A SUZAKU DISCOVERY OF A SLOWLY VARYING HARD X-RAY CONTINUUM FROM THE TYPE I SEYFERT GALAXY NGC 3516

Journal Article · Wed Jul 10 04:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/771/2/100· OSTI ID:22140150

Noda, Hirofumi ^[1]; Makishima, Kazuo; Nakazawa, Kazuhiro ^[2]; Yamada, Shin'ya ^[3]

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1. Department of Astronomy, School of Science, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
2. Department of Physics, School of Science, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
3. Cosmic Radiation Laboratory, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198 (Japan)

The bright type I Seyfert galaxy NGC 3516 was observed by Suzaku twice, in 2005 October 12-15 and 2009 October 28-November 2, for a gross time coverage of 242 and 544 ks and a net exposure of 134 and 255 ks, respectively. The 2-10 keV luminosity was 2.8 Multiplication-Sign 10{sup 41} erg s{sup -1} in 2005 and 1.6 Multiplication-Sign 10{sup 41} erg s{sup -1} in 2009. The 1.4-1.7 keV and 1.7-10 keV count rates both exhibited peak-to-peak variations of a factor of {approx}2 in 2005 and {approx}4 in 2009. In both observations, the 15-45 keV count rate was less variable. The 2-10 keV spectrum in 2005 was significantly more convex than that in 2009. Through a count-count plot technique, the 2-45 keV signals in both sets of data were successfully decomposed in a model-independent way into two distinct broadband components. One is a variable emission with a featureless spectral shape, and the other is a non-varying hard component accompanied by a prominent Fe-K emission line at 6.33 keV (6.40 keV in the rest frame). The former was successfully fitted by an absorbed power-law model, while the latter requires a new hard continuum in addition to a reflection component from distant materials. The spectral and variability differences between the two observations are mainly attributed to long-term changes of this new hard continuum, which was stable on timescales of several hundreds of kiloseconds.

• OSTI ID: 22140150
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 771; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COUNTING RATES
HARD COMPONENT
HARD X RADIATION
KEV RANGE
LUMINOSITY
REFLECTION
SEYFERT GALAXIES
SPECTRA
X-RAY GALAXIES