TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1150 SUBJECT: GRB011121: possible optical counterpart DATE: 01/11/22 06:47:19 GMT FROM: Krzysztof Z. Stanek at CfA Lukasz Wyrzykowski (Warsaw University Observatory), K. Z. Stanek (Harvard-Smithsonian CfA) and P. M. Garnavich (Notre Dame) report: R-band observations of the optical afterglow of the GRB011121 carried out with the OGLE 1.3m telescope (+8kx8k OGLE-III mosaic) at the Las Campanas Observatory, starting at UT 011122 05:08 (10.3 hours after the burst), reveal a new, bright source in the refined BeppoSAX-WFC error box (GCN 1149). Its position, based on the GSC, is: 11:34:30.38, -76:01:41.3 (J2000). Comparing to star "A" (R=17.4) from the USNO catalog (located at 11:34:18.9, -76:01:38.1, J2000), we estimate the R-band magnitude of the possible GRB011121 afterglow to be R=18.3\pm 0.1 (subject to possible systematic error due to the calibration of the catalog). Additional data will be obtained. The E(B-V) Galactic reddening from Schlegel et al. is E(B-V)=0.5, or A_R=1.33. This message can be cited.