TITLE: GCN CIRCULAR NUMBER: 29903 SUBJECT: GRB 210427A: Fermi GBM Final Real-time Localization DATE: 21/04/27 05:07:38 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 04:57:12 UT on 27 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210427A (trigger 641192237.991858 / 210427206). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 177.3, Dec = -53.4 (J2000 degrees, equivalent to J2000 11h 49m, -53d 23'), with a statistical uncertainty of 1.1 degrees. The angle from the Fermi LAT boresight is 146.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210427206/quicklook/glg_skymap_all_bn210427206.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210427206/quicklook/glg_healpix_all_bn210427206.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210427206/quicklook/glg_lc_medres34_bn210427206.gif