GCN Circular 40621
Subject
GRB 250601A: Fermi GBM Observation
Date
2025-06-03T15:42:16Z (3 days ago)
From
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov>
Via
Web form
V. Sharma (NASA-GSFC/UMBC) and C. Meegan (UAH) report on behalf of the
Fermi Gamma-ray Burst Monitor Team:
"At 17:29:35 UT on 1 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250601A (trigger 770491780 / 250601729).
which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 40600)
and Swift/XRT (K.L. Page et al. 2025, GCN 40604).
The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.
The angle from the Fermi LAT boresight is 24 degrees.
The GBM light curve consists of main emission episode with a
duration (T90) of about 3 s (50-300 keV). The time-averaged
spectrum from T0-0.5 to T0+2.4 s is best fit by a power law
function with an exponential high-energy cutoff. The
power law index is -0.58 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 873 +/- 142 keV.
The event fluence (10-1000 keV) in this time interval is
(2.7 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1 s in the 10-1000 keV band is 4.9 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"