GCN Circular 39171
Subject
GRB 250205A: Fermi GBM Observation
Date
2025-02-06T15:42:40Z (16 days ago)
From
oindabimukherjee@gmail.com
Via
Web form
O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 21:25:33.72 UT on 05 February 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250205A (trigger 760483538/250205893).
which was also detected by SVOM (Saccardi et al. 2025, GCN 39154), Swift XRT (Kennea et al. 2025, GCN 39161),
and OSIRIS+/GTC with z = 3.55 (Postigo et al. 2025, GCN 39160).
The Fermi GBM on-ground location is consistent with the SVOM position.
The angle from the Fermi LAT boresight is 59 degrees.
The GBM light curve consists of multiple peaks with a duration (T90)
of about 105 s (50-300 keV). The time-averaged spectrum
from T0-63 to T0+75 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.2 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 83 +/- 3 keV. A Band function
with Epeak = 80 +/- 5 keV,
alpha = -0.2 +/- 0.16 and beta = -3.11 +/- 0.39 fits the spectrum equally well.
The event fluence (10-1000 keV) in this time interval is
(6.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.38 s in the 10-1000 keV band is 2 +/- 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/"