//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21157 SUBJECT: GRB 170527A: Fermi GBM detection DATE: 17/05/27 20:09:57 GMT FROM: C. Michelle Hui at MSFC/Fermi-GBM M. Stanbro (UAH), C. M. Hui (NASA/MSFC), C. Meegan (UAH) and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: At 11:31:02.37 UT on 27 May 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170527A (trigger 517577467 / 170527480). The on-ground calculated location, using the GBM trigger data, is RA = 195.19 , DEC = +0.94 (J2000 degrees, equivalent to 13h 00m, +0d 54.0'), with an uncertainty of 1.00 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error [Connaughton et al. 2015, ApJS, 216, 32] ). The trigger resulted in an Autonomous Repoint Request (ARR) by the GBM Flight Software owing to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. The initial angle from the Fermi LAT boresight is 37.00 degrees. The GBM light curve shows a sharp peak with multiple sub-structures with a duration (T90) of about 49.2 s (50-300 keV). The time-averaged spectrum from T0+1.1 s to T0+50.3 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.03 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 1001.00 +/- 33.50 keV The event fluence (10-1000 keV) in this time interval is (8.430 +/- 0.003)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.8 s in the 10-1000 keV band is 22.19 +/- 0.36 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21164 SUBJECT: IPN Triangulation of GRB 170527A DATE: 17/05/30 15:11:47 GMT FROM: Anna Kozlova at Ioffe Institute K. Hurley, on behalf of the IPN, I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team, A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, on behalf of the Fermi GBM team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, report: The long-duration GRB 170527A (Stanbro et al.,GCN 21157) was detected by Fermi(GBM), Konus-Wind, and Mars-Odyssey(HEND), at about 41467 s UT (11:31:07). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 192.3245 -1.4883 Corners: 192.3882 -1.5179 197.2538 +8.1347 196.7137 +7.4412 192.2608 -1.4588 188.2675 -10.5805 188.0687 -11.4344 --------------------------------------------- The error box area is 2.9 sq. deg, and its maximum dimension is 21.6 deg (the minimum one is 8.4 arcmin). The Sun distance was about 125 deg. This box may be improved. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB170527_T41466/IPN/ The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21166 SUBJECT: Konus-Wind observation of GRB 170527A DATE: 17/05/30 16:11:27 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 170527A (IPN localization: Hurley et al., GCN 21164) triggered Konus-Wind at T0=41466.714 s UT (11:31:06.714). The KW light curve shows a multi-peaked emission with a total duration of ~57 s. The emission is seen up to ~5 MeV. As observed by Konus-Wind, the burst had a fluence of (8.9 ± 0.6)x10^-5 erg/cm2 and a 64-ms peak energy flux, measured from T0+0.640, of (1.79 ± 0.13)x10^-5 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+48.128 s) is best fit in the 20 keV - 15 MeV range by a cutoff power-law (CPL) function with the following model parameters: the photon index alpha = -0.71(-0.09,+0.09), and the peak energy Ep = 571(-47,+55) keV, chi2 = 103/98 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep and an upper limit on beta of -2.5, chi2 = 102/97 dof. The spectrum near the peak count rate (measured from T0 to T0+7.168 s) is best fit in the 20 keV - 15 MeV range by the CPL function with the following model parameters: the photon index alpha = -0.23(-0.10,+0.10), and the peak energy Ep = 714(-44,+48) keV, chi2 = 113/98 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep, and an upper limit on beta of -3.9, chi2 = 113/97 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170527_T41466/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.