[vsnet-grb-info 20856] GRB 180715A: COATLI Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22954
SUBJECT: GRB 180715A: COATLI Optical Observations 
DATE:    18/07/17 04:44:52 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William
H. Lee (UNAM), Carlos Román-Zúñiga (UNAM), Alexander Kutyrev (GSFC), and
Eleonora Troja (GSFC) report:

We observed the field of the short GRB 180715A (Ukwatta et al., GCN Circ.
22947) 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 2018-07-16 03:40:25 to 08:07:12 UTC
(9.55 to 14.00 hours after the trigger), obtaining a total of 3.33 hours
of exposure in the w filter.

We do not detect any optical sources coincident with the five X-ray
sources reported by Kennea et al. (GCN Circ. 22953) to a 5-sigma limiting
magnitude of

w > 22.4

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 Ángeles, Oscar Chapa,
Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosalía Langarica,
Fernando Quirós, and Carlos Tejada) and the staff of the Observatorio
Astronómico Nacional.