TITLE: GCN CIRCULAR NUMBER: 39944 SUBJECT: GRB 250330A: Fermi GBM Final Localization DATE: 25/03/30 12:59:41 GMT FROM: Utkarsh Pathak at IIT Bombay utkarshpathak.07@gmail.com

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

"At 06:07:38.42 UT on 30 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250330A (trigger 765007663/250330255).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 254.96, Dec = -66.02 (J2000 degrees, equivalent to J2000 16h 51m, -86d 52'), with a statistical uncertainty of 6.9 degrees. This localization is consistent with Swift-BAT location (Cenko et al. 2025, GCN 39938) and Swift-XRT (Page et al. 2025, 39940).

The angle from the Fermi LAT boresight is 46 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/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/bn250330255/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/q..."

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