Search for Sources of IceCube Astrophysical Neutrinos

The IceCube Neutrino Observatory instruments a cubic-kilometer of glacial ice under the Amundsen-Scott South Pole Station, Antarctica to detect neutrinos above ~100 GeV and perform astro-particle observations of the Universe.  Astrophysical neutrinos are expected to be created in the birthplaces of high-energy cosmic rays, and point the way back to these elusive sources.  Since IceCube's detection of a diffuse flux of high-energy astrophysical neutrinos in 2013, identifying their sources has been the primary science goal.  This talk with will present the latest measurements of the astrophysical neutrino flux and highlight results from realtime alerts generated by astrophysical neutrino detections that trigger rapid follow-up observations by the community.  In particular, a neutrino alert in September, 2017 triggered world-wide astronomical observations, and provide evidence that the Fermi-LAT identified blazar TXS 0506+056 is the first multi-messenger source producing neutrinos, as well as an accelerator of cosmic rays.