Radial Velocity Variations of K-Giants

这一奖项是为了表彰一项为期两年的创新仪器技术的试点研究，该技术可以获得精确的恒星径向速度。这项技术是将最近建造的一个装满碘气体的容器插入麦克唐纳天文台库德光谱仪的光束中。这种气体将吸收已知波长的恒星光，从而提供一组散布在光谱中的恒星线的校准线。有了这项创新，PI有望获得精度为-5米/秒(约8英里/小时)的径向速度。然后，他将获得几颗亮红色巨星的光谱时间序列，并寻找其中的脉动。PI已经使用了一种相关的仪器技术来验证红巨星大角星是否存在1.8天的周期。如果大角星的这种脉动是其他红巨星的典型特征，那么一类新的变星就会被发现。这些数据将用于各种其他天体物理目的，包括研究这些恒星表面的对流环流细胞和磁“活动”。要么是脉动，要么是磁活动，或者两者兼而有之，都可能导致红巨星的外层大气(色球)升温。反过来，色球被认为会导致质量损失，这可能会显著影响恒星随后的演化历史。

This award is for a two-year pilot study of an innovative instrumental technique to obtain precise radial velocities of stars. The technique is to insert a recently constructed container filled with iodine gas in beam of a coude spectrometer at McDonald Observatory. This gas will absorb starlight at well known wavelengths, thereby providing a set of calibration lines interspersed with the stellar lines in the spectrum. With this innovation, the PI expects to obtain radial velocities to an accuracy of +-5 m/sec (roughly 8 mph). He will then obtain a time series of spectra for several bright red giant stars and search for pulsations in them. The PI has already used a related instrumental technique to verfify the existence of a 1.8-day period in the red giant Arcturus. If this pulsation in Arcturus is typical of other red giants, then a new class of variable stars will have been discovered. The data will be used for a variety of other astrophysical purposes, including the study of convective circulation cells and magnetic "activity" on these stars surfaces. Either pulsations, magnetic activity, or both of these phenomena, could be responsible for heating the outer atmospheres ("chromospheres") of red giants. Chromospheres, in turn, are thought to cause a mass loss, which can significantly affect the subsequent history of the star's evolution.