论文标题
I型X射线爆发中的URCA核素产生及其对核物理学的影响
Urca Nuclide Production in Type-I X-ray Bursts and Implications for Nuclear Physics Studies
论文作者
论文摘要
中子恒星中的中子核的吸收恒星的热结构受到中子恒星外壳中的存在。可以在I型X射线爆发的灰烬中产生具有乌尔卡核素的核等铁，但是尚未探索其生产的细节。使用代码{\ tt Mesa}，我们使用认为类似于源GS 1826-24的天体条件在一维I型X射线突发的一维模型中研究了URCA核素产生。我们发现，在X射线爆发中，高质量（$ a \ geq55 $）在与爆发光曲线的尾部相对应的过程中，主要在X射线爆发中产生。 $ \ sim0.4 $ - 0.6〜GK温度与这些URCA核素的核合成相关的温度远低于$ \ sim1 $ 〜GK温度与X射线爆发光曲线最相关的核反应速率，涉及高质量核素的核反应速率。通常假定后一种温度用于核物理学研究。因此，我们的发现改变了化合物核对URCA核素产生的核物理学研究的激发能范围。我们证明，在某些情况下，在计划核物理实验时需要考虑这一点。此外，我们表明，URCA核素产量的较低温度范围解释了为什么在模型计算中某些核反应速率的变化会影响爆发光曲线，而不会影响突发灰分的局部特征。
The thermal structure of accreting neutron stars is affected by the presence of urca nuclei in the neutron star crust. Nuclear isobars harboring 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 {\tt 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 ($A\geq55$) 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 $\sim0.4$--0.6~GK temperature relevant for nucleosynthesis of these urca nuclides is much lower than the $\sim1$~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.
