Exploring the Mass Segregation Effect of X-Ray Sources in Globular Clusters. III. Signs of Binary Disruption in M28
Exploring the Mass Segregation Effect of X-Ray Sources in Globular Clusters. III. Signs of Binary Disruption in M28
复制标题
探索球状星团中 X 射线源的质量偏析效应。
DOI：
10.3847/1538-4357/ab7933
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Xiangdong Li
中科院分区：
文献类型：
--
作者：
Zhongqun Cheng;Huijun Mu;Zhiyuan Li;Xiaojie Xu;Wei Wang;Xiangdong Li
利用钱德拉观测资料，得到了球状星团M28的最新点源星表。该星表包含502个X射线源，面积约为475弧分（2），其中90%以上的X射线源是在该星群中首次发现的。我们发现M28中X射线源的径向分布轮廓有明显的倾斜，明亮（L-X大于或接近4.5 × 10（30）erg s（-1））X射线源的投影距离和分布倾斜的宽度大于暗淡（L-X小于或接近4.5 × 10（30）erg s（-1））源。拟合与“广义国王模型”给出了一个稍大的平均质量为明亮的源（1.30 - 0.15 M）比微弱的（1.09 - 0.14 M），这支持了普遍的延迟在球状星团中的重物体之间的质量分离。我们发现，M28的动力学年龄与Terzan 5相当，比47 Tuc小得多，但M28的演化速度更快（即，具有较短的两体弛豫时间尺度）比47 Tuc。这些特征可能暗示了M28的潮汐冲击对星团动力学演化的加速作用。此外，我们还发现M28的中心区域（R小于或接近15）的X射线源相对于其外围区域的异常缺乏，这表明M28可能在中心区域遭受过早期的原始双星破裂，而随着星系团演化到更老的动力学年龄，质量分凝效应将消除这种现象.
Using archival Chandra observations with a total effective exposure of 323 ks, we derive an updated catalog of point sources in the bulge globular cluster M28. The catalog contains 502 X-ray sources within an area of similar to 475 arcmin(2), and more than 90% of these sources are first detected in this cluster. We find significant dips in the radial distribution profiles of X-ray sources in M28, and the projected distance and width of the distribution dip for bright (L-X greater than or similar to 4.5 x 10(30) erg s(-1)) X-ray sources are larger than for faint (L-X less than or similar to 4.5 x 10(30) erg s(-1)) sources. Fitting with the "generalized King model" gives a slightly larger average mass for the bright sources (1.30 0.15 M) than for the faint ones (1.09 0.14 M), which supports a universal delay in mass segregation between heavy objects in globular clusters. We show that the dynamical age of M28 is comparable to that of Terzan 5 and much smaller than that of 47 Tuc, but M28 is evolving faster (i.e., with a shorter two-body relaxation timescale) than 47 Tuc. These features may suggest an acceleration effect of cluster dynamical evolution by tidal shock in M28. Besides, we find an abnormal deficiency of X-ray sources in the central region (R less than or similar to 15) of M28 compared with its outskirts, which indicates that M28 may have suffered an early phase of primordial binary disruption within its central region, and the mass segregation effect will erase such a phenomenon as clusters evolve to an older dynamical age.