TITLE: GCN CIRCULAR NUMBER: 18351 SUBJECT: Fermi GBM trigger bn150920977 is not due to a GRB DATE: 15/09/21 02:38:37 GMT FROM: George A. Younes at George Washington U G. Younes reports on behalf of the Fermi GBM Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 464484416/150920977 at 23:26:52.22 UT on 20 September 2015, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is due to particle activity."