TITLE: GCN CIRCULAR NUMBER: 44258 SUBJECT: GRB 260410A: Fermi GBM Observation DATE: 26/04/10 17:00:13 GMT FROM: rhamburg@usra.edu R. Hamburg (USRA), U. Pathak (IIT Bombay) and R. Sonawane (IISER TVM) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:03:57.00 UT on 10 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260410A (trigger 797497441/260410294), which was also detected by Fermi-LAT (Holzmann Airasca et al. 2026, GCN 44253) and SVOM/GRM (Wang et al. 2026, GCN 44257). The Fermi GBM real-time localization (GCN 44252) is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 49 degrees. The GBM light curve consists of a single bright emission episode with a duration (T90) of about 1 s (50-300 keV). The time-averaged spectrum from T0-0.07 to T0+0.30 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.17 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 960 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (1.33 +/- 0.01)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 12.0 +/- 1.0 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/44258. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...