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 (GC) Terzan 5. Our catalog covers an area of 58.1 arcmin 2 ( R  ≤ 4.′3) 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 ( L X  ≳ 9.5 × 10 30 erg s −1 ) X-ray sources larger than those of the faint ( L X  ≲ 9.5 × 10 30 erg s −1 ) sources. By fitting the radial distribution of the X-ray sources with a “generalized King model,” we estimated an average mass of 1.48 ± 0.11 and 1.27 ± 0.13 M ⊙ 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 the tidal stripping effect also plays an important role in accelerating the dynamical evolution of this cluster.