TITLE:   GCN CIRCULAR
NUMBER:  29979
SUBJECT: GRB 210509A: RATIR Optical and NIR Upper Limits 
DATE:    21/05/10 14:11:26 GMT
FROM:    Alan M Watson at 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 210509A (Page et al., GCN Circ. 29970) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson
Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir
from 2021/05 10.47 to 2021/05 10.48 UTC (19.34 to 19.70 hours after the BAT
trigger), obtaining a total of 0.21 hours exposure in the r and i bands and 0.08
hours exposure in the Z, Y, J, and H bands.

For a source within the Swift-XRT error circle, in comparison with the SDSS DR9
and 2MASS catalogs, we obtain the following upper limits (3-sigma):

  r	> 21.28
  i	> 21.09
  Z	> 18.17
  Y	> 19.19
  J	> 19.57
  H	> 17.30

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