Gamma-ray Burst 150922A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #18357
  S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  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,
  V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, 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, and
  W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, report:
  The short-duration, hard-spectrum GRB 150922A has been detected by Konus-Wind, Fermi (GBM trigger 464593053/150922234), Mars-Odyssey (HEND), and INTEGRAL (SPI-ACS), so far, at about 20249 s UT (05:37:29).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

    ---------------------------------------------
     RA(2000), deg                 Dec(2000), deg
    ---------------------------------------------
    Center:
     294.381 (19h 37m 31s)  -5.486 ( -5d 29' 10")
    Corners:
     294.315 (19h 37m 16s)  -6.116 ( -6d 06' 57")
     294.303 (19h 37m 13s)  -5.399 ( -5d 23' 56")
     294.448 (19h 37m 48s)  -4.881 ( -4d 52' 51")
     294.458 (19h 37m 50s)  -5.573 ( -5d 34' 25")
    ---------------------------------------------
  

  The error box area is 385 sq. arcmin, and its maximum dimension is 75 arcmin (the minimum one is 9.1 arcmin). The Sun distance was 115 deg.
  This box may be improved.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB150922_T20250/IPN/
  The time history and spectrum will be given in forthcoming GCN Circulars.
• GCN Circular #18358
  O.J. Roberts (UCD), A. von Kienlin (MPE) and C. Meegan (UAH),report on behalf of the Fermi GBM Team:
  "At 05:37:29.08 UT on 22 September 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150922A (trigger 464593053 / 150922234), which was also detected by IPN (Svinkin et al. 2015, GCN 18357). The GBM on-ground location is consistent with the IPN position. The angle from the Fermi LAT boresight is about 38 degrees.
  The GBM light curve shows a short burst with a duration (T90) of 0.144 s (50-300 keV). The time-averaged spectrum from T0-0.016 to T0+0.128 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.55 +/- 0.11 and the cutoff energy, parameterized as Epeak, is 625 +/- 97 keV.
  The event fluence (10-1000 keV) in this time interval is (8.0 +/- 0.4) E-07 erg/cm^2. The 64 ms peak photon flux measured starting from T0-0.016 s in the 10-1000 keV band is 23.0 +/- 1.3 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #18360
  S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, report:
  The short-duration, hard-spectrum GRB 150922A (IPN triangulation: Golenetskii et al., GCN 18357; Fermi GBM detection: Roberts et al., GCN 18358) triggered Konus-Wind at T0=20250.916 s UT (05:37:30.916).
  The burst light curve shows a multipeak structure with a total duration of ~0.16 s. The emission is seen up to ~2 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150922_T20250/
  As observed by Konus-Wind, the burst had a fluence of 7.94(-1.93,+2.25)x10^-7 erg/cm2, and a 16-ms peak flux, measured from T0-0.008 s, of 1.34(-0.52,+0.59)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+0.064 s) is best fit in the 20 keV - 2 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.17(-0.66,+1.10) and Ep = 393(-132,+222) keV (chi2 = 11/13 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 (chi2 = 11/12 dof)
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.