RR Lyrae Stars of the Inner Halo and Thick Disk

天琴座的恒星是银河系中最古老的恒星之一，长期以来一直被认为是研究星系晕和厚盘形成过程的重要探测器。然而，我们对距离太阳几千秒差距内的天琴座RR星群的了解仍然非常不完整。密歇根州立大学的Horace Smith博士将使用机器人光学瞬态搜索实验（ROTSE）获得的观测结果来识别和表征天琴座RR星在赤纬-30度以北的特征。天琴座RR型的贝利ab型和c型恒星将被探测到极限星等V = 15，对应于大约8kpc的距离。这次调查预计将包括大约5000颗天琴座RR星。在这次调查中，大多数变星都是新发现的。ROTSE的调查将使史密斯博士能够研究RR天琴座恒星的密度和特性如何随着距离银河系中心和距离银河系平面的距离而变化。他将测试天琴座RR星场揭示双晕存在的假设：一个内部平坦的系统，天琴座RR星具有Oosterhoff II型球状星团的特征，而一个外部不那么平坦的系统，天琴座RR星具有Oosterhoff I型球状星团的特征。天琴座RR的样本也将被用来对当地的天琴座RR密度和厚盘的天琴座RR的尺度高度进行新的估计。ROTSE调查将使追踪RR天琴座恒星在整个银河系的分布和特性成为可能，从凸起，到太阳附近，再到遥远的光晕。它还将提供一个数据库，用于为后续的光谱研究选择恒星。史密斯博士将开始这一过程，确定迄今为止经常被忽视的贝利c型RR天琴座的光谱金属丰度和径向速度。这些将用于确定统计视差解决方案并研究RRc变量的运动。ROTSE巡天还将系统地识别太阳附近的多模RR天琴座恒星，包括双模恒星和布拉齐克效应变量

AST 0205813SmithRR Lyrae stars are among the oldest stars in the Galaxy, and have long been recognized asimportant probes of the processes by which the halo and thick disk formed. Nevertheless, ourknowledge of the RR Lyrae population within several kiloparsecs of the Sun remains veryincomplete. Dr. Horace Smith at Michigan State University will use observations obtained by the Robotic Optical Transient Search Experiment (ROTSE) to identify and characterize RR Lyrae stars north of declination -30 degrees. RR Lyrae stars of Bailey types ab and c will be detected to a limiting magnitude of V = 15, corresponding to a distance of about 8 kpc. This survey is expected to include about 5000 RR Lyrae stars. Most of these variable stars will be newly discovered in this survey. The ROTSE survey will enable Dr. Smith to investigate how the density and properties of RR Lyrae stars change as a function of distance from the galactic center and distance from the galactic plane.He will test the hypothesis that field RR Lyrae reveal the presence of a dual halo: an inner flattened system, with RR Lyrae stars that have the characteristics of those in Oosterhoff type II globular clusters, and an outer, less flat, system with RR Lyrae stars that have the characteristics of those in Oosterhoff type I globular clusters. The RR Lyrae sample will also be used to make a new estimate of the local RR Lyrae density and of the scale height of the RR Lyrae of the thick disk. The ROTSE survey will make it possible to trace the distribution and properties of RR Lyrae stars throughout the Galaxy, from the bulge, through the solar vicinity, to the distant halo. It will also provide a database to be used in selecting stars for follow-up spectroscopic studies. Dr. Smith will begin this process with the determination of spectroscopic metal-abundances and radial velocities for the hitherto often neglected RR Lyrae of Bailey type c. These will be used to determine a statistical parallax solution and to study the motions of RRc variables. The ROTSE survey will also systematically identify multi-mode RR Lyrae stars in the solar vicinity, including double-mode stars and Blazhko effect variables.***