Instrumentation for Global Time-Series Photometry

可能除了太阳之外，脉动白矮星在用实验手段探测恒星内部结构方面表现出最大的潜力。各种各样的振动波在这些恒星中被激发，在恒星内部相互干扰，在恒星的表面可以看到它们亮度的变化。干涉的模式可以用来推断每一波穿过的物质的数量，从而最终确定物质在恒星中的分布。这些原理与地震学家在地球上使用了几十年的原理类似，现在首次被应用于遥远的恒星。白矮星是最好的候选者，不仅因为它们表现出如此多的振动，而且因为它们的周期足够短，可以通过观察恒星的光变化来跟踪许多波周期。首席研究员在他的大部分研究生涯中都在设计和建造光度测量仪器，以进行精确的光测量。在之前的国家科学基金会奖中，PI和他的合作者发现，他们建造的一个原型三通道光度计（一个通道用于计划恒星，一个通道用于恒定的“标准”，一个用于无星的“天空”）增加了天文学家在夜间实际收集数据的时间。新的合同将允许PI建造该原型的两个便携式复制品。这些仪器将由他的同事运送到世界各地的观测点。作为“观测活动”的一部分，当地球旋转时，这些观测者将依次观测目标恒星。在这次活动之后，这些数据将被合并，并产生一个连续几天的字符串，这是分析白矮星内部特性所必需的。

With the possible exception of the Sun, pulsating white dwarfs show the greatest potential for probing the interior structures of stars by experimental means. A rich variety of vibrating waves, visible at the surface by their change in the star's luminosity, are excited in these stars that interfere with one another throughout the star's interior. The pattern of interferences can be used to infer the amount of material each wave travels through, and hence the distribution of material through the star can ultimately be determined. These principles, similar to those used for decades by seismologists on the Earth, are now being applied to distant stars for the first time. The white dwarf stars are the best candidates not only because they exhibit so many vibrations but because their periods are short enough that many wave cycles can be followed by observing the stars' light variations. The Principal Investigator has spent most of his research career designing and building photometric instrumentation to make accurate light measurements. In a previous NSF award, the PI and his collaborators found that a prototype three-channel photometer they had constructed (one channel for the program star, one for a constant "standard", and one for a starless "sky") increases the amount of time during a night that an astronomer can spent actually collecting data. The new award will permit the PI to construct two portable duplicates of this prototype. These instruments will be transported by his colleagues to observing sites around the world. As part of an "observing campaign", target stars will then be observed in tandem by each of these observers as the Earth rotates. Following this campaign the data will be combined and a continuous several day-long string produced that is necessary for the analysis of interior properties of white dwarf stars.