TITLE: GCN CIRCULAR NUMBER: 18201 SUBJECT: GRB 150824A: Fermi GBM detection DATE: 15/08/24 16:04:33 GMT FROM: Elisabetta Bissaldi at U.Innsbruk/IAPP E. Bissaldi (INFN Bari) and E. Burns (UAH) report on behalf of the Fermi GBM Team: "At 01:53:31.76 UT on 24 August 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150824A (trigger 462074015 / 150824079). The on-ground calculated location, using the GBM trigger data, is RA = 161.3 DEC = -55.9 (J2000 degrees, equivalent to 10h 45m, -55d 55'), with an uncertainty of 1.0 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ). The angle from the Fermi LAT boresight at the GBM trigger time is 74 degrees. The GBM light curve consists of several peaks with a duration (T90) of about 13 s (50-300 keV). The time-averaged spectrum from T0 to T0+15 s is best fit by a Band function with Epeak = 187 +/- 9 keV, alpha = -0.77 +/- 0.03, and beta = -2.40 +/- 0.10. The event fluence (10-1000 keV) in this time interval is (2.03 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1 s in the 10-1000 keV band is 22.2 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."