TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2579 SUBJECT: GRB 040423 (=H3175): A Long GRB Localized by HETE DATE: 04/04/24 13:27:26 GMT FROM: George Ricker at MIT 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.