TITLE:   GCN CIRCULAR
NUMBER:  22865
SUBJECT: GRB 180626A: RATIR Optical Observations 
DATE:    18/06/27 05:11:57 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:

We observed the field of GRB 180626A (Evans, et al., GCN Circ. 22850)
with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astronómico Nacional on Sierra San Pedro Mártir from 2018/06 27.16 to
2018/06 27.20 UTC (19.60 to 20.46 hours after the BAT trigger),
obtaining a total of 0.71 hours exposure in the r and i bands.

For a source at the position of the UVOT counterpart, in comparison with
the SDSS DR9 catalog, we obtain the following detections:

  r	= 22.39 +/- 0.20
  i	= 21.92 +/- 0.15

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

The source flux has faded approximately as t^-0.35 since our previous
observations (Troja et al., GCN Circ. 22855).

We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Mártir.