TITLE:   GCN CIRCULAR
NUMBER:  32692
SUBJECT: GRB 221009A: COATLI Detection of the Afterglow
DATE:    22/10/11 16:41:09 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Simone Dichiara (PSU), Rosa L.
Becerra (UNAM), 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 bright GRB 220930A (Dichiara et al., GCN
Circ. 32632, Veres et al., GCN Circ. 32636) 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
2022-10-11 06:05 UTC to 06:39 UTC (40.2 hours after the trigger),
obtaining a total of 405 seconds of exposure in each of the g, r, i, and
z filters.

At the position of the UVOT afterglow (Dichiara et al., GCN Circ.
32632), we detect a source with the following magnitudes and 3-sigma
upper limit:

g > 20.27

r = 19.48 +/- 0.13

i = 18.49 +/- 0.07

z = 17.92 +/- 0.08

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.