TITLE:   GCN CIRCULAR
NUMBER:  22614
SUBJECT: GRB 180407A: COATLI Upper Limits
DATE:    18/04/07 04:37:08 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 GRB 180407A (Deich et al., GCN 22612) with the
COATLI 50-cm telescope and interim imager
(http://coatli.astroscu.unam.mx) at the Observatorio Astron��mico
Nacional on the Sierra de San Pedro M��rtir from 2018-04-07 02:26:12 to
03:01:38 (0.52 to 1.12 hours after trigger) obtaining a total of 510
seconds of exposure in the w filter.

The images were obtained at high airmass (above 3.1) and during
twilight.

For a source within the Swift/BAT error circle, in comparison with the
USNO-B1 catalog, we obtain the following 10-sigma upper limit:

w > 16.53

This magnitude is in the USNO 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.


-- 
Dr. Alan M. Watson
Instituto de Astronom��a
Universidad Nacional Aut��noma de M��xico