后AGB恒星中的开普勒盘和外流：AC Herculis，89 Herculis，IRAS 19125+0343和R Scuti
Keplerian disks and outflows in post-AGB stars: AC Herculis, 89 Herculis, IRAS 19125+0343, and R Scuti
摘要：
有一类后AGB双星具有显著的近红外线过剩，它们被开普勒或准开普勒盘包围，并由从盘中逃逸的气体组成的扩展外流。开普勒动力学在四个例子中得到了很好的识别，即红色矩形，AC Her，IW Car和IRAS 08544-4431。在这些天体中，流出物的质量约占星云质量的10%，盘状星云是星云的主要组成部分。给出了89 Her中12 CO和13 CO J=2-1以及AC Her、IRAS 19125+0343和R Sct中12 CO J=2-1的干涉NOEMA图。通过数据和模型拟合得到了星云的一些性质，包括结构、密度、温度分布以及动力学。我们还讨论了导出值的不确定性。AC Her中是否存在膨胀成分是值得怀疑的，但由于新的地图和模型，我们估计出流出物的质量上限小于3 10^-5 Mo，也就是说，流出物的质量小于星云总质量的5%。对于89 Her，我们发现星云的总质量为1.4 × 10^-2 Mo，其中约50%来自沙漏形的延伸外流。在IRAS 19125+0343的例子中，星云质量为1.1 × 10^-2 Mo，其中外流贡献了总质量的约70%。R Sct的星云质量为3.2 × 10^-2 Mo，其中约75%对应于围绕着盘的非常广泛的外流。我们对IRAS 19125+0343和R Sct的研究结果使我们引入了一个新的后AGB双星子类，其中外流是星云的主要组成部分。此外，流出的质量分数发现在AC她是小于在其他磁盘占主导地位的二元后AGB星。89 Her将代表两个子类之间的中间情况。
英文摘要：
There is a class of binary post-AGB stars with a remarkable near-infrared excess that are surrounded by Keplerian or quasi-Keplerian disks and extended outflows composed of gas escaping from the disk. The Keplerian dynamics had been well identified in four cases, namely the Red Rectangle, AC Her, IW Car, and IRAS 08544-4431. In these objects, the mass of the outflow represents ~ 10 % of the nebular mass, the disk being the dominant component of the nebula. We present interferometric NOEMA maps of 12CO and 13CO J=2-1 in 89 Her and 12CO J=2-1 in AC Her, IRAS 19125+0343, and R Sct. Several properties of the nebula are obtained from the data and model fitting, including the structure, density, and temperature distributions, as well as the dynamics. We also discuss the uncertainties on the derived values. The presence of an expanding component in AC Her is doubtful, but thanks to new maps and models, we estimate an upper limit to the mass of this outflow of < 3 10^-5 Mo, that is, the mass of the outflow is < 5 % of the total nebular mass. For 89 Her, we find a total nebular mass of 1.4 10^-2 Mo, of which ~ 50 % comes from an hourglass-shaped extended outflow. In the case of IRAS 19125+0343, the nebular mass is 1.1 10^-2 Mo, where the outflow contributes ~ 70 % of the total mass. The nebular mass of R Sct is 3.2 10^-2 Mo, of which ~ 75 % corresponds to a very extended outflow that surrounds the disk. Our results for IRAS 19125+0343 and R Sct lead us to introduce a new subclass of binary post-AGB stars, for which the outflow is the dominant component of the nebula. Moreover, the outflow mass fraction found in AC Her is smaller than those found in other disk-dominated binary post-AGB stars. 89 Her would represent an intermediate case between both subclasses.
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