TITLE: GCN CIRCULAR NUMBER: 32799 SUBJECT: GRB 221009A: Continued LDT Afterglow Monitoring DATE: 22/10/19 03:59:58 GMT FROM: Brendan O'Connor at UMD oconnorb@umd.edu

B. O'Connor (UMD/GWU), S. B. Cenko (NASA/GSFC), E. Troja (UTV/ASU), S. Dichiara (PSU), A. Kutyrev (NASA/GSFC), S. Veilleux (UMD), J. Durbak (UMD), on behalf of a larger collaboration:

We performed target of opportunity observations of GRB 221009A (Dichiara et al., GCN 32632, Veres et al., GCN 32636) with the 4.3m Lowell Discovery Telescope (LDT) in Happy Jack, AZ. Observations began on October 13, 2022 at 02:05:29 UT corresponding to ~9.5 d after the GRB. We obtained images in the riz filters at an airmass ~1.1 with seeing ~1.7".

The afterglow is clearly detected in each filter. We obtain the following magnitudes calibrated against the PS1 catalog:

r = 21.68 +/- 0.07 AB mag i = 20.72 +/- 0.05 AB mag

These magnitudes are not corrected for Galactic extinction.

We thank the staff of the Lowell Observatory for assistance with these observations.