Urca nuclide production in Type-I X-ray bursts and implications for nuclear physics studies
Urca nuclide production in Type-I X-ray bursts and implications for nuclear physics studies
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DOI：
10.1093/mnras/staa3414
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发表时间：
2019-10
影响因子：
4.8
通讯作者：
G. Merz;Z. Meisel
中科院分区：
文献类型：
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作者：
G. Merz;Z. Meisel
吸积中子星的热结构受中子星壳中urca核存在的影响。含有urca核素的核等压线可以在I型x射线爆发的灰烬中产生，但其产生的细节尚未被探索。使用MESA代码，我们使用被认为类似于源GS 1826-24的天体物理条件，在I型x射线爆发的一维模型中研究了urca核素的产生。我们发现高质量（A≥55）的urca核主要在x射线爆发的后期产生，在氢燃烧冻结期间，对应于爆发光曲线的尾部。与这些urca核素的核合成相关的~ 0.4-0.6 GK温度远低于与涉及高质量核素的核反应速率对x射线爆发光曲线影响最相关的~ 1 GK温度。核物理学研究通常假定后一种温度。因此，我们的发现改变了urca核素产生的核物理研究中化合物核的激发能范围。我们证明，在某些情况下，在核物理实验的计划中需要考虑到这一点。此外，我们表明urca核素产生的较低温度范围解释了为什么模型计算中某些核反应速率的变化会影响爆发光曲线，而不会影响爆发灰烬的局部特征。
The thermal structure of accreting neutron stars is affected by the presence of urca nuclei in the neutron star crust. Nuclear isobars harbouring urca nuclides can be produced in the ashes of Type I X-ray bursts, but the details of their production have not yet been explored. Using the code MESA, we investigate urca nuclide production in a one-dimensional model of Type I X-ray bursts using astrophysical conditions thought to resemble the source GS 1826-24. We find that high-mass (A ≥ 55) urca nuclei are primarily produced late in the X-ray burst, during hydrogen-burning freeze-out that corresponds to the tail of the burst light curve. The ∼0.4–0.6 GK temperature relevant for the nucleosynthesis of these urca nuclides is much lower than the ∼1 GK temperature most relevant for X-ray burst light curve impacts by nuclear reaction rates involving high-mass nuclides. The latter temperature is often assumed for nuclear physics studies. Therefore, our findings alter the excitation energy range of interest in compound nuclei for nuclear physics studies of urca nuclide production. We demonstrate that for some cases this will need to be considered in planning for nuclear physics experiments. Additionally, we show that the lower temperature range for urca nuclide production explains why variations of some nuclear reaction rates in model calculations impacts the burst light curve but not local features of the burst ashes.