TITLE: GCN CIRCULAR NUMBER: 23035 SUBJECT: GRB 180723A: Fermi GBM detection DATE: 18/07/25 02:37:32 GMT FROM: Suraj Poolakkil at UAH S.Poolakkil and C. Meegan (both UAH) report on behalf of the Fermi GBM Team: "At 18:09:48.16 UT on 23 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180723A (trigger 554062193/ 180723757). The on-ground calculated location, using the GBM trigger data, is RA = 7.84, DEC = -66.11, with an uncertainty of 1 degree (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 132 degrees. The GBM light curve consists of a single bright peak with a duration (T90) of about 19.71 s (50-300 keV). The time-averaged spectrum from T0-2.05 s to T0+31.74 s is best fit by a power-law function with an exponential high-energy cutoff. The power law index is -1.22 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 178 +/- 5 keV. The event fluence (10-1000 keV) in this time interval is (4.616 +/- 0.057)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.39 s in the 10-1000 keV band is 41.2 +/- 0.81 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."