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首页> 外文期刊>Astronomy and astrophysics >Helium ignition in rotating magnetized CO white dwarfs leading to fast and faint rather than classical Type Ia supernovae
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Helium ignition in rotating magnetized CO white dwarfs leading to fast and faint rather than classical Type Ia supernovae

机译：旋转的磁化CO白矮星中的氦气点火导致快速而微弱，而不是经典的Ia型超新星

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Context. Based mostly on stellar models that do not include rotation, CO white dwarfs that accrete helium at rates of about ~ 10 ~(-8) M _(⊙)/ yr have been put forward as candidate progenitors for a number of transient astrophysical phenomena, including Type Ia supernovae and the peculiar and fainter Type Iax supernovae. Aims. Here we study the impact of accretion-induced spin-up including the subsequent magnetic field generation, angular momentum transport, and viscous heating on the white dwarf evolution up to the point of helium ignition. Methods. We resolve the structure of the helium accreting white dwarf models with a one-dimensional Langrangian hydrodynamic code, modified to include rotational and magnetic effects, in 315 model sequences adopting different mass-transfer rates ( 10~(-8)?10~(-7) M _(⊙)/ yr ), and initial white dwarf masses ( 0.54?1.10 M _(⊙) ) and luminosities ( 0.01?1 ? L _(⊙) ). Results. We find magnetic angular momentum transport, which leads to quasi-solid-body rotation, profoundly impacts the evolution of the white dwarf models, and the helium ignition conditions. Our rotating lower mass ( 0.54 and 0.82 M _(⊙) ) models accrete up to 50% more mass up to ignition than the non-rotating case, while it is the opposite for our more massive models. Furthermore, we find that rotation leads to helium ignition densities that are up to ten times smaller, except for the lowest adopted initial white dwarf mass. Ignition densities on the order of 10~(6) ?g/cm ~(3) are only found for the lowest accretion rates and for large amounts of accreted helium ( ? 0.4 M _(⊙) ). However, correspondingly massive donor stars would transfer mass at much higher rates. We therefore expect explosive He-shell burning to mostly occur as deflagrations and at ? & 2 × 10~(-8) M _(⊙)/ yr , regardless of white dwarf mass. Conclusions. Our results imply that helium accretion onto CO white dwarfs at the considered rates is unlikely to lead to the explosion of the CO core or to classical Type?Ia supernovae, but may instead produce events that belong to the recently identified classes of faint and fast hydrogen-free supernovae.
机译：上下文。主要基于不包括旋转的恒星模型，提出了以约10〜（-8）M _（⊙）/年的速率增加氦气的CO白矮星，作为许多短暂天体物理现象的候选祖先，包括Ia型超新星和奇特而微弱的Iax型超新星。目的在这里，我们研究了包括后继磁场产生，角动量传输和粘性加热在内的增生诱导的自旋向上对白矮星演化直至氦点火的影响。方法。我们采用一维Langrangian流体力学代码解析了吸积氦的白矮星模型的结构，将其修改为包括旋转和磁效应的315个模型序列，采用了不同的传质速率（10〜（-8）？10〜（- 7）M _（⊙）/ yr），初始白矮星质量（0.54？1.10 M _（⊙））和光度（0.01？1？L _（⊙））。结果。我们发现磁角动量传输会导致准固体旋转，深刻影响白矮星模型的演化以及氦气的点火条件。与非旋转情况相比，我们旋转的较低质量（0.54和0.82 M _（ignition））的模型在点火时的质量增加了多达50％，而对于更大质量的模型则相反。此外，我们发现，旋转会导致氦气点火密度减小多达十倍，除了采用的最低初始白矮星质量。仅在最低的吸积率和大量的氦气堆积（≥0.4 M _（⊙））下才能找到10〜（6）μg/ cm〜（3）量级的点火密度。但是，相应大量的捐助恒星将以更高的速率转移质量。因此，我们预计爆炸性的He壳燃烧主要是在爆燃和？ ＆ 2×10〜（-8）M _（⊙）/年，与白矮星质量无关。结论。我们的结果表明，以适当的速率将氦气吸收到CO白矮星上不太可能导致CO核或经典的Type Ia超新星爆炸，但可能会产生属于最近确定的微弱和快速氢类的事件。无超新星。

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