GCN Circular 30672

Subject

GRB 210820A: RATIR Optical Detections

Event

Date

2021-08-21T15:52:28Z (4 years ago)

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),
Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey Moseley (GSFC),
Rosa
L. Becerra (UNAM), Simone Dichiara (UMD), and Oc��lotl L��pez (UNAM) report:

We observed the field of GRB 210820A (Beardmore, et al., GCN 30664Loading...
 
 ) 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 2021/08 21.27 to 2021/08 21.50 UTC (12.47 to 17.96
hours after the BAT trigger), obtaining a total of 3.70 hours exposure
in the r and i bands.

We detect one source within the Swift-XRT error circle (Beardmore, et al.,
GCN 30667Loading...
 
 ).  In comparison with the SDSS DR9 and 2MASS catalogs, we obtain:

  r = 22.84 +/- 0.22
  i = 22.66 +/- 0.18

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

The source is located at RA, Dec = 1:22:33.47, +4:36:28.1 (J2000, +/-0.5").
This is 0.2 arcsec away from the UVOT OT (GCN 30664Loading...
 
 ).

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