Complete RR Lyrae Las Campanas spectra

This directory contains spectra that have been used in multiple papers on RR Lyrae stars by George Preston and collaborators (e.g, ``The Axial Rotation and Variable Macroturbulence of RR Lyrae Stars'', 2019, AJ, 157, 153; G. W. Preston, C. Sneden, M. Chadid, I. B. Thompson, and S. A. Shectman), and in related investigations (e.g., ``On the Use of Field RR Lyrae as Galactic Probes. II. A new Delta-S calibration to estimate their metallicity'', 2021, ApJ, 908, 20; J. Crestani et al.). These spectra of RR Lyrae variables were obtained with the Las Campanas Observatory Du Pont Telescope and its echelle spectrograph. This instrument has a spectral resolving power R ~= 27,000. Integration times were almost always < 900 sec in order to avoid velocity phase smearing of the absorption features. Therefore the typical S/N values are < 30 in the individual spectra. Essentially all Du Pont spectra for this work collected in the years 2006-2014 on the RR Lyrae work led by George Preston are gathered here. The doubly-dimensioned echelle spectra are fully reduced and are on a laboratory wavelength scale. They are organized in subdirectories labeled by year and month of the observation. For example, subdirectory "files1005" contains the spectra obtained in May 2010. In a separate subdirectory "velocities" we have placed MS-EXCEL files that give the velocities of the target stars, along with the velocity uncertainties. Tabulated values of VREL, VOBS, and VHELIO are those defined in the VELOCITY COMPUTATION ALGORITHM section of the IRAF help page for fxcor.本数据集目录收录了乔治·普雷斯顿（George Preston）及其合作者在多篇天琴座RR型变星（RR Lyrae stars）相关研究论文中使用过的光谱数据，例如2019年发表于《天文期刊》（Astronomical Journal, AJ）第157卷第153页的《天琴座RR型变星的轴向自转与宏观湍流变化》，以及G. W. Preston、C. Sneden、M. Chadid、I. B. Thompson与S. A. Shectman的相关研究；同时也涵盖后续相关探索工作的光谱数据，比如2021年发表于《天体物理学杂志》（Astrophysical Journal, ApJ）第908卷第20页的《以天琴座RR型变星作为银河探针的应用研究 Ⅱ：用于估算其金属丰度的新型Δ-S定标方法》，以及J. Crestani等人的相关成果。这批天琴座RR型变星的光谱均通过拉斯坎帕纳斯天文台杜邦望远镜（Las Campanas Observatory Du Pont Telescope）及其阶梯光栅摄谱仪（echelle spectrograph）获取，该仪器的光谱分辨率R≈27000。为避免吸收特征出现速度相位弥散，单次积分时长几乎均小于900秒，因此单张光谱的典型信噪比（S/N）低于30。本数据集收录了2006年至2014年间，乔治·普雷斯顿主导的天琴座RR型变星研究项目中收集的全部杜邦望远镜光谱数据。这批双维度阶梯光栅光谱（doubly-dimensioned echelle spectra）已完成全部归算流程，并采用实验室波长标尺进行定标。数据按观测年份与月份划分至不同子目录，例如子目录"files1005"对应2010年5月获取的光谱。在单独的"velocities"子目录中，我们存放了MS-EXCEL格式文件，其中包含目标恒星的视向速度及其不确定度。其中VREL、VOBS与VHELIO的制表值，均遵循IRAF（Image Reduction and Analysis Facility）辅助页面中fxcor工具的"速度计算算法"章节所定义的标准。