Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (UTV), Alexander Kutyrev
(GSFC), William H. Lee (UNAM), 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 220412A (Klingler et al. GCN 31881) 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 2022-04-14 03:28 to 07:30 UTC (44.9 to 48.9 hours after the trigger)
obtaining 2.31 hours of exposure in the i band.
In comparison with the SDSS DR9 catalog, the afterglow candidate reported by
Watson et al. (GCN Circ. 31882, 31898) is detected at i = 21.51 +/- 0.10.
We note that the optical light curve appears to have steepened. The temporal
index between our observations at 21 hours (Watson et al., GCN Circ 31898) and
47 hours is close to -1.0.
Further observations are continuing.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro M��rtir.