TITLE: GCN GRB OBSERVATION REPORT NUMBER: 438 SUBJECT: GRB991106, optical observation at SAO-RAS DATE: 99/11/07 17:22:21 GMT FROM: Nicola Masetti at ITeSRE,CNR,Bologna S. Mitronova, A. Kopylov, S. Zharikov, T. Fatkhullin, I. Karachentsev, V. Sokolov, S. Kaisin (SAO-RAS), N. Masetti (ITeSRE/CNR, Bologna), on behalf of the BeppoSAX GRB collaboration, communicate: "We acquired on Nov 6.776 UT one R-band (300s exposure) image of the central part of the GRB991106 error box (GCN #434, #435) using the CCD camera of the 6m SAO-RAS telescope. The 3-sigma limiting magnitude of the image, estimated using USNO-A1.0 field stars, is R~23.5. Comparison of our image with the DSS did not reveal any new object brighter than the DSS limit (R~21) 7.7 hours after the GRB trigger. The FITS file of the R frame as well as a .gif image can be found at the URL http://www.sao.ru/~zhar/home/GRB/991106.html .". This message can be cited.