TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3189 SUBJECT: GRB 050408 (=H3711): A Long X-Ray-Rich GRB Detected by HETE DATE: 05/04/08 18:23:42 GMT FROM: Don Lamb at U.Chicago GRB 050408 (=H3711): A Long X-Ray-Rich GRB Detected by HETE T. Sakamoto, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team; M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, K. Tanaka, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team; N. Butler, G. Crew, J. Doty, 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; M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team; report: The HETE FREGATE, WXM, and SXC instruments detected GRB 050408 (=H3711) at 16:22:50.93 UT (58970.93 SOD) on 8 April 2005. WXM and SXC flight localizations were reported in a GCN Notice issued at 16:23:02, which was 11 sec after the burst trigger and while the burst was still in progress. The final WXM and SXC flight localizations were reported in a GCN Notice issued at 16:23:13 UT. The final WXM flight localization can be expressed as a circle of 14 arcminutes radius (90% confidence) that is centered at WXM-Flight: RA = 12h 01m 55s, DEC = +10d 51' 38" (J2000). The final SXC flight localization can be expressed as a circle of 150 arcseconds radius that is centered at SXC-Flight: RA = +12h 02m 15s, DEC = +10d 51' 03" (J2000). Ground analysis produced an updated SXC localization that was reported in a GCN Notice issued at 17:36:02. This ground SXC localization can be expressed as a circle of 80 arcseconds radius that is centered at SXC-Ground: RA = +12h 02m 15s, DEC = +10d 52' 01" (J2000). The burst has a duration T_90 of ~34 seconds in 7-40 keV and 7-80 keV, and T_90 of ~15 seconds in 30-400 keV. Preliminary spectral analyses show the 2-30 keV fluence of GRB 050408 to be ~1.4 x 10-6 ergs cm-2 and the 30-400 keV fluence to be ~1.9 x 10-6 ergs cm-2. Therefore GRB 050408 is an "X-ray-rich" GRB. A light curve, skymap, and spectral information for GRB 050408 are provided at the following URL: http://space.mit.edu/HETE/Bursts/GRB050408 This message may be cited.