TITLE: GCN CIRCULAR NUMBER: 44179 SUBJECT: GRB 260401A: Fermi GBM Observation DATE: 26/04/01 23:33:42 GMT FROM: Daniel Fernandez at University of Alabama In Huntsville (UAH) <df0062@uah.edu> D. Fernandez (UAH), M. Dafčíková (MUNI) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 10:53:26.00 UT on 01 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260401A (trigger 796733611/260401454), which was also detected by MAXI (T. Usuki et al. 2026, GCN 44176). The Fermi GBM on-ground location (GCN 44174) is consistent with the MAXI position. The angle from the Fermi LAT boresight is 60 degrees. The GBM light curve consists of a bright emission episode with multiple peaks with a duration (T90) of about 27 s (50-300 keV). The time-averaged spectrum from T0-0.8 to T0+32.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.78 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 239 +/- 1 keV. The event fluence (10-1000 keV) in this time interval is (1.80 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+7.5 s in the 10-1000 keV band is 21.1 +/- 0.4 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/" View this GCN Circular online at https://gcn.nasa.gov/circulars/44179. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...