TITLE: GCN CIRCULAR NUMBER: 13985 SUBJECT: GRB 121123A: Fermi GBM observation DATE: 12/11/23 19:16:43 GMT FROM: Suzanne Foley at MPE S. Foley (UCD) reports on behalf of the Fermi GBM Team: "At 10:06:00.59 UT on 23 November 2012, the Fermi Gamma-Ray Burst Monitor triggered and located the second emission episode of GRB 121123A (trigger 375357963 / 121123421) which was also detected by the Swift/BAT (Helder et al. 2012, GCN 13982, http://gcn.gsfc.nasa.gov/notices_s/sw00539358000msbx.gif). The emission detected by GBM is contemporaneous with the UVOT observation of an afterglow candidate for GRB 121123A reported by Helder et al. The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 85 degrees. The GBM light curve consists of a single peak with a long tail with a duration (T90) of about 102 s (50-300 keV). The time-averaged spectrum from T0+3.1 s to T0+106.5 s is well fit by a Band function with Epeak = 85 (+/-3) keV, alpha = -0.25 (+/-0.09), and beta = -3.0 (+0.2/-0.3). The event fluence (10-1000 keV) in this time interval is (2.20 +/- 0.08)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+32.6 s in the 10-1000 keV band is 4.00 +/- 0.25 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."