Gamma-ray Burst 031109

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN notice #2442
  XRF031109 (=H2919): A very long XRF localized by HETE
  T. Tamagawa, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team;
  T. Donaghy, C. Graziani, E. Fenimore, M. Galassi, M. Matsuoka, T. Sakamoto, Y. Shirasaki, M. Suzuki, K. Torii, A. Yoshida, Y. Nakagawa, R. Satoh, Y. Urata, T. Yamazaki and Y. Yamamoto, on behalf of the HETE WXM Team;
  A. Dullighan, R. Vanderspek, G. Crew, J. Doty, G. Prigozhin, J. Villasenor, J. G. Jernigan, N. Butler, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
  M. Boer, J-F Olive, J-P Dezalay, C. Barraud, and K. Hurley on behalf of the HETE FREGATE Team;
  report:
  At 19:28:59 UTC (70138 s UT) on 9 November 2003, the HETE FREGATE and WXM instruments detected event H2919, a very long X-ray Flash (XRF).
  The burst triggered the WXM in the 2-25 keV energy band. No prompt notification was distributed due to the low image S/N of the burst in the flight analysis. Initial ground analyses showed the burst to be soft, with a duration of ~20s. Because this burst was detected seven minutes before the star cameras had come on line, although the
  WXM data localized the burst to a 15' radius, the original error estimate for the celestial coordinates was four degrees.
  Further analysis of the burst data set has revealed that the burst continued at a low level for at least seven and perhaps 10 minutes: we estimate t50 to be 310 seconds, t90 to be 480s. Localization of the photons detected near the end of the burst, and therefore just before the beginning of star tracker operations, allows the burst to be localized to an error circle of 20' radius centered at

     R.A. = 00h 17m 03s.49,  (J2000)
     Dec. =  -7o 08' 41"
  

  An automated fit of a cutoff power-law spectrum has been performed for H2919. The fit of the model to the data is posted at
  http://space.mit.edu/HETE/Bursts/GRB031109
  The automated fit for the first 52 seconds of the burst gives the following values of Epeak and the burst fluence (25-100 keV):

  -- Epeak      = 29 keV
  -- Fluence    = 1.1e-06 erg/cm^2
  

  NB: The S/N of the fit decreases significantly for longer integration times.
  Also posted at the above website are the following data, in the formats described by Vanderspek (GCN 2421):

  -- Fregate light curve and ascii data tables (energy bands A [7-30 keV],
      B [7-80 keV], and C [30-400 keV])
  -- Color-color plot location of H2919 relative to other HETE-localized bursts
  -- Signal-to-noise histogram location of H2919 in Fregate Band C  
      relative to other HETE-localized bursts
  

  This message may be cited.
• GCN notice #2452
  K. Hurley and T. Cline, on behalf of the Ulysses, HETE, and Mars Odyssey GRB teams,
  G. Ricker, J-L Atteia, N. Kawai, D. Lamb, S. Woosley, J. Doty, R. Vanderspek, J. Villasenor, G. Crew, G. Monnelly, N. Butler, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, J. Braga, R. Manchanda, G. Pizzichini, Y. Shirasaki, C. Graziani, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, T. Donaghy, M. Boer, J-F Olive, and J-P Dezalay, on behalf of the HETE GRB team,
  I. Mitrofanov, S. Charyshnikov, V. Grinkov, A. Kozyrev, M. Litvak, and A. Sanin, on behalf of the HEND-Odyssey GRB team, and
  W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on behalf of the GRS/Odyssey GRB team, report:
  Ulysses, Mars Odyssey-HEND, and HETE (FREGATE and WXM) observed this GRB at 40308 seconds. Its duration was approximately 20 seconds.
  As the two triangulation annuli (Ulysses/HETE and Ulysses/Odyssey) are practically coincident, the IPN localization can best be expressed as a single annulus centered at RA, Decl(2000)=350.299, -15.584 degrees, whose radius is 42.882 +/- 0.076 degrees.
  GRB031109 was detected by HETE as trigger H2917. The burst was detected just a few seconds after the start of FREGATE and WXM operations: it is seen as a two-peaked burst with a hard spectrum (Epeak > 300 keV) and a 25-100 keV fluence of 3E-6 erg/cm2. The burst occurred well before the onset of star tracker operations, so the satellite aspect at the time of the trigger is not well known: the HETE localization is a circle of 10 degree radius centered at RA = 21h 35m, dec = 25d 30'.
  The IPN annulus intersects this circle at four points to form an error box whose area is approximately 7900 sq. arcmin. The intersection points are:

       RA(2000)    DEC(2000)
       320.708      15.912
       334.747      24.605
       320.885      15.865
       334.721      24.431
  

  A map has been posted at ssl.berkeley.edu/ipn3/031109. HETE lightcurves and the results of automated spectral analyses can be found on the HETE web page http://space.mit.edu/HETE/Bursts/GRB031109a This error box may be improved.