TITLE: GCN CIRCULAR NUMBER: 31898 SUBJECT: GRB 220412A: RATIR Observations of the Fading Afterglow DATE: 22/04/13 20:05:34 GMT FROM: Alan M Watson at UNAM 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 2022-04-12 06:39 to 06:56 UTC (0.04 to 0.33 hours after the trigger) and 2022-04-13 03:16 to 04:38 UTC (20.65 to 22.00 hours after the trigger) obtaining totals of 0.21 and 1.07 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) has faded from i = 19.27 +/- 0.10 to i = 20.64 +/- 0.08. This photometry for the first night supersedes the preliminary photometry reported by Watson et al. We note that the optical light curve does not seem to show the same steep decline as the XRT light curve reported by the UKSSDC. From 0.33 to 21 hours, the XRT light curve falls by a factor of about 50, whereas our photometry only falls by a factor of about 3.5. We have checked the SDSS DR9 i image, and there is no apparent host galaxy present at the position of the afterglow bright enough to explain the apparent slow decline. Further observations are planned. We thank the staff of the Observatorio Astron��mico Nacional in San Pedro M��rtir.