CCD Photometry of RR Lyrae Stars

天琴座RR型变星是一组脉动恒星， 银河系的古老区域，如球状星团和 一般星系晕。 因为这些变星 已知具有几乎相同的光度，它们首先被用作 “标准蜡烛”由哈洛夏普利早在本世纪， 确定太阳到银河系中心的距离。 此外，由于这些恒星中的许多被认为是 形成于银河系崩溃的早期 在大爆炸之后，它们的年龄在确定年龄方面很重要。 宇宙的最高点 最近的研究表明， 天琴座RR型恒星毕竟对它们的 金属含量和年龄。 此外，还有一个重要的 关于球状星团是否都是 形成于大爆炸后不久， 时间 要解决这些问题， 这些恒星在各种球状星团中的出现率， 它们的周期分布， 发光体的表面温度。 过去的努力，以提高我们的知识的性质RR 天琴座的恒星由于它们的微弱和 聚集在天空中密集的星星团中。 的 首席研究员建议监测光度 大量的RR型天琴座恒星在贫金属和 富含金属的球状星团分离出 这些物理特性的依赖性。 研究者 将在小型望远镜上使用现代电荷耦合器件， 执行这项工作。 这种设备即使对小的 光输出的变化。 此外，由于许多星星 图像可以独立地聚焦在检测器表面上， 可以使用同一张图像上的不变星来减去 仪器不稳定引起的灵敏度变化 和地球的大气层

RR Lyrae variables are a group of pulsating stars that occur in old regions of the Galaxy, such as in globular clusters and the general galactic halo. Because these variable stars are all known to have nearly the same luminosity, they were first used as "standard candles" by Harlow Shapley earlier this century to determine the distance from the Sun to the Galaxy's center. Moreover, since many of these stars are thought to have been formed during the early stages of the Galaxy's collapse soon after the Big Bang, their age is important in determining the age of the Universe. Recent work has shown that the luminosities of RR Lyrae stars have a residual dependence after all on their metal content and age. Additionally, there is an important standing controversy over whether globular clusters were all formed soon after the Big Bang or over an extended period of time. To resolve these issues requires a careful determination of the incidence of these stars among various globular clusters, the distribution of their periods, and the dependence of their luminosiites on their surface temperatures. Past efforts to improve our knowledge of the properties of RR Lyrae stars have been hampered by their faintness and their crowding together in dense star conglomerates in the sky. The Principle Investigator proposes to monitor the luminosity variations of a large number of RR Lyrae stars in metal-poor and metal-rich globular clusters to separate out the residual dependences of these physical characteristics. The Investigator will use a modern Charge Coupled Device on a small telescope to perform this work. Such devices are sensitive even to small variations in light output. Additionally, because many star images may be focussed independently on the detector surface, one may use non-variable stars on the same image to subtract out changes in sensitivity caused by instabilities in the instrument and the Earth's atmosphere.