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γ-ray observations of extraterrestrial neutrino track events.

Brown, Anthony M. and Adams, Jenni and Chadwick, Paula M. (2015) 'γ-ray observations of extraterrestrial neutrino track events.', Monthly notices of the Royal Astronomical Society., 451 (1). pp. 323-331.


In this paper we report the results of a γ-ray study of IceCube's extraterrestrial neutrino candidates detected as track-like events. Using 70 months of Fermi-Large Area Telescope (LAT) observations, a likelihood analysis of all 1–300 GeV photons within 5° of the track-like neutrino candidates’ origin was undertaken, to search for spatially coincident γ-ray emission. One of IceCube's HESE (High Energy Starting Event) track events was found to be spatially coincident with a γ-ray bright active galactic nucleus (AGN), PKS 0723-008. We find however that the chance probability for Fermi-LAT detected AGN to be spatially coincident with a single HESE track-like event is high (∼37 per cent). We therefore find no evidence of γ-ray emission associated with the detection of IceCube's HESE track-like neutrino candidates. Upper limits were calculated in the energy range of 1–300 GeV, assuming a point source origin for the neutrino events considered. The implications for the non-detection of γ-ray emission from the source of the HESE track-like events are briefly discussed. The large time period analysed in our study did however reveal two new γ-ray point sources. With a flux of (1.28 ± 0.08) × 10−9 photons cm−2 s−1, in the 1–300 GeV energy range, and an associated TS value of 220.6, one of these new point sources is positionally coincident with the AGN PKS 1346-112. The other point source has a 1–300 GeV flux of (7.95 ± 1.23) × 10−10 photons cm−2 s−1 and an associated TS value of 92.4. This new point source is spatially coincident with the radio source NVSS J072534 + 021645 suggesting that it too is an AGN.

Item Type:Article
Keywords:Neutrinos, Galaxies: active, Gamma rays: galaxies, Gamma-rays: general.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:21 April 2015
Date deposited:29 June 2015
Date of first online publication:July 2015
Date first made open access:No date available

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