G. Ricker, D. Lamb, and S. Woosley on behalf of the HETE Science Team;
R. Vanderspek, G. Crew, J. Doty, G. Monnelly, J. Villasenor; N. Butler, T. Cline, J.G. Jernigan, A. Levine, F. Martel, G. Pizzichini, and G. Prigozhin, on behalf of the HETE Operations and HETE Optical-SXC Teams;
N. Kawai, M. Matsuoka, Y. Shirasaki, T. Tamagawa, A. Yoshida, E. Fenimore, M. Galassi, and C. Graziani, on behalf of the HETE WXM Team;
J-L Atteia, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team;
On 26 March 2001 at 08:33:12 UTC (=30792s UT), a soft spectrum, high energy transient at high galactic latitude was detected and localized by HETE. (NB: This is the second GRB detected by HETE on 26 March 2001.)
Both the WXM and the FREGATE instruments detected the event. The burst triggered FREGATE in the 6-120 keV band, at the 160ms timescale.
The preliminary coordinates of the burst are R.A. = 11h24m23.36s, Dec. = -11o09'57", derived from combining data from the WXM and Boresighted Optical Cameras. The statistical error radius in the WXM localization is 18 arcmin (90% confidence). In addition, we estimate a systematic error radius at present of 10 arcmin about this location. The spacecraft aspect was known to an accuracy of +/- 30 arcsec (95% confidence) from the optical cameras, and will be improved.
The peak flux seen with FREGATE (6-30 keV) was ~4 Crab; with WXM (2-25 keV), ~2 Crab. The burst duration was about 4 seconds.
The high galactic latitude of the source, well away from the Galactic Bulge, and the shape of its spectrum suggest that it is a gamma-ray burst similar to those reported for "X-ray rich" GRBs by Heise et al (2001) from BeppoSAX observations.
Follow-up observations of this unusual transient are encouraged.
HETE=High Energy Transient Explorer
FREGATE=French Gamma Ray Telescope
WXM=Wide Field X-ray Monitor
SXC=Soft X-ray Camera
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Last modified: March 26, 2001