TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2554
SUBJECT: GRB 040319 (=H3128): An X-Ray-Rich GRB Localized by the HETE-2 WXM and SXC
DATE:    04/03/25 18:25:00 GMT
FROM:    Don Lamb at U.Chicago  <lamb@oddjob.uchicago.edu>

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

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

R. Vanderspek, N. Butler, G. Crew, J. Doty, A. Dullighan, G. Prigozhin,
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 07:46:00.57 UTC (27960.57s UT) on 19 March 2004, the HETE-2 FREGATE,
WXM, and SXC instruments detected event H3128, a long GRB.

The burst triggered FREGATE in the 6-80 keV energy band; the time
history SNR was 23.3 and T90 is 7.4s.  A WXM flight localization was
disseminated, but was incorrect due to the low SNR of the burst in the
WXM YA-detector.  The WXM flight localization was retracted in a GCN
Notice at 09:41:13 UT.  Ground analysis of the WXM data produced a
preliminary localization that was reported in a GCN Notice at 09:54:44
UT.  Further ground analysis of the WXM data produced a refined
localization that was reported in a GCN Notice at 21:15:53 UT.  The
refined WXM ground localization SNR was 4.2 in the X-detector and 2.3
in the Y-detector.  The refined WXM localization can be expressed as a
90% confidence rectangle whose center is at

WXM-ground: RA = +10h 42m 15s, Dec = -23d 48' 34" (J2000),

and whose corners lie at

WXM-ground: RA =  +10h 41m 05.5s, Dec = -19d 36' 40"
            RA =  +10h 41m 05.3s, Dec = -27d 55' 59"
            RA =  +10h 43m 24.7s, Dec = -28d 01' 05"
            RA =  +10h 43m 25.2s, Dec = -19d 40' 37" (J2000).


Ground analysis of the SXC data produced a 1-dimensional SXC
localization that was also reported in the GCN Notice at 21:15:53 UT.
The SXC ground localization SNR was 3 in the X-camera.  The SXC
1-dimensional X-camera localization, truncated by the WXM Y-detector
localization, can be expressed as a 90% confidence rectangle, whose
center is at

SXC/WXM-ground: RA = +10h 41m 37s, Dec = -23d 47' 19" (J2000),

and whose corners lie at

SXC/WXM-ground: RA = +10h 41m 30.5s, Dec = -19d 37' 23"
                RA = +10h 41m 31.7s, Dec = -27d 56' 56"
                RA = +10h 41m 43.2s, Dec = -27d 57' 22"
                RA = +10h 41m 41.8s, Dec = -19d 37' 41" (J2000).

The width and the length of the rectangle are 2.6 arcminutes and 8.3
degrees, respectively, and the area of the rectangle is 1290 square
arcminutes.


The fluence of the burst is 0.56 x 10-6 erg cm-2 in the 2-30 keV energy
band and 1.1 x 10-6 erg cm-2 in the 30-400 keV energy band.  Thus
S(2-30 keV)/S(30-400 keV) = 0.5, making this burst an X-ray-rich GRB.

A light curve and skymaps for GRB 040319 are provided at the following
URL:

http://space.mit.edu/HETE/Bursts/GRB040319.