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