TITLE: GCN CIRCULAR NUMBER: 18207 SUBJECT: Fermi GBM trigger 150828520 is not a GRB DATE: 15/08/28 20:34:50 GMT FROM: Hoi-Fung Yu at MPE H.-F. Yu reports on behalf of the Fermi GBM Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 462457770/150828520 at 12:29:26.76 UT on the 28 August 2015, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is due to a particle event."