[vsnet-grb-info 19800] GRB 170906C: COATLI Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21837
SUBJECT: GRB 170906C: COATLI Observations
DATE:    17/09/06 19:47:21 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), Carlos
Román-Zúñiga (UNAM), and William H. Lee (UNAM) report:

We observed the field of the GRB 170906C (Siegel et al., GCN Circ.
21826) with the COATLI 50-cm telescope and interim CCD imager (Watson et
al. 2016, Proc. SPIE, 9908, 50) at the Observatorio Astronómico Nacional
on the Sierra de San Pedro Mártir from 2017-09-06 08:17 to 12:11
obtaining a total of 2.93 hours of observation in the clear w filter.

We do not detect a source within the enhanced XRT error region reported
by Evans et al. (GCN Circ. 21831). Calibrating with respect to the
USNO-B1 catalog, we estimate a 3-sigma upper limit of:

w > 21.7

This magnitude is in the 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.