TITLE: GCN GRB OBSERVATION REPORT NUMBER: 463 SUBJECT: GRB 991216: Extremely bright BATSE burst DATE: 99/12/16 23:40:52 GMT FROM: R. Marc Kippen at BATSE/UAH/MSFC R. M. Kippen, R. D. Preece and T. Giblin (University of Alabama in Huntsville) report on behalf of the BATSE GRB team: An extremely bright gamma-ray burst was detected by BATSE on 1999 December 16.671544 UT (trigger number 7906). The event began with a weak precursor pulse lasting about 3 seconds, followed about 15 seconds later by an intense multi-peaked complex. The main emission lasted about 20 seconds, but a long decay tail persisted for another 30 seconds. Using preliminary rapid burst response data (not corrected for deadtime), we estimate that the peak flux was >60 photons cmE-2 sE-1 (50-300 keV; integrated over 1.024 s), and the total fluence was >2 x 10E-4 erg cmE-2 (>20 keV). This burst is thus one of the brightest (if not the brightest) ever detected by BATSE. The spectral properties appear to be typical of other GRBs. The BATSE rapid burst response location of this event is (Ra, Dec J2000) = (79.81, 10.79) degrees, with a total uncertainty radius of 2.4 deg (68% conf.). Given that more precise localizations from RXTE-PCA and IPN and probable, we strongly encourage observations by wide-field telescopes. A location sky-map and lightcurve for this event are available at http://www.batse.msfc.nasa.gov/~kippen/batserbr/ -eof-