2009/06/01 by Hiromi Seta, Naoki Isobe, Makoto S. Tashiro +99 · 3 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Blazar #Cutoff #Flare #Flux (metallurgy) #Gamma-ray bursts and supernovae #Photon #Spectral energy distribution #Spectral index #Spectral line #Synchrotron radiation #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1093/pasj/61.5.1011
22 pages, 8 figures; accepted for publication in PASJ
arxiv created 2009/06/01 · openalex publication_date 2009/10/25 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Abstract Suzaku observations of the blazar OJ 287 were performed in 2007 April 10–13 and November 7–9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well-described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be Γ= 1.65 ± 0.02 and S\rm 1 keV= 215 ± 5 nJy in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum (Γ= 1.50 ± 0.01) with a nearly doubled X-ray flux density of S\rm 1 keV= 404+6-5 nJy. Moreover, significant hard X-ray signals were detected up to ∼ 27 keV. In cooperation with Suzaku, simultaneous radio, optical, and very-high-energy γ -ray observations of OJ 287 were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 ± 0.46 Jy and 8.93 ± 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found to be higher by a factor of 2–3 than those in the quiescent state (1.73 ± 0.26 Jy and 3.03 ± 0.01 mJy at 86.75 Hz and in the V-band, respectively). No notable γ -ray events were detected in either observation. The spectral energy distribution of OJ 287 indicated that the X-ray spectrum was dominated by inverse Compton radiation in both observations, while synchrotron radiation exhibited a spectral cutoff at around the optical frequency. Furthermore, no significant difference in the synchrotron cutoff frequency was found between the quiescent and flaring states. According to a simple synchrotron self-Compton model, the change of the spectral energy distribution is due to an increase in the energy density of electrons with small changes of both the magnetic field strength and the maximum Lorentz factor of electrons.