GCN Circular 1315

GRB020331(=H1963): The "Easter" Burst Detected by HETE

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

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

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

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

write:


At 16:32:28.76 UTC (59548.76 s UT) on 31 March 2002, the HETE FREGATE 
and WXM instruments detected event H1963, a long (~50 sec) GRB. A GCN 
Alert Notice was issued at 16:39:31 UT. A preliminary localization 
was reported as a GCN Position Notice at 17:12:51 UT, ~40 min after 
the burst. The ground analysis has produced a refined location which 
can be expressed as a circle with a 90% confidence radius of 8 
arcminutes centered at:

RA = 13h 16m 22s.7, Dec = -17o 55' 23" (J2000)

In the FREGATE 8-40 keV band, H1963 had a duration of ~20 seconds.  A 
total of 2320 net counts were detected during that interval, 
corresponding to a fluence of ~4 x 10-7 ergs cm-2. The peak flux 
averaged over 0.85 s was ~1 x 10-7 ergs cm-2 s-1 (ie 4 x Crab flux). 
In the WXM 2-25 keV band, the localization SNR was >9.

Further information (including a light curve) for GRB020331is 
provided at the following URL:

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

This message is citable.