TITLE: GCN CIRCULAR NUMBER: 44548 SUBJECT: GRB 260511A: Fermi GBM Detection DATE: 26/05/11 13:25:00 GMT FROM: oliver.roberts@universityofgalway.ie O.J. Roberts (Uni. Of Galway, Ireland) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 06:13:30.286 UT on 11 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260511A (trigger 800172815/260511259), which was also detected by SVOM /ECLAIRs and MXT (Godet et al. 2026, GCN 44532), with an optical counterpart was initially detected by Colibri (Akl et al. 2026, GCN 44534). The angle from the Fermi LAT boresight is 118 degrees. The GBM light curve consists of a two bright emission episodes with a duration (T90) of about 14 s (50-300 keV). The time-averaged spectrum from T0-0.26 to T0+18.43 s is best fit by a Band function, with Epeak = 166 +/- 9 keV, alpha = -0.66 +/- 0.05, and beta = -2.31 +/- 0.07. The event fluence (10-1000 keV) in this time interval is (1.973 +/- 0.032) E-05 erg/cm^2. The 1-s peak photon flux measured starting from T0+2.6 s in the 10-1000 keV band is 27.3 +/- 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/44548. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...