GCN Circular 2735

GRB 040924(=H3564):  A Short, Bright GRB Localized in Real Time by HETE

    
E. E. Fenimore, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley,
on behalf of the HETE Science Team;

T. Donaghy,  M. Galassi, C. Graziani, M. Matsuoka, Y. Nakagawa, 
T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, Y. Urata, 
T. Yamazaki, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team;

N. Butler, G. Crew, J. Doty, A. Dullighan, G. Prigozhin, R. Vanderspek,
J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga,
R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and
HETE Optical-SXC Teams;

C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of 
the HETE FREGATE Team;

report:

The HETE Fregate and WXM instruments detected GRB 040924 (=H3564) at 
11:52:11 UT (42731 SOD) on 24 September 2004.  The WXM flight software 
localized the burst in real time, resulting in a GCN Notice 14 seconds 
after the burst trigger.  The flight error region was a circle of 
14 arcminutes radius (90% confidence) centered at

  RA = 02h 06m 40s, DEC = +16d 08' 10" (J2000).

Ground analyses of the burst data allow the error region to be refined
to a circle of 6.4 arcminutes radius (90% confidence) centered at

  RA = 02h 06m 19s, DEC = +16d 01' 26" (J2000).

The burst is short, although not particularly hard:  the burst durations, 
as measured by T50, are 1.2s, 1.0s, and 0.6s in the 7-30 keV, 7-80 keV,
and 30-400 keV bands, respectively.  Preliminary spectral analyses show 
GRB 040924 to have an Epeak of 42 +/- 6 keV.  The 7-30 keV fluence is 
1.6e-6 erg/cm2, and the 30-400 keV fluence is 2.6e-6 erg/cm2:  the fluence 
ratio is 0.6, allowing us to classify GRB 040924 as an X-ray rich GRB.  
The empirical redshift indicator ("pseudo-z"; Atteia 2003) for GRB 040924
is 0.5.

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