GCN Circular 20921

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), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy
(UMD) report:

We observed the field of GRB 170318B (Cholden-Brown et al., GCN 20908
Not found
 
 
)
with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astron��mico Nacional on Sierra San Pedro M��rtir from 2017/03 19.47 to
2017/03 19.51 UTC (19.76 to 20.76 hours after the BAT trigger),
obtaining a total of 0.71 hours exposure in the r and i bands and 0.30
hours exposure in the Z, Y, J, and H bands.

For a source within the Swift-XRT enhanced error circle (Goad et al.,
GCN 20910
Not found
 
 
), in comparison with the USNO-B1 and 2MASS catalogs, we obtain
the following upper limits (3-sigma):

 r    > 25.64
 i    > 24.39
 Z    > 22.65
 Y    > 22.43
 J    > 21.38
 H    > 20.98

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

We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.