Seeking Multimessenger High-Energy Neutrino + Fermi Gamma-ray Transients: Archival Analysis Results and Real-Time Alert Prospects

We have been seeking to identify individual sources or subthreshold source populations of high-energy neutrino + gamma-ray ("nu+gamma") emitting transients by coincidence analysis of Fermi LAT gamma-ray and high-energy neutrino datasets. Our analysis has the potential to detect either individual nu+gamma transient sources (durations less than 1000~s), if they exhibit sufficient gamma-ray or neutrino multiplicity, or a statistical excess of nu+gamma transients of individually lower multiplicities. I will present on our initial analysis of IceCube + Fermi LAT data and the followup analysis of ANTARES + Fermi LAT data. Although we identify no single high-confidence transients nor evidence of a subthreshold source population, we do find a possible correlation between IceCube (59-string) neutrino positions and persistently bright portions of the Fermi LAT sky; we plan to explore this possible correlation in future work. We have since extended and applied our approach to the full 8-year ANTARES neutrino dataset, and have begun implementation and deployment of the first real-time nu+gamma (candidate) transient alerts via the Astrophysical Multimessenger Observatory Network (AMON). Monte Carlo simulations confirm that our alerts are capable of triggering on single-neutrino (ANTARES or IceCube) coincidences with high-multiplicity Fermi LAT sources, including LAT-detected gamma-ray bursts. I will present the latest results of these archival and real-time multimessenger transient searches.