Suzaku Observations of the Hard X-Ray Variability of MCG −6–30–15: the Effects of Strong Gravity around a Kerr Black Hole

• Published in: Publications of the Astronomical Society of Japan 2007-01, Vol.59 (sp1), p.S315-S325
• Main Authors: Miniutti, Giovanni, Fabian, Andrew C., Anabuki, Naohisa, Crummy, Jamie, Fukazawa, Yasushi, Gallo, Luigi, Haba, Yoshito, Hayashida, Kiyoshi, Holt, Steve, Kunieda, Hideyo, Larsson, Josefin, Markowitz, Alex, Matsumoto, Chiho, Ohno, Masanori, Reeves, James N., Takahashi, Tadayuki, Tanaka, Yasuo, Terashima, Yuichi, Torii, Ken’ichi, Ueda, Yoshihiro, Ushio, Masayoshi, Watanabe, Shin, Yamauchi, Makoto, Yaqoob, Tahir
• Format: Article
• Language: English
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/59.sp1.S315

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 14–45 keV 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 2–10 keV 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.