GCN Circular 2579

GRB 040423 (=H3175): A Long GRB Localized by HETE

M. Boer, 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, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, 
K. Torii, 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;

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

report:

At 09:54:35.69 UTC (35675.69s UT) on 2004 April 23, the FREGATE, WXM, 
and SXC instruments on HETE detected trigger H3175, a long GRB.

The burst triggered in the FREGATE 30-400 keV band.  The flight 
localization by WXM was not distributed automatically, due to the low 
image S/N in the WXM Y-camera.

Ground analysis confirmed that the burst was detected and localizable 
with the WXM X camera, but was out of the field-of-view of the WXM 
Y-camera. The burst was also in the SXC field-of-view. Since the 
trigger time occurred in orbit twilight, scattered sunlight still 
contaminated a major portion of  SXC CCD area. Nonetheless, an SXC 
X-location, but not a Y-location, was derived from the uncontaminated 
CCD area. Consequently it has been possible to derive an 11-degree by 
3-arcminute 1-dimensional error box, whose long dimension is 
constrained by the relative count rates observed on the wires of the 
WXM X detector.

The localization can be expressed as a 90% confidence rectangle whose 
corners lie at J2000 coordinates:

R.A. = +15h 09m 46.6s, Dec. = -30d 18' 36"
R.A. = +15h 03m 54.6s, Dec. = -19d 15' 54"
R.A. = +15h 03m 42.0s, Dec. = -19d 16' 27"
R.A. = +15h 09m 33.4s, Dec. = -30d 19' 30"

The T90 duration of the burst was 30s in the FREGATE 30-400 keV 
energy band.  The fluence of the burst was 6E-06 erg cm^-2 in the 
25-100 keV band, and the peak flux was 6E-8 erg cm^-2 s^-1 in the 
8-30 keV band.

A light curve, automated spectral fits, and a skymap for GRB040423 
are provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB040423

This message may be cited.