TITLE:   GCN CIRCULAR
NUMBER:  32087
SUBJECT: GRB 220521A: RATIR Optical and NIR Observations
DATE:    22/05/22 15:02:40 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), William H. Lee (UNAM), Alexander
Kutyrev (GSFC), Eleonora Troja (UTV), Michael G. Richer (UNAM), Ori Fox (STScI),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz (UCSC), Jes��s
Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey Moseley (GSFC), Rosa L.
Becerra (UNAM), Simone Dichiara (PSU), and Oc��lotl L��pez (UNAM) report:

We observed the field of GRB 220521A (Dichiara et al., GCN Circ. 32076) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson
Telescope at the Observatorio Astron��mico Nacional on Sierra San Pedro M��rtir
from 2022/05 22.22 to 2022/05 22.47 UTC (6.04 to 12.03 hours after the BAT
trigger), obtaining a total of 2.98 hours exposure in the r and i bands and 1.23
hours exposure in the Z, Y, J, and H bands.

For a source within the enhanced (Evans et al., GCN Circ. 32081) Swift-XRT error
circle, in comparison with the USNO-B1 and 2MASS catalogs, we obtain the
following 3-sigma upper limits:

  r	> 23.07
  i	> 22.77
  Z	> 21.13
  Y	> 21.87
  J	> 21.75
  H	> 21.30

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

Our non-detection of the NOT afterglow (Malesani & Pursimo, GCN Circ. 32078) is
consistent with a temporal power-law index steeper than about -0.5.

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