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Fermi-LAT observations of extreme spectral variability in IC 310

Graham, Jamie A; Brown, Anthony M; Chadwick, Paula M

Fermi-LAT observations of extreme spectral variability in IC 310 Thumbnail


Jamie A Graham

Anthony M Brown


We investigate the physical mechanisms of high-energy gamma-ray emission from the TeV-emitting misaligned active galactic nucleus IC 310. 8 yr of data from the Fermi Large Area Telescope (Fermi-LAT) between 100 MeV and 500 GeV are reduced and analysed to study the temporal and spectral characteristics of IC 310. Point spread function-partitioned instrument response functions are used to improve the resolvability of IC 310 from nearby NGC 1275. Systematic effects due to this choice of instrument response functions and the proximity of NGC 1275 are investigated. We find strong spectral variability and detect the hard flaring state of IC 310 along with a previously undiscovered soft state in quiescent periods, and the first detection with Fermi-LAT below 1 GeV. This represents a shift in peak Compton energy of more than 5 orders of magnitude. Possible interpretations are discussed, but we lack the instantaneous sensitivity with Fermi to probe the underlying physics.

Journal Article Type Article
Acceptance Date Feb 18, 2019
Online Publication Date Feb 28, 2019
Publication Date May 31, 2019
Deposit Date Mar 22, 2019
Publicly Available Date Mar 22, 2019
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 485
Issue 3
Pages 3277-3287
Public URL
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Published Journal Article (2.7 Mb)

Copyright Statement
© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.

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