Asteroseismic test of rotational mixing in low-mass white dwarfs
Asteroseismic test of rotational mixing in low-mass white dwarfs
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DOI：
10.1051/0004-6361/201629876
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发表时间：
2016-10
影响因子：
6.5
通讯作者：
A. Istrate;G. Fontaine;A. Gianninas;L. Grassitelli;P. Marchant;T. Tauris;N. Langer
中科院分区：
文献类型：
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作者：
A. Istrate;G. Fontaine;A. Gianninas;L. Grassitelli;P. Marchant;T. Tauris;N. Langer
我们利用最近在混合大气（He/H）中发现的脉动，极低质量白矮星前体（ELM原型- wds）来验证旋转混合是低质量氦核白矮星形成和演化的基本过程这一命题。旋转混合已被证明是一种能够有效对抗重力沉降的机制，因此自然地解释了He的存在，以及通常在ELM原型wds大气中发现的微量金属，如Mg和Ca。在这里，我们研究旋转混合是否可以在恒星的深层驱动区保持足够数量的He，从而可以通过hei - heiii电离为这类恒星中观测到的脉动提供燃料。使用MESA计算的最先进的进化模型，我们表明旋转混合确实可以定性地解释已知脉动混合大气ELM原型wds的存在和一般性质。此外，这些天体很可能在它们最后的WD冷却阶段再次脉动。
We exploit the recent discovery of pulsations in mixed-atmosphere (He/H), extremely low-mass white dwarf precursors (ELM proto-WDs) to test the proposition that rotational mixing is a fundamental process in the formation and evolution of low-mass helium core white dwarfs. Rotational mixing has been shown to be a mechanism able to compete efficiently against gravitational settling, thus accounting naturally for the presence of He, as well as traces of metals such as Mg and Ca, typically found in the atmospheres of ELM proto-WDs. Here we investigate whether rotational mixing can maintain a sufficient amount of He in the deeper driving region of the star, such that it can fuel, through Heii-Heiii ionization, the observed pulsations in this type of stars. Using state-of-the-art evolutionary models computed with MESA, we show that rotational mixing can indeed explain qualitatively the very existence and general properties of the known pulsating, mixed-atmosphere ELM proto-WDs. Moreover, such objects are very likely to pulsate again during their final WD cooling phase.