TITLE:   GCN CIRCULAR
NUMBER:  30191
SUBJECT: GRB 210610A: RATIR Optical and NIR Detection 
DATE:    21/06/11 05:59:57 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 210610A (Page et al., GCN Circ. 30160) 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 2021/06 11.18 to 2021/06 11.23 UTC (13.00 to 14.06 
hours after the BAT trigger), obtaining a total of 0.61 hours exposure 
in the r and i bands and 0.25 hours exposure in the Z, Y, J, and H bands.

We detect the afterglow with the following magnitudes and 3-sigma upper limit:

  r = 21.39 +/- 0.06
  i = 21.35 +/- 0.07
  Z = 20.74 +/- 0.10
  Y = 21.05 +/- 0.22
  J = 20.70 +/- 0.25
  H > 20.12

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 Astronómico Nacional in San Pedro 
Mártir.