TITLE: GCN CIRCULAR NUMBER: 44971 SUBJECT: GRB 260616A: Fermi GBM Observation DATE: 26/06/18 02:49:59 GMT FROM: Matt Godwin <msg0028@uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 03:21:54.33 UT on 16 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260616A (trigger 803272919/260616140), which was also detected by Fermi-LAT ( et al. 2026, GCN 44960). The Fermi GBM on-ground location is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 111 degrees. The GBM light curve consists of one long burst with a duration (T90) of about 69 s (50-300 keV). The time-averaged spectrum from T0+0.3 to T0+74.1 s is best fit by a Band function with Epeak = 246 +/- 1 keV, alpha = -0.63 +/- 0.01, and beta = -2.00 +/- 0.01. The event fluence (10-1000 keV) in this time interval is (1.22 +/- 0.02)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+50 s in the 10-1000 keV band is 16.9 +/- 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/44971. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...