TITLE: GCN CIRCULAR NUMBER: 31009 SUBJECT: GRB 211025A: Optical Afterglow Detection DATE: 21/10/26 18:11:21 GMT FROM: Robert Strausbaugh at U. of the Virgin Islands <robert.strausbaugh@uvi.edu> R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (College of Marin) report on behalf of a larger collaboration: We observed Swift GRB 211025A (Gropp, et al., GCN 30986) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on October 25, from 11:27 to 11:49 UT (corresponding to 6.28 to 6.82 hours from the GRB trigger time) with the Bessel R and I filters. We performed a series of 4x160s exposures in R and I bands. We detect a source consistent with the Swift UVOT detection coordinates (Oates, et al., GCN 30991) in R-band, but not in I-band. The following magnitudes and upper limits are calculated using the USNO-B.1 catalog as reference: R=20.51+/-0.27 I>18.04 These magnitudes are not corrected for galactic extinction. R.S. is funded by NSF AST grant #1831682