Gamma-ray Burst 170320A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #20927
  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,
  D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova, and T. Cline on behalf of the Konus-Wind team,
  A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
  S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team,
  and
  W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, report:
  A long-duration, intense GRB 170320A has been detected by Konus-Wind, Mars-Odyssey (HEND), INTEGRAL (SPI-ACS), and Swift (BAT), so far, at about 13359 s UT (03:42:39). The burst was outside the coded field of view of the BAT.
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

    ---------------------------------------------
     RA(2000), deg                 Dec(2000), deg
    ---------------------------------------------
    Center:
     320.074 (21h 20m 18s) +55.060 (+55d 03' 35")
    Corners:
     320.632 (21h 22m 32s) +57.567 (+57d 34' 00")
     320.255 (21h 21m 01s) +57.396 (+57d 23' 46")
     319.649 (21h 18m 36s) +52.549 (+52d 32' 57")
     319.971 (21h 19m 53s) +52.726 (+52d 43' 35")
    ---------------------------------------------
  

  The error box area is 3245 sq. arcmin, and its maximum dimension is 5.05 deg (the minimum one is 11.2 arcmin). The Sun distance was 62 deg.
  This box may be improved.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB170320_T13359/IPN
  The time history and spectrum will be given in forthcoming GCN Circulars.
• GCN Circular #20934
  Yi Zhao (IHEP), Yuanhao Wang (IHEP), Zhengheng Li (IHEP) report on behalf of the POLAR collaboration:
  At 2017-03-20T03:42:39.00 UT (T0), during a routine on-ground search of data, POLAR detected the GRB 170320A, which was also detected by INTEGRAL/SPIACS (ID 170320.15474) and the KONUS-Wind.
  The POLAR light curve consists of a single peak, with a duration (T90) of 5.74 s measured from T0+2.79 s. The 1-s peak rate measured from T0+3.00 s is 2258.1 cnts/s. The total counts is about 5844 cnts.
  LC_URL: http://polar.ihep.ac.cn/grb/2017/03/GRB170320A/lc/POLAR_lc_grb170320A.png
  The above results are not dead time corrected. The above measurements are in the energy range of about 80-500 keV.
  All analysis results presented above are preliminary.
  POLAR is a dedicated Gamma-Ray Burst polarimeter (50-500 keV) on-board the Chinese space laboratory Tiangong-2 launched on Sep 15,2016. More information about POLAR can be found at http://polar.ihep.ac.cn/en/ , http://isdc.unige.ch/polar/ and http://polar.psi.ch/pub/.
  
• GCN Circular #20935
  A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline on behalf of the Konus-Wind team, report:
  The long-duration, intense GRB 170320A (IPN Triangulation: Hurley et al., GCN 20927; POLAR Observation: Zhao et al., GCN 20934) triggered Konus-Wind at T0=13359.957 s UT (03:42:39.957).
  The burst light curve shows a multipeaked structure with a total duration of ~30 s. The emission is seen up to ~5 MeV.
  As observed by Konus-Wind, the burst had a fluence of 1.87(-0.30,+0.34)x10^-5 erg/cm2, and a 64-ms peak energy flux, measured from T0+0.592 s, of 1.01(-0.19,+0.20)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The time-integrated spectrum of the burst (measured from T0 to T0+35.072 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.35(-0.15,+0.21), the high energy photon index beta = -2.41(-0.46,+0.22), the peak energy Ep = 111(-22,+23) keV, chi2 = 99/97 dof.
  The spectrum near the peak count rate (measured from T0 to T0+2.304 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.52(-0.17,+0.20), the high energy photon index beta = -2.21(-0.18,+0.13), the peak energy Ep = 178(-24,+29) keV, chi2 = 79/69 dof.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170320_T13359/
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.