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arXiv 1105.0754astro-ph.SR
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Ia型超新星超软X射线位相的二元布居合成研究

Binary population synthesis study on supersoft X-ray phase of single degenerate type Ia supernova progenitors

Xiangcun Meng, Wuming Yang

摘要:

在Ia型超新星(SNe Ia)的单简并(SD)方案中,质量吸积的白矮星预计将经历超软X射线源(SSS)阶段。然而,最近的一些观测表明,无论是在螺旋星系还是椭圆星系中,质量吸积WD的预期数量都远低于理论预测。本文采用二元布居合成方法研究了WDs导致SNe Ia的SSS阶段相对于其整个质量增长阶段的持续时间。我们发现,约40%的祖先系统的相对持续时间小于2%,平均相对持续时间的演变表明,无论是年轻的还是年老的Ia型SNe,其相对持续时间都小于5%。另外,在超新星Ia爆发前,超过55%的祖星系统处于矮新星阶段,只有不到10%的祖星系统处于SSS阶段。这些结果与最近的观测结果是一致的,并暗示,无论是在早期和晚期类型的星系,只有一小部分的质量吸积WD导致超新星Ia有助于超软X射线通量。因此,尽管我们的结果与超新星Ia的前身星系的X射线输出没有直接关系,但早期型星系中观测到的低超软X射线光度并不能排除SD模型的有效性。相反,这是支持SD情景的证据。

英文摘要:

In the single degenerate (SD) scenario for type Ia supernovae (SNe Ia), a mass-accreting white dwarf is expected to experience a supersoft X-ray source (SSS) phase. However, some recent observations showed that the expected number of the mass-accreting WD is much lower than that predicted from theory, whatever in spiral or elliptical galaxies. In this paper, we did a binary population synthesis study on the relative duration of the SSS phase to their whole mass-increasing phase of WDs leading to SNe Ia. We found that for about 40% progenitor systems, the relative duration is shorter than 2% and the evolution of the mean relative duration shows that it is always smaller than 5%, whatever for young or old SNe Ia. In addition, before SNe Ia explosion, more than 55% progenitor systems are experiencing a dwarf novae phase, and only no more than 10% is staying SSS phase. These results are consistent with the recent observations, and imply that both in early- and late-type galaxies, only a small fraction of mass-accreting WD resulting in SNe Ia contribute to the supersoft X-ray flux. So, although our results are not directly related to the X-ray output of SN Ia progenitor, the low supersoft X-ray luminosity observed in early type galaxies may have no ability to exclude the validity of SD model. On the contrary, it is evidence to support the SD scenario.

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