Radio–gamma-ray connection and spectral evolution in 4C +49.22 (S4 1150+49): the Fermi, Swift and Planck view

Author/Creator ORCID

Date

2014-11-07

Department

Program

Citation of Original Publication

S. Cutini, S. Ciprini, M. Orienti, A. Tramacere, F. D'Ammando, F. Verrecchia, G. Polenta, L. Carrasco, V. D'Elia, P. Giommi, J. González-Nuevo, P. Grandi, D. Harrison, E. Hays, S. Larsson, A. Lähteenmäki, J. León-Tavares, M. López-Caniego, P. Natoli, R. Ojha, B. Partridge, A. Porras, L. Reyes, E. Recillas, E. Torresi, Radio–gamma-ray connection and spectral evolution in 4C +49.22 (S4 1150+49): the Fermi, Swift and Planck view, Monthly Notices of the Royal Astronomical Society, Volume 445, Issue 4, 21 December 2014, Pages 4316–4334, https://doi.org/10.1093/mnras/stu2011

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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 2020 Oxford University Press Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Subjects

Abstract

The Large Area Telescope on board the Fermi Gamma-ray Space Telescope detected a strong γ-ray flare on 2011 May 15 from a source identified as 4C +49.22, a flat spectrum radio quasar (FSRQ) also known as S4 1150+49. This blazar, characterized by a prominent radio–optical–X-ray jet, was in a low γ-ray activity state during the first years of Fermi observations. Simultaneous observations during the quiescent, outburst and post-flare γ-ray states were obtained by Swift, Planck and optical–IR–radio telescopes (Instituto Nacional de Astrofísica, Óptica y Electrónica, Catalina Sky Survey, Very Long Baseline Array [VLBA], Metsähovi). The flare is observed from microwave to X-ray bands with correlated variability and the Fermi, Swift and Planck data for this FSRQ show some features more typical of BL Lac objects, like the synchrotron peak in the optical band that outshines the thermal blue-bump emission, and the X-ray spectral softening. Multi-epoch VLBA observations show the ejection of a new component close in time with the GeV γ-ray flare. The radio-to-γ-ray spectral energy distribution is modelled and fitted successfully for the outburst and the post-flare epochs using either a single flaring blob with two emission processes (synchrotron self-Compton (SSC), and external-radiation Compton), and a two-zone model with SSC-only mechanism.