[vsnet-grb-info 20761] GRB 180626A: COATLI Optical Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22859
SUBJECT: GRB 180626A: COATLI Optical Detection 
DATE:    18/06/26 17:10:10 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 GRB 180626A (Evans et al., GCN 22850) 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 2018-06-20 08:21:50.6 to
11:18:41.7 UTC (from 33.7 seconds after the trigger or 17.9 seconds
after the alert to 2.95 hours after the trigger), obtaining a total of
7020 seconds of exposure in the w filter.

Within the enhanced XRT error region (Osborne et al., GCN Circ. 22852),
we detect the afterglow previously reported by Evans et al. (GCN Circ.
22850), Martone et al. (GCN Circ. 22854), and Breeveld et al. (GCN Circ.
22857) with

  w = 21.4 +/- 0.9

In our first set of 30 images each of 5 seconds of exposure, from
08:21:50.6 to 08:27:10.1 UTC, we do not detect the afterglow with a
10-sigma limiting magnitude of

  w > 19.2

These magnitudes are calibrated against the Pan-STARRS1 catalog and the
USNO-B1 catalog (adjusted to an approximate AB system) and are 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.