Suzaku observation of OJ 287 ; Quiescence and predicted flare in 2007

Suzaku observations are reported of the BL Lacertae object OJ 287, performed on 2007 April 10– 13 during the optical quiescent phase and on 2007 November 7–9 during the optical flaring phase. We organized the simultaneous the radio and optical observations with the Nobeyama Millimeter Array and optical KANATA telescope at Hiroshima University, respectively. The X-ray spectrum obtained in the quiescent phase was described by a single power-low model with a photon index of Γ = 1.65 ± 0.02 and the flux density was measured to be 216 ± 6 nJy at 1 keV. In the flare phase, the X-ray spectrum became harder (Γ = 1.50 ± 0.01), and the flux density has doubled to be 398 ± 7 nJy at 1 keV. Our multi-wavelength spectrum exhibited the SR and IC components, and the X-ray spectra cannot be explained as an extension from the SR components, but suggest that the X-rays are dominated by the IC component. We suggested electron spectrum indices are variable for each phase. Thus, for the 2nd-flare, SR and IC components increased without extending energy band. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.