Gamma-ray Burst 220521B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #32104
  A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars-Odyssey team,
  A. Ridnaia, D. Frederiks, D. Svinkin, A. Lysenko, and T. Cline on behalf of the Konus-Wind team,
  E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
  and
  W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report:
  A long-duration GRB 220521B has been detected by Konus-Wind, INTEGRAL (SPI-ACS), and Mars-Odyssey (HEND), so far, at about 54210 s UT (15:03:30).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

   ---------------------------------------------
    RA(2000), deg                 Dec(2000), deg
   ---------------------------------------------
   Center:
     55.464 (03h 41m 51s) +38.990 (+38d 59' 25")
   Corners:
     57.749 (03h 51m 00s) +34.608 (+34d 36' 29")
     52.895 (03h 31m 35s) +43.109 (+43d 06' 34")
     52.823 (03h 31m 18s) +43.047 (+43d 02' 49")
     57.684 (03h 50m 44s) +34.535 (+34d 32' 05")
   ---------------------------------------------
  

  The error box area is 2520 sq. arcmin, and its maximum dimension is 9.3 deg (the minimum one is 5 arcmin). The Sun distance was 14 deg.
  This box may be improved.
  A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB220521_T54209/IPN/
  The time history and spectrum will be given in forthcoming GCN Circulars.
• GCN Circular #32106
  A.Ridnaia, D. Frederiks, A.Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
  The long-duration GRB 220521B (IPN triangulation: Kozyrev at al., GCN Circ. 32104) triggered Konus-Wind at T0=54209.631 s UT (15:03:29.631).
  The burst light curve shows a single emission pulse, which starts at ~T0-0.4 s and has a total duration of ~2.3 s. The emission is seen up to ~4 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB220521_T54209/
  As observed by Konus-Wind, the burst had a fluence of 3.99(-0.43,+0.50)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0+0.038 s, of 5.03(-2.05,+2.89)x10^-6 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 - 4 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.66(-0.35,+0.41) and Ep = 153(-21,+29) keV (chi2 = 91/78 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 91/77 dof).
  The spectrum near the peak energy flux (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 4 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.84(-0.39,+0.52) and Ep = 585(-232,+646) keV (chi2 = 43/31 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -1.6 (chi2 = 43/30 dof).
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
• GCN Circular #32128
  T. Sakamoto, A. Yoshida, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration:
  The long GRB 220521B (Konus-Wind detection: A.Ridnaia et al., GCN Circ 32106; IPN triangulation: Kozyrev et al., GCN Circ 32104) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 15:03:34.307 UTC on 21 May 2022 (http://cgbm.calet.jp/cgbm_trigger/flight/1337180454/index.html). The burst signal was seen by only SGM detector. No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal).
  The burst light curve shows a single pulse which starts at T-0.5 sec, peaks at T+0.8 sec, and ends at T+1.5 sec. The T90 and T50 durations measured by the SGM data are 1.6 +/- 0.3 sec and 0.8 +/- 0.2 sec (40-1000 keV), respectively.
  The ground processed light curve is available at
  http://cgbm.calet.jp/cgbm_trigger/ground/1337180454/
  The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.