S-过程元素丰度分布规律的研究

Study on the S-process Abundance Distribution

利用指数辐照理论的解析解研究了AGB星S过程元素的丰度分布规律 .结果表明 ,在低金属丰度下 ,AGB星核合成产量强烈依赖于金属丰度 ,但如果将Sm( 88<A≤ 2 0 4)部分按质量数分为Smh( 14 0≤A≤ 2 0 4)和Sml( 88<A <14 0 )后 ,在任何金属丰度下 ,Smh和Sml核素丰度分别与太阳系的相应分布基本相同或相似 ,因此它们各自的积累结果即各金属丰度的平均分布也与太阳系基本相同或相似 ,从而太阳系的Sm元素丰度分布具有典型性 。

Using the solution of S process chain with an exponential neutron irradiation the S process abundance distribution of AGB stars of different metallicities is investigated.The results show that the S process production varies as a function of metallicity at low metallicity. However, if separate the main S process component into two parts, 88< A <138(S ml) and 140< A <204(S mh), the abundance distribution of the S_mh component for the bulk of isotopes 140≤ A ≤204 is strongly similar to the solar S m pattern at any metallicity, while the abundance distribution of the S_ml component part with A <140 are nearly similar to the corresponding solar elements abundance distributions. Thus the cumulative consequence of long term Galactic chemical evolution starting from low metallicity AGB stars is of same characteristics. Consequently the solar elements abundance distributions of the two parts are both typical and each can serve as a basis (standard pattern) in investigating the abundance distribution of elements covering all metallicity intervals.