题目：White dwarf-red giant mergers, early-type R stars, J stars and lithium

报告人：张先飞 博士

报告人单位：英国 Armagh 天文台

时间：2013年12月25日（星期三）上午9:30

地点：主楼四楼401会议室

摘要：

　　Early-type R stars and J stars are a special type of carbon star, having enhanced nitrogen ([N/Fe] ≈ 0.5), lithium, a low 12C/13C ratio (<15) and no s-element enhancements. The merger of a helium white dwarf with a red giant is regarded to be a possible model for the origin of early-type R stars, but the details of nucleosynthesis are not clear. In this paper, we investigate three possible channels for helium white dwarf + red giant mergers, and find that, amongst the three, only a high-mass helium white dwarf subducted into a low-core-mass red giant can make an early-type R star. Nucleosynthesis of the elements carbon, nitrogen, oxygen and lithium corresponds well with the observations. Furthermore, we find that the J stars may represent a short and luminous stage in the evolution of an early-type R star.

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大样本恒星演化组

中国科学院天体结构与演化重点实验室

云南天文台学术委员会

2013-12-23