GCN Circular 40342
Subject
GRB 250504A: Fermi GBM Final Real-time Localization
Date
2025-05-04T23:36:31Z (a day ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 23:25:54 UT on 4 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250504A (trigger 768093959.78286 / 250504976).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 265.4, Dec = -40.9 (J2000 degrees, equivalent to J2000 17h 41m, -40d 53'), with a statistical uncertainty of 2.1 degrees.
The angle from the Fermi LAT boresight is 113.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250504976/quicklook/glg_skymap_all_bn250504976.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250504976/quicklook/glg_healpix_all_bn250504976.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250504976/quicklook/glg_lc_medres34_bn250504976.gif