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Localizing the γ-ray emission region during the 2014 June outburst of 3C 454.3

Coogan, Rosemary T.; Brown, Anthony M.; Chadwick, Paula M.

Localizing the γ-ray emission region during the 2014 June outburst of 3C 454.3 Thumbnail


Rosemary T. Coogan


In 2014 May–July, the flat spectrum radio quasar 3C 454.3 exhibited strong flaring behaviour. Observations with the Large Area Telescope detector on-board the Fermi Gamma-ray Space Telescope captured the γ-ray flux at energies 0.1 ≤ Eγ ≤ 300 GeV increasing fivefold during this period, with two distinct peaks in emission. The γ-ray emission is analysed in detail, in order to study the emission characteristics and put constraints on the location of the emission region. We explore variability in the spectral shape of 3C 454.3, search for evidence of a spectral cutoff, quantify the significance of very high energy emission and investigate whether or not an energy-dependence of the emitting electron cooling exists. γ-ray intrinsic doubling time-scales as small as τint = 0.68 ± 0.01 h at a significance of >5σ are found, providing evidence of a compact emission region. Significant Eγ, emitted ≥ 35 GeV and Eγ, emitted ≥ 50 GeV emission are also observed. The location of the emission region can be constrained to r ≥ 1.3 × RoutBLRRBLRout, a location outside the broad-line region. The spectral variation of 3C 454.3 also suggests that these flares may be originating further downstream of the supermassive black hole than the emission before and after the flares.


Coogan, R. T., Brown, A. M., & Chadwick, P. M. (2016). Localizing the γ-ray emission region during the 2014 June outburst of 3C 454.3. Monthly Notices of the Royal Astronomical Society, 458(1), 354-365.

Journal Article Type Article
Acceptance Date Feb 21, 2016
Online Publication Date Mar 7, 2016
Publication Date May 1, 2016
Deposit Date Mar 8, 2016
Publicly Available Date Apr 11, 2016
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 458
Issue 1
Pages 354-365
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Published Journal Article (3.2 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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