平均中子辐照量计算公式对钡星的应用  

Applicaton of the Calculating Formula for Mean Neutron Exposure on Barium stars

作　　者：张凤华 张璐[3] 崔文元 张波[2] 

机构地区：[1]沧州师范学院物理与信息工程学院,沧州061001 [2]河北师范大学物理科学与信息工程学院,石家庄050024 [3]河北师范大学数学与信息科学学院,石家庄050024

出　　处：《天文学报》2017年第6期117-126,共10页Acta Astronomica Sinica

基　　金：国家自然科学基金项目(11673007;11643007);河北省自然科学基金项目(A2014110008)资助

摘　　要：最新的研究结果表明:目前流行的13C壳层(13C pocket)在热脉冲间隔期间辐射燃烧的低质量AGB(Asymptotic Giant Branch)星s-过程核合成模型,其核合成区域的中子辐照量分布可视为指数形式,平均中子辐照量τ0和模型参量之间的关系为τ0=-?τ/ln[q/(1-r+q)],式中?τ为每次照射的中子辐照量,r为重叠因子,q为13C壳层占氦中间壳层的质量比例.将该公式应用到26颗钡星样品星,对其可靠性进行了检验,在此基础上对26颗Ba星的中子辐照特点进行了分析.研究结果表明:公式是可靠的;26颗Ba星中,至少有8颗星的AGB伴星具有指数形式的中子辐照量分布,有12颗星极有可能经历指数中子辐照,有4颗星更倾向于经历单辐照;26颗Ba星的AGB伴星中,大多数在s-过程核素丰度达渐近分布前可能只经历很少次数的中子照射.Latest studies have shown that, in the s-process nucleosynthesis model for the low-mass asymptotic giant branch （AGB） star with ^13C pocket radiative burning during the interpulse period, the distribution of neutron exposures in the nucleosynthesis region can be regarded as an exponential function, and the relation between the mean neutron exposure 70 and the model parameters is τ0=-△τ/ln[q/（1-r＋q）], in which △τ is the exposure value of each neutron irradiation, r is the overlap factor, and q is the mass ratio of the 13C shell to the He intershell. In this paper the formula is applied to 26 samples of barium stars to test its reliability, and furthermore the neutron exposure nature in the AGB companion stars of 26 barium stars are analyzed. The results show that, the formula is reliable; in the AGB companion stars of 26 barium stars, at least 8 stars definitely have and 12 stars are highly likely to have exponential distribution of neutron exposures, while 4 stars tend to experience single neutron exposure; most of the AGB companion stars may have experienced fewer times of neutron irradiations before the element abundance distribution of the s-process comes to asymptotic condition.

关 键 词：恒星 AGB和后AGB 恒星 中子 钡星 丰度 

分 类 号：P144[天文地球—天体物理]