个完全双简并的紧凑系统，该系统应该会自旋下降，并有可能演化成一颗热的亚矮星星星。单个的热次矮星被观测到，但祖先系统一直难以捉摸。
We present EVR-CB-001, the discovery of a compact binary with an extremely low-mass (0.21 ± 0.05M⊙) helium core white dwarf progenitor (pre-He WD) and an unseen low-mass (0.32 ± 0.06M⊙) helium white dwarf (He WD) companion. He WDs are thought to evolve from the remnant helium-rich core of a main-sequence star stripped during the giant phase by a close companion. Low-mass He WDs are exotic objects (only about 0.2% of WDs are thought to be less than 0.3 M⊙), and are expected to be found in compact binaries. Pre-He WDs are even rarer, and occupy the intermediate phase after the core is stripped, but before the star becomes a fully degenerate WD and with a larger radius (≈0.2R⊙) than a typical WD. The primary component of EVR-CB-001 (the pre-He WD) was originally thought to be a hot subdwarf (sdB) star from its blue color and under-luminous magnitude, characteristic of sdBs. The mass, temperature (Teff = 18,500 ± 500 K), and surface gravity ( ) solutions from this work are lower than values for typical hot subdwarfs. The primary is likely to be a post-red-giant branch, pre-He WD contracting into a He WD, and at a stage that places it nearest to sdBs on color–magnitude and Teff–log(g) diagrams. EVR-CB-001 is expected to evolve into a fully double degenerate, compact system that should spin down and potentially evolve into a single hot subdwarf star. Single hot subdwarfs are observed, but progenitor systems have been elusive.