丽江站富锂色球活动恒星高色散光谱和偏振光谱观测平台建立

From the understanding of stellar internal structure to the model needed to limit the big bang of the early universe, the lithium abundance plays an important role in many aspects. For solar-type stars, it is generally believed tha chromospheric emission and Li abundance should both decrease with age.However, there are a number of stars with low Ca II emission and high Li content. The Li line is also strong in many K-type chromospherically active stars including members of RS CVn binaries. Some of these stars may be young or even pre-main sequence objects; many other, however, are apparently evolved post-main sequence stars. These have proved a difficult challenge for stellar evolution theory. Based on high-dispersion Spectrograph of 2.4m and 1.8m telescope at Lijiang, we will establish the platform of high-resolution spectral observation and polarimetric observation. On the basis of high-resolution spectroscopic and polarimetric observations, we will study the influence of magnetic fields on the evolution of chromospherically active stars and try to find the case enhance the Li abundance of chromospherically active stars. It will provide a solid basis for study for the dissipation mechanism of lithium in the stellar atmosphere and explore the mixing of thestellar interior material.

从对恒星内部结构理解，到限定宇宙大爆炸模型所需的轻元素丰度，锂丰度在很多方面起着十分重要的作用。按照传统观点，类太阳恒星色球活动和锂吸收线强度均随恒星年龄的增加而减弱。但是，人们发现一些类太阳恒星具有较高的锂丰度和较低的Ca II线辐射强度，一些K型色球活动星（包括RS CVn双星）具有很强的锂吸收线。这其中的确有年轻或者主序前恒星，但是其中大多数已经演化到后主序阶段。这给恒星演化理论提出了严重的挑战。本项目旨在以丽江观测站2.4米、1.8米望远镜及其高色散光谱仪为基础，建立包括高色散光谱和高色散偏振光谱观测平台.基于对色球活动恒星的高色散光谱和偏振光谱观测，研究磁场作用下色球活动恒星演化规律，发现色球活动恒星锂元素丰度异常的原因。为研究恒星大气中锂元素的衰减机制和探讨恒星内部物质的混合提供坚实的观测基础。

国家自然科学基金（天文联合基金）项目“丽江富锂色球活动恒星高色散光谱和偏振光谱观测平台建立”(U1831125)执行三年，我们较好地完成了预定计划中的各项工作。完成了基于中国科学院云南天文台丽江天文观测站2.4米、1.8米望远镜高色散光谱仪的偏振光谱观测系统搭建；完成高色散（偏振）光谱观测数据处理与分析系统平台搭建；基于观测数据研究了类太阳活动恒星锂元素丰度和恒星磁场活动（X射线是研究恒星磁场活动的理想工具）关系，发现X射线光度强的类太阳活动恒星锂丰度值大于X射线较弱的恒星；研究了类太阳活动恒星锂元素丰度和恒星钙II H和K线指数之间的关系，发现其中活动性较强的恒星具有更高的锂丰度。并且，发现这些恒星中自转周期长（或者说自转较慢）的恒星锂丰度值较小。另一方面，罗斯贝数较小的恒星锂丰度较大。这些结论为研究恒星大气中锂元素的衰减机制、探讨恒星内部物质的混合提供了坚实的观测基础。