TITLE: GCN CIRCULAR NUMBER: 13085 SUBJECT: GRB 120316A: Fermi-GBM and Fermi-LAT Observations DATE: 12/03/21 21:22:59 GMT FROM: Giacomo Vianello at SLAC Giacomo Vianello (CIFS/SLAC), Nicola Omodei (Stanford U.), J. L. Racusin (NASA/GSFC), P. Jenke (MSFC/NPP) report on behalf of the Fermi GBM and LAT Teams: At 00:11:02.56 UT on 16 March 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120316A (trigger 353549464 / 120316008), which was also detected by Konus-Wind (GCN 13074) and triangulated by the IPN (GCN 13073). The GBM H.I.T.L. location is found to be RA, Dec (J2000) = 48.5, -64.3 with a error radius (90% containment, statistical) of 1.2 degrees. The GBM light curve shows multiple peaks with a duration of T90 = 27.5 +/- 0.4 seconds, and a signal extending to 500 keV in the NaI's and 850 keV in the BGO's. The GRB is barely detected by the LAT, with a Test Statistic slightly below the TS=25 threshold usually adopted for issuing circulars. The best LAT on-ground location is found to be RA,Dec (J2000) = 57.97, -56.46 with an error radius of 0.65 deg (90% containment, statistical error only). This was 9.7 deg from the LAT boresight at the time of the trigger. The LAT position is compatible with that found by Zheng et al. (GCN 13070) and by Hurley et al. (GCN 13073), and is ~9 deg away from the best GBM localization. Modeling of the uncertainties in GBM localizations, using known reference locations, suggests that whilst the majority (>90%) are well-represented by a ~3 deg systematic error, GRB120316A appears to belong to a small tail which has a much larger systematic uncertainty, centered on ~10 deg (see Connaughton et al., in preparation). The spectrum of this GRB from 10 keV to 300 GeV, integrated over the time interval 0-32 s from the trigger time, is well described by a Band function with Epeak = 552 -25 +22 keV, alpha = -0.77 +/- 0.02, beta = -2.90 +/-0.15. The fluence in the 10 keV - 1 MeV energy range is 2.57 ( +/- 0.03 (stat) +/- 0.2 (sys) ) x 10^-5 erg/cm2, compatible with the value found by Golenetskii et al (GCN 13074). The spectral analysis results presented above are preliminary; The Fermi LAT point of contact for this burst is Giacomo Vianello (giacomov@slac.stanford.edu). The GBM point of contact is Peter Jenke (peter.a.jenke@nasa.gov). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.