TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2402
SUBJECT: XRF030824 (=H2821):  An X-Ray Flash Localized by the HETE WXM
DATE:    03/09/25 04:11:45 GMT
FROM:    Don Lamb at U.Chicago  <lamb@oddjob.uchicago.edu>

M. Galassi, C. Graziani, Y. Shirasaki, G. Ricker, J-L. Atteia, N.
Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team;

T. Donaghy, E. Fenimore, M. Matsuoka, T. Sakamoto, M. Suzuki, T.
Tamagawa, K. Torii, A. Yoshida, Y. Nakagawa, R. Satoh, Y. Urata, T.
Yamazaki and Y. Yamamoto, on behalf of the HETE WXM Team;

A. Dullighan, N. Butler, G. Crew, J. Doty, 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;

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

report:

At 16:47:35.10 UTC (60455.10 s UT) on 24 August 2003, the HETE FREGATE
and WXM instruments detected event H2821, an X-Ray Flash.

The burst triggered FREGATE in the 6-80 keV energy band.  The WXM
flight localization was correct, but was not sent to the GCN because
the low fluence of the burst and its location at the edge of the WXM
FOV did not meet the criteria for automatic propagation.  Ground
analysis of the WXM data provided a localization that was reported in a
GCN Notice at 17:47:22 UT, 60 minutes after the burst.  Further ground
analysis of the WXM data provided a refined localization that was
reported in a GCN Notice at 19:13:33 UT.  The refined WXM ground
localization SNR was 6. The refined WXM localization can be expressed
as a 90% confidence circle, whose radius is 11.2 arcminutes and whose
center is at:

WXM-Ground:  R.A. = +00h 05m 02s, Dec. = +19d 55' 37" (J2000).

The SXC had not yet turned on because the burst occurred just before
orbit dusk.

The T90 duration for the burst was > 16 seconds in the WXM 2-25 keV
energy band.  The peak flux of the burst in 1 second is 5.4 x 10-8 erg
cm-2 s-1 in the 7-30 kev energy band and 2.1 x 10-8 erg cm-2 s-1 in the
30-400 keV energy band.  The fluence of the burst is 8.9 x 10-7 erg cm-2
and 5.8 x 10-7 erg cm-2 in the same energy bands, respectively.  Thus
S(2-30 keV)/S(30-400 keV) = 1.5, making this burst an X-ray flash.

A light curve and skymap for XRF030824 is provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB030824