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arXiv 1105.5698astro-ph.SR
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Ia型超新星共包络末期的环双星盘和核简并情形

A Circumbinary Disk in the Final Stages of Common Envelope and the Core-Degenerate Scenario for Type Ia Supernovae

Amit Kashi, Noam Soker

摘要:

我们研究了共同包络(CE)演化的最后阶段,发现相当一部分的喷射质量没有达到逃逸速度。为了得出这个结论,我们在简化假设下使用自相似解。伴随白矮星(WD)的大部分引力能量在很短的时间内被释放到大质量渐近巨星分支(AGB)或红巨星分支(RGB)恒星的包层中。这种快速的能量释放在外壳中形成冲击波。我们遵循从AGB中心向外的爆炸波传播,并表明约1- 10%的喷射信封仍然绑定到残余的二元系统。我们认为,由于角动量守恒和进一步与双星系统的相互作用,后备材料形成了一个circumbinary磁盘周围的后AGB核心和同伴WD。环双星盘与双星系统的相互作用将减少轨道分离,这比单独从CE的动力学阶段(包层被弹出)所预期的要多得多。较小的轨道间隔有利于在CE阶段结束时或之后的短时间内合并,而核心仍然是热的。这是另一个通道,形成一个巨大的WD,具有超克拉塞卡质量,可能爆炸为Ia型超新星。我们称之为核心退化(CD)的情况。

英文摘要:

We study the final stages of the common envelope (CE) evolution and find that a substantial fraction of the ejected mass does not reach the escape velocity. To reach this conclusion we use a self-similar solution under simplifying assumptions. Most of the gravitational energy of a companion white dwarf (WD) is released in the envelope of a massive asymptotic giant branch (AGB) or the red giant branch (RGB) star in a very short time. This rapid energy release forms a blast wave in the envelope. We follow the blast wave propagation from the center of the AGB outwards, and show that ~1-10 per cent of the ejected envelope remains bound to the remnant binary system. We suggest that due to angular momentum conservation and further interaction with the binary system, the fallback material forms a circumbinary disk around the post-AGB Core and the companion WD. The interaction of the circumbinary disk with the binary system will reduce the orbital separation much more than expected from the dynamical phase (where the envelope is ejected) of the CE alone. The smaller orbital separation favors a merger at the end of the CE phase or a short time after, while the core is still hot. This is another channel to form a massive WD with super-Chandrasekhar mass that might explode as a type Ia supernova. We term this the core-degenerate (CD) scenario.

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