观测证据对小质量AGB星^(13)C中子源的约束  

Constraints of Observational Evidences on the^(13)C Neutron Source in Low-mass AGB Stars

作　　者：张凤华 张璐[2] 马坤 崔文元[3] 马文娟 张波[3] ZHANG Feng-hua;ZHANG Lu;MA Kun;CUI Wen-yuan;MA Wen-juan;ZHANG Bo(Department of Physics and Information Engineering,Cangzhou Normal College,Cangzhou 061001,China;College of Mathematics Science,Hebei Normal University,Shijiazhuang 050024,China;College of Physics,Hebei Normal University,Shijiazhuang 050024,China)

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

出　　处：《天文学进展》2023年第3期303-313,共11页Progress In Astronomy

基　　金：河北省自然科学基金(A2019110051,A2021205006);河北省科技厅科学普及专项(21556202K);河北省“三三三人才工程”重点资助;沧州师范学院科研创新团队资助(cxtdl1902)。

摘　　要：^(13)C(α,n)^(16)O反应是小质量渐近巨星分支(asymptotic giant branch,AGB)星(M/M_⊙≤3,M和M_⊙分别表示AGB星的质量和太阳质量)内s过程(慢中子俘获过程)的主要中子源。在对流热脉冲间隔期间,一个储层(即所谓的“^(13)C袋”)内的^(13)C在辐射条件下(约8 keV)燃烧并释放中子。到目前为止,^(13)C袋的物理形成过程仍远未被充分理解,因此^(13)C袋的结构也一直无法被完全确定。在后处理核合成计算中,^(13)C袋通常是利用观测数据通过自由的参数化来约束。从基本原理、主要效果及局限性等方面综述了不同观测证据对^(13)C袋的约束作用,最后展望了^(13)C中子源约束问题未来可能的研究方向。The^(13)C(α,n)^(16)O reaction is the major neutron source for the s-process(slow neutron captures)in Low-mass AGB Stars(M=M⊙63,M and M⊙represent the mass of AGB stars and the mass of the sun respectively).It is activated within a^(13)C reservoir(so called^(13)C pocket),in radiative conditions(at about 8 keV)in the interpulse phase.To date,the physical processes leading to the formation of the^(13)C pocket are still far from being fully understood,and so the structure of the pocket has never been completely determined.In the postprocessing model calculations,the pocket is usually constrained by free parameterization using the observed data.The solar system s-process abundance pattern and the spectroscopic observations of stars with different metallicities could limit the range of total amount of^(13)C nuclei within the^(13)C pocket.And the s-process enhancements observed recently in young stellar populations,as well as the high-precision measurement of isotopic ratios in presolar SiC grains,require that most AGB stars should have^(13)C pockets with greater mass,lower concentration and flatter distribution profile than traditionally assumed.These characteristic conditions should help to finally reveal the physical mechanism for the^(13)C-pocket formation.In this paper,the constraints of different observational evidences on^(13)C pockets are reviewed from the aspects of basic principles,main effects and limitations.In the end,few possible directions for future studies of constraints on^(13)C neutron source are prospected.

关 键 词：AGB星 约束 中子源 s过程 

分 类 号：P144[天文地球—天体物理]