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arXiv 2303.03409astro-ph.SRastro-ph.HEphysics.plasm-ph
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超巨质量O-Ne白矮星中$^{56}$Fe的蒸馏

Distillation of $^{56}$Fe in Ultramassive O-Ne White Dwarfs

Matthew E. Caplan, Simon Blouin, Ian F. Freeman

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8 pages, 3 figures, accepted for publication in ApJ
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AI总结：

本文通过计算O-Ne-Fe混合物相图，研究超巨质量O-Ne白矮星中$^{56}$Fe的蒸馏过程，揭示其形成Fe内核或壳层的条件及对冷却延迟和超新星富中子元素产率的影响。

摘要：

当白矮星冻结时，其中的等离子体混合物会发生分离过程，从而可能使恒星的成分分布发生根本性变化。富中子元素（如$^{22}$Ne或$^{56}$Fe）的丰度决定了第一批晶体是比周围流体更致密还是更稀疏，从而决定了它们是下沉还是上浮。这些过程目前已在C-O-Ne和C-O-Fe混合物中得到研究，发现白矮星中可能存在蒸馏和沉淀过程。在本工作中，我们计算了更复杂的O-Ne-Fe混合物的相图，并对分离后白矮星的内部结构作出了预测。存在两种可能的结果，由Ne丰度、$^{22}$Ne比例和$^{56}$Fe丰度之间复杂的相互作用决定。要么Fe发生蒸馏形成内核，因为第一批O-Ne固体具有浮力；要么形成O-Ne内核，Fe在液体中积累，直到Fe蒸馏开始并形成Fe壳层。在形成Fe壳层的情况下，可能产生Rayleigh-Taylor不稳定性并使核心翻转。无论哪种情况，Fe蒸馏可能只会产生约0.1 Gyr量级的冷却延迟，因为这些过程发生在白矮星高光度的早期阶段。Fe内核和壳层可能通过星震学被探测到，并可能提高超新星中$^{55}$Mn和$^{58}$Ni等富中子元素的产率。

英文摘要：

When white dwarfs freeze the plasma mixtures inside them undergo separation processes which can produce radical changes in the composition profile of the star. The abundance of neutron rich elements, such as $^{22}$Ne or $^{56}$Fe, determines whether or not the first crystals are more or less dense than the surrounding fluid and thus whether they sink or float. These processes have now been studied for C-O-Ne and C-O-Fe mixtures, finding that distillation and precipitation processes are possible in white dwarfs. In this work, we calculate the phase diagram of more complicated O-Ne-Fe mixtures and make predictions for the internal structure of the separated white dwarf. There are two possible outcomes determined by a complicated interplay between the Ne abundance, the $^{22}$Ne fraction, and the $^{56}$Fe abundance. Either Fe distills to form an inner core because the first O-Ne solids are buoyant, or an O-Ne inner core forms and Fe accumulates in the liquid until Fe distillation begins and forms a Fe shell. In the case of an Fe shell, a Rayleigh-Taylor instability may arise and overturn the core. In either case, Fe distillation may only produce a cooling delay of order 0.1 Gyr as these processes occur early at high white dwarf luminosities. Fe inner cores and shells may be detectable through asteroseismology and could enhance the yield of neutron rich elements such as $^{55}$Mn and $^{58}$Ni in supernovae.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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