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

9521605梅克斯纳质量损失对中等质量恒星的最终演化有着深远的影响。不幸的是，驱动渐近巨星分支(AGB)极端质量损失率的物理机制还不清楚。伊利诺伊大学厄巴纳-香槟分校的玛格丽特·梅克斯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性质进行观测调查：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(过渡J=1-0)成像项目利用伯克利-伊利诺伊州-马里兰毫米波阵列(BIMA)和NRAO 12米望远镜进行观测，并使用详细的辐射传输软件代码来分析数据。预期的结果将包括更准确地确定质量损失率和描述在所有演化恒星中发现的大规模晕(半径约70角秒)；以及致密(小于4角秒)的快速分子气体区，它们存在于原行星星云(PPNe)等过渡天体中，并掌握着AGB到行星星云(PNE)过渡过程的线索。中红外波长成像项目涉及分析环绕AGB恒星PPNe和年轻PNE的55个恒星周围尘埃壳的高分辨率(小于1角秒)中红外波长图像，将使用轴对称辐射转移尘埃代码进行。此外，中红外波长项目包括使用两台中红外波长阵列相机(mirac和Keck LWIRC)在类似波长和更长波长以及高角度分辨率(约0.1角秒)下对PPNe和极端AGB星进行进一步观测。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的起源的洞察，并洞察这种轴对称产生的进化阶段。Me Ixner博士计划开展三项活动，为未来的研究奠定基础。首先，计划于1995年6月与MIRAC小组一起进行一次观察，以观察大约12个PPNe。其次，将使用一个新的轴对称计算机软件DASD程序来模拟当前样品中的几幅PPNe和PNE的中红外图像，从而展示该程序的应用。最后，将使用一种名为镶嵌的新干涉测量技术构建三个对象的一氧化碳波长发射数据立方体，从而证明该技术的可行性。

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.