CCD Photometry of RR Lyrae Stars

天琴座 RR 星的 CCD 光度测量

• 批准号: 9015728
• 负责人: Horace Smith
• 金额: $ 11.33万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-10-01 至 1995-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9015728&HistoricalAwards=false
• 关键词: CCD; Photometry; RR; Lyrae; Stars; CCD; Photometry; RR; Lyrae; Stars

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.

RR Lyrae变量是一组脉动恒星，发生在银河系的旧区域中，例如球状簇和一般的银河晕。 由于这些变量恒星都具有几乎相同的光度，因此Harlow Shapley本世纪初首次将它们用作“标准蜡烛”，以确定从太阳到银河系中心的距离。 此外，由于人们认为其中许多恒星是在大爆炸后不久倒塌的早期阶段形成的，因此它们的年龄对于确定宇宙的年龄很重要。 最近的工作表明，RR Lyrae恒星的亮度在其金属含量和年龄之后具有残留依赖性。 此外，关于球状簇是在大爆炸之后不久还是在很长一段时间内都形成的，这是一个重要的争议。 为了解决这些问题，需要仔细确定这些恒星在各个球状簇中的发生率，其周期分布以及其发光岩对其表面温度的依赖性。 过去的努力提高了我们对RR Lyre明星特性的了解的努力受到了它们的淡淡和在天空中浓密的星星集团中的拥挤而受到阻碍。 该原则研究者建议监测金属贫困和金属富含金属的球状簇中大量RR Lyrae星的光度变化，以分离这些物理特征的残留依赖性。 研究人员将在小型望远镜上使用现代电荷耦合设备来执行这项工作。 此类设备甚至对光输出的较小变化也很敏感。 此外，由于许多恒星图像可能独立于探测器表面，因此可以在同一图像上使用不可变化的恒星来减去由仪器和地球大气中不稳定性引起的灵敏度的变化。