TY - JOUR T1 - Blazar Flares as an Origin of High-energy Cosmic Neutrinos? Y1 - 2018 A1 - Murase, Kohta A1 - Oikonomou, Foteini A1 - Petropoulou, Maria KW - astroparticle physics KW - Astrophysics - Astrophysics of Galaxies KW - Astrophysics - Cosmology and Nongalactic Astrophysics KW - Astrophysics - High Energy Astrophysical Phenomena KW - galaxies: active KW - galaxies: jets KW - gamma rays: galaxies KW - High Energy Physics - Phenomenology KW - neutrinos KW - radiation mechanisms: non-thermal AB - We consider implications of high-energy neutrino emission from blazar flares, including the recent event IceCube-170922A and the 2014-2015 neutrino flare that could originate from TXS 0506+056. First, we discuss their contribution to the diffuse neutrino intensity taking into account various observational constraints. Blazars are likely to be subdominant in the diffuse neutrino intensity at sub-PeV energies, and we show that blazar flares like those of TXS 0506+056 could make ≲1%-10% of the total neutrino intensity. We also argue that the neutrino output of blazars can be dominated by the flares in the standard leptonic scenario for their γ-ray emission, and energetic flares may still be detected with a rate of ≲ 1 {yr}}-1. Second, we consider multi-messenger constraints on the source modeling. We show that luminous neutrino flares should be accompanied by luminous broadband cascade emission, emerging also in X-rays and γ-rays. This implies that not only γ-ray telescopes like Fermi but also X-ray sky monitors such as Swift and MAXI are critical to test the canonical picture based on the single-zone modeling. We also suggest a two-zone model that can naturally satisfy the X-ray constraints while explaining the flaring neutrinos via either photomeson or hadronuclear processes. VL - 865 SN - 0004-637X UR - https://ui.adsabs.harvard.edu/abs/2018ApJ...865..124M JO - The Astrophysical Journal ER -