TITLE: GCN CIRCULAR NUMBER: 39171 SUBJECT: GRB 250205A: Fermi GBM Observation DATE: 25/02/06 15:42:40 GMT FROM: oindabimukherjee@gmail.com
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/"
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