White dwarf binaries suggest a common envelope efficiency α ∼ 1/3
White dwarf binaries suggest a common envelope efficiency α ∼ 1/3
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白矮星双星表明共同的包络效率 α ≤ 1/3
DOI：
10.1093/mnras/stac3313
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发表时间：
2022
影响因子：
4.8
通讯作者：
Fuller, Jim
中科院分区：
文献类型：
--
作者：
Scherbak, Peter;Fuller, Jim
共同包层（CE）的演化对于创建短期双星和相关的天体物理事件至关重要，可以通过对此类双星形成历史的逆向建模来限制。通过对具有低质量主星的约束良好的白矮星 (WD) 双星样本（七个食双 WD、两个非食双 WD、一个 WD 棕矮星）样本的分析，我们估计了解开氢包层所需的 CE 能量效率 αC。我们使用氦核和二氧化碳核 WD 模型网格来确定与每个主 WD 半径和温度相匹配的质量和冷却年龄。假设引力波驱动的轨道衰变，我们然后计算CE后轨道周期的相关范围。通过将 WD 模型映射到红巨星祖星网格，我们确定了 CE 演化启动点的总包络结合能和可能的轨道周期，从而限制了 αCE。假设 He 核 WD 的祖细胞为 0.9–2.0 M⊙，我们发现 αCE∼ 0.2–0.4 与我们建模的每个系统一致。更高质量的祖细胞和 CO 核心 WD 需要显着更高的 αCE 值，因此这些情况被认为是不可能的。我们的值与之前对 CE 后 WD 双星的研究基本一致，并且它们表明产生 He 核 WD 的 CE 事件具有几乎恒定且较低的包络喷射效率。
Common envelope (CE) evolution, which is crucial in creating short-period binaries and associated astrophysical events, can be constrained by reverse modelling of such binaries’ formation histories. Through analysis of a sample of well-constrained white dwarf (WD) binaries with low-mass primaries (seven eclipsing double WDs, two non-eclipsing double WDs, one WD-brown dwarf), we estimate the CE energy efficiency αCEneeded to unbind the hydrogen envelope. We use grids of He- and CO-core WD models to determine the masses and cooling ages that match each primary WD’s radius and temperature. Assuming gravitational wave-driven orbital decay, we then calculate the associated ranges in post-CE orbital period. By mapping WD models to a grid of red giant progenitor stars, we determine the total envelope binding energies and possible orbital periods at the point CE evolution is initiated, thereby constraining αCE. Assuming He-core WDs with progenitors of 0.9–2.0 M⊙, we find αCE∼ 0.2–0.4 is consistent with each system we model. Significantly higher values of αCEare required for higher mass progenitors and for CO-core WDs, so these scenarios are deemed unlikely. Our values are mostly consistent with previous studies of post-CE WD binaries, and they suggest a nearly constant and low envelope ejection efficiency for CE events that produce He-core WDs.