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arXiv 2201.10125astro-ph.SRastro-ph.HE
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经典新星的混合分数

Mixing fraction in classical novae

Yunlang Guo, Chengyuan Wu, Bo Wang

备注：
14 pages, 6 figures, 2 tables, accepted for publication in A&A
发表信息：
A&A 660, A53 (2022)
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摘要：

上下文经典新星是由吸积的白矮星（WD）表面发生的热核失控提供动力的。在观测中，已经检测到新星喷出物中重元素的富集，表明在新星爆发之前，吸积物质与来自下伏WD外层的物质之间存在混合过程。然而，在经典新星的混合分数仍然是不确定的。目标。本文的目的是调查一些元素的丰度比在新星爆发，可用于估计WD混合分数在经典新星。方法.利用恒星演化程序MESA（Modules for Experiments in Stellar Astrophysics），考虑不同的WD混合分数，模拟了一系列的新星爆发过程，初始CO WD质量范围为$0.7-1.0\,M_\odot$.结果我们确定了四种元素丰度比（即$\rm (H+He)/\sum CNO$、$\rm (H+He)/Ne$、$\rm \sum CNO/Mg,$和$\rm \sum CNO/Si$）满足确定WD混合分数的条件，其中$\rm (H+He)/\sum CNO$是最合适的混合计。我们还估计了一些典型的经典新星的WD混合分数。此外，我们发现，更高的金属丰度（即更高的WD混合分数）优先伴随着较长的$t_{\rm 2}$（下降的时间从峰值光度的两个幅度）在新星爆发。我们的结果可以用来约束经典新星的混合过程。

英文摘要：

Context. Classical novae are powered by thermonuclear runaways occurring on the surface of accreting white dwarfs (WDs). In the observations, the enrichments of heavy elements in nova ejecta have been detected, indicating a mixing process between the accreted matter and the matter from the outer layers of the underlying WDs prior to nova outbursts. However, the mixing fraction in classical novae is still uncertain. Aims. The purpose of this article is to investigate some elemental abundance ratios during nova outbursts that can be used to estimate the WD mixing fraction in classical novae. Methods. By considering different WD mixing fractions with the stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA), we carried out a series of simulations of nova outbursts, in which the initial CO WD masses range from $0.7-1.0\,M_\odot$. Results. We identified four elemental abundance ratios (i.e. $\rm (H+He)/\sum CNO$, $\rm (H+He)/Ne$, $\rm \sum CNO/Mg,$ and $\rm \sum CNO/Si$) that satisfy the conditions for determining the WD mixing fraction, in which $\rm (H+He)/\sum CNO$ is the most suitable mixing meter. We also estimated the WD mixing fraction in some representative classical novae. Additionally, we found that a higher metallicity (i.e. higher WD mixing fraction) is preferentially accompanied by a longer $t_{\rm 2}$ (the time of decline by two magnitudes from peak luminosity) during nova outbursts. Our results can be used to constrain the mixing process in classical novae.

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