Population synthesis for double white dwarfs. I. Close detached systems.
Population synthesis for double white dwarfs. I. Close detached systems.
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DOI：
10.1051/0004-6361:20000147
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发表时间：
2000-10
影响因子：
6.5
通讯作者：
G. Nelemans;L. Yungelson;S. P. Zwart;F. Verbunt
中科院分区：
文献类型：
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作者：
G. Nelemans;L. Yungelson;S. P. Zwart;F. Verbunt
我们对银河系中双白矮星的数量进行建模，由于两项改进，与早期研究相比，我们的结果与观测更为吻合。第一项是对不稳定物质转移第一阶段的处理，第二项是对白矮星冷却的建模。如果我们假设初始双星比例约为50%，并且质量最低的白矮星（$M<0.45M_{\odot}$）是由质量比为$q<0.2$的双星系统形成的，那么就能与当地白矮星样本的观测结果达成令人满意的一致。我们预测了双白矮星系统的各种性质：AM CVn系统的诞生率为$0.005$年$^{-1}$，总质量超过钱德拉塞卡极限（可能是Ia型超新星的前身）的双星并合率为$0.003$年$^{-1}$，行星状星云的形成率为$1$年$^{-1}$。我们估计银河系中双白矮星的总数为$2.5\times10^{8}$。在一个极限星等为$V_{\rm lim}=15$的可观测样本中，我们预测存在约855颗白矮星，其中约220颗是密近双星。在这些密近双星中，有10颗是碳氧（CO）双白矮星，其中一颗总质量超过钱德拉塞卡极限，并将在哈勃时间内并合。
We model the population of double white dwarfs in the Galaxy and find a better agreement with observations compared to earlier studies, due to two modifications. The first is the treatment of the first phase of unstable mass transfer and the second the modelling of the cooling of the white dwarfs. A satisfactory agreement with observations of the local sample of white dwarfs is achieved if we assume that the initial binary fraction is ∼ 50% and that the lowest mass white dwarfs ($M -1 , a birth rate of AM CVn systems of 0.005 yr -1 , a merger rate of pairs with a combined mass exceeding the Chandrasekhar limit (which may be progenitors of SNe Ia) of 0.003 yr -1 and a formation rate of planetary nebulae of 1 yr -1 . We estimate the total number of double white dwarfs in the Galaxy as 2.5 10 8 . In an observable sample with a limiting magnitude $V_{\rm lim} = 15$ we predict the presence of ∼ 855 white dwarfs of which ∼ 220 are close pairs. Of these 10 are double CO white dwarfs of which one has a combined mass exceeding the Chandrasekhar limit and will merge within a Hubble time.