TITLE: GCN CIRCULAR NUMBER: 15528 SUBJECT: GRB 131127B: Fermi GBM detection DATE: 13/11/28 12:53:49 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 14:12:18.36 UT on 27 November 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 131127B (trigger 407254341 / 131127592). The on-ground calculated location, using the GBM trigger data, is RA = 306.1, DEC = -0.8 (J2000 degrees, equivalent to 20h 24m, -00d 48'), with an uncertainty of 1.0 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 88 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. Three candidates for an optical afterglow were found by iPTF (Singer et al, GCN 15524) using the GBM on-ground location. The GBM light curve is multi-peaked with a duration (T90) of about 18 s (50-300 keV). The time-averaged spectrum from T0-0.003 s to T0+20.480 s is best fit by a Band function with Epeak = 181.7 (+7.9/-7.2) keV, alpha = -1.05 +/- 0.02 , and beta = -2.24 (+0.05/-0.06) The event fluence (10-1000 keV) in this time interval is (3.85 +/- 0.03)E-05 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+5.824 s in the 10-1000 keV band is 37.6 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."