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

格劳尔将使用时间序列光度法来研究恒星演化的后期阶段，从行星状星云喷射阶段到白矮星冷却阶段。他将专注于行星状星云的中心恒星、可变的白矮星和双星。他将使用一种新的便携式双星光度计，这是他帮助开发的(美国国家科学基金会授予AST87-12249)，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范围网络，这是一项从全球各地的天文台观测变星的国际努力，目的是独立于当地的日周期。天文学家研究的中心课题之一是恒星的诞生、演化和死亡。格劳尔将专注于恒星演化的最后阶段，其中许多恒星脱离外层形成所谓的行星星云(与行星无关的物体)。外层消失后，剩下的恒星收缩成极其致密的物体，称为白矮星，其质量与太阳相当，大小与地球相似。一些白矮星脉动，周期约为几分钟。它们也被发现在其他恒星的附近，两颗恒星都以小时级的周期绕着对方运行。对这种脉动和轨道恒星的有效观测需要特殊的观测设备和技术，而格劳尔拥有这两种设备和技术。格劳尔将在NSF的本科生机构研究计划(RUI)下招收本科生。

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.