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A Multimessenger Picture of the Flaring Blazar TXS 0506+056: Implications for High-energy Neutrino Emission and Cosmic-Ray Acceleration

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posted on 09.09.2019, 15:12 by A Keivani, K Murase, M Petropoulou, DB Fox, SB Cenko, S Chaty, A Coleiro, JJ DeLaunay, S Dimitrakoudis, PA Evans, JA Kennea, FE Marshall, A Mastichiadis, JP Osborne, M Santander, A Tohuvavohu, CF Turley
Detection of the IceCube-170922A neutrino coincident with the flaring blazar TXS 0506+056, the first and only ~3σ high-energy neutrino source association to date, offers a potential breakthrough in our understanding of high-energy cosmic particles and blazar physics. We present a comprehensive analysis of TXS 0506+056 during its flaring state, using newly collected Swift, NuSTAR, and X-shooter data with Fermi observations and numerical models to constrain the blazar's particle acceleration processes and multimessenger (electromagnetic (EM) and high-energy neutrino) emissions. Accounting properly for EM cascades in the emission region, we find a physically consistent picture only within a hybrid leptonic scenario, with γ-rays produced by external inverse-Compton processes and high-energy neutrinos via a radiatively subdominant hadronic component. We derive robust constraints on the blazar's neutrino and cosmic-ray emissions and demonstrate that, because of cascade effects, the 0.1–100 keV emissions of TXS 0506+056 serve as a better probe of its hadronic acceleration and high-energy neutrino production processes than its GeV–TeV emissions. If the IceCube neutrino association holds, physical conditions in the TXS 0506+056 jet must be close to optimal for high-energy neutrino production, and are not favorable for ultrahigh-energy cosmic-ray acceleration. Alternatively, the challenges we identify in generating a significant rate of IceCube neutrino detections from TXS 0506+056 may disfavor single-zone models, in which γ-rays and high-energy neutrinos are produced in a single emission region. In concert with continued operations of the high-energy neutrino observatories, we advocate regular X-ray monitoring of TXS 0506+056 and other blazars in order to test single-zone blazar emission models, clarify the nature and extent of their hadronic acceleration processes, and carry out the most sensitive possible search for additional multimessenger sources.


The authors thank the IceCube Collaboration for publicly distributing HE neutrinos in real-time, the Swift and NuSTAR teams for their rapid responses to our target of opportunity requests, and the Fermi collaboration for their publicly available data and analysis software. The authors acknowledge helpful discussions with L. Hagen, J. Charlton, and M. Eracleous. A.K., D.B.F., J.J.D., and C.F.T. acknowledge support from the National Science Foundation under grant PHY-1412633; A.K. acknowledges support from the National Aeronautics and Space Administration Swift Guest Investigator Program under grant NNX17AI95G. The work of K.M. is supported by NSF Grant No. PHY-1620777 and the Alfred P. Sloan Foundation. A.K. and K.M. gratefully acknowledge support from the Institute for Gravitation and the Cosmos at the Pennsylvania State University. J.K. and A.T. acknowledge support from NASA contract NAS5-00136. P.A.E. and J.P.O. acknowledge support from the UK Space Agency. M.P. acknowledges support from the L. Jr. Spitzer Postdoctoral Fellowship. S.C. thanks the Centre National d'Etudes Spatiales (CNES) for support and funding. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO program 099.D-0640(A). Software: XSPEC (Arnaud 1996), HEAsoft (v6.22.1), X-shooter pipeline (v.2.9.3; Goldoni et al. 2006; Modigliani et al. 2010), Reflex (Freudling et al. 2013), Molecfit (Kausch et al. 2015; Smette et al. 2015), Fermi Science Tools (, SOPHIA (Mücke et al. 2000).



The Astrophysical Journal, 2018, 864:84

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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American Astronomical Society, IOP Publishing





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