TITLE:   GCN CIRCULAR
NUMBER:  32318
SUBJECT: GRB 220701A: COATLI Optical Upper Limit
DATE:    22/07/02 17:50:14 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

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

We observed the field of GRB 220701A (Evans et al., GCN Circ. 32306) with the
COATLI 50-cm telescope and interim imager at the Observatorio Astronómico
Nacional on the Sierra de San Pedro Mártir (http://coatli.astroscu.unam.mx) from
2022-07-02 03:45 UTC to 11:21 UTC (22.81 to 30.41 hours after the trigger),
obtaining a total of 21405 seconds of exposure in the r filter.

We do not detect any uncataloged sources in the XRT error region (Evans et al.,
GCN Circ. 32306) to a 3-sigma limit of r = 23.7.

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

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