//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21429 SUBJECT: GRB 170808B: Fermi GBM observation DATE: 17/08/09 04:42:21 GMT FROM: Peter Veres at UAH P Veres and C Meegan (both UAH) report on behalf of the Fermi GBM Team: "At 22:27:43.10 UT on 8 August 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170808B (trigger 523924068 / 170808936). The on-ground calculated location, using the GBM trigger data, is RA = 146.49, DEC = -2.96 (J2000 degrees, equivalent to 09 h 46 m, -02 d 58 '), with an uncertainty of 1 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] ). This burst was also independently detected by INTEGRAL SPI-ACS. The trigger resulted in an Autonomous Repoint Request (ARR) by the GBM Flight Software owing to the high fluence 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 to the GBM ground best location is 69 degrees. The GBM light curve shows multiple overlapping pulses with a duration (T90) of about 17.7 s (50-300 keV). The time-averaged spectrum from T0 to T0+27.1 s is best fit by a Band function with Epeak = 262 +/- 5 keV, alpha = -1.01+/- 0.01, and beta = -2.30 +/- 0.03. The event fluence (10-1000 keV) in this time interval is (1.176 +/- 0.005)E-4 erg/cm^2. The 1-sec peak photon flux measured starting from T0+15.9 s in the 10-1000 keV band is 169.4 +/- 0.7 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: 21430 SUBJECT: GRB 170808B: Fermi LAT Detection DATE: 17/08/09 05:59:27 GMT FROM: Daniel Kocevski at GSFC F. Longo (University and INFN, Trieste) and D. Kocevski (NASA MSFC) report on behalf of the Fermi-LAT team: At 22:27:43.10 UT on August 08, 2017, Fermi-LAT detected high-energy emission from GRB 170808B, which was also detected by Fermi-GBM (Veres and Meegan GCN 21429). The best LAT on-ground location is found to be RA, Dec 145.66, 2.18 deg, J2000 with an error radius of 0.34 deg (90% containment, statistical error only). This was 69 deg from the LAT boresight at the time of the trigger and triggered an autonomous repoint of the spacecraft. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the GBM detection with high significance. The highest-energy photon is a 1.62 GeV event which is observed 162 seconds after the GBM trigger. A Swift ToO has been requested for this burst. The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo@ts.infn.it). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. [GCN OPS NOTE(09aug17): Per author's request, the extraneous url listed in the original distribution has been removed.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21447 SUBJECT: Konus-Wind observation of GRB 170808B DATE: 17/08/10 18:38:28 GMT FROM: Anna Kozlova at Ioffe Institute A.Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration, very bright GRB 170808B (Fermi GBM observation: Veres et al., GCN 21429; Fermi LAT Detection: Longo et al., GCN 21430) triggered Konus-Wind at T0=80859.187 s UT (22:27:39.187). The burst light curve shows a double-peaked structure which starts at ~T0-2.3 s and has a total duration of ~18.5 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of 2.20(-0.08,+0.08)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+15.008 s, of 7.54(-1.02,+1.03)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+23.808 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.92(-0.06,+0.07), the high energy photon index beta = -2.33(-0.09,+0.07), the peak energy Ep = 238(-16,+17) keV (chi2 = 96/98 dof) The spectrum near the maximum count rate (measured from T0+14.848 to T0+15.616 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.52(-0.12,+0.13), the high energy photon index beta = -2.45(-0.13,+0.10), the peak energy Ep = 282(-26,+29) keV (chi2 = 80/67 dof) The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170808_T80859/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.