TY - JOUR
T1 - Investigation of Two Fermi-LAT Gamma-Ray Blazars Coincident with High-energy Neutrinos Detected by IceCube
AU - Icecube Collaboration
AU - Collaboration, Fermi Lat
AU - Collaboration, Asas Sn
AU - Garrappa, S.
AU - Buson, S.
AU - Franckowiak, A.
AU - Shappee, B. J.
AU - Beacom, J. F.
AU - Dong, S.
AU - Holoien, T. W.S.
AU - Kochanek, C. S.
AU - Prieto, J. L.
AU - Stanek, K. Z.
AU - Thompson, T. A.
AU - Aartsen, M. G.
AU - Ackermann, M.
AU - Adams, J.
AU - Aguilar, J. A.
AU - Ahlers, M.
AU - Ahrens, M.
AU - Alispach, C.
AU - Andeen, K.
AU - Anderson, T.
AU - Ansseau, I.
AU - Anton, G.
AU - Argüelles, C.
AU - Auffenberg, J.
AU - Axani, S.
AU - Backes, P.
AU - Bagherpour, H.
AU - Bai, X.
AU - Barbano, A.
AU - Barwick, S. W.
AU - Baum, V.
AU - Bay, R.
AU - Beatty, J. J.
AU - Becker, K. H.
AU - Tjus, J. Becker
AU - Benzvi, S.
AU - Berley, D.
AU - Bernardini, E.
AU - Besson, D. Z.
AU - Binder, G.
AU - Bindig, D.
AU - Blaufuss, E.
AU - Blot, S.
AU - Bohm, C.
AU - Börner, M.
AU - Böser, S.
AU - Botner, O.
AU - Kiryluk, J.
N1 - Publisher Copyright:
© 2019. The American Astronomical Society. All rights reserved..
PY - 2019/8/1
Y1 - 2019/8/1
N2 - After the identification of the gamma-ray blazar TXS 0506+056 as the first compelling IceCube neutrino source candidate, we perform a systematic analysis of all high-energy neutrino events satisfying the IceCube realtime trigger criteria. We find one additional known gamma-ray source, the blazar GB6 J1040+0617, in spatial coincidence with a neutrino in this sample. The chance probability of this coincidence is 30% after trial correction. For the first time, we present a systematic study of the gamma-ray flux, spectral and optical variability, and multiwavelength behavior of GB6 J1040+0617 and compare it to TXS 0506+056. We find that TXS 0506+056 shows strong flux variability in the Fermi-Large Area Telescope gamma-ray band, being in an active state around the arrival of IceCube-170922A, but in a low state during the archival IceCube neutrino flare in 2014/15. In both cases the spectral shape is statistically compatible (≤2σ) with the average spectrum showing no indication of a significant relative increase of a high-energy component. While the association of GB6 J1040+0617 with the neutrino is consistent with background expectations, the source appears to be a plausible neutrino source candidate based on its energetics and multiwavelength features, namely a bright optical flare and modestly increased gamma-ray activity. Finding one or two neutrinos originating from gamma-ray blazars in the given sample of high-energy neutrinos is consistent with previously derived limits of neutrino emission from gamma-ray blazars, indicating the sources of the majority of cosmic high-energy neutrinos remain unknown.
AB - After the identification of the gamma-ray blazar TXS 0506+056 as the first compelling IceCube neutrino source candidate, we perform a systematic analysis of all high-energy neutrino events satisfying the IceCube realtime trigger criteria. We find one additional known gamma-ray source, the blazar GB6 J1040+0617, in spatial coincidence with a neutrino in this sample. The chance probability of this coincidence is 30% after trial correction. For the first time, we present a systematic study of the gamma-ray flux, spectral and optical variability, and multiwavelength behavior of GB6 J1040+0617 and compare it to TXS 0506+056. We find that TXS 0506+056 shows strong flux variability in the Fermi-Large Area Telescope gamma-ray band, being in an active state around the arrival of IceCube-170922A, but in a low state during the archival IceCube neutrino flare in 2014/15. In both cases the spectral shape is statistically compatible (≤2σ) with the average spectrum showing no indication of a significant relative increase of a high-energy component. While the association of GB6 J1040+0617 with the neutrino is consistent with background expectations, the source appears to be a plausible neutrino source candidate based on its energetics and multiwavelength features, namely a bright optical flare and modestly increased gamma-ray activity. Finding one or two neutrinos originating from gamma-ray blazars in the given sample of high-energy neutrinos is consistent with previously derived limits of neutrino emission from gamma-ray blazars, indicating the sources of the majority of cosmic high-energy neutrinos remain unknown.
UR - https://www.scopus.com/pages/publications/85071924328
U2 - 10.3847/1538-4357/ab2ada
DO - 10.3847/1538-4357/ab2ada
M3 - Article
AN - SCOPUS:85071924328
SN - 0004-637X
VL - 880
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 103
ER -