TITLE:   GCN CIRCULAR
NUMBER:  34611
SUBJECT: GRB 230903A: LCOGT Optical Upper Limits
DATE:    23/09/03 22:06:53 GMT
FROM:    Robert Strausbaugh at Eastern Illinois University <rstrausbaugh@eiu.edu>

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

We observed the Swift GRB 230903A (D'ai et al., GCN 34610) field with the LCOGT 1-meter Sinistro instrument at the South African Astronomical Observatory site, on September 3,  from 20:08 to 20:41 UT (corresponding to 2.77 to 3.32 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 3x300s exposures in each band.  We do not detect a source within the Swift-XRT error region (D'Ai et al., GCN 34610) in either band.

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

R > 20.5
I > 19.0

These magnitudes are not corrected for galactic extinction.