论文标题
二进制恒星对OB与GAIA DR2数据内部速度分散的贡献
Contribution of binary stars to the velocity dispersion inside OB associations with Gaia DR2 data
论文作者
论文摘要
我们估计了二进制系统对gaia dr2适当动作的OB缔合内部速度分散的贡献。对速度分散剂的最大贡献是由p = 5.9年革命的系统给出的，其成分在GAIA DR2观测的基础线时，其组件的距离大约在系统的直径上移动。我们采用了两种方法来研究二进制系统的光上心的运动：第一个使用初始可见性周期之间的总位移，而第二个则基于求解定义时间T_N位移的N方程的系统。第一种和第二种方法分别产生非常相似的Sigma_bn值为0.90和0.87 km S-1。考虑到轨道是椭圆形的事实，可以稍微降低推断的Sigma_bn。我们估计偏心率平均的sigma_bn值为sigma_bn = 0.81 km S-1，假设大型二进制系统的轨道偏心率在[0，0.9]间隔中均匀分布。在幂律分布中的指数伽玛在二进制系统的组件质量比q = m_2/m_1中的p_q〜 q^gamma中的选择似乎对sigma_bn几乎没有影响。伽马从0（平面分布）变为-2.0（具有低质量组件的系统的优势）将Sigma_bn从0.90变为1.07 km S-1。
We estimated the contribution of binary systems to the velocity dispersion inside OB-associations derived from Gaia DR2 proper motions. The maximum contribution to the velocity dispersion is given by the systems with the period of revolution of P=5.9 yr whose components shift by a distance of about the diameter of the system during the base-line time of Gaia DR2 observations. We employed two methods to study the motion of the photocenter of the binary system: the first one uses the total displacement between the initial and final visibility periods and the second one is based on solving a system of n equations defining the displacements at the times t_n. The first and second methods yield very similar sigma_bn values of 0.90 and 0.87 km s-1, respectively. Taking into account the fact that orbits are elliptical slightly decreases the inferred sigma_bn. We estimated the eccentricity-averaged sigma_bn value to be sigma_bn=0.81 km s-1 assuming that the orbital eccentricities of massive binary systems are distributed uniformly in the [0, 0.9] interval. The choice of the exponent gamma in the power-law distribution, p_q ~ q^gamma, of the component-mass ratios q=M_2/M_1 of binary systems appears to have little effect on sigma_bn. A change of gamma from 0 (flat distribution) to -2.0 (preponderance of systems with low-mass components) changes sigma_bn from 0.90 to 1.07 km s-1.
