GCN Circular 22027
O.J. Roberts (USRA), R. Hamburg (UAH), M.S. Briggs (UAH), V. Connaughton (USRA), C. Kouveliotou (GWU) and G. Younes (GWU) report on behalf of the Fermi-GBM Team: "At 01:01:16.25 UT on 19 October 2017, the Fermi Gamma-Ray Burst Monitor triggered (trigger 530067681 / 171019043) on a bright SGR-like burst. The GBM on-ground location is consistent with the position of the known source AXP CXOU J164710.2-455216/PSR J1647-4552, which later triggered Swift-BAT (Beardmore et al., GCN 22024 and Lien et al., GCN 22025). MAXI also triggered on a transient from a position consistent with the source. The GBM light curve shows two bright, short peaks each with a duration (T90) of about 0.1 s. The time-averaged spectrum over both peaks from T0-0.064 to T0+0.384 is best fit by a power-law function with an exponential high-energy cutoff. The power law index is 0.04 +/- 0.13 and the cutoff energy, parameterized as Epeak, is 35 +/- 1 keV. The event fluence (10-1000 keV) in this time interval is (7.4 +/- 0.12)E-07 erg/cm^2. The photon flux measured starting from T0-0.64 s in the 10-1000 keV band is 37 +/- 1 ph/s/cm^2. An offline search of the GBM time-tagged event data optimized to find sub-threshold short GRBs uncovered at least one additional burst that could have come from this source. This is consistent with the ongoing source activity reported by Lien et al. (GCN 22025). The offline search results are distributed as GCN notices (https://gcn.gsfc.nasa.gov/admin/fermi_gbm_subthreshold_announce.txt) with the notice archive available at https://gcn.gsfc.nasa.gov/fermi_gbm_subthresh_archive.html. The results of a dedicated search for magnetar bursts will be presented in a future circular."