TITLE:   GCN CIRCULAR
NUMBER:  30680
SUBJECT: GRB 210822A: RATIR Optical Detections
DATE:    21/08/22 16:59:44 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), Eleonora Troja (GSFC), Michael G. Richer (UNAM), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz
(UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley
(GSFC), Rosa L. Becerra (UNAM), Simone Dichiara (UMD), and Océlotl López
(UNAM) report:

We observed the field of GRB 210822A (Page, et al., GCN 30677) 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 2021/08 22.39 to 2021/08 22.41 UTC (1.2 minutes to 0.49
hours after the BAT trigger), obtaining a total of 0.19 hours exposure in
the r and i bands.

We detect the fading OT (see, Zheng & Filippenko, GCN 30679) with high
confidence.   The flux varies approximately as t^(-1) from i = 13.2 to i =
15.8 (and r=15.6).  These preliminary 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 Astronómico Nacional in San Pedro
Mártir.