TITLE:   GCN CIRCULAR
NUMBER:  2209
SUBJECT: XRF030416 (=U10897): An X-Ray Flash Localized by the HETE WXM
DATE:    03/05/06 18:52:28 GMT
FROM:    Don Lamb at U.Chicago  <lamb@oddjob.uchicago.edu>

J.G. Jernigan, N. Butler, R. Vanderspek, G. Crew, J. Doty, J.
Villasenor, G. Monnelly, T. Cline, A. Levine, F. Martel, E. Morgan, G.
Prigozhin, 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;

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

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

write:

At 11:03:59.00 UTC (39839.00 s UT) on 16 Apr 2003, the HETE FREGATE and
WXM instruments detected event U10897, an X-ray flash.

The burst had essentially no flux in the FREGATE 30-400 keV trigger
band.  The FREGATE 6-80 keV trigger and the WXM trigger were not active
at the time, to avoid triggers due to flaring activity from Sco X-1.
Consequently, the burst did not produce an on-board trigger.  The SXC
was off because of illumination by the full moon.

The event was noticed by operators on the ground.  Ground analysis of
the WXM data for the burst produced a location which was reported in a
GCN Notice at 02:47:53 UTC on 17 April 2003, about 16 hours after the
burst. The WXM ground localization SNR was 16.  The WXM localization
can be expressed as a 90% confidence circle that is 7 arcminutes in
radius and is centered at:

R.A. = 11h 06m 51s, Dec. = -02d 52' 58" (J2000).

The T_90 duration of the burst in the 2-25 keV WXM energy band was
~ 50 s.  The fluence of the burst was ~ 5 x 10^-7 erg cm^-2 in the
2-25 keV energy band and ~ 1 x10^-7 erg cm^-2 in the 30-400 keV energy
band; thus S(2-25)/S(30-400 keV) ~ 5.  Therefore this burst is an XRF.

A light curve and skymap for GRB030416 is provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB030416