TITLE: GCN GRB OBSERVATION REPORT NUMBER: 496 SUBJECT: VLT spectra of GRB991216 DATE: 99/12/19 02:18:37 GMT FROM: Paul Vreeswijk at U of Amsterdam P.M. Vreeswijk, E. Rol (U. of Amsterdam), J. Hjorth (U. of Copenhagen), C. Kouveliotou (USRA, NASA/MSFC), E. Pian, E. Palazzi (ITESRE, Bologna), H. Pedersen (U. of Copenhagen), J. Gorosabel, A. Castro-Tirado (LAEFF-INTA, Madrid) and J. Greiner (AIP, Potsdam) report on behalf of a larger European collaboration: At Dec. 18.17 UT, we took two 30-minute low resolution spectra of the optical counterpart to GRB991216 (GCN #472) with the VLT-Antu telescope at the European Southern Observatory (ESO, Chile). These spectra roughly cover the wavelength range 400-900nm. We detect several absorption features that we can identify with the following lines: FeII(at 237.45nm, 238.28nm, 258.67nm and 260.02nm), MgII(279.64nm/280.35nm) and MgI(285.30nm), assuming there exist three absorption systems at the redshifts z=0.77, z=0.80 and z=1.02. No clear emission features are detected. We are planning to take more spectra around Dec. 19.2 UT, which should allow us to verify these preliminary results. This message can be cited.