{
  "id": "2002.12051",
  "version": "v1",
  "published": "2020-02-27T11:49:22.000Z",
  "updated": "2020-02-27T11:49:22.000Z",
  "title": "Exploring the Mass Segregation Effect of X-ray Sources in Globular Clusters. III. Signs of Binary Disruption in M28",
  "authors": [
    "Zhongqun Cheng",
    "Huijun Mu",
    "Zhiyuan Li",
    "Xiaojie Xu",
    "Wei Wang",
    "Xiangdong Li"
  ],
  "comment": "18 pages, 5 figures, accepted for publication in ApJ",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "Using archival {\\it 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 $\\sim475\\, \\rm arcmin^{2}$, 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, with the projected distance and width of the distribution dip for bright ($L_{X} \\gtrsim 4.5\\times 10^{30} {\\rm\\ erg\\ \\,s^{-1}}$) X-ray sources are larger than the faint ($L_{X} \\lesssim 4.5\\times 10^{30} {\\rm\\ erg\\ \\,s^{-1}}$) sources. The \"generalized King model\" fitting give a slightly larger average mass for the bright sources ($1.30\\pm0.15\\,M_{\\odot}$) than the faint sources ($1.09\\pm0.14\\,M_{\\odot}$), which support a universal mass segregation delay between heavy objects in GCs. Compared with 47 Tuc and Terzan 5, we show that the dynamical age of M28 is comparable to Terzan 5 and much smaller than 47 Tuc, but it is evolving more fast (i.e., with smaller 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 ($R \\lesssim 1.5 \\rm~arcmin$) of M28 than its outskirts, which indicate that M28 may have suffered an early phase of primordial binary disruption within its central region, and mass segregation effect will erase such a phenomenon as cluster evolve to older dynamical age.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-02-27T11:49:22.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "x-ray sources",
      "mass segregation effect",
      "central region",
      "smaller two-body relaxation timescale",
      "bulge globular cluster m28"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 18,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}