TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4970 SUBJECT: GRB 060418, SMARTS optical/IR afterglow observations DATE: 06/04/18 05:05:45 GMT FROM: Bethany Cobb at Yale U B. E. Cobb (Yale), part of the larger SMARTS consortium, reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 060418 (Falcone et al. GCN 4966) beginning ~1 hours post-burst (2006-04-18 04:05 UT). Several dithered images were obtained in each filter, with total summed exposure times of 180s in each of BRIYJK and 120s in each of H and V. The afterglow candidate reported by Falcone et al. and confirmed by Covino et al. (GCN 4967) and Melandri et al. (GCN 4968) is visible in all wavebands, from B to K. At a mid-exposure time of 1.2 hrs post-burst, the preliminary K-band magnitude of the afterglow candidate is K = 14.1 +/- 0.1. This value is obtained by comparison with nearby 2MASS standards. The lack of a Lyman-alpha forest absorption break suggest this GRB has a redshift of z<~3.