RUI: A Study of Evolved Stars with Time-Series Photometry

格劳尔将使用时间序列测光来研究恒星演化的后期阶段，从行星状星云喷射阶段到白色矮星冷却阶段。他将专注于行星状星云的中心恒星、变白色矮星和双星。他将使用一种新的便携式双星光度计，这是他帮助开发的（国家科学基金会（NSF）格兰特AST 87-12249），他将在美国和国外的几个天文台使用。此外，他还将参加扩大覆盖网络，这是一项从地球仪的观测站观测变星的国际努力，以便不受当地日周期的影响。天文学家研究的中心课题之一是恒星的诞生、演化和死亡。Grauer将专注于恒星演化的最后阶段，当其中许多恒星脱落外层形成所谓的行星状星云（与行星无关的物体）时。在失去外层后剩下的恒星收缩成非常紧凑的物体，称为白色矮星，质量与太阳相当，大小与地球相当。有些白色矮星的脉动周期为几分钟。它们也被发现与其他恒星非常接近，两颗恒星都以小时为周期绕着彼此运行。要有效地观测这种脉动和轨道运行的恒星，需要特殊的观测设备和技术，这两样格劳尔都拥有。Grauer将参与NSF本科院校研究（RUI）计划下的本科生。

Grauer will use time-series photometry to study the late stages of stellar evolution, from the planetary nebula ejection phase through the white dwarf cooling phases. He will be focusing on the central stars of planetary nebulae, variable white dwarfs, and binary stars. He will be using a new portable two-star photometer, which he helped develop (National Science Foundation (NSF) Grant AST 87-12249) and which he will be using at several observatories in the United States and abroad. Furthermore, he will be participating in the Extended Coverage Network, which is an international effort of observing variable stars from observatories around the globe in order to be independent of the local diurnal cycle. One of the central topics studied by astronomers is the birth, evolution, and death of stars. Grauer will focus on the final stages in the evolution of stars, when many of them shed their outer layers forming so-called planetary nebulae (objects unrelated to planets). The stars remaining after the loss of their outer layers contract into extremely compact objects, called white dwarfs, with masses comparable to that of the sun and sizes like the Earth's. Some of the white dwarfs pulsate, with periods of the order of minutes. They also are found in close proximity of other stars, with both stars orbiting about each other with periods of the order of hours. The efficient observing of such pulsating and orbiting stars requires special observing equipment and techniques, both of which Grauer possesses. Grauer will be involving undergraduate students under NSF's Research for Undergraduate Institutions (RUI) Program.