X-ray and optical correlation of type I Seyfert NGC 3516 studied with Suzaku and Japanese ground-based telescopes

Journal Article · Sat Sep 10 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/828/2/78· OSTI ID:22868709

Noda, Hirofumi ^[1]; Minezaki, Takeo; Kokubo, Mitsuru; Morokuma, Tomoki ^[2]; Watanabe, Makoto; Nakao, Hikaru; Imai, Masataka ^[3]; Kawaguchi, Kenji; Itoh, Ryosuke; Takaki, Katsutoshi; Kawabata, Miho; Nakaoka, Tatsuya ^[4]; Morihana, Kumiko; Arai, Akira; Takagi, Yuhei ^[5]; Saito, Yoshihiko ^[6]; Moritani, Yuki ^[7]; Uemura, Makoto; Kawabata, Koji; Yoshida, Michitoshi ^[8] ; others, and

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1. Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramakiazaaoba, Aoba-ku, Sendai, Miyagi 980-8578 (Japan)
2. Institute of Astronomy, Graduate School of Science, The University of Tokyo, Mitaka, Tokyo 181-0015 (Japan)
3. Department of Cosmosciences, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810 (Japan)
4. Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)
5. Nishi-harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nichigaichi, Sayo-cho, Sayo, Hyogo 670-5313 (Japan)
6. Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
7. Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa 277-8583 (Japan)
8. Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

From 2013 April to 2014 April, we performed X-ray and optical simultaneous monitoring of the type 1.5 Seyfert galaxy NGC 3516. We employed Suzaku and five Japanese ground-based telescopes—the Pirka, Kiso Schmidt, Nayuta, MITSuME, and the Kanata telescopes. The Suzaku observations were conducted seven times with various intervals ranging from days or weeks to months, with an exposure of ∼50 ks each. The optical B-band observations not only covered those of Suzaku almost simultaneously, but also followed the source as frequently as possible. As a result, NGC 3516 was found in its faint phase with a 2–10 keV flux of 0.21–2.70 × 10{sup −11} erg s{sup −1} cm{sup −2}. The 2–45 keV X-ray spectra were composed of a dominant variable hard power-law (PL) continuum with a photon index of ∼1.7 and a non-relativistic reflection component with a prominent Fe–Kα emission line. Producing the B-band light curve by differential image photometry, we found that the B-band flux changed by ∼2.7 × 10{sup −11} erg s{sup −1} cm{sup −2}, which is comparable to the X-ray variation, and we detected a significant flux correlation between the hard PL component in X-rays and the B-band radiation, for the first time in NGC 3516. By examining their correlation, we found that the X-ray flux preceded that in the B band by 2.0{sub −0.6}{sup +0.7} days (1σ error). Although this result supports the X-ray reprocessing model, the derived lag is too large to be explained by the standard view, which assumes a “lamppost”-type X-ray illuminator located near a standard accretion disk. Our results are better explained by assuming a hot accretion flow and a truncated disk.

• OSTI ID: 22868709
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 828; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
COMPARATIVE EVALUATIONS
CORRELATIONS
EMISSION
KEV RANGE 01-10
PHOTOMETRY
PHOTONS
REFLECTION
RELATIVISTIC RANGE
SEYFERT GALAXIES
TELESCOPES
X RADIATION
X-RAY GALAXIES
X-RAY SPECTRA