TITLE: GCN CIRCULAR NUMBER: 15228 SUBJECT: Fermi/GBM Detection of two SGR-like bursts possibly associated with SGR J1833-0832 DATE: 13/09/14 16:56:56 GMT FROM: Chryssa Kouveliotou at MSFC Andrew C. Collazzi (NASA/ORAU), Shaolin Xiong (UAH), and Chryssa Kouveliotou (NASA/MSFC), report on behalf of the GBM-Magnetar Team: At 15:00:28.44 UT on 13 September 2013, the Fermi Gamma-Ray Burst Monitor triggered and located a very bright, SGR-like burst (trigger 400777231/130913625). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 278.88, Dec = -8.49 (J2000 degrees, equivalent to J2000 18h 35m, -8d 29'), with a statistical 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). This burst consists of a single pulse, with a duration of T90 = 112 +/- 6 ms. The burst is well-fit by a two blackbody model with blackbody temperatures of kT1 = 5.3 +/- 0.2 keV and kT2 = 13.0 +/- 0.4 keV. The corresponding peak flux integrated over 4ms (8-200 keV) is (1.12 +/- 0.02)E-05 erg/s/cm^2. The fluence during T0-0.016s to T0+0.132s is (1.66 +/- 0.02)E-6 erg/cm^2. This interval is also well fit by a Comptonized model with Epeak = 32.4 +/- 0.6 and alpha = -0.40 +/- 0.09. This burst was followed by another, fainter, SGR-like trigger at 18:10:05.95 UT (trigger 400788608/130913757). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 281.25, Dec = -8.35 (J2000 degrees, equivalent to J2000 18h 35m, -8d 29'), with a statistical uncertainty of 7.6 degrees (see above on GBM location errors). The second burst comprises a single pulse with a duration of T90 = 72 +/- 25 ms. Its spectrum is best fit by a OTTB model with kT = 58.0 +/- 12.0 keV. The corresponding peak flux, integrated over 4ms (8-200 kev), is (6.2 +/- 0.7)E-07 erg/s/cm^2. The fluence during T0-0.032s to T0+0.080s is (6.9 +/- 0.81)E-8 erg/cm^2. Given the closeness of these bursts in location and in time, we suggest that they come from the same source, most likely SGR J1833-0832; however, we note that the 3-sigma contour for both bursts contains several known magnetar sources. The analysis results presented above are preliminary.