TITLE:   GCN CIRCULAR
NUMBER:  32775
SUBJECT: GRB 221016A: LCOGT Optical Afterglow Detection
DATE:    22/10/17 03:23:46 GMT
FROM:    Robert Strausbaugh at University of Minnesota  <rstrausb@umn.edu>

R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:

We observed the GRB 221016A (Page et al., GCN 32774) field with the LCOGT
1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory,
Chile site, on October 17, from 01:39 to 02:06 (corresponding to 2.00 to
2.55 hours from the GRB trigger time) with the Bessel I and R filters.

We performed a series of 3x300s exposures in each band.  We detect an
uncataloged optical source within the XRT error region (Page et al., GCN
32774), in R band, and marginally in I-band (2-sigma detection).

The following magnitudes are calculated using the USNO-B1.0 catalog as
reference:

R = 21.22 +/- 0.18
I = 20.03 +/- 0.17

These magnitudes are not corrected for galactic extinction.  Gemini
imaging+spectroscopic follow up is ongoing.