TITLE:   GCN CIRCULAR
NUMBER:  22323
SUBJECT: GRB 180111A: RATIR Optical and NIR Observations
DATE:    18/01/12 15:36:30 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

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), 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 180111A (Lien, et al., GCN 22318) 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 2018/01 12.21 to 2018/01 12.56 UTC (12.35 to
20.68 hours after the BAT trigger), obtaining a total of 5.31 hours
exposure in the r and i bands and 2.22 hours exposure in the Z and Y bands.

We find a source within the Swift-XRT error circle (Evans, et al., 22319).
In comparison with the SDSS DR9 and 2MASS catalogs, we measure:

 r = 20.90 +/- 0.10
 i = 20.41 +/- 0.10
 Z = 20.61 +/- 0.15
 Y = 20.41 +/- 0.15

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  We note that there is an r=22.7
mag SDSS source, perhaps the host galaxy, within the XRT error region and
at a position consistent with our source position.

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