GCN Circular 3727
M. Holman (CfA), P. Garnavich (Notre Dame), K.Z. Stanek (Ohio State) The photometry of the GRB 050730 afterglow and comparison star reported on GCN 3716 requires correction. The CCD gain between the standard star and GRB observations differed by 20%. The IMACS photometry of the afterglow taken on July 30 23:57 (UT) should be R=17.73 +/-0.05 mag and the comparison star at 14:08:14.62 -03:46:29 (2000) has R=17.41 +/-0.05 mag. The photometry of Burenin et al. (GCN 3718) based on our old calibration should be made 0.23 mag fainter. Even without these corrections, the R-band observations imply a power-law decay index of -1.7 between 4 hours and 23 hours after the burst. This is much steeper than the V-band index suggested by Swift UVOT photometry (Blustin et al. GCN 3717). The Swift V-band data between 12 minutes and 6.5 hours after the burst is consistent with a power-law decay index of -0.9. If the spectral index has not changed significantly, then the combined Swift and ground data suggests a steepening in the power-law decay occurred between 6 hours and 23 hours post-burst.