GCN Circular 41169
Subject
GRB 250725A: Fermi GBM Observation
Event
Date
2025-07-25T17:08:33Z (a year ago)
From
Matt Godwin <msg0028@uah.edu>
Via
Web form
Matt Godwin (UAH), R. Sonawane (IISER TVM) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 01:51:34.81 UT on 25 July 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250725A (trigger 775101099/250725077).
which was also detected by Swift XRT (Evans et al. 2025, GCN 41152), Konus-Wind (Frederiks et al. 2025, GCN 41166),
and Fermi LAT (Airasca et al. 2025, GCN 41161). The Fermi GBM on-ground location is consistent with the Swift XRT position.
The redshift observed by VLT (Thakur et al. 2025, GCN 41160) is z = 5.26.
The angle from the Fermi LAT boresight is 24 degrees.
The GBM light curve consists of one main peak and a weaker secondary peak with a duration (T90)
of about 9.5 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+11.904 s is best fit by
a Band function with Epeak = 161 +/- 7 keV,
alpha = -0.47 +/- 0.05, and beta = -2.7 +/- 0.2.
The event fluence (10-1000 keV) in this time interval is
(1.18 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.7 s in the 10-1000 keV band is 18 +/- 0.4 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/"