TITLE: GCN CIRCULAR NUMBER: 44861 SUBJECT: GRB 260607B: Fermi GBM Observation DATE: 26/06/08 02:49:06 GMT FROM: eliza.neights@gmail.com E. Neights (GWU, NASA GSFC) and E. Palafox (INAOE-Mexico) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:19:28.70 UT on 07 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260607B (trigger 802531173/260607555), which was also detected by Fermi LAT (Holzmann Airasca et al. 2026, GCN 44860). The Fermi GBM on-ground location is consistent with the Fermi LAT position. The angle from the Fermi LAT boresight is 72 degrees. The GBM light curve consists of multiple emission episodes, with a duration (T90) of about 47 s (50-300 keV). The time-averaged spectrum from T0+2.9 to T0+57.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.92 +/- 0.004 and the cutoff energy, parameterized as Epeak, is 728 +/- 2 keV. The event fluence (10-1000 keV) in this time interval is (2.999 +/- 0.006)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+53 s in the 10-1000 keV band is 66.9 +/- 0.5 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/44861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...