TITLE:   GCN CIRCULAR
NUMBER:  27705
SUBJECT: GRB 200509A: LCO Optical Afterglow Detection
DATE:    20/05/09 18:36:17 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 200509A (Troja et al., GCN 27701) with the LCO 1-m Sinistro instrument at the South African Astronomical Observatory site, on May 9, from 16:46 to 17:08 UT (corresponding to 9.63 to 10.0 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 5x120s exposures in R and I. We detect an optical source in stacked images within the Enhanced Swift-XRT position (Evans et al., GCN 27703) that is not present in either USNO or 2MASS catalogs.  Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:

R = 20.94 +/- 0.09

I = 19.44 +/- 0.18

These magnitudes are not corrected for galactic extinction.

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