Suzaku Observations of the Hard X-Ray Variability of MCG -6-30-15: the Effects of Strong Gravity around a Kerr Black Hole
Fabian, Andrew C.; Kunieda, Hideyo; Haba, Yoshito; Yaqoob, Tahir; Fukazawa, Yasushi; Ohno, Masanori; Takahashi, Tadayuki; Yamauchi, Makoto; Ueda, Yoshihiro; Terashima, Yuichi; Hayashida, Kiyoshi; Reeves, James N.; Anabuki, Naohisa; Miniutti, Giovanni; Tanaka, Yasuo; Watanabe, Shin; Ushio, Masayoshi; Markowitz, Alex; Matsumoto, Chiho; Larsson, Josefin; Crummy, Jamie; Gallo, Luigi; Holt, Steve; Torii, Ken'ichi
United Kingdom, Japan, Germany, United States
Abstract
Suzaku has, for the first time, enabled the hard X-ray variability of the Seyfert 1 galaxy MCG -6-30-15 to be measured. The variability in the 14-45keV band, which is dominated by a strong reflection hump, is quenched relative to that at a few keV. This directly demonstrates that the whole reflection spectrum is much less variable than the power-law continuum. The broadband spectral variability can be decomposed into two components -- a highly variable power-law and constant reflection -- as previously inferred from other observations in the 2-10keV band. The strong reflection and high iron abundance give rise to a strong broad iron line, which requires the inner disc radius to be at about 2 gravitational radii. Our results are consistent with the predictions of the light bending model which invokes the very strong gravitational effects expected very close to a rapidly spinning black hole.