TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2308 SUBJECT: H2768, H2770, and H2771: Three Bursts from SGR1806-20 DATE: 03/07/19 04:37:36 GMT FROM: George Ricker at MIT H2768, H2770, and H2771: Three Bursts from SGR1806-20 K. Hurley, J-L. Atteia, N. Kawai, D. Lamb, G. Ricker, and S. Woosley on behalf of the HETE Science Team; C. Barraud, M. Boer, J-F Olive, and J-P Dezalay on behalf of the HETE FREGATE Team; N. Butler, G. Crew, J. Doty, A. Dullighan, G. Prigozhin, R. Vanderspek, J. Villasenor, T. Cline, J. G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Monnelly, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams; T. Tamagawa, M. Suzuki, C. Graziani, Y. Shirasaki, T. Donaghy, 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; report: At 08:02:20.59 UT on 17 July, the HETE FREGATE and WXM instruments detected and localized H2768, a short duration, soft spectrum burst event from the vicinity of the soft gamma repeater SGR1806-20. The coordinates (J2000) of H2768 derived by the WXM are: R.A. = 271.716 deg Dec. = -20.461 deg The one sigma (statistical) error circle for the localization is 5.2 arcmin in radius. SGR1806-20 lies about 24 arcmin from the HETE position. However, a number of factors combined to produce larger-than-normal systematic errors for H2768. They are related to the fact that H2768 was detected in orbit day, after star camera turnoff. Using reasonable assumptions about the spacecraft drift, the position derived for H2768 is believed to be completely compatible with that of SGR1806-20. At 23:43:12.12 UT on 18 July, a second short duration event (H2770), was detected and localized from the vicinity of SGR1806-20. The duration (t50) of H2770 was 60 +/- 7 ms in the 7-40 keV band. The coordinates (J2000) derived by the WXM are: R.A. = 272.176 deg Dec. = -20.590 deg The localization for H2770 was determined on board HETE by the flight software, and disseminated 7 minutes later. The error circle (90% confidence) for the flight localization is 30 arcmin in radius. SGR1806-20 lies about 10 arcmin from the center of the HETE WXM error circle. Thus, the position derived for H2770 is also fully consistent with that of SGR1806-20. Most recently, at 03:24:15.28 UT on 19 July, a third short duration event (H2771), was detected and localized from the vicinity of SGR1806-20. The duration (t50) of H2771 was 90 +/- 25 ms in the 7-40 keV band. The coordinates (J2000) of H2771 derived by the WXM are: R.A. = 272.241 deg Dec. = -20.626 deg The localization for H2771 was determined on board HETE by the flight software, and disseminated 20 seconds later. The error circle (90% confidence) for the flight localization is 30 arcmin in radius. SGR1806-20 lies about 12 arcmin from the center of the HETE WXM error circle. Thus, the position derived for H2771 is also fully consistent with that of SGR1806-20. Based on the accurate localization and the rapid cadence of these three HETE burst events, we conclude that the soft gamma repeater SGR1806-20 has evidently entered a heightened state of burst activity. This message may be cited.