RUI: High-Resolution Observational Study of Proto-Planetary Nebulae

RUI：原行星状星云的高分辨率观测研究

• 批准号: 9900846
• 负责人: Bruce Hrivnak
• 金额: $ 12.72万
• 依托单位: Valparaiso University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-06-15 至 2004-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9900846&HistoricalAwards=false
• 关键词: RUI; Resolution; Observational; Study; Proto

Abstract Hrivnak AST 99-00846The observational properties of intermediate and low mass stars have been well documented in most phases of their evolution, from the main sequence to the white dwarf phase. The most poorly observed phase of evolution, however, is the transition from red giants to planetary nebulae, in what is known as the proto-planetary nebulae (PPN) phase. This is because the transition occurs relatively rapidly; the stars are often significantly obscured by circumstellar dust; and because until recently there was not efficient means to identify such objects. In the past decade, however, as a result of observations obtained from the IRAS satellite infrared sky survey, about 50 good PPN candidates have been identified based upon the infrared emission from their dust shells.The goal of this project is to determine quantitatively the observational properties of the central stars and circumstellar shells of a representative number of objects in this transitional phase. High-resolution spectroscopic observations will be obtained at visible and near-infrared wavelengths. From the data of these observations, the photospheric abundances and the chemistry and dynamics of the circumstellar envelopes will be determined. The results will help test theories of nucleosynthesis and mass loss in low- and medium-mass stars. It has been found that most proto-planetary nebulae vary in brightness and also pulsate. The pulsation velocity is measured by observing the Doppler effects in the observed emissions from the stars. This unique program to monitor this variability of the proto-planetary nebulae will be carried out over the next three years. In principle, the results obtained may lead to information on the internal structure of these objects

中低质量恒星从主序星到白矮星的大部分演化阶段的观测特性已经被很好地记录下来。然而，观测最少的演化阶段是从红巨星到行星状星云的转变，即所谓的原行星状星云（PPN）阶段。这是因为这种转变发生得相对较快；恒星经常被星周尘埃明显地遮蔽；因为直到最近，还没有有效的方法来识别这些物体。然而，在过去的十年中，根据IRAS卫星红外巡天的观测结果，根据其尘埃壳的红外发射已经确定了大约50个良好的PPN候选者。这个项目的目标是定量地确定在这个过渡阶段有代表性的一些天体的中心恒星和星周壳的观测特性。在可见光和近红外波段将获得高分辨率光谱观测。根据这些观测数据，将确定光球丰度以及星周包层的化学和动力学。这些结果将有助于测试低质量和中等质量恒星的核合成和质量损失理论。人们已经发现，大多数原行星状星云在亮度上有变化，也有脉动。脉动速度是通过观测恒星辐射的多普勒效应来测量的。这个监测原行星状星云变化的独特项目将在未来三年内进行。原则上，所获得的结果可能导致关于这些物体的内部结构的信息