TITLE:   GCN CIRCULAR
NUMBER:  29431
SUBJECT: GRB 210207B: LCO Optical Afterglow Detection
DATE:    21/02/08 16:56:16 GMT
FROM:    Robert Strausbaugh at U. of the Virgin Islands  <robert.strausbaugh@uvi.edu>

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 210207B (Lien, GCN 29420) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 8, from 11:23 to 11:34 UT (corresponding to 13.30 to 13.48 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 5x60s exposures in R and I. We clearly detect an optical source in R and I band in stacked images at a location consistent the initial UVOT detection (Lien, GCN 29420).  Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:

R = 20.24 +/- 0.13

I = 20.56 +/- 0.24

These magnitudes are not corrected for galactic extinction.  A quick catalog search found no galaxies at this brightness at this location.  Further observations are encouraged.

R.S. is funded by NSF AST grant #1831682