TITLE: GCN CIRCULAR NUMBER: 21028 SUBJECT: Fermi GBM trigger 514436208/170421123 is not a GRB DATE: 17/04/21 08:49:42 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 514436208/170421123 at 02:56:43.38 UT on 21 April 2017, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is due to local particles."