TITLE: GCN CIRCULAR NUMBER: 29578 SUBJECT: GRB 210226A: Fermi GBM detection DATE: 21/02/27 03:20:46 GMT FROM: Joshua Wood at MSFC/Fermi-GBM J. Wood (NASA/MSFC) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 04:43:56.56 UT on 26 February 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210226A (trigger 636007441 / 210226197) which was also detected by the Swift/BAT and Swift/XRT (A.P. Beardmore et al. 2019, GCN 29568). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 58.6 degrees. The GBM light curve consists of a single peak with a duration (T90) of about 26 s (50-300 keV). The time-averaged spectrum from T0-6 s to T0+18 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 170 +/- 29 keV The event fluence (10-1000 keV) in this time interval is (2.7 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.2 s in the 10-1000 keV band is 4.1 +/- 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/"