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arXiv 1208.6446astro-ph.HEastro-ph.SR
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来自合并双白矮星的Ia型超新星祖先:使用新的人口合成模型

Supernova Type Ia progenitors from merging double white dwarfs: Using a new population synthesis model

Silvia Toonen, Gijs Nelemans, Simon Portegies Zwart

摘要:

Ia型超新星的研究极大地改善了天体物理学中许多领域的见解,但仍然缺乏对这些事件起源的理论解释。我们研究了合并的双碳氧白矮星对SNIa速率的潜在贡献。我们的目标是开发一个模型,适合所观察到的SNIa祖细胞以及所观察到的密切双白矮星人口。我们区分两种情况下的共同信封(CE)的演变,α-形式主义的基础上的能量方程和γ-形式主义的基础上的角动量方程。在一个模型中,我们总是应用α-形式主义。在第二个模型中的伽玛形式主义的应用,除非二进制包含一个紧凑的对象或CE是由潮汐不稳定的α-形式主义使用触发。二进制人口合成代码SeBa被用来从零年龄的主序星演化二进制系统,形成双白矮星和随后的合并。自上次发布代码内容以来,SeBa已经进行了全面更新。观测到的双白矮星的有限样本是更好地代表了使用伽玛形式主义比阿尔法形式主义的模拟人口。对于CE形式主义,我们发现,虽然模拟延迟时间分布的形态匹配的误差内的观测,归一化和时间积分率每恒星质量是一个因素7-12低于观察。此外,合并的双碳-氧白矮星的模拟人口的特点进行了讨论,并提出了替代SNIa合并双白矮星模型的背景下。

英文摘要:

The study of Type Ia supernovae (SNIa) has lead to greatly improved insights into many fields in astrophysics, however a theoretical explanation of the origin of these events is still lacking. We investigate the potential contribution to the SNIa rate from the population of merging double carbon-oxygen white dwarfs. We aim to develope a model that fits the observed SNIa progenitors as well as the observed close double white dwarf population. We differentiate between two scenarios for the common envelope (CE) evolution; the alpha-formalism based on the energy equation and the gamma-formalism that is based on the angular momentum equation. In one model we apply the alpha-formalism always. In the second model the gamma-formalism is applied, unless the binary contains a compact object or the CE is triggered by a tidal instability for which the alpha-formalism is used. The binary population synthesis code SeBa was used to evolve binary systems from the zero-age main sequence to the formation of double white dwarfs and subsequent mergers. SeBa has been thoroughly updated since the last publication of the content of the code. The limited sample of observed double white dwarfs is better represented by the simulated population using the gamma-formalism than the alpha-formalism. For both CE formalisms, we find that although the morphology of the simulated delay time distribution matches that of the observations within the errors, the normalisation and time-integrated rate per stellar mass are a factor 7-12 lower than observed. Furthermore, the characteristics of the simulated populations of merging double carbon-oxygen white dwarfs are discussed and put in the context of alternative SNIa models for merging double white dwarfs.

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