GCN Circular 3110
B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS consortium, report: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained additional optical/IR imaging of the reported optical afterglow candidate (GCN 3100, Kelson & Berger) of GRB 050315 (GCN 3094, Parsons et al.) beginning ~35.6 hours post-burst. Total summed exposure times amounted to 10 minutes R and I and 12.5 minutes in J. The source identified as the afterglow candidate has dimmed since our previous observations (GCN 3104, Cobb & Bailyn). Preliminary comparison with Landolt Standards PG 1047+003 and RU 149 yields the following approximate afterglow magnitudes: R = 21.6 I = 21.5 The counterpart was again not detected in the IR, with a magnitude limit of J > 18.6. Our R and I observations are summarized below: time post-burst: R magnitude: I magnitude: 11.6 hours 20.9 20.3 35.6 hours 21.6 21.5 We note that the I-band observations are close to the detection limit, and have measurement errors of >0.2 magnitudes, so the evidence for a color change should be treated with caution. The R-band magnitudes have errors of ~0.2, so assuming a power-law afterglow decay (afterglow flux proportional to t^alpha), then this corresponds to an alpha of -0.57 +\- 0.25.