An interesting question in nuclear astrophysics is the fate of X-ray burst ashes as they descend under gravity to the deep layers of an accreting neutron star crust. As the ashes sink, they are subject to a range of nuclear reactions which transmute the nuclei. The primary of these reaction mechanisms are electron capture reactions, which are activated for different isotopes depending on the electron Fermi energy. At sufficiently high mass densities (rho =2.1x109 g cm-3 for 12C+12C and rho = 3.2 x1012 g cm -3 for 40Mg + 40Mg), density induced fusion reactions, known as pycnonuclear reactions, begin to occur.;By combining existing electron capture formalism and a phenomenological expression for pycnonuclear reactions (specifically developed for a multi component plasma environment) with a network solver, the fate of the X-ray burst ashes have been addressed. In this context it has been found that with increasing mass density, the rigid Coulomb lattice of the neutron star crust dissolves into the isotopes 40Mg and 46Si, with an integrated energy release of between ∼ 1.8 MeV/u and ∼ 2.4 MeV/u, depending on lattice models. This result is fairly insensitive to the initial abundance distribution. The production of 46Si is determined to be the result of a cyclical pycnonuclear fusion, electron capture process.;The magnitude of the pycnonuclear reactions have been found to be dependent on the mass fraction contained in the nuclei, and consequently to drop off quickly at mass densities greater than the neutron drip density. To large effect this halts the production cycle of 46Si.
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机译:核天文物理学中一个有趣的问题是,X射线爆发的灰烬在重力作用下下降到积聚的中子星地壳深层的命运。随着骨灰的下沉,它们会发生一系列改变核的核反应。这些反应机理的主要是电子俘获反应,根据电子费米能,该俘获反应针对不同的同位素而被激活。在足够高的质量密度下(对于12C + 12C,rho = 2.1x109 g cm-3;对于40Mg + 40Mg,rho = 3.2 x1012 g cm -3),开始发生密度诱发的融合反应,即所谓的核核反应。现有的电子捕获形式和网络反应器对核反应(专门为多组分等离子体环境开发的)的现象学表达,已经解决了X射线爆炸灰烬的命运。在这种情况下,已经发现随着质量密度的增加,中子星壳的刚性库仑晶格溶解到同位素40Mg和46Si中,积分能量释放在〜1.8 MeV / u和〜2.4 MeV / u之间,这取决于在晶格模型上。该结果对初始丰度分布相当不敏感。确定46Si的产生是周期性核核聚变,电子捕获过程的结果;已发现核核反应的大小取决于核中所含的质量分数,因此其质量迅速下降密度大于中子滴落密度。在很大程度上影响了46Si的生产周期。
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