TITLE:   GCN CIRCULAR
NUMBER:  31995
SUBJECT: GRB 220427A: LCO Optical Observations
DATE:    22/05/03 18:41:20 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 GRB220427A (D'Ai et al. GCN 31960) with the LCO 1-m Sinistro instrument at the South African Astronomical Observatory site, on April 27, from 22:57 to 23:24 UT (corresponding to 1.95 to 2.40 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 3x300s exposures in I and R bands. We detect an optical counterpart at the location of the Swift optical counterpart that is consistent with other optical detections (Ugarte Postigo, et al., GCN 31967; Klotz, et al., GCN 31991). The following magnitudes are calculated using the USNO-B.1 catalog as reference:

R=20.35+/-0.12
I=20.15+/-0.30

These magnitudes are not corrected for galactic extinction.

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