TITLE: GCN CIRCULAR NUMBER: 13099 SUBJECT: GRB 120323A: Fermi GBM detection DATE: 12/03/24 16:02:47 GMT FROM: David Gruber at MPE David Gruber (MPE) and Valerie Connaughton (UAH) report on behalf of the Fermi GBM Team: "At 12:10:19.72 UT on 23 March 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120323A (trigger 354197421 / 120323507). The on-ground calculated location, using the GBM trigger data, is RA = 346.8, DEC = 27.2 (J2000 degrees, equivalent to 23 h 07 m, 27 d 12 '), with an uncertainty of 1 degree (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). (This location has been updated from an earlier GCN notice). The angle from the Fermi LAT boresight is 43 degrees. Moreover, this burst was bright enough to result in a Fermi spacecraft autonomous rapid repoint (ARR) maneuver. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of a very bright, double-peaked FRED-like pulse with a duration (T90) of about 0.446 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+0.512 s is best fit by a Band function with Epeak = 64.8 +/- 3.8 keV, alpha = -0.82 +/- 0.07, and beta = -2.01 +/- 0.02. The event fluence (10-1000 keV) in this time interval is (1.080 +/- 0.002)E-05 erg/cm^2. The 0.064-sec peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 574.7 +/- 7.8 ph/s/cm^2. This peak flux is the highest of the mission to date. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."