TITLE: GCN CIRCULAR NUMBER: 40713 SUBJECT: GRB 250612C: Fermi GBM Observation DATE: 25/06/12 21:54:11 GMT FROM: eliza.neights@gmail.com
E. Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 14:53:16.58 UT on 12 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250612C (trigger 771432801/250612620). which was also detected by SVOM/GRM (Wang et al. 2025, GCN 40708).
The Fermi-GBM position was reported in GCN 40708 (Fermi GBM Team 2025).
The angle from the Fermi LAT boresight is 96 degrees.
The GBM light curve consists of multiple emission episodes with a duration (T90) of about 1.62 s (50-300 keV). The time-averaged spectrum from T0-0.128 to T0+2.688 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.97 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 2110 +/- 70 keV.
A Band function fits the spectrum equally well with Epeak = 2110 +/- 70 keV, alpha = -0.97 +/- 0.01, and beta = -4 +/- 1.
The event fluence (10-1000 keV) in this time interval is (2.80 +/- 0.02)E-05 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.77 s in the 10-1000 keV band is 154 +/- 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/"
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