TITLE: GCN CIRCULAR NUMBER: 17496 SUBJECT: Fermi GBM Observations of SGR 1935+2154 DATE: 15/02/23 08:28:08 GMT FROM: Eric Burns at U of Alabama E. Burns (UAH) and G. Younes (GWU) report on behalf of the Fermi GBM Team: "At 17:57:05.99 UT on 22 February 2015, the Fermi Gamma-Ray Burst Monitor triggered (446320628/150222748) on a burst from SGR 1935+2154, which was reported to be in outburst by Burrows et al. (GCN 17485). The GBM burst occurred over 5 hours after the bursts detected by the Swift BAT. The GBM on-ground location is consistent with the known source position. The burst consists of a single pulse, with a duration of about 0.05 s. The burst is well-fit with a power law function with an exponential high-energy cutoff parameterized as Epeak = 29 +/- 1 keV and an Index -0.25 +/- 0.31. The corresponding peak flux integrated over 16ms (10-1000 keV) is (146 +/- 8)E-06 erg/s/cm^2. The fluence during T0-0.048s to T0+0.000s is (1.6 +/- 0.1)E-07 erg/cm^2. A fit to a double black-body spectrum is a statistical tie with the exponential power-law fit, with one extra parameter and blackbody temperatures of 4.3 +/- 0.7 keV and 10.4 +/- 1.0 keV. The other models reported in Krimm et al. (GCN 17490) are not statistically favored. This burst was followed by four further triggers at 19:44:16.94 UT (trigger 446327059/150222822) on 22 February 2015, 01:38:07.99 UT (446348290/150223068), 05:24:54.16 UT (446361897/150223226), and 06:45:40.13 UT (446366743/150223282) on 23 February 2015, all consistent with being from SGR 1935+2154. All of these triggers consist of a single peak. The third trigger, 150223068, is several times more intense than the others, which are of about equal intensity. The analysis results presented above are preliminary. These bursts are bright enough that some are being classified by the flight software as GRBs. We will correct this classification in the online catalog at the Fermi Science Support Center: http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigtrig.html but will not issue further circulars to correct the classification." [GCN OPS NOTE(23feb15): Per author's request, the date was corrected in the first line from "23 Feb" to "22 Feb".]