GCN Circular 33806

O.J. Roberts (USRA/NASA-MSFC), S. Bala (USRA), J. Wood (NASA-MSFC) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 21:21:34.01 UT on 10 May 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 230510B (trigger 705446499 /230510890), which was also detected by MAXI/GSC (M. Nakajima et al. 2023, GCN 33760), CALET (P.S. Marrocchesi et al. 2023, GCN 33763), and CZTI/AstroSat (P.K. Navaneeth et al. 2023, GCN 33772). The Fermi GBM Final Real-time Localization (GCN 33759) is consistent with the MAXI/GSC position. The angle from the Fermi LAT boresight at the GBM trigger time is 60 degrees. The GBM light curve consists of two distinct peaks with multiple short peaks in between with a duration (T90) of about 466 s (50-300 keV). The time-averaged spectrum from T0-5.12 s to T0+650.81 s is best fit by a Band function, with Epeak= 341 +/- 28 keV, alpha = -1.32 +/- 0.02, and beta = -2.01 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (1.28 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+194 s in the 10-1000 keV band is 8.12 +/- 0.26 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/"