TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1442 SUBJECT: GRB020625 (=H2081): A Long Burst Localized by HETE DATE: 02/06/25 22:00:39 GMT FROM: Don Lamb at U.Chicago G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team; N. Butler, J. Doty, R. Vanderspek, J. Villasenor, G. Crew, G. Monnelly, T. Cline, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams; Y. Shirasaki, C. Graziani, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, and T. Donaghy, on behalf of the HETE WXM Team; M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team; write: At 11:25:49.32 UTC (41149.32 s UT) on 25 June 2002, the HETE FREGATE instrument detected event H2081. This event, which triggered FREGATE in Band C (30-400 keV), was very hard: the event is strongly evident (SNR ~ 12) in FREGATE Band C and is evident in FREGATE Band B (6-80 keV), but is barely visible, if at all, in FREGATE Band A (6-40 keV) and in the WXM 2-25 keV energy band. A second event occurred 86 sec later. This event was much softer: it is barely visible in FREGATE Band C, but is discernible in FREGATE bands A and B. This second event is also strongly evident in the WXM 2-25 keV energy band (SNR ~ 8). Triggers on the WXM data are currently off in order to avoid inundating the astronomical community with XRB triggers, and therefore no WXM flight location was calculated for this event. The probability of the HETE FREGATE and WXM instruments detecting two separate GRBs within 100 sec is very small. We therefore interpret the two events as part of a single, long GRB, consisting of two main peaks and having a duration > 125 sec. No real-time spacecraft aspect was available because of the full moon (99% illumination). Ground analysis produced a location, using the spacecraft aspect at the time of trigger H2081 (corresponding to the beginning of the first peak), that was reported in a GCN Position Notice at 14:19:24 UT, 173 min after the burst. Further ground analysis revealed that the spacecraft had drifted by an unusually large amount (~10 arcminutes) during the burst. Therefore a refined location, using the spacecraft aspect at the time of the second peak, which could be localized using WXM data, was reported in a second GCN Position Notice at 15:16:17 UT, 230 min after the burst. The refined location can be expressed as a 90% confidence rectangle that is 18 arcminutes by 32 arcminutes. The center and the corners of the rectangle lie at the following J2000 coordinates: RA = 20h 44m 14s, Dec = +07o 10' 12" (center) RA = 20h 43m 09s, Dec = +07o 18' 32" (corner) RA = 20h 44m 08s, Dec = +07o 28' 08" (corner) RA = 20h 45m 20s, Dec = +07o 01' 52" (corner) RA = 20h 44m 21s, Dec = +06o 52' 16" (corner). The first peak of GRB020625 had a peak flux >6 Crab and a duration of ~20 sec in FREGATE Band C (30-400 keV), during which a total of 1200 net counts were detected. The second peak had a peak flux ~2.0 x 10^-8 ergs cm-2 s-1 (i.e., ~1 x Crab flux) averaged over 1.2 sec and a duration of ~17 sec in FREGATE Band A (6-40 keV). During this time interval a total of 830 net counts were detected, corresponding to a fluence of ~1.5 x 10^-7 ergs cm-2. In the WXM 2-25 keV band, the second peak had a duration of 25 seconds. The WXM localization SNR was ~9. Further information (including a light curve) for GRB020625 is provided at the following URL: http://space.mit.edu/HETE/Bursts/ This message is citable.