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), Oc��lotl L��pez (UNAM), Diego
Gonz��lez (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
Astron��mico Nacional on the Sierra de San Pedro M��rtir (
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
Astron��mico Nacional.