{
  "id": "1903.05188",
  "version": "v1",
  "published": "2019-03-12T20:15:55.000Z",
  "updated": "2019-03-12T20:15:55.000Z",
  "title": "Optical Counterparts of ULXs and Their Host Environments in NGC 4490/4485",
  "authors": [
    "Senay Avdan",
    "Aysun Akyuz",
    "Alexander Vinokurov",
    "Nazım Aksaker",
    "Hasan Avdan",
    "Sergei Fabrika",
    "Azamat Valeev",
    "Inci Akkaya-Oralhan",
    "Şölen Balman"
  ],
  "comment": "20 pages, 13 figures, submitted to ApJ",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "We report the identification of the possible optical counterparts of five out of seven Ultraluminous X-ray Sources (ULXs) in NGC 4490/4485 galaxy pair. Using archival Hubble Space Telescope ({\\it HST}) imaging data, we identified a single optical candidate for two ULXs (X-4 and X-7) and multiple optical candidates for the other three ULXs (X-2, X-3 and X-6) within $\\sim$ $0\\farcs2$ error radius at the 90\\% confidence level. Of the two remaining ULXs, X-1 has no {\\it HST} imaging data and photometry could not be performed due to the position of X-5 in NGC4490. Absolute magnitudes ($M_{V}$) of the optical candidates lie between $-5.7$ and $-3.8$. Color-Magnitude Diagrams (CMDs) have been used to investigate the properties of counterparts and their environments. The locations of the counterparts of X-2, X-4, and X-6 suggest possible association with nearby group of stars while others have no association with a star cluster or group of stars. For comparison purposes, we analyzed previously unused three archival XMM-Newton observations. The long-term X-ray light curves of the sources (except transient X-7) show variability by a factor of three in a time scale more than a decade. The use of disk blackbody model for the mass of the compact objects indicates that these objects might have masses most likely in the range 10$-$15 $M_{\\sun}$.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-03-12T20:15:55.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "optical counterparts",
      "host environments",
      "optical candidate",
      "long-term x-ray light curves",
      "imaging data"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}