TITLE: GCN CIRCULAR NUMBER: 18066 SUBJECT: GRB 150724B: Fermi GBM detection DATE: 15/07/25 16:22:15 GMT FROM: Peter Veres at ELTE,Budapest P. Veres (UAH), V. Connaughton (USRA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 18:45:37.714 UT on 24 July 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150724B (trigger 459456341 / 150724782) which was also detected by the Fermi/LAT (Bissaldi et al. 2008, GCN 18065). The GBM on-ground location is consistent with the Fermi/LAT position. The on-ground calculated location, using the GBM trigger data, is RA = 350.92, DEC = +10.160 (J2000 degrees, equivalent to 23h 24m, 10d 10'), with an uncertainty of 1.05 degrees (radius, 1-sigma containment, statistical only). The GBM light curve consists of two emission episodes with a total duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0-6.1 s to T0+46 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.75 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 729 +/- 35 keV. The event fluence (10-1000 keV) in this time interval is (3.55 +/- 0.04)E-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+40 s in the 8-1000 keV band is 8.3 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."