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

Graham, Jamie A. and Brown, Anthony M. and Chadwick, Paula M. (2019) 'Fermi-LAT observations of extreme spectral variability in IC 310.', Monthly notices of the Royal Astronomical Society., 485 (3). pp. 3277-3287.


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.

Item Type:Article
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Publisher statement:© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.
Date accepted:18 February 2019
Date deposited:22 March 2019
Date of first online publication:28 February 2019
Date first made open access:22 March 2019

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