GCN Circular 2313

XRF030723 (=H2777): An X-ray Flash Localized by the HETE WXM and SXC

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

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

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

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

write:

At 06:28:17.45 UTC (23297.45 s UT) on 23 July 2003, the HETE FREGATE, 
WXM, and SXC instruments detected an X-ray flash, designated 
XRF030723 (=H2777), located at high galactic latitude (b = 50 
degrees).

The burst triggered the WXM in the 2-25 keV energy band. The burst 
signal-to-noise was ~9.  A GCN burst alert was issued 42s later, 
reporting a flight-derived WXM localization with a 30 arcmin radius 
(90% confidence). Ground analysis of the WXM data produced a 
localization that was reported in a GCN Notice at 09:47:25 UT. The 
WXM data provided a localization that can be expressed as a 90% 
confidence circle that is 9.4 arcminutes in radius and is centered 
at--

WXM-ground:   RA= +21h 48m 52s,  Dec= -27d 41' 16"  (J2000)

Ground analysis of the SXC data provided an initial localization that 
was disseminated as a GCN Notice at 13:38:19 UT. A refined SXC 
localization can be expressed as a 90% confidence circle that is 2 
arcmin in radius and is centered at--

SXC-Ground:   RA= +21h 49m 27.4s, Dec= -27d 42' 01"  (J2000)


The burst duration (t90) in the 7-30 keV band was ~23 s. A total of 
1210 counts were detected by Fregate during that interval, 
corresponding to a fluence of ~2 x 10-7 ergs cm-2. The peak flux in a 
1.2 s bin was >3 x 10-8 ergs cm-2 s-1 (ie >0.9 x Crab flux) in the 
same energy band.

In the 30-400 keV band, the fluence was < 0.7 x 10-7 ergs cm-2, which 
is  < 0.4 times the fluence in the 7-30 keV band; thus we conclude 
that H2777 is an X-ray flash.

A light curve and finding chart for XRF030723 is provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB030723

This message may be cited.