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Title: Suzaku studies of the central engine in the typical type I Seyfert NGC 3227: detection of multiple primary X-ray continua with distinct properties

The type I Seyfert galaxy NGC 3227 was observed by Suzaku six times in 2008, with intervals of ∼1 week and net exposures of ∼50 ks each. Among the six observations, the source varied by nearly an order of magnitude; it was brightest in the first observation with a 2-10 keV luminosity of 1.2 × 10{sup 42} erg s{sup –1}, while faintest in the fourth observation with 2.9 × 10{sup 41} erg s{sup –1}. As it became fainter, the continuum in the 2-45 keV band became harder, while the narrow Fe-Kα emission line, detected on all occasions at 6.4 keV of the source rest frame, remained approximately constant in the photon flux. Through a method of variability-assisted broadband spectroscopy, the 2-45 keV spectrum of NGC 3227 was decomposed into three distinct components. One is a relatively soft power-law continuum with a photon index of ∼2.3, weakly absorbed and highly variable on timescales of ∼5 ks; it was observed only when the source was above a threshold luminosity of ∼6.6 × 10{sup 41} erg s{sup –1} (in 2-10 keV), and was responsible for further source brightening beyond. Another is a harder and more absorbed continuum with a photon index of ∼1.6,more » which persisted through the six observations and varied slowly on timescales of a few weeks by a factor of ∼2. This component, carrying a major fraction of the broadband emission when the source is below the threshold luminosity, is considered as an additional primary emission. The last one is a reflection component with the narrow iron line, produced at large distances from the central black hole.« less
Authors:
 [1] ; ; ; ;  [2] ;  [3]
  1. Nishina Center, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198 (Japan)
  2. Department of Physics, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
  3. Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397 Japan (Japan)
Publication Date:
OSTI Identifier:
22370525
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 794; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; BLACK HOLES; DETECTION; DISTANCE; EMISSION; IRON; KEV RANGE; LUMINOSITY; PHOTONS; REFLECTION; SEYFERT GALAXIES; SPECTRA; SPECTROSCOPY; X RADIATION; X-RAY GALAXIES