{
  "id": "1809.04076",
  "version": "v1",
  "published": "2018-09-11T18:00:00.000Z",
  "updated": "2018-09-11T18:00:00.000Z",
  "title": "BAT AGN Spectroscopic Survey -- XII. The relation between coronal properties of Active Galactic Nuclei and the Eddington ratio",
  "authors": [
    "C. Ricci",
    "L. C. Ho",
    "A. C. Fabian",
    "B. Trakhtenbrot",
    "M. J. Koss",
    "Y. Ueda",
    "A. Lohfink",
    "T. Shimizu",
    "F. E. Bauer",
    "R. Mushotzky",
    "K. Schawinski",
    "S. Paltani",
    "I. Lamperti",
    "E. Treister",
    "K. Oh"
  ],
  "comment": "Accepted for publication in MNRAS",
  "categories": [
    "astro-ph.HE",
    "astro-ph.CO",
    "astro-ph.GA"
  ],
  "abstract": "The bulk of the X-ray emission in Active Galactic Nuclei (AGN) is produced very close to the accreting supermassive black hole (SMBH), in a corona of hot electrons which up scatters optical and ultraviolet photons from the accretion flow. The cutoff energy ($E_{\\rm C}$) of the primary X-ray continuum emission carries important information on the physical characteristics of the X-ray emitting plasma, but little is currently known about its potential relation with the properties of accreting SMBHs. Using the largest broad-band (0.3-150 keV) X-ray spectroscopic study available to date, we investigate how the corona is related to the AGN luminosity, black hole mass and Eddington ratio ($\\lambda_{\\rm Edd}$). Assuming a slab corona the median values of the temperature and optical depth of the Comptonizing plasma are $kT_{\\rm e}=105 \\pm 18$ keV and $\\tau=0.25\\pm0.06$, respectively. When we properly account for the large number of $E_{\\rm C}$ lower limits, we find a statistically significant dependence of the cutoff energy on the Eddington ratio. In particular, objects with $ \\lambda_{\\rm Edd}>0.1$ have a significantly lower median cutoff energy ($E_{\\rm C}=160\\pm41$ keV) than those with $\\lambda_{\\rm Edd}\\leq 0.1$ ($E_{\\rm C}=370\\pm51$ keV). This is consistent with the idea that radiatively compact coronae are also cooler, because they tend to avoid the region in the temperature-compactness parameter space where runaway pair production would dominate. We show that this behaviour could also straightforwardly explain the suggested positive correlation between the photon index ($\\Gamma$) and the Eddington ratio, being able to reproduce the observed slope of the $\\Gamma-\\lambda_{\\rm Edd}$ trend.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-09-11T18:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "bat agn spectroscopic survey",
      "active galactic nuclei",
      "eddington ratio",
      "emission carries important information",
      "continuum emission carries important"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}