TITLE: GCN CIRCULAR NUMBER: 44564 SUBJECT: GRB 260510C: Fermi GBM Observation DATE: 26/05/11 20:51:58 GMT FROM: Eva MP at INAOE <eva.palafox@gmail.com> E. Palafox (INAOE, Mexico) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 17:13:43.99 UT on 10 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260510C (trigger 800126028/260510718), which was also detected by SVOM/ECLAIRs (Gotz et al. 2026, GCN 44521), MAXI (Iwakiri et al. 2026, GCN 44526), COLIBRI (Angulo et al. 2026, GCN 44530), SVOM/VT (Li et al. 2026, GCN 44527 and GCN 44540), EP-FXT (Fu et al. 2026, GCN 44541) and AstroSat CZTI (Arya et al. 2026,GCN 44544). The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position. The angle from the Fermi LAT boresight is 68 degrees. The GBM light curve consists of two bright emission episodes with a duration (T90) of about 162 s (50-300 keV). The time-averaged spectrum from T0-8.2 to T0+143.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.3 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 176 +/- 55 keV. The event fluence (10-1000 keV) in this time interval is (4.9 +/- 0.7)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+120 s in the 10-1000 keV band is 2.6 +/- 0.3 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/44564. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...