{
  "bibcode": "2009GCN..9499....1V",
  "body": "A. J. van der Horst, V. Connaughton, C. Kouveliotou, M. S. Briggs, and\nW. S. Paciesas report for the Fermi/GBM team,\n\nV. Pal'shin, S. Golenetskii, R. Aptekar, D. Frederiks, E. Mazets,\nP. Oleynik, D. Svinkin, M. Ulanov, and K. Hurley report for the Konus-RF \nteam,\n\nJ. R. Cummings, D. Palmer, and N. Gehrels report for the Swift-BAT team\n\n\"The Fermi Gamma-Ray Burst Monitor (GBM) has triggered on two SGR-like\nbursts on June 5 at 20:40:48.88 (trigger 265927250 / 090605862) and\n21:01:35.06 UT (trigger 265928497 / 090605876). Their on-ground calculated\nlocations, using the Fermi GBM trigger data, are:\n- RA, Dec (J2000) = 70.0, +55.6 (equivalent to 4h40m, +55d35'), with a\n1-sigma statistical uncertainty of 4.8 degrees, and\n- RA, Dec (J2000) = 60.5, +55.4 (equivalent to 4h02m, +55d22'), with a\n1-sigma statistical uncertainty of 6.0 degrees, respectively.\nFor both triggers there is additionally a systematic error which is\ncurrently estimated to be 2 to 3 degrees.\nThe angles from the Fermi LAT boresight are 81 and 66 degrees, \nrespectively.\n\nThe time-averaged GBM spectra of both triggers are best fit by a power law\nwith a high-energy exponential cutoff. The indices are -0.26 +/- 0.39 and\n-0.38 +/- 0.76, and the cutoff energies, parametrized as Epeak, are\n36.0 +/- 2.4 and 22.9 +/- 3.3, for the first and second trigger, \nrespectively.\nThe first event was a single pulse of 0.03 seconds, while the second\ntrigger was double-peaked with a duration of 0.09 seconds.\n\nThe first burst was also seen by Konus-RF which was triggered at\n2009-06-05 74448.88972 s UT (20:40:48.890).\nWe have triangulated this burst to a Konus-RF - GBM annulus centered at\nRA, Dec (J2000) = 84.314 (05h 37m 15s), -6.669 (-6d 40' 07\"), with a\nradius of 66.544 +/- 4.812 deg (3 sigma). This annulus is consistent with\nthe two on-ground calculated GBM locations. The nearby, confirmed SGR\nsource, SGR 0501+4518 (RA, Dec (J2000) = 75.265, +45.272) is ~12 degrees\naway from the centerline of this annulus and is, therefore, excluded as the\norigin of these two new emissions.\n\nSwift BAT triggered on the first GBM event (BAT trigger #354187). No\nsource was found onboard. After the alert through the IPN network,\nthe event data were analyzed on the ground, and a low-significance\nsource was found at a position consistent with the GBM position and\nIPN annulus. The position is RA, Dec (J2000) = 64.606, +57.489,\nequivalent to\nRA(J2000) = 04h 18m 25s\nDec(J2000) = +57d 29' 16''\nwith an uncertainty of 4 arcmin (radius, statistical+systematic, 90%\ncontainment). As seen in BAT, the burst T90 was 3.5 +/- 1.0 ms.\nThere was no emission seen above 100 keV.\n\nWe have also used the BAT light curve to obtain a BAT-GBM annulus\ncentered at RA, Dec (J2000) = 129.334 (08h 37m 20s), +0.546 (+0d 32' 45\"),\nwith a radius of 76.480 +/- 1.452  deg  (3 sigma).  The annulus contains\nthe Swift localization and is consistent with both GBM locations.\nThe second GBM event was seen very weakly in BAT, but did not cause a\nrate trigger, so no further data are available.\n\nA map of the GBM, BAT locations, and the Konus-RF - GBM and BAT-GBM\nannuli can be obtained at:\nhttp://gammaray.nsstc.nasa.gov/gbm/science/magnetars.\n\nThe Galactic coordinates of the Swift location are L, B = 148.00, 5.07 deg,\nplacing the source on the galactic plane. We tentatively propose this as \na new\nsoft gamma repeater source, SGR 0418+5729.\"\n\n[GCN OPS NOTE(09jun09): Per author JC's request, the  BAT Trigger Number\nin 4th paragraph was changed fro 351188 to 351187.]",
  "circularId": 9499,
  "createdOn": 1244521467000,
  "email": "Alexander.J.VanDerHorst@nasa.gov",
  "subject": "Discovery of a new soft gamma repeater source, SGR 0418+5729",
  "submitter": "Alexander van der Horst at NASA/MSFC  <Alexander.J.VanDerHorst@nasa.gov>",
  "eventId": "SGR 0418+5729"
}