TITLE:   GCN CIRCULAR
NUMBER:  32966
SUBJECT: GRB 221120A: Liverpool Telescope Upper Limits
DATE:    22/11/21 22:03:04 GMT
FROM:    Ben Gompertz at U of Birmingham  <b.gompertz@bham.ac.uk>

B. P. Gompertz, M. Nicholl (U. Birmingham), N. Tanvir, G. Lamb, P. O'Brien (U. Leicester) and K. Wiersema (U. Lancaster) report:
 
We observed short GRB 221120A (Eyles-Ferris et al., GCN 32955) with the IO:O optical camera on the 2m robotic Liverpool Telescope. Observations began on November 20, 2022 at 23:50:33 UT (~2.5h after the Swift trigger) and consist of a series of 10x150s exposures in each of the SDSS r' and i' filters.

We place the following 3-sigma upper limits on an optical source at the location of the the X-ray afterglow (Goad et al., GCN 31962) at the time of observation:
 
r' > 21.82
i' > 21.88
 
Magnitudes are in the AB system, calibrated against nearby PS1 stars, and are not corrected for the Galactic reddening of E(B-V) = 0.08 magnitudes along the line of sight (Schlafly & Finkbeiner 2011). Our observations are only weakly constraining to any evolution in the afterglow candidate identified by O'Connor et al. (GCN 32957), precluding power-law decays steeper than ~t^-4 between the two epochs.