TITLE: GCN GRB OBSERVATION REPORT NUMBER: 440 SUBJECT: GRB 991106 Optical Observations DATE: 99/11/08 20:00:09 GMT FROM: Brian Lindgren Jensen at U.of Copenhagen B. L. Jensen, H. Pedersen, J. Hjorth, S. Larsen (University of Copenhagen), and E. Costa (CNR, Rome; on behalf of the BeppoSAX consortium) report: Using the ALFOSC instrument at the 2.5-m Nordic Optical Telescope, La Palma, we have obtained five 2x2 mosaics, covering the error circle (Piro, GCN #435). All exposures were taken in the R band and lasted 300 s. The first data (three mosaics) were obtained from 6.872 to 6.921 Nov 1999 UT, i.e. starting ~10 hours after the event, and the last (two mosaics) were obtained from 7.845 to 7.884 Nov 1999 UT. On the first night the seeing was ~1.4", on the second ~1.4-1.8". We have compared the exposures both internally and to the DSS-2 (POSS-II R), finding no variable objects. The limiting magnitude of the first night's data is approximately R ~ 23.5. The corresponding figure for the second night is R ~ 22.0 (due to variable cloud cover). Comparison between the data of the first and second night sets a limit of R ~ 22 (Nov 7.8 1999 UT) on possible optical transients varying by more than 0.5 magnitude (relative to Nov 6.9 Nov 1999 UT). A .jpg-image of the field can be found at: http://www.astro.ku.dk/~brian_j/grb/grb991106