TITLE: GCN CIRCULAR NUMBER: 30754 SUBJECT: GRB 210903B: Fermi GBM Final Localization DATE: 21/09/03 16:37:03 GMT FROM: Joshua Wood at MSFC/Fermi-GBM joshua.r.wood@nasa.gov

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

At 00:30:46.05 UT on 3 Sep 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210903B (trigger 652321851 / 210903021).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 270.9, Dec = +15.6 (J2000 degrees, equivalent to J2000 18h 03m, +15d 36'), with a statistical uncertainty of 26.1 degrees.

The angle from the Fermi LAT boresight is 66.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210903021/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/bn210903021/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210903021/q...