GCN Circular 41919
Subject
GRB 250920B: Fermi GBM Observation
Event
Date
2025-09-20T21:03:38Z (3 months ago)
From
Rushikesh Digambar Sonawane PHD231014 at IISER, TVM <rushikesh23@iisertvm.ac.in>
Via
Web form
R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 08:46:26.16 UT on 20 September 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250920B (trigger 780050791/250920366).
which was also detected by Swift BAT (R. Gupta et al. 2025, GCN 41898),
SVOM C-GFT (WU et al. 2025, GCN 41908), and Swift UVOT (Kuin et al. 2025, GCN 41915) .
The Fermi GBM Final Real-time localization (GCN 41897) is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 56 degrees.
The GBM light curve consists of multiple emission episodes with a duration (T90)
of about 127.7 s (50-300 keV). The time-averaged spectrum
from T0-3.6 to T0+141.8 s is best fit by
a Band function with Epeak = 118 +/- 7 keV,
alpha = -0.85 +/- 0.05, and beta = -2.09 +/- 0.05.
The event fluence (10-1000 keV) in this time interval is
(3.33 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+9.4 s in the 10-1000 keV band is 8.8 +/- 0.3 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/"