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TwitterA&A 492, 93-99 (2008)
DOI: 10.1051/0004-6361:200810674
The efficient low-mass Seyfert MCG–05–23–016
V. Beckmann1, 2, 3, T. J. -L. Courvoisier1, 2, N. Gehrels4, P. Lubiński1, 5, J. Malzac6, P.-O. Petrucci7, C. R. Shrader4, and S. Soldi1, 21 ISDC Data Centre for Astrophysics, Chemin d'Écogia 16, 1290 Versoix, Switzerland
e-mail: Volker.Beckmann@unige.ch
2 Observatoire Astronomique de l'Université de Genève, Chemin des Maillettes 51, 1290 Sauverny, Switzerland
3 University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
4 Astrophysics Science Division, NASA Goddard Space Flight Center, Code 661, MD 20771, USA
5 Centrum Astronomiczne im. M. Kopernika, Bartycka 18, PL-00-716 Warszawa, Poland
6 Centre d'Étude Spatiale des Rayonnements (CESR), OMP, UPS, CNRS, BP 44346, 31028 Toulouse Cedex 4, France
7 Laboratoire d'Astrophysique de Grenoble, Univ. J. Fourier/CNRS, UMR 5571, BP 53X, 38041 Grenoble Cedex, France
Received 25 July 2008 / Accepted 10 October 2008
Abstract
Aims. The Seyfert 1.9 galaxy MCG–05–23–016 has been shown to exhibit a complex X-ray spectrum. This source has moderate X-ray luminosity, hosts a
comparably low-mass black hole, but accretes at a high Eddington rate,
and allows us to study a super massive black hole in an early stage.
Methods. Three observations of the INTEGRAL satellite simultaneous with
pointed Swift/XRT observations performed from December 2006 to June
2007 are used in combination with public data from the INTEGRAL archive to study the variability of the hard X-ray components and to generate a high-quality spectrum
from 1 to 150 keV.
Results. The AGN shows little variability in the hard X-ray spectrum, with
some indication of a variation in the high-energy cut-off energy
ranging from 50 keV to 
100 keV, with an electron plasma temperature in the 10–90 keV range. The reflection component is not evident and, if present, the reflected fraction can be constrained to R < 0.3 for the combined data set. Comparison to previous observations shows that the reflection component has to be variable. No variability in the UV and optical range is observed on a time scale of 1.5 years.
Conclusions. The hard X-ray spectrum of MCG–05–23–016 appears to be stable
with the luminosity and underlying power law varying moderately and the optical/UV flux staying constant. The reflection component and the iron K
line seem to have decreased between December 2005 and the observations presented here. The spectral energy distribution appears to be similar to that of Galactic black hole systems, e.g. XTE 1118+480 in the low state. The AGN exhibits a remarkably high Eddington ratio of $L_{\rm bol}/L_{\rm Edd} \mathrel{>\kern-1.0em\lower0.9ex\hbox{~}}0.8$ (or $L_{\rm bol}/L_{\rm Edd} \mathrel{>\kern-1.0em\lower0.9ex\hbox{~}}0.1$, if we consider a higher mass of the central engine) and, at the same time, a low cut-off
energy around 70 keV. Objects like MCG–05–23–016 might indicate the early
stages of super massive black holes, in which a strong accretion flow
feeds the central engine.
Key words: galaxies: active -- galaxies: Seyfert -- X-rays: galaxies -- galaxies: individual: MCG–05–23–016 -- accretion, accretion discs
© ESO 2008