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TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2401 SUBJECT: XRF030823 (=H2818): An X-Ray Flash Localized by the HETE WXM and SXC DATE: 03/09/25 03:55:45 GMT FROM: Don Lamb at U.Chicago <lamb@oddjob.uchicago.edu> Y. Shirasaki, G. Crew, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team; T. Donaghy, C. Graziani, T. Tamagawa, M. Suzuki, M. Matsuoka, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, Y. Nakagawa, R. Satoh, Y. Urata, T. Yamazaki and Y. Yamamoto, on behalf of the HETE WXM Team; A. Dullighan, N. Butler, 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, C. Barraud and K. Hurley on behalf of the HETE FREGATE Team; report: At 08:52:40.64 UTC (31960.64 s UT) on 23 August 2003, the HETE FREGATE, WXM, and SXC instruments detected event H2818, an X-Ray Flash. The burst triggered FREGATE in the 6-80 keV energy band. The burst occurred at the extreme edge of the FOV of the WXM Y-detector, and therefore no flight localization was possible. Ground analysis of the WXM data provided a localization that was reported in a GCN Notice at 11:10:20 UT. The WXM ground localization SNR was 19. The localization can be expressed as a 90% confidence rectangle, whose center is at: WXM-Ground: R.A. = 21h 30m 46s, Dec. = +21d 55' 43" (J2000), and whose corners lie at: R.A. = 21h 31m 02.6s, Dec. = 21d 37' 55" R.A. = 21h 30m 21.1s, Dec. = 21d 37' 23" R.A. = 21h 30m 29.0s, Dec. = 22d 13' 30" R.A. = 21h 31m 10.6s, Dec. = 22d 14' 02" (J2000). The SXC Y-camera detected the burst, but the X-camera did not. The SXC Y-camera localization further constrains the WXM location to an error box that was reported in a GCN Notice at 12:06:16 UT. This joint WXM/SXC localization can be expressed as a 90% confidence rectangle, whose center is at: SXC/WXM-Ground: R.A. = 21h 30m 47s, Dec. = +21d 59' 46" (J2000), and whose corners lie at: R.A. = 21h 30m 26.9s, Dec. = 22d 01' 44" R.A. = 21h 30m 25.9s, Dec. = 21d 57' 14" R.A. = 21h 31m 07.4s, Dec. = 22d 02' 17" R.A. = 21h 31m 06.5s, Dec. = 21d 57' 50" (J2000). The T90 duration of the burst was 56 seconds in the WXM 2-25 keV energy band. The peak flux of the burst in 1 second is 4.5 x 10-8 erg cm-2 s-1 in the 7-30 keV energy band and 5.5 x 10-8 erg cm-2 s-1 in the 30-400 keV energy band. The fluence of the burst is 2.3 x 10-6 erg cm-2 and 1.5 x 10-6 erg cm-2 in the same energy bands, respectively. Thus S(2-30 keV)/S(30-400 keV) = 1.5, making this burst an X-ray flash. A light curve and skymap for XRF030823 is provided at the following URL: http://space.mit.edu/HETE/Bursts/GRB030823
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