A New High Resolution Charge-Coupled Device Spectrometer for McDonald Observatory

德克萨斯大学麦克唐纳天文台将建立一个新型设计的高分辨率光谱仪，该光谱仪结合了大梯队光栅和棱镜交叉色散。光谱将被投射到最大的电荷耦合器件（CCD）图像探测器上——新的泰克TK2048M。这款55毫米见方的固态硅图像探测器每次曝光将产生超过400万个图像元素。通过这种组合，将以高分辨率同时获得一个天体在大气紫外（UV）截止点和CCD灵敏度的近红外（IR）极限之间的整个光谱。1小时的曝光将获得V等11级恒星的光谱，信噪比为100，而3小时可以获得15等的有用光谱。新仪器的主要动机是它能够快速和完整地收集所需的光谱，以确定星团中CNO（碳、氮和氧）的丰度，以及古老的贫金属矮星中镁（Mg）的同位素丰度，这些恒星比这些研究的当前极限更暗。在附近明亮恒星周围寻找行星将依赖于高径向速度精度，这是通过统计大量同时测量的谱线轮廓来确定由行星轨道运动引起的母恒星中的小周期运动。

The University of Texas McDonald Observatory will build a high- resolution spectrograph of novel design incorporating a large echelle grating and prism cross dispersion. Spectra will be projected onto the largest Charge Coupled Device (CCD) image detector available -- the new Tektronix TK2048M. This 55-mm square solid state silicon image detector will produce over 4 million picture elements per exposure. With this combination the entire spectrum of an astronomical object between the atmospheric ultraviolet (UV) cutoff and the near-infrared (IR) limit of CCD sensitivity will be acquired simultaneously at high resolution. A 1-hour exposure will obtain spectra of stars at V magnitude 11 with signal-to-noise 100, while useful spectra can be obtained to magnitude 15 in 3 hours. Major motivations for the new instrumentation are its ability to gather quickly and completely spectra needed to determine CNO, (Carbon, Nitrogen, and Oxygen) abundances in cluster stars and magnesium (Mg) isotopic abundances in old metal-poor dwarfs, stars that are fainter than current limits for these studies. The search for planets around nearby bright stars will rely on the high radial velocity precision enabled by the statistics of large numbers of simultaneously-measured spectral line profiles to determine small periodic motions in the parent star induced by orbital motion of the planet.