R-process Elements in the First Generation Stars and High-redshift Objects and the Galactic-and Cosmic-Age Problem.

第一代恒星和高红移天体中的 R 过程元素以及银河和宇宙时代问题。

基本信息

批准号：
10640236
负责人：
KAJINO Toshitaka
金额：
$ 1.86万
依托单位：
National Astronomical Observatory
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Observational study of the r-process elements was one of the utlimate purposes in this project, and it has just started in the year 2000 with the construction of SUBARU TELESCOPE which is equipped with High-Dispersion-Spectrograph (HDS) at the top of Mt.Kea. We have already carried out several test observations of SUBARU-HDS, which proves to work very well as we designed. Using this spectrograph, several metal-deficient halo stars have already been observed in order to detect metal absorption lines from Th232 (half life 14.1 Gy), U238 (4.5 Gy), Re187 (43.5 Gy), and many others. Data analysis is now underway. Theoretical studies of the r-process nucleosynthesis in supernova explosions also have been carried out to reach deep understanding of the nucleosynthesis mechanism. Actinoids are ideal heavy radioactive nuclei whose half life is of order of cosmic age. In this project, it was theoretically clarified that most heavy r-process elements, including some amounts of actinoids, are produced in explosive nucleosynthesis associated with Type II SN explosions. Dependence of the calculated yields of these elements on the physical conditions of stellar environments were studied in detail : It was clarified the relation between r-process abundance yields and physical parameters such as neutrino flux from the center of proto-neutron star, mass and radius of the neutron star, entropy and dynamic time scale which are closely related to the neutrino heating proceses in the neutrino-driven winds.

r过程元素的观测研究是该项目的最终目的之一，它于2000年随着在山顶配备高色散光谱仪（HDS）的SUBARU望远镜的建造而开始。 .基亚。我们已经对 SUBARU-HDS 进行了多次测试观察，事实证明它按照我们的设计工作得很好。使用该摄谱仪，已经观察到了几颗缺乏金属的晕星，以便检测来自 Th232（半衰期 14.1 Gy）、U238（4.5 Gy）、Re187（43.5 Gy）等的金属吸收线。数据分析正在进行中。对超新星爆炸中r过程核合成的理论研究也已开展，以深入了解核合成机制。锕系元素是理想的重放射性核，其半衰期约为宇宙年龄。在该项目中，从理论上阐明了大多数重 r 过程元素，包括一定量的锕系元素，是在与 II 型 SN 爆炸相关的爆炸性核合成过程中产生的。详细研究了这些元素的计算产量对恒星环境物理条件的依赖性：阐明了r过程丰度产量与原中子星中心中微子通量、质量和半径等物理参数之间的关系中子星的熵和动态时间尺度与中微子驱动风中的中微子加热过程密切相关。