TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2712 SUBJECT: GRB040916 (= H3558): A Long XRF Localized by HETE DATE: 04/09/16 03:01:51 GMT FROM: Roland Vanderspek at MIT GRB040916 (= H3558): A Long XRF Localized by HETE T. Yamazaki, 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, Y. Urata, 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: At 00:03:30 UT (209 SOD) on 16 September 2004, the WXM instrument on HETE detected GRB040916 (= H3558), a long, two-peaked XRF. The burst has been localized to a circle of 18' radius centered on RA = 23h 01m 44s, Dec = -5d 37' 43" (J2000) The burst consists of two peaks separated by ~250s, each ~100s in duration. No formal spectral analysis has been performed using WXM data, but the dearth of counts in bands > 10 keV in either peak is a strong indication that GRB040916 is an XRF. We anticipate providing additional spectral information from this unusual event in a subsequent GCN Circular. This message may be cited.