Searching for Neutrinos in KamLAND in Coincidence with the Brightest Gamma Ray Burst of All Time

In October 2022, we observed the brightest gamma ray burst of all time (GRB221009A) by several metrics. Observations were performed with gamma-ray telescopes, and led to followup searches for neutrino emission with the IceCube detector. In this talk, I will present the results of an analysis searching for low-energy antineutrino emission from GRB221009A in the KamLAND neutrino detector. KamLAND provides unique sensitivity to electron antineutrinos between 1.8 and 500 MeV, enabling new multimessenger searches. For a variety of time windows surrounding the event, we search for antineutrinos coincident with the GRB. No significant antineutrino excesses were observed. Assuming different source emission spectra, we place upper limits on the neutrino flux from this extremely rare astrophysical event.