Element synthesis in the late and explosive stages of stellar evolution

1. 我们开发了一种计算机代码，可以用详细的核网络处理大质量恒星的演化。通过这个代码我们计算了太阳>的8M < -太阳>的25m <的演化过程。对于太阳>的8M <和太阳>的3.3M <的氦星，其铁核质量分别为太阳>的1.6M <和太阳>的1.2M <。这个小的铁核（太阳>的1.2米）具有特殊的重要性，因为在坍缩阶段产生的冲击波可以在几毫秒内炸毁外部区域。对于10-11M <太阳>的恒星，氖燃烧锋向中心传播，预计会出现爆炸性的氖闪光。对I型超新星的碳燃烧白矮星模型的元素合成结果与光谱、光曲线和x射线发射等观测数据进行了比较。他们的意见很一致。作为I型超新星前身的C+O白矮星模型已经被研究过。当吸积速率大于2x <10^(-6)> M <太阳> <y^(-1)>时，碳闪光向中心传播，预计将形成中子星。我们也研究了非球面构型。然而，重盘的形成不太可能发生，而且由于引力辐射，两颗白矮星之间的距离变小了。因此，质量开始从系统中流出，两颗白矮星开始合并。但所达到的最大密度还不足以引发超新星爆炸。

1. We have developed a computer code which can handle the massive star evolution with detail nuclear network. By this code we computed evolution of 8M <of sun> -25M <of sun> stars. For 8M <of sun> and 3.3M <of sun> helium star the mass of the iron core is 1.6M <of sun> and 1.2M <of sun> , respectively. This small iron core (1.2M <of sun> ) has special importance because the shock wave generated during the collapse stage will be able to blow up the outer region in a few millisecond. For 10-11M <of sun> stars neon burning front propagates towards the center and an explosive neon flash will be expected.2. The results from elementsynthesis of carbon burning white dwarf model for Type I supernova have been compared to the obseravtional data such as specrtum, light curve and X-ray emission. Their agreement is quite well. C+O white dwarf models as progenitor of Type I supernova have been studied. By assuming a spherical model we computed mass accretion and carbon burning When the accretion rate is greater than 2x <10^(-6)> M <of sun> <y^(-1)> , the carbon flash propagates towards the center and a neutron satr will be expected to form. We also studied non-spherical configurations. However the heavy disk formation is unlikely to occur and due to the garvitational radiation separation between two white dwarfs becomes small. Thus mass begins to flow out from the system and two white dwarfs begins to merge. But the maximum density reached is not high enough to trigger the supernova explosion.