TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2735 SUBJECT: GRB 040924(=H3564): A Short, Bright GRB Localized in Real Time by HETE DATE: 04/09/24 15:19:21 GMT FROM: Roland Vanderspek at MIT GRB 040924(=H3564): A Short, Bright GRB Localized in Real Time by HETE E. E. Fenimore, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team; T. Donaghy, M. Galassi, C. Graziani, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, 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; C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team; report: The HETE Fregate and WXM instruments detected GRB 040924 (=H3564) at 11:52:11 UT (42731 SOD) on 24 September 2004. The WXM flight software localized the burst in real time, resulting in a GCN Notice 14 seconds after the burst trigger. The flight error region was a circle of 14 arcminutes radius (90% confidence) centered at RA = 02h 06m 40s, DEC = +16d 08' 10" (J2000). Ground analyses of the burst data allow the error region to be refined to a circle of 6.4 arcminutes radius (90% confidence) centered at RA = 02h 06m 19s, DEC = +16d 01' 26" (J2000). The burst is short, although not particularly hard: the burst durations, as measured by T50, are 1.2s, 1.0s, and 0.6s in the 7-30 keV, 7-80 keV, and 30-400 keV bands, respectively. Preliminary spectral analyses show GRB 040924 to have an Epeak of 42 +/- 6 keV. The 7-30 keV fluence is 1.6e-6 erg/cm2, and the 30-400 keV fluence is 2.6e-6 erg/cm2: the fluence ratio is 0.6, allowing us to classify GRB 040924 as an X-ray rich GRB. The empirical redshift indicator ("pseudo-z"; Atteia 2003) for GRB 040924 is 0.5. This message may be cited.