Hunting for Neutrino Emission from Multifrequency Variable Sources

Pinpointing the neutrino sources is crucial to unveil the mystery of high-energy cosmic rays. The search for neutrino source candidates from coincident neutrino-photon signatures and objects with particular electromagnetic flaring behaviors can increase our chances of finding neutrino emitters. In this paper, we first study the temporal correlations of astrophysical flares with neutrinos, considering a few hundred multifrequency sources from the Atacama Large Millimeter/submillimeter Array, the Wide-field Infrared Survey Explorer (WISE), Swift, and Fermi in the containment regions of IceCube high-energy alerts. Furthermore, the spatial correlations between blazars and neutrinos are investigated using the subset of 10 yr IceCube track-like neutrinos with around 250,000 events. In a second test, we account for 2700 blazars with different types of flaring stages in addition to their position. No significant neutrino emissions were found from our analyses. Our results indicate an interesting trend showing that the infrared flaring phases of WISE blazars might be correlated with the arrival times of the neutrino alerts. A possible overflow of neutrinos associated with two of our selected blazar samples is discussed in detail. One is characterized by a significant flaring lag in infrared with respect to γ-rays, as seen for TXS 0506+056, and the other is characterized by highly simultaneous infrared and γ-ray flares. Our investigation suggests the need to improve current multifrequency light-curve catalogs to pair with the advent of more sensitive neutrino observatories.