TITLE:   GCN CIRCULAR
NUMBER:  22855
SUBJECT: GRB 180626A: RATIR Optical Detection
DATE:    18/06/26 12:36:12 GMT
FROM:    Eleonora Troja at GSFC  <eleonora.troja@nasa.gov>

Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM),
Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB),
Antonino Cucchiara (UVI), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jesus Gonzalez (UNAM), Carlos Roman-Zuniga (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 22850) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astronomico Nacional on
Sierra San Pedro Martir from 2018/06 26.42 to 2018/06 26.43 UTC (1.61
to 2.06 hours after the BAT trigger), obtaining a total of 0.36 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    = 21.57 +/- 0.22
   i    = 20.91 +/- 0.13

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. These magnitudes are fainter
than the values reported by Martone et al. (GCN 22854) suggesting that
the source is indeed the fading GRB afterglow.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.