GCN Circular 28797
R. Hamburg (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 22:37:33.06 UT on 26 October 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 201026A (trigger 625444658 / 201026943), which was initially misclassified as a distant particle event by the GBM flight software. GRB 201026A was also detected by the Swift/BAT and the Swift/XRT (Cenko et al. 2020, GCN 28784). 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 degrees. The GBM light curve shows a main pulse with a duration (T90) of about 35 s (50-300 keV). There is also later emission extending to approximately T0+280 s. We cannot conclusively confirm it is related to the main emission episode with GBM data alone; however, similar late-time emission can be seen in the Swift-XRT lightcurve (Evans et al. 2020, GCN 28796). The time-averaged spectrum of the main pulse from T0-16 s to T0+23 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.83 +/- 0.10 and the cutoff energy, parameterized as Epeak, is 68 +/- 3 keV. A Band function fits the spectrum equally well with Epeak = 63 +/- 5 keV, alpha = -0.73 +/- 0.14 and beta = -2.84 +/- 0.34. The event fluence (10-1000 keV) in this time interval is (3.96 +/- 0.14)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.47 s in the 10-1000 keV band is 3.04 +/- 0.22 ph/s/cm^2. For the later emission episode, the time-averaged spectrum from T0+188 s to T0+237 s is best fit by a simple power law function with index -1.84 +/- 0.04. The event fluence (10-1000 keV) in this time interval is (4.51 +/- 0.29)E-06 erg/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/"