TITLE: GCN CIRCULAR NUMBER: 9416 SUBJECT: GRB 090423: Fermi GBM T90 follow-up analysis results DATE: 09/05/21 14:26:47 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE), C. Kouveliotou (NASA/MSFC) and V. Connaughton (UAH) report on behalf of the Fermi GBM Team: "We performed a detailed follow-up analysis of the T90 of the high redshift GRB 090423 (H. Krimm et al., GCN Circ. # 9198) to determine the nature of the extended pulse centered at T+30s as reported earlier (A. von Kienlin, GCN # 9229). Due to the low significance of the detection, we were not able to accurately locate this later pulse (the emission was only significantly seen with one of the two triggered detectors). We conclude, therefore, that this pulse is most probably due to background fluctuations. The final GBM T90 derived between 10-300 keV is 11.5 +/- 2.0 sec. This duration agrees within the error with the value of 10.3 +/- 1.1 sec reported by the Swift team (H. Krimm et al., GCN Report 211.2)"