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The nearby Hyades cluster harbors four giants comma which have almost identical optical appearances. However comma the activity of these very similar stars differs comma with two stars being active comma while the stars HD28305 and HD27697 are inactivedoublePoint The X-ray luminosities of these stars differ by more than a facor of 100! An evolutionary study shows the former two at the beginning of their helium burning phase comma while the latter two have already developed a carbon-oxygen core. Detailed X-ray spectroscopy is available for the two bright giants comma yet none for the two fainter giants comma for which we propose deep XMM-Newton EPIC spectroscopy. We want to perform a detailed analysis of the X-ray spectra comma search for spectral differences and relate them to the different states of activity and stellar evolution.邻近的毕星团（Hyades Cluster）包含四颗光学外观近乎完全一致的巨星。然而，这批外观高度相似的恒星，其活动状态却存在显著差异：其中两颗处于活跃状态，而HD28305与HD27697则处于非活跃状态。这些恒星的X射线光度差异更是超过100倍！演化研究表明，前两颗恒星正处于氦燃烧初始阶段，而后两颗则已形成碳氧核心。目前针对两颗亮巨星的详细X射线光谱数据已可获取，但两颗暗弱巨星却缺乏此类数据；为此我们提议开展深度XMM-牛顿（XMM-Newton）EPIC光谱观测。我们计划对这批X射线光谱展开详尽分析，探寻光谱差异，并将其与恒星不同的活动状态及演化阶段建立关联。