RR Lyrae Stars of the Inner Halo and Thick Disk

AST 0205813史密斯RR天琴座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晕和厚盘形成过程的重要探针。尽管如此，我们对太阳几千秒差距内天琴座RR的了解仍然非常不完整。密歇根州立大学的霍勒斯·史密斯博士将利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北纬30度以北的RR型天琴座恒星。贝利型ab和c的天琴座RR型星将被探测到，其极限星等为V = 15，对应的距离约为8千秒差距。这次调查预计将包括大约5000颗天琴座RR型恒星。这些变星中的大多数将是这次巡天中新发现的。ROTSE巡天将使史密斯博士能够研究天琴座RR型恒星的密度和性质如何随着与银河系中心的距离和与银道面的距离而变化。他将检验天琴座RR型恒星场揭示双晕存在的假设：一个内部扁平的系统，拥有具有奥斯特霍夫II型球状星团特征的天琴座RR型恒星，以及一个外部不那么平坦的系统，系统的RR天琴座恒星具有奥斯特霍夫I型球状星团的特征。RR型天琴座样本也将用于对当地RR型天琴座密度和厚盘RR型天琴座的尺度高度进行新的估计。 ROTSE巡天将有可能追踪整个银河系中天琴座RR型恒星的分布和性质，从凸起到太阳附近，再到遥远的晕。它还将提供一个数据库，用于选择恒星进行后续光谱研究。史密斯博士将开始这一过程，测定光谱金属丰度和径向速度的迄今经常被忽视的RR天琴座的贝利c型。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巡天还将系统地确定太阳附近的多模天琴座RR星，包括双模星和Blazhko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.***