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arXiv 1802.04019astro-ph.SR
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IRAS 08544-4431的高分辨率观测。绕后AGB星运行的盘和慢盘风的探测

High-resolution observations of IRAS 08544-4431. Detection of a disk orbiting a post-AGB star and of a slow disk wind

V. Bujarrabal, A. Castro-Carrizo, H. Van Winckel, J. Alcolea, C. Sanchez Contreras, M. Santander-Garcia, M. Hillen

备注：
10 pages, 7 figures, accepted by A&A
发表信息：
A&A 614, A58 (2018)
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摘要：

我们正在研究一类后AGB双星，它们似乎被赤道盘和缓慢的外流系统地包围着。虽然旋转动力学只在三个案例中得到了很好的识别，但对这种结构的研究被认为是理解演化恒星周围星云形成的基础。我们目前的ALMA地图的12 CO和13 CO J=3-2线在这些来源之一，IRAS 08544 -4431。我们通过星云模型对数据进行了分析，这些模型可以解释星云的复合源，并可以重现数据。从我们的建模，我们估计了主要的星云参数，包括结构和动力学以及密度和温度分布。我们讨论的不确定性的派生值，特别是，它们的依赖的距离。我们的观测揭示了一个旋转的赤道盘的存在;还发现了一个低速外流，可能是由从盘中排出的气体形成的。我们对IRAS 08544 -4431的观测和建模的主要特征与更好研究的对象相似，证实了我们的解释。圆盘的旋转表明总的中心质量约为1.8 Mo，距离为1100 pc。圆盘被发现相对较长，典型直径约为4 × 10^16 cm。星云的总质量约为2 10^-2 Mo，其中约90%与盘相对应。假设外流是由于从磁盘的质量损失，我们得出一个磁盘的寿命约10000年。发现盘的角动量与目前双星系统的角动量相当。假设盘的角动量是从双星系统转移过来的，正如预期的那样，在这个盘和其他类似的盘中，盘的角动量的高值表明恒星轨道的大小由于盘的形成而显著减小。

英文摘要：

We are studying a class of binary post-AGB stars that seem to be systematically surrounded by equatorial disks and slow outflows. Although the rotating dynamics had only been well identified in three cases, the study of such structures is thought to be fundamental to the understanding of the formation of nebulae around evolved stars. We present ALMA maps of 12CO and 13CO J=3-2 lines in one of these sources, IRAS08544-4431. We analyzed the data by means of nebula models, which account for the expectedly composite source and can reproduce the data. From our modeling, we estimated the main nebula parameters, including the structure and dynamics and the density and temperature distributions. We discuss the uncertainties of the derived values and, in particular, their dependence on the distance. Our observations reveal the presence of an equatorial disk in rotation; a low-velocity outflow is also found, probably formed of gas expelled from the disk. The main characteristics of our observations and modeling of IRAS08544-4431 are similar to those of better studied objects, confirming our interpretation. The disk rotation indicates a total central mass of about 1.8 Mo, for a distance of 1100 pc. The disk is found to be relatively extended and has a typical diameter of ~ 4 10^16 cm. The total nebular mass is ~ 2 10^-2 Mo, of which ~ 90% corresponds to the disk. Assuming that the outflow is due to mass loss from the disk, we derive a disk lifetime of ~ 10000 yr. The disk angular momentum is found to be comparable to that of the binary system at present. Assuming that the disk angular momentum was transferred from the binary system, as expected, the high values of the disk angular momentum in this and other similar disks suggest that the size of the stellar orbits has significantly decreased as a consequence of disk formation.

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