Gamma-ray Burst 121127A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #14021
  S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  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,
  V. Connaughton, M. Briggs, C. Meegan, and V. Pelassa, on behalf of the Fermi GBM 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, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, and
  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, report:
  A short-duration, hard spectrum GRB 121127A was observed by Konus-Wind, Fermi (GBM: trigger 375746163), INTEGRAL (SPI-ACS), MESSENGER (GRNS), Swift (BAT), Mars Odyssey (HEND), and Suzaku (WAM) at about 78960 s UT (21:56:00).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

    ---------------------------------------------
     RA(2000), deg                 Dec(2000), deg
    ---------------------------------------------
    Center:
     176.438 (11h 45m 45s) -52.414 (-52d 24' 52")
    Corners:
     176.369 (11h 45m 29s) -52.649 (-52d 38' 58")
     176.255 (11h 45m 01s) -52.512 (-52d 30' 44")
     176.507 (11h 46m 02s) -52.179 (-52d 10' 45")
     176.620 (11h 46m 29s) -52.316 (-52d 18' 59")
    ---------------------------------------------
  

  The error box area is 158 sq. arcmin, and its maximum dimension is 29 arcmin (the minimum one is 9 arcmin; the minimum annulus width is 3.6 arcmin).
  This box can be improved.
  The time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #14022
  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 short-duration hard-spectrum GRB 121127A (IPN localization: Golenetskii at al., GCN 14021) triggered Konus-Wind at T0=3D78957.290s UT (21:55:57.290)
  The light curve shows a single pulse with a duration of ~0.25 s. The emission is seen up to ~6 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB121127_T78957/
  As observed by Konus-Wind the burst had a fluence of (3.8 =B1 0.8)x10-6 erg/cm2, and a 16-ms peak flux, measured from T0+0.016 s, of (2.6 =B1 0.6)x10-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The spectrum of the burst (measured T0 to T0+0.192 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 0.0 =B1 0.3, the high energy photon index beta =3D -2.0 =B1 0.3, the peak energy Ep =3D 600 =B1 170 keV, chi2 =3D 11/19 dof.
  All the quoted results are preliminary.
• GCN Circular #14044
  Y.Ishida, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, K. Takahara,=E3=80=80M. Asahina, S. Kobayashi, A. Sakamoto, H. Ueno, S. Sugimoto (Saitama=E3=80=80U.), M. Akiyama, N. Ohmori, E. Mochinaga, M. Yamauchi (Univ. of=E3=80=80Miyazaki), K. Yamaoka, M. Kokubun, T. Takahashi (ISAS/JAXA), Y.=E3=80=80Hanabata, T. Kawano, K. Takaki, R. Nakamura, Y.Tanaka, M. Ohno, Y.=E3=80=80Fukazawa (Hiroshima U.), S. Sugita (Nagoya U.), Y. E. Nakagawa (Waseda=E3=80=80U.), Y. Urata, P. Tsai (NCU), K. Nakazawa, K. Makishima (Univ. of=E3=80=80Toky= o), on behalf of the Suzaku WAM team, report:
  The short, IPN localized GRB 121127A (Golenetskii et al., GCN 14021) was detected by the the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 21:56:01 UT (=3DT0).
  The observed light curve shows a single peak starting at T0-1s, ending at T0s with a duration (T90) of about 1 seconds. The fluence in 100 - 1000 keV was 9.34(+0.73/-2.40) x 10^-7 erg/cm^2. The 1-s peak flux measured from T0-1s was 1.78(+0.16/-0.47) photons/cm^2/s in the same energy range.
  Preliminary result shows that the time-averaged spectrum from T0-1s to T0s is well fitted by a power-law with exponential cutoff model :

     dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
     alpha 0.55(+0.57/-0.80), and
     Epeak 759(+273/-166) keV (chi^2/d.o.f. =3D 32.6/29).
  

  All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included.
  The light curves with 1-sec time resolution for this burst will be appeared at:
  http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table= .html