TITLE:   GCN CIRCULAR
NUMBER:  34289
SUBJECT: GRB 230728A: LCOGT Optical Upper Limit
DATE:    23/07/28 14:44:26 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 230728A (Salvaggio et al., GCN 34282) field with the
LCOGT 1-meter Sinistro instrument at the Teide Observatory, Tenerife site,
on July 28, from 03:15 to 03:48 UT (corresponding to 0.42 to 0.97 hours
from the GRB trigger time) with the SDSS r and i filters.

We performed a series of 3x300s exposures in each band.  We do not detect
any source within the enhanced Swift-XRT error region (Evans et al., GCN
34286) in either band, consistent with later optical upper limits (Xu et
al., GCN 34285).

The following upper limits are calculated using the PanSTARRS catalog as
reference:

r > 23.3
i > 22.8

These magnitudes are not corrected for galactic extinction.