//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22759 SUBJECT: GRB 180602B: Fermi GBM detection DATE: 18/06/04 01:18:55 GMT FROM: Suraj Poolakkil at UAH S.Poolakkil and C. Meegan (both UAH) report on behalf of the Fermi GBM Team: "At 22:31:05.34 UT on 02 June 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180602B (trigger 549671470/ 180602938). The on-ground calculated location, using the GBM trigger data, is RA = 86.05, DEC = -62.78, with an uncertainty of 2 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 9 degrees. The GBM light curve consists of a single bright peak with a duration (T90) of about 0.01 s (50-300 keV). The time-averaged spectrum from T0-0.06 s to T0+0.06 s is best fit by a power-law function with an exponential high-energy cutoff. The power law index is -0.68 +/- 0.18 and the cutoff energy, parameterized as Epeak, is 395 +/- 105 keV. The event fluence (10-1000 keV) in this time interval is (3.0 +/- 0.4)E-07 erg/cm^2. The 64 ms peak photon flux measured starting from T0-0.06 s in the 10-1000 keV band is 14 +/- 1 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."