HETE-2 Localization and Observations of the Gamma-Ray Burst GRB 020813
/ Authors
R. Sato, T. Sakamoto, J. Kataoka, A. Yoshida, Motoko Suzuki, J. Kotoku, Y. Urata, Y. Yamamoto, M. Arimoto, T. Tamagawa
and 33 more authors
Y. Shirasaki, K. Torii, M. Matsuoka, Y. Nakagawa, T. Yamazaki, Kaoru Tanaka, M. Maetou, M. Yamauchi, K. Takagishi, D. Lamb, J. Atteia, R. Vanderspek, C. Graziani, G. Prigozhin, J. Villaseñor, J. Jernigan, G. Crew, K. Hurley, G. Ricker, S. Woosley, N. Butler, A. Levine, J. Doty, T. Donaghy, E. Fenimore, M. Galassi, M. Boer, J. Dezalay, J. Olive, J. Braga, R. Manchanda, G. Pizzichini, N. Kawai
/ Abstract
A bright, long gamma-ray burst (GRB) was detected and localized by the instruments on board the High Energy Transient Explorer 2 satellite (HETE-2) at 02:44:19.17 UTC (9859.17s UT) on 2002 August 13. The location was reported to the GRB Coordinates Network (GCN) about 4min after the burst. In the prompt emission, the burst had a duration of approximately 125s, and more than four peaks. We analyzed the time-resolved 2–400keV energy spectra of the prompt emission of GRB 020813 using the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE) in detail. We found that the early part of the burst (17–52s after the burst trigger) shows a depletion of low-energy photons below about 50keV. It is difficult to explain the depletion by either synchrotron self-absorption or Comptonization. One possibility is that the low-energy depletion may be understood as a mixture of “jitter” radiation with the usual synchrotron radiation component.
Journal: Publications of the Astronomical Society of Japan