Merging binary stars and the magnetic white dwarfs
Merging binary stars and the magnetic white dwarfs
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DOI：
10.1093/mnras/stu2539
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发表时间：
2014-12
影响因子：
4.8
通讯作者：
G. Briggs;L. Ferrario;C. Tout;D. Wickramasinghe;J. Hurley
中科院分区：
文献类型：
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作者：
G. Briggs;L. Ferrario;C. Tout;D. Wickramasinghe;J. Hurley
恒星合并时产生的由差异旋转驱动的磁发电机可以解释某些类别的磁星中的强场，包括高场磁白矮星(HFMWD)。在他们的例子中，差异旋转的位置被不同地提出在一个共同的包层内，即合并的简并核心的巨大热外部区域，或者由潮汐分裂的伴星形成的吸积盘，随后并入简并核心。我们合成了一组双星系统来研究观测到的单个HFMWD的恒星合并假说。我们的计算提供了质量分布和白矮星在公共包络阶段合并或在后公共包络阶段作为双简并系统合并的分数。我们改变了常见的包络效率参数α，并与观测结果进行了比较。我们发现，这一假设既可以解释观察到的磁性入射，也可以解释大范围α范围内HFMWDS的质量分布。在这个模型中，大多数HFMWD是碳氧型的，并合并在一个共同的包膜中。只有不到四分之一的HFMWD起源于双简并恒星，它们在共同的包层演化后合并，这些恒星占据了HFMWD质量分布的高质量尾部。
A magnetic dynamo driven by differential rotation generated when stars merge can explain strong fields in certain classes of magnetic stars, including the high field magnetic white dwarfs (HFMWDs). In their case the site of the differential rotation has been variously proposed to be within a common envelope, the massive hot outer regions of a merged degenerate core or an accretion disc formed by a tidally disrupted companion that is subsequently incorporated into a degenerate core. We synthesize a population of binary systems to investigate the stellar merging hypothesis for observed single HFMWDs. Our calculations provide mass distribution and the fractions of white dwarfs that merge during a common envelope phase or as double degenerate systems in a post common envelope phase. We vary the common envelope efficiency parameter alpha and compare with observations. We find that this hypothesis can explain both the observed incidence of magnetism and the mass distribution of HFMWDs for a wide range of alpha. In this model, the majority of the HFMWDs are of the Carbon Oxygen type and merge within a common envelope. Less than about a quarter of a per cent of HFMWDs originate from double degenerate stars that merge after common envelope evolution and these populate the high-mass tail of the HFMWD mass distribution.