TITLE:   GCN CIRCULAR
NUMBER:  23496
SUBJECT: GRB 181202A: RATIR Optical and NIR Observations
DATE:    18/12/03 17:27:42 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 181202A (Cannizzo et al., GCN 23482) 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 2018/12 3.09 to 2018/12 3.11
UTC (19.43 to 20.04 hours after the BAT trigger), obtaining a total of
0.09 hours exposure in the r and i bands and 0.12 hours exposure in the
Z, Y, J, and H bands in poor conditions.

For a source within the Swift-XRT error circle, in comparison with the
USNO-B1 and 2MASS catalogs, we obtain the following 3-sigma upper
limits:

 r	> 19.18
 i	> 19.17
 Z	> 16.52
 Y	> 16.30
 J	> 16.00
 H	> 16.31

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

However, we note that in our optimally-combined all-filter image, there
appears to be a very faint source present in the Swift-XRT error circle.
This suggests that there may be a source present at low significance in
at least some of our individual images.

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