TITLE:   GCN CIRCULAR
NUMBER:  30028
SUBJECT: GRB 210515C: LCO Optical Upper Limit
DATE:    21/05/16 17:02:11 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 210515C (D'Ai, et al., GCN 30020) with the LCO 1-m Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on May 16, from 09:37 to 09:51 UT (corresponding to 13.58 to 13.82 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 3x130s exposures in R and I. We do not detect an uncatalogued optical source in the coadded images in the XRT enhanced error region (Osborne, et al., GCN 30023).  Using the USNO-B.1 catalog as reference, we calculate the following upper limits:

R>21.47

I>20.62

These magnitudes are not corrected for galactic extinction.

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