Multiwavelength Follow-up Observations of Astrophysical Neutrino Events

On September 22, 2017, the IceCube Neutrino Observatory detected a high-energy neutrino of potential astrophysical origin which was found by follow-up electromagnetic observations to spatially and temporally coincide with the flaring state of a known blazar, TXS 0506+056. Since then, several additional neutrino events have been found in spatial correlation with known high-energy sources. Multiwavelength follow-up observations of astrophysical neutrino events such as these, and the continued monitoring of previously-identified sources such as TXS 0506+056 are imperative in finding sources of the diffuse neutrino flux detected by IceCube as well as the origins of high-energy cosmic rays. Here, we present results from multiwavelength follow-up observations of astrophysical neutrino candidate events with potential gamma-ray counterparts, including observations at X-ray and gamma-ray energies performed by the Neil Gehrels Swift Observatory, NuSTAR, and the Fermi Gamma-ray Space Telescope.