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造一台设计新颖的高分辨率光谱仪，其中包括大型梯形光栅和棱镜交叉色散。光谱将投射到市面上最大的电荷耦合器件(CCD)图像探测器--新型Tektronix TK2048M上。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400万个像素。通过这种组合，将在高分辨率下同时获取从大气紫外线(UV)截止到近红外(IR)的CCD灵敏度极限之间的天文物体的全部光谱。1小时的曝光将获得V等11的恒星的光谱，信噪比为100，而有用的光谱可以在3小时内获得15等的光谱。新仪器的主要动机是它能够快速而完整地收集确定星团恒星中CNO(碳、氮和氧)丰度所需的光谱，以及旧的贫金属矮星中的镁(MG)同位素丰度，这些矮星的亮度低于这些研究的当前限制。搜索附近明亮恒星周围的行星将依赖于大量同时测量的谱线轮廓的统计所带来的高径向速度精度，以确定由行星轨道运动引起的母星中的小周期运动。

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.