TITLE:   GCN CIRCULAR
NUMBER:  39133
SUBJECT: GRB 250202B: Fermi GBM Detection
DATE:    25/02/03 17:22:25 GMT
FROM:    sumanbala2210@gmail.com

S. Bala (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 03:57:17.32 UT on 02 February 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250202B (trigger 760161442/250202165).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 347.80, Dec = 16.48 (J2000 degrees, equivalent to
J2000 23h 11m, +16d 29'), with a statistical uncertainty of 1.43 degrees.
(radius, 1-sigma containment, statistical only; there is additionally a
systematic error which we have characterized as a mixture of two Gaussians,
one with a radius of 1.8 degrees (52% contribution) and one with a radius
of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).

The angle from the Fermi LAT boresight is 128 degrees.

The GBM light curve consists of many bright peaks with a duration (T90)
of about 89 s (50-300 keV). The time-averaged spectrum
from T0-0.1 to T0+109.4 s is best fit by
a Band function with Epeak = 252 +/- 5 keV,
alpha = -0.81 +/- 0.01, and beta = -2.56 +/- 0.05.

The event fluence (10-1000 keV) in this time interval is
(1.77 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.7 s in the 10-1000 keV band is 43.4 +/- 0.7 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/"