TITLE:   GCN CIRCULAR
NUMBER:  32888
SUBJECT: GRB 221028A: COATLI Upper Limits
DATE:    22/10/29 17:43:28 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Rosa Becerra (UNAM), Simone
Dichiara (PSU), Tzveti Dimitrova (ASU), Océlotl López (UNAM), Diego
González (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Margarita
Pereyra (UNAM), Eleonora Troja (UTV/ASU) and report:

We observed the field of the GRB 221028A (Lien et al., GCN Circ. 32874)
with the COATLI 50-cm telescope and HUITZI f/8 imager at the Observatorio
Astronómico Nacional on the Sierra de San Pedro Mártir (
http://coatli.astroscu.unam.mx) from 2022-10-29 02:13 UTC to 08:03 UTC
(13.5 to 19.3 hours after the trigger), obtaining a total of 244 minutes of
exposure in the r filter.

At the position of the XRT afterglow (Lien et al., GCN Circ. 32874), we do
not detect a source to the following 3-sigma upper limit:

r > 23.4

Our photometry is calibrated against the Pan-STARRS1 catalog, is on an
approximate AB system, and is not corrected for Galactic extinction in the
direction of the GRB.

We thank the COATLI/HUITZI technical team and the staff of the Observatorio
Astronómico Nacional.