TITLE: GCN CIRCULAR NUMBER: 39951 SUBJECT: GRB 250330B: Fermi GBM Final Real-time Localization DATE: 25/03/30 22:03:10 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 SHORT GRB

At 21:52:22 UT on 30 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250330B (trigger 765064347.102666 / 250330911).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 114.1, Dec = 13.3 (J2000 degrees, equivalent to J2000 07h 36m, 13d 18'), with a statistical uncertainty of 3.1 degrees.

The angle from the Fermi LAT boresight is 81.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330911/q...

The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330911/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330911/q...

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