Gamma-ray Burst 181121A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #23429
  *A.Ursi (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), * *N. Parmiggiani (INAF/IASF-Bo), A. Argan, M. Cardillo, Y. Evangelista, G. Minervini, G. Piano (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), F. Lucarelli, C. Pittori, (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, F. Fuschino (INAF/IASF-Bo), M. Marisaldi (INAF/IASF-Bo, and Bergen University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ. Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi) report on behalf of the AGILE Team:The AGILE Mini-CALorimeter (MCAL) detected a short burst at T0 = 2018-11-21 20:43:36.283 +/- 0.01 s (UTC).*
  *The light curve shows a sharp peak lasting about 0.16 s, that released a total number of ~334 counts in the detector (in the 0.4-100 MeV energy range), above an average background rate of 573 counts / s. Two weaker pulses are present at T0+0.32 s and T0+0.67 s*
  *.* *The GRB is clearly detected also by AGILE scientific ratemeters; in particular, by the Super-AGILE (20-60 keV), **Anti-Coincidence (50-200 keV), and MCAL (0.4-100 MeV) ratemeters.*
  *Further analysis is still in progress.The AGILE-MCAL detector has a full solid angle acceptance, and is operational in the range 0.4 - 100 MeV.*
• GCN Circular #23449
  A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  K. Hurley, on behalf of the IPN,
  A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
  and A. Ursi, N. Parmiggiani, F. Verrecchia, A. Bulgarelli, A. Trois, M. Marisaldi, C. Pittori, M. Tavani, Y. Evangelista, I. Donnarumma, M. Cardillo, G. Piano, G. Minervini, A. Argan, F. Lucarelli, A. Zoli, V. Fioretti, F. Fuschino, M. Pilia, F. Longo, A. Giuliani on behalf of the AGILE team report:
  The short-duration GRB 181121A (Ursi et al., GCN Circ. 23429) was detected by Konus-Wind, INTEGRAL (SPI-ACS), and AGILE (MCAL), at about 74617 s UT (20:43:37).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

   ---------------------------------------------
    RA(2000), deg                 Dec(2000), deg
   ---------------------------------------------
   Center:
     14.424 (00h 57m 42s) -11.977 (-11d 58' 38")
   Corners:
     11.772 (00h 47m 05s)  -9.257 ( -9d 15' 24")
     13.883 (00h 55m 32s) -11.751 (-11d 45' 05")
     17.495 (01h 09m 59s) -14.686 (-14d 41' 10")
     14.969 (00h 59m 53s) -12.200 (-12d 12' 00")
   ---------------------------------------------
  

  The error box area is 1.6 sq. deg, and its maximum dimension is 7.8 deg (the minimum one is 29 arcmin). The Sun distance was 126 deg.
  This box may be improved.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB181121_T74619/IPN
  The time history and spectrum will be given in forthcoming GCN Circulars.
• GCN Circular #23456
  A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report:
  The short-duration GRB 181121A (AGILE/MCAL detection: Ursi et al., GCN 23429; AstroSat CZTI detection: Sharma et al., GCN 23447; IPN Triangulation: Kozlova et al., GCN 23449) triggered Konus-Wind at T0=74619.153 s UT (20:43:39.153).
  The burst light curve shows a multipeaked structure which starts at ~T0 s and has a total duration of ~1.4 s. The emission is seen up to ~2 MeV.
  As observed by Konus-Wind, the burst had a fluence of 1.46(-0.26,+0.44)x10^-5 erg/cm2, and a 16-ms peak flux, measured from T0+0.118 s, of 9.44(-1.53,+1.77)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+8.448 s) is best fit in the 20 keV - 2 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.83(-0.20,+0.46), the high energy photon index beta = -2.58(-1.04,+0.46), the peak energy Ep = 226(-65,+45) keV (chi2 = 72/56 dof).
  The spectrum near the maximum count rate (measured from T0+0.064 to T0+0.192 s) is best fit in the 20 keV - 2 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.27(-0.24,+0.32), the high energy photon index beta = -2.54(-0.47,+0.28), the peak energy Ep = 271(-47,+50) keV (chi2 = 57/42 dof).
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB181121_T74619/
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.