TY - JOUR
T1 - Suzaku discovery of a hard component varying independently of the power-law emission in MCG-6-30-15
AU - Noda, Hirofumi
AU - Makishima, Kazuo
AU - Uehara, Yuuichi
AU - Yamada, Shin'Ya
AU - Nakazawa, Kazuhiro
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2011/4/25
Y1 - 2011/4/25
N2 - Focusing on hard X-ray variability, we reanalyzed Suzaku data of the Type I Seyfert galaxy MCG-6-30-15 obtained in 2006. Intensity-sorted spectroscopy and a principal-component analysis consistently revealed a very hard component that varies independently of the dominant power-law emission. Although the exact nature of this hard component has not yet been identified, it can be modeled as a power-law with a photon index of ∼2 affected by a partial covering absorption, or as a thermal Comptonization emission with a relatively large optical depth. When this component is included in the fitting model, the time-averaged 2.5-55 keV spectrum of MCG-6-30-15 can be reproduced successfully by invoking a mildly broadened iron line with its emission region located at ≥8 times the gravitational radii from the central black hole, and a moderate reflection with a covering fraction of ∼3.4π. This result implies that the solution of a highly spinning black hole in MCG-6-30-15, obtained byMiniutti et al. (2007, PASJ, 59, S315) using the same Suzaku data as ours, is a model-dependent result.
AB - Focusing on hard X-ray variability, we reanalyzed Suzaku data of the Type I Seyfert galaxy MCG-6-30-15 obtained in 2006. Intensity-sorted spectroscopy and a principal-component analysis consistently revealed a very hard component that varies independently of the dominant power-law emission. Although the exact nature of this hard component has not yet been identified, it can be modeled as a power-law with a photon index of ∼2 affected by a partial covering absorption, or as a thermal Comptonization emission with a relatively large optical depth. When this component is included in the fitting model, the time-averaged 2.5-55 keV spectrum of MCG-6-30-15 can be reproduced successfully by invoking a mildly broadened iron line with its emission region located at ≥8 times the gravitational radii from the central black hole, and a moderate reflection with a covering fraction of ∼3.4π. This result implies that the solution of a highly spinning black hole in MCG-6-30-15, obtained byMiniutti et al. (2007, PASJ, 59, S315) using the same Suzaku data as ours, is a model-dependent result.
KW - Active-galaxies
KW - Galaxies
KW - Individual (MCG-6-30-15)-galaxies
KW - Seyfert-X-rays
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U2 - 10.1093/pasj/63.2.449
DO - 10.1093/pasj/63.2.449
M3 - Article
AN - SCOPUS:79956350064
VL - 63
SP - 449
EP - 458
JO - Publications of the Astronomical Society of Japan
JF - Publications of the Astronomical Society of Japan
SN - 0004-6264
IS - 2
ER -