半人马座欧米茄中蓝钩星的光谱分析：后期热闪光情景的检验
Spectroscopic Analyses of the "Blue Hook" Stars in omega Centauri: A Test of the Late Hot Flasher Scenario
摘要：
在球状星团中，半人马座ω包含了已知数量最多的极热水平分支（HB）恒星。最近的紫外线观测（Whitney等人，1998年; D 'Cruz等人，2000年）表明，在零年龄水平分支（"蓝钩“星）以下存在大量的热星，这不能用典型的恒星演化来解释。在红巨星分支上遭受异常大的质量损失，从而在白矮星冷却曲线下降时经历氦核闪光的恒星可以居住在这个区域。理论预测，这些“后期热闪光”应该比最热的标准HB星显示出更高的温度，并且应该有富含氦和碳的大气。我们获得并分析了蓝钩星样本的中分辨率光谱，以获得它们的大气参数。蓝钩星确实比经典的极端HB星更热（Teff > 35，000 K），也更富氦。此外，我们发现一个大的增强的碳丰度相对于集群丰度的迹象。
英文摘要：
omega Cen contains the largest population of very hot horizontal branch (HB) stars known in a globular cluster. Recent UV observations (Whitney et al. 1998; D'Cruz et al. 2000) show a significant population of hot stars below the zero-age horizontal branch (``blue hook'' stars), which cannot be explained by canonical stellar evolution. Stars which suffer unusually large mass loss on the red giant branch and thus experience the helium core flash while descending the white dwarf cooling curve could populate this region. Theory predicts that these ``late hot flashers'' should show higher temperatures than the hottest canonical HB stars and should have helium- and carbon-rich atmospheres. We obtained and analysed medium resolution spectra of a sample of blue hook stars to derive their atmospheric parameters. The blue hook stars are indeed both hotter (Teff > 35,000K) and more helium-rich than classical extreme HB stars. In addition we find indications for a large enhancement of the carbon abundance relative to the cluster abundance.
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