TITLE:   GCN CIRCULAR
NUMBER:  23089
SUBJECT: GRB 180805B: COATLI Optical Observations
DATE:    18/08/06 17:18:16 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William
H. Lee (UNAM), Carlos Rom��n-Z����iga (UNAM), Alexander Kutyrev (GSFC), and
Eleonora Troja (GSFC) report:

We observed the field of the short GRB 180805B (D'Avanzo et al., GCN
Circ. 23076) with the COATLI 50-cm telescope and interim imager at the
Observatorio Astron��mico Nacional on the Sierra de San Pedro M��rtir
(http://coatli.astroscu.unam.mx) from 2018-08-06 08:01 to 11:48 UTC
(18.98 to 22.77 hours after the trigger), obtaining a total of 2.98
hours of exposure in the w filter.

We do not detect any optical sources within the enhanced XRT error
region (Evans et al., GCN Circ. 23077) to a 5-sigma limiting magnitude
of

w > 22.5

This magnitude is calibrated against the USNO-B1 catalog (adjusted to an
approximate AB system) and is not corrected for Galactic extinction in
the direction of the GRB.

We thank the COATLI technical team (Fernando ��ngeles, Oscar Chapa,
Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosal��a Langarica,
Fernando Quir��s, and Carlos Tejada) and the staff of the Observatorio
Astron��mico Nacional.