Two active states of the narrow-line gamma-ray-loud AGN GB 1310+487
Creators: name: Sokolovsky, K. V.
name: Schinzel, F. K.
name: Tanaka, Y. T.
name: Abolmasov, P. K.
name: Angelakis, E.
name: Bulgarelli, A.
name: Carrasco, L.
name: Cenko, S. B.
name: Cheung, C. C.
name: Clubb, K. I.
name: D'Ammando, F.
name: Escande, L.
name: Fegan, S. J.
name: Filippenko, A. V.
name: Finke, J. D.
name: Fuhrmann, L.
name: Fukazawa, Y.
name: Hays, E.
name: Healey, S. E.
name: Ikejiri, Y.
name: Itoh, R.
name: Kawabata, K. S.
name: Komatsu, T.
name: Kovalev, Yu. A.
name: Kovalev, Y. Y.
name: Krichbaum, T. P.
name: Larsson, S.
name: Lister, M. L.
name: Lott, B.
name: Max-Moerbeck, W.
name: Nestoras, I.
name: Pittori, C.
name: Pursimo, T.
name: Pushkarev, A. B.
name: Readhead, A. C. S.
name: Recillas, E.
name: Richards, J. L.
name: Riquelme, D.
name: Romani, R. W.
name: Sakimoto, K.
name: Sasada, M.
name: Schmidt, R.
name: Shaw, M. S.
name: Sievers, A.
name: Thompson, D. J.
name: Uemura, M.
name: Ungerechts, H.
name: Vercellone, S.
name: Verrecchia, F.
name: Yamanaka, M.
name: Yoshida, M.
name: Zensus, J. A.
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Previously unremarkable, the extragalactic radio source GB 1310+487 showed a gamma-ray flare on 2009 November 18, reaching a daily flux of ~10^-6 photons/cm^2/s at energies E&gt;100 MeV and becoming one of the brightest GeV sources for about two weeks. Its optical spectrum is not typical for a blazar, instead, it resembles those of narrow emission-line galaxies. We investigate changes of the object's radio-to-GeV spectral energy distribution (SED) during and after the prominent GeV flare with the aim to determine the nature of the object and constrain the origin of the variable high-energy emission. The data collected by the Fermi and AGILE satellites at gamma-ray energies, Swift at X-ray and ultraviolet, Kanata, NOT, and Keck telescopes at optical, OAGH and WISE at infrared, and IRAM 30m, OVRO 40m, Effelsberg 100m, RATAN-600, and VLBA at radio, are analysed together to trace the SED evolution on timescales of months. The gamma-ray/radio-loud narrow-line active galactic nucleus (AGN) is located at redshift z=0.638. It is shining through an unrelated foreground galaxy at z=0.500. The AGN light is likely amplified by a factor of a few because of gravitational lensing. The AGN SED shows a two-humped structure typical of blazars and gamma-ray-loud NLSy1 galaxies, with the high-energy (inverse-Compton) emission dominating by more than an order of magnitude over the low-energy (synchrotron) emission during gamma-ray flares. The difference between the two SED humps is smaller during the low-activity state. Fermi observations reveal a strong correlation between the gamma-ray flux and spectral index, with the hardest spectrum observed during the brightest gamma-ray state. If the gamma-ray flux is a mixture of synchrotron self-Compton (SSC) and external Compton (EC) emission, the observed GeV spectral variability may result from varying relative contributions of these two emission components.
description: 18 pages, 10 figures, 6 tables; accepted to A&amp;A