标题： 恒星长期活动变化的HARPS M型矮星样本：活动指数比较 显示英文标题

标题： Long-term stellar activity variations of stars from the HARPS M-dwarf sample: Comparison between activity indices

摘要： 我们使用了四个已知的色球层活动指标，来测量来自HARPS行星搜索计划样本中的23颗M型矮星的长期活动变化。 我们使用加权皮尔逊相关系数比较了这些指标，并发现一般来说（i）$S_{CaII}$和\ion{Na}{i}之间的相关性非常强，且不依赖于恒星的活动水平，（ii）我们定义的$S_{CaII}$与 H$\alpha$之间的相关性似乎依赖于恒星的活动水平，（iii）对于这类恒星，$S_{CaII}$和\ion{He}{i}之间没有很强的相关性。 显示英文摘要

摘要： We used four known chromospheric activity indicators to measure long-term activity variations in a sample of 23 M-dwarf stars from the HARPS planet search program. We compared the indices using weighted Pearson correlation coefficients and found that in general (i) the correlation between $S_{CaII}$ and \ion{Na}{i} is very strong and does not depend on the activity level of the stars, (ii) the correlation between our $S_{CaII}$ and H$\alpha$ seems to depend on the activity level of the stars, and (iii) there is no strong correlation between $S_{CaII}$ and \ion{He}{i} for these type of stars.