TITLE: GCN CIRCULAR NUMBER: 9333 SUBJECT: GRB 090509, SMARTS optical/IR afterglow observations DATE: 09/05/10 02:05:34 GMT FROM: Bethany Cobb at UC Berkeley B. E. Cobb (UC Berkeley) reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 090509 (Grupe et al. GCN 9325) beginning approximately 0.8 hours post-burst (2009-05-09 05:59 UT). Several dithered images were obtained in each filter, with total summed exposure times of 180s in each of BRIJK and 120s in each of H and V. The GRB afterglow (Olivares et al. GCN 9326, Covino et al. GCN 9327) is detected in all filters with the following magnitudes at a mid-exposure time of 2009-05-09 06:14 UT (1.07 hours post-burst): B= 20.18 +/- 0.13 V= 19.68 +/- 0.16 R= 19.02 +/- 0.10 I= 18.76 +/- 0.09 J= 17.70 +/- 0.16 H= 17.07 +/- 0.15 K= 16.48 +/- 0.22 (Optical photometry is calibrated against Landolt standard stars and IR photometry is calibrated against 2MASS stars in the field.)