An Observational Investigation of Mass Loss in Evolved Stars Using Millimeter Interferometry and Mid-IR Wavelength Imaging

质量损失对中质量恒星的最终演化有着深远的影响。不幸的是，在渐近巨枝（AGB）上驱动极端质量损失率的物理机制尚不清楚。伊利诺伊大学厄巴纳-香槟分校的玛格丽特·梅克纳博士将使用两个波段的成像技术对演化恒星质量损失的本质进行观测研究：毫米波长（3毫米）和中红外波长（8-25微米）。一氧化碳发射毫米波（跃迁J=1-0）成像项目利用伯克利-伊利诺伊-马里兰毫米波阵列（BIMA）和NRAO 12m望远镜进行观测，并使用详细的辐射传输软件代码对数据进行分析。预期的结果将包括更精确地测定质量损失率和描述在所有演化恒星中发现的大尺度晕（半径约70角秒）；紧凑（小于4弧秒）的快速分子气体区域，这些区域存在于原行星状星云（PPNe）等过渡天体中，并为AGB向行星状星云（Pne）的过渡过程提供了线索。中红外波段成像项目将使用轴对称辐射传输尘埃编码对AGB星、PPNe星和年轻Pne星周围55颗星周尘埃壳（CDSs）的高分辨率（小于1弧秒）中红外波段成像进行分析。此外，中红外波长项目还包括使用两个中红外波长阵列相机（MIRAC和Keck LWIRC）以相似和更长的波长和高角分辨率（约0.1角秒）进一步观测PPNe和极端AGB恒星。这个中红外波长成像项目的结果将提供对Pne中常见的轴对称形态结构起源的深入了解，以及对这种轴对称产生的进化阶段的深入了解。梅伊克斯纳博士计划了三项活动，为未来的研究奠定基础。首先，计划在1995年6月与MIRAC小组进行一次观测，观察大约12个PPNe。其次，利用一种新的轴对称计算机软件dust code对当前样品中PPNe和Pne的中红外图像进行建模；从而演示了该代码的应用。最后，利用一种新的干涉测量技术——镶嵌技术，构建三个目标的一氧化碳波长发射数据立方体；从而证明了该技术的可行性。

9521605 Meixner Mass loss has a profound effect on the final evolution of intermediate mass stars. Unfortunately, the physical mechanism driving the extreme mass loss rates on the asymptotic giant branch (AGB) is not understood. Dr. Margaret Meixner of the University of Illinois, Urbana-Champaign, will conduct an observational investigation of the nature of the mass loss in evolved stars using imaging techniques in two wavebands: millimeter wavelength (3 mm), and mid-IR wavelength (8-25 microns). The carbon monoxide emission millimeter wavelength (transition J=1-0) imaging project utilizes the Berkeley-Illinois-Maryland millimeter wavelength array (BIMA) and the NRAO 12m telescope for observations, and a detailed radiative transfer software code for the analysis of the data. The expected results will include more accurate determination of mass loss rates and characterization of the large scale halos (radii about 70 arc seconds) which are found in all evolved stars; and compact (less than 4 arc seconds) fast molecular gas regions, which are found in transition objects such as proto-planetary nebulae (PPNe) and hold a clue to the AGB to planetary nebula (Pne) transition process. The mid-IR wavelength imaging project involves the analysis of high resolution (less than 1 arc second) mid-IR wavelength images of 55 circumstellar dust shells (CDSs) surrounding AGB stars, PPNe and young Pne, will be carried out using an axially symmetric radiative transfer dust code. Moreover, the mid-IR wavelength project includes further observations of PPNe and extreme AGB stars at similar and longer wavelengths and at high angular resolutions (about 0.1 arc seconds) using two mid-IR wavelength array cameras (MIRAC and the Keck LWIRC). The results from this mid-IR wavelength imaging project will provide insight into the origin of axially symmetric morphological structures commonly found in Pne and insight into the evolutionary stage at which this axial symmetry arises. Dr. Me ixner has three activities planned that will lay ground work for the future research. Firstly, an observing run is planned with the MIRAC team in June 1995 to observe approximately one dozen PPNe. Secondly, a new axially symmetric computer software dust code will be used to model several mid-IR images of PPNe and Pne from the current sample; thereby demonstrating the application of this code. Finally, carbon monoxide wavelength emission data cubes of three objects will be constructed using a new interferometry technique called mosaicing; thereby demonstrating the feasibility of this technique.