Exploring the Mass Segregation Effect of X-ray Sources in Globular Clusters. II. The Case of Terzan 5

Abstract: Using archival Chandra observations with a total effective exposure of 734 ks, we derive an updated catalog of point sources in the massive globular cluster Terzan 5. Our catalog covers an area of   58.1arcmin2   (   R4.3arcmin   ) with 489 X-ray sources, and more than   75%   of these sources are first detected in this cluster. We find significant dips in the radial distribution profiles of X-ray sources in Terzan 5, with the projected distance and width of the distribution dips for bright (   LX9.5×1030 erg s1   ) X-ray sources are larger than that of the faint (   LX9.5×1030 erg s1   ) sources. By fitting the radial distribution of the X-ray sources with a"generalized King model", we estimated an average mass of   1.48±0.11M   and   1.27±0.13M   for the bright and faint X-ray sources, respectively. These results are in agreement with that observed in 47 Tuc, which may suggest a universal mass segregation effect for X-ray sources in GCs. Compared with 47 Tuc, we show that the two-body relaxation timescale of Terzan 5 is much smaller, but its dynamical age is significantly younger than 47 Tuc. These features suggest that the evolution of Terzan 5 is not purely driven by two-body relaxation, and tidal stripping effect also plays an important role in accelerating the dynamical evolution of this cluster.

Authors: Zhongqun Chen, Zhiyuan Li, Taotao Fang, Xiangdong Li, Xiaojie Xu

Accepted for publication in ApJ.

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