论文标题
S型共生星中恒星风积聚的不对称积聚盘形成
Formation of the Asymmetric Accretion Disk from Stellar Wind Accretion in an S-type Symbiotic Star
论文作者
论文摘要
使用闪光代码通过3D流体动力学模拟研究了典型的S型共生恒星中的积聚过程。不管巨型恒星的风速如何，围绕白色矮人的积聚盘总是形成。在风模型中，比白色矮人的轨道速度快，磁盘的大小和积聚速率与邦迪 - 霍伊尔 - 莱特顿（BHL）条件下的预测一致。在较慢的风模型中，与BHL预测不同，磁盘的大小不会增长，积聚率提高到较高的水平，高达巨型恒星的质量损失率的$> 20 \％$。我们的基准模型中的积聚磁盘的特征是半径为0.16〜AU的喇叭盘，尺度高度为0.03 au。 $ \ sim 5 \ times 10^{ - 8} m_ \ odot $的磁盘质量是不对称分布的，密度峰向巨型恒星，比磁盘中的密度最小值高约50美元。清楚地识别出两个流动的螺旋特征，并指出它们与磁盘方位角不对称的相关性。发现积聚磁盘中的流量是次生级的，大约$ 90 \％的开普勒速度，这表明从6825Å和7082Å处的拉曼散布O VI特征的光谱中高估O VI发射区域的警告。
The accretion process in a typical S-type symbiotic star, targeting~AG Draconis, is investigated through 3D hydrodynamical simulations using the FLASH code. Regardless of the wind velocity of the giant star, an accretion disk surrounding the white dwarf is always formed. In the wind models faster than the orbital velocity of the white dwarf, the disk size and accretion rate are consistent with the predictions under the Bondi-Hoyle-Lyttleton (BHL) condition. In slower wind models, unlike the BHL predictions, the disk size does not grow and the accretion rate increases to a considerably higher level, up to $>20\%$ of the mass-loss rate of the giant star. The accretion disk in our fiducial model is characterized by a flared disk with a radius of 0.16~au and a scale height of 0.03 au. The disk mass of $\sim 5 \times 10^{-8} M_\odot$ is asymmetrically distributed with the density peak toward the giant star, being about $50\%$ higher than the density minimum in the disk. Two inflowing spiral features are clearly identified and their relevance to the azimuthal asymmetry of disk is pointed out. The flow in the accretion disk is found to be sub-Keplerian with about $90\%$ of the Keplerian speed, which indicates the caveat of overestimating the O VI emission region from spectroscopy of Raman-scattered O VI features at 6825 Å and 7082 Å.
