Chromospheric activity and late stellar evolution

利用我们位于墨西哥瓜纳华托的TIGRE机器人望远镜，我们已经开始了一项长期的巨星监测计划，以系统地研究这些恒星的大气和色球特性;在过去四年中，我们特别使用高分辨率光谱学观察了30颗晚型巨星的样本。在威尔逊山H&K项目的背景下，很大一部分样本星已经被监测了十多年，在某些情况下甚至更长，这些监测数据最近已经公开。 由于各种原因（在我们的申请中详细讨论），Mt. Wilson H&K关于巨星的数据从来没有被正确分析和发表过。对这些档案数据的检查显示--有点令人惊讶--在红色和渐近巨星分支的高处，巨星的色球活动似乎正在增加，这与最近对这些物体磁场的测量一致。然而，缺少的是对这些天体的色球能量损失的定量测量以及对其时间变化特征的深入研究，因此，在本项目应用的背景下，我们建议恰恰做到这一点。我们特别提出了研究和定量表征红巨星在其红巨星和渐近巨星分支上的活动增加，发展高分辨光谱中Ca~II H&K线和Ca~II红外三重线的巨星色球通量定量测量方法。从这些，我们建议开发的工具，定量解释的S-指数数据的巨人，从而研究和表征色球变化的巨人在几年到十年的时间尺度。最后，我们建议使用这些数据来比较巨星和主序星的光谱和时间变化模式。

Using our robotic TIGRE telescope located in Guanajuato, Mexico, we have begun a long-term monitoring program of giants to systematically study the atmospheric and chromospheric properties of these stars; we have specifically been observing a sample of 30 late-type giants over the last four years using high-resolution spectroscopy. A large fraction of the sample stars had already earlier been monitored in the context of the Mount Wilson H&K project over more than a decade and in some cases even longer, and these monitoring data have recently become publicly available. For various reasons (discussed in detail in our application) the Mt. Wilson H&K data on giants have never been properly analyzed and published.An examination of these archival data shows that --somewhat surprisingly-- the chromospheric activity of giants high up on the red and asymptotic giant branches appears to be increasing, in line with recent measurements of magnetic fields in such objects. What is missing, however, is a quantitative measure of the chromospheric energy losses of such objects as well as an in-depth study of their temporal variability characteristics.In the context of this project application we therefore propose to do exactly this. We specifically propose to study and characterize quantitatively the activity increase of red giants on their red and asymptotic giant branches, to develop quantitative methods to measure chromospheric fluxes from giant stars in the Ca~II H&K lines and the Ca~II infrared triplet lines measured in high-resolution spectra. From these we propose to develop the tools to quantitatively interpret the S-index data for giants and hence to study and characterize chromospheric variability of giants on time scales of years to decade. Finally, we propose to use the data to compare the spectral and temporal variability patterns of giants and main sequence stars.