Gamma-ray Burst 121118B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #13977
  K. Hurley on behalf of the Mars Odyssey and MESSENGER GRB teams,
  I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
  J. Goldsten, on behalf of the MESSENGER GRNS GRB team,
  S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team,
  A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
  K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada, T. Murakami, and K. Makishima, on behalf of the Suzaku WAM team,
  G. Di Cocco, F. Fuschino, M. Galli, C. Labanti, and M. Marisaldi, on behalf of the AGILE MCAL team,
  S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, report:
  The long-duration, intense GRB 121118B was observed by Konus-Wind, INTEGRAL (SPI-ACS), MESSENGER (GRNS), Mars Odyssey (HEND), Swift (BAT), AGILE (MCAL), and Suzaku (WAM), at about 80826 s UT (22:27:06). 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:
      171.704 (11h 26m 49s)  -3.059 ( -3d 03' 31")
     Corners:
      172.128 (11h 28m 31s)  -2.327 ( -2d 19' 38")
      170.954 (11h 23m 49s)  -4.797 ( -4d 47' 48")
      171.309 (11h 25m 14s)  -3.726 ( -3d 43' 33")
      172.662 (11h 30m 39s)  -0.850 ( +0d 51' 00")
     ---------------------------------------------
  

  The error box area is 0.4 sq. deg, and its maximum dimension is 4.3 deg (the minimum one is 1.1 deg, the minimum annulus width is 8.5 arcmin).
  This box can be improved.
  The time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #13979
  S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
  The long-duration intense GRB 121118B (IPN detection and localization: Hurley et al., GCN 13977) triggered Konus-Wind at T0=3D80847.239s UT (22:27:27.239)
  The light curve shows multiple pulses with increasing amplitude in the time interval starting at ~60s before KW trigger and ending at ~T0+40s. The emission is seen up to 9 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB121118_T80847/
  As observed by Konus-Wind the burst had a fluence of (8.5 =B1 0.3)x10-5 erg/cm2, and a 64-ms peak flux, measured from T0+13.696 s, of (1.0 =B1 0.6)x10-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The time-integrated spectrum of the triggered part of the burst (measured T0 to T0+32.512 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha =3D -1.30 =B1 0.05, the high energy photon index beta =3D -3.05 =B1 0.70, the peak energy Ep =3D 520 =B1 64 keV, chi2 = 78.4/82 dof.
  The spectrum at the maximum count rate (measured T0+8.448 to T0+16.128 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff (CPL) model, for which: the photon index alpha = -1.18 =B1 0.04 and the peak energy Ep = 599 =B1 52 keV, chi2 =3D 91.4/83 dof. Fitting this spectrum with the Band function yields the same alpha and Ep with only an upper limit for beta <-3.0 (90% conf.)
  All the quoted results are preliminary.
• GCN Circular #14000
  T. Kawano, M. Ohno, Y. Hanabata, Y. Tanaka, R. Nakamura, K Takaki, Y. Fukazawa (Hiroshima U.), A. Sakamoto, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, K. Takahara, M. Asahina, S. Kobayashi, H. Ueno (Saitama U.), M. Akiyama, N. Ohmori, E. Mochinaga, M. Yamauchi (Univ. of Miyazaki), Y. E. Nakagawa (Waseda U.), S. Sugita (Nagoya U.), K. Yamaoka, M. Kokubun, T. Takahashi (ISAS/JAXA), Y. Urata, P. Tsai (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report:
  The long, IPN localized GRB 121118B: (Hurley et al., GCN 13977) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 22:27:6.662 UT (=T0).
  The observed light curve shows a multi-peaked structure starting at T0-30 s, ending at T0+70 s, with a duration (T90) of about 50 seconds. The fluence in 100 - 1000 keV was 4.52(-1.27 +0.85) x 10^-5 erg/cm^2. The 1-s peak flux measured from T0-0.5s was 8.48(-0.64 +0.56) photons/cm^2/s in the same energy range.
  Preliminary result shows that the time-averaged spectrum from T0-30s to T0+70s is well fitted by a power-law with exponential cutoff model: dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with alpha 1.39(-0.67 +0.50), and Epeak 450(-224 +121) keV (chi^2/d.o.f. = 28.5/22).
  All the quoted errors are at statistical 90% confidence level. Due to the brightness of this burst, a 3% systematic error was added for low energy channels.
  The light curves for this burst will be available at:
  http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html