{
  "id": "2309.11182",
  "version": "v1",
  "published": "2023-09-20T10:07:17.000Z",
  "updated": "2023-09-20T10:07:17.000Z",
  "title": "Unveiling the accretion scenario of BH-ULXs using XMM-Newton observations",
  "authors": [
    "Seshadri Majumder",
    "Santabrata Das",
    "Vivek. K. Agrawal",
    "Anuj Nandi"
  ],
  "comment": "21 pages, 11 figures, 6 tables, accepted for publication in MNRAS",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "We present a comprehensive spectro-temporal analysis of five ultraluminous X-ray sources (ULXs) with central object likely being a black hole, using archival {\\it XMM-Newton} observations. These sources, namely NGC 1313 X-1, NGC 5408 X-1, NGC 6946 X-1, M82 X-1 and IC 342 X-1, reveal short-term variability with fractional variance of $1.42-27.28\\%$ and exhibit QPOs with frequency $\\nu_{\\rm QPO} \\sim 8-667$ mHz. Long-term evolution of ULXs energy spectra ($0.3 - 10$ keV; excluding M82 X$-$1) are described satisfactorily with a model combination that comprises a thermal Comptonization component (\\texttt{nthComp}, yielding $\\Gamma_{\\rm nth} \\sim 1.48 - 2.65$, $kT_{\\rm e} \\sim 1.62 - 3.76$ keV, $\\tau \\sim 8 - 20$, y-par $\\sim 1.16 - 6.24$) along with a standard disc component (\\texttt{diskbb}, $kT_{\\rm in} \\sim 0.16 - 0.54$ keV). We find that these ULXs generally demonstrate anti-correlation between disc luminosity and inner disc temperature as $L_{\\rm disc} \\propto T_{\\rm in}^\\alpha$, where $\\alpha = - 3.58 \\pm 0.04$ for NGC 1313 X-1 and IC 342 X-1, $\\alpha = - 8.93 \\pm 0.11$ for NGC 6946 X-1, and $\\alpha = - 10.31 \\pm 0.10$ for NGC 5408 X-1. We also obtain a linear correlation between bolometric luminosity $L_{\\rm bol}$ and $\\Gamma_{\\rm nth}$ that indicates spectral softening of the sources when $L_{\\rm bol}$ increases. We observe that in presence of QPO, Comptonized seed photon fraction varies in between $\\sim 5 - 20 \\%$, while the Comptonized flux contribution ($50 - 90\\%$) dominates over disc flux. Utilizing $\\nu_{\\rm QPO}$ and $L_{\\rm bol}$, we constrain ULXs mass by varying their spin ($a_{\\rm k}$) and accretion rate ($\\dot m$). We find that NGC 6946 X-1 and NGC 5408 X-1 seem to accrete at sub-Eddington accretion rate provided their central sources are rapidly rotating, whereas IC 342 X-1 and NGC 1313 X-1 can accrete in sub/super-Eddington limit irrespective to their spin values.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-09-20T10:07:17.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "xmm-newton observations",
      "accretion scenario",
      "reveal short-term variability",
      "inner disc temperature",
      "comptonized seed photon fraction varies"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 21,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}