Evolution of helium star plus carbon-oxygen white dwarf binary systems and implications for diverse stellar transients and hypervelocity stars
Evolution of helium star plus carbon-oxygen white dwarf binary systems and implications for diverse stellar transients and hypervelocity stars
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DOI：
10.1051/0004-6361/201935322
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发表时间：
2019-04
影响因子：
6.5
通讯作者：
P. Neunteufel;S.-C. Yoon;N. Langer
中科院分区：
文献类型：
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作者：
P. Neunteufel;S.-C. Yoon;N. Langer
上下文氦吸积引起的CO白色矮星（WD）爆炸被认为是许多观测到的恒星瞬变类型的有希望的候选者，包括Ia型和Iax型超新星（SNe）。然而，一个明确的最喜欢的结果还没有出现。目标。我们探讨的条件下，氦点燃的WD和最终命运的氦星WD双星作为其初始轨道周期和组件质量的函数。方法.我们计算了274个模型的二元系统的二元演化代码，其中两个组件是完全解决的。恒星和轨道演化计算包括质量和角动量转移，潮汐，引力波发射，差分旋转，和内部流体动力学和磁性角动量输运。我们制定了参数空间的部分导致WD上的吸积氦层的爆炸，可能导致WD的完全中断爆燃，WD的CO核心可能保持完整，并避免WD中的氦点火。结果我们发现氦爆炸只在初始轨道周期最短的系统中发生，并且对于初始质量较大的WD（MWD ≥ 1.0 M <$）和较低质量的施主（Mdonor ≤ 0.8 M <$），它们的氦积累层大多超过0.1 M <$。爆炸后，这些系统将释放捐助者作为超高速前WD失控星星，我们预测的运动学和恒星性质的预期范围。具有更大质量施主或初始周期超过1.5 h的系统在积累了0.1 - 0.001 M的氦后可能会发生氦爆燃。氦点火的WD是避免在系统中的氦捐助者低于10.6 M的恒星，并导致三个明显不同的群体双WD系统。结论.氦爆炸的参数空间的大小只相当于银河系超新星Ia速率的3%和超新星Iax速率的10%，而预测的大量氦（0.1 M）的祖先不能很容易地与原型超新星Ia的观测相一致。然而，从这些系统中出现的瞬变可能会对大质量氦新星，富钙的SNe Ib，以及可能非常接近的双简并系统做出重大贡献，这些系统最终可能会产生普通或特殊的SNe Ia，或者，对于最小的考虑质量，北冕座R星。
Context. Helium accretion induced explosions in CO white dwarfs (WDs) are considered promising candidates for a number of observed types of stellar transients, including supernovae (SNe) of Type Ia and Type Iax. However, a clear favorite outcome has not yet emerged. Aims. We explore the conditions of helium ignition in the WD and the final fates of helium star-WD binaries as functions of their initial orbital periods and component masses. Methods. We computed 274 model binary systems with the Binary Evolution Code, in which both components are fully resolved. Both stellar and orbital evolution were computed including mass and angular momentum transfer, tides, gravitational wave emission, differential rotation, and internal hydrodynamic and magnetic angular momentum transport. We worked out the parts of the parameter space leading to detonations of the accreted helium layer on the WD, likely resulting in the complete disruption of the WD to deflagrations, where the CO core of the WD may remain intact and where helium ignition in the WD is avoided. Results. We find that helium detonations are expected only in systems with the shortest initial orbital periods, and for initially massive WDs (MWD ≥ 1.0 M⊙) and lower mass donors (Mdonor ≤ 0.8 M⊙), which have accumulated helium layers mostly exceeding 0.1 M⊙. Upon detonation, these systems would release the donor as a hypervelocity pre-WD runaway star, for which we predict the expected range of kinematic and stellar properties. Systems with more massive donors or initial periods exceeding 1.5 h likely undergo helium deflagrations after accumulating 0.1 − 0.001 M⊙ of helium. Helium ignition in the WD is avoided in systems with helium donor stars below ∼0.6 M⊙, and leads to three distinctly different groups of double WD systems. Conclusions. The size of the parameter space open to helium detonation corresponds to only about 3% of the galactic SN Ia rate and to 10% of the SN Iax rate, while the predicted large amounts of helium (0.1 M⊙) in progenitors cannot easily be reconciled with observations of archetypical SN Ia. However, the transients emerging from these systems may contribute significantly to massive helium novae, calcium-rich SNe Ib, and, potentially, very close double degenerate systems that may eventually produce either ordinary or peculiar SNe Ia, or, for the smallest considered masses, R Coronae Borealis stars.