TITLE: GCN CIRCULAR NUMBER: 30752 SUBJECT: GRB 210903A: Fermi GBM Final Real-time Localization DATE: 21/09/03 02:00:41 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM do_not_reply@GIOC.nsstc.nasa.gov

The Fermi GBM team reports the detection of a likely LONG GRB

At 01:50:17 UT on 3 Sep 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210903A (trigger 652326622.389106 / 210903077).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 178.6, Dec = 39.1 (J2000 degrees, equivalent to J2000 11h 54m, 39d 06'), with a statistical uncertainty of 5.4 degrees.

The angle from the Fermi LAT boresight is 102.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210903077/q...

The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210903077/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210903077/q...