TITLE: GCN GRB OBSERVATION REPORT NUMBER: 669 SUBJECT: GRB 000418, Optical observation DATE: 00/05/12 11:20:41 GMT FROM: Mark R. Metzger at CIT M. R. Metzger (Caltech) and A. Fruchter (STScI) report: "The suggested afterglow candidate for GRB 000418 (Klose et al. GCN645) was imaged in the R band with the Keck I telescope + LRIS on UT May 6.42. We measure R = 23.57 +- 0.10 for the object at this epoch. When combined with the photometry of Mirabal et al. (GCNs 646, 650, 653), this suggests that the decay rate has steepened to a t ^ -1.2 power law from the shallower slope of the early photometry. We also note that in our stacked image having approx. 0".6 FWHM seeing, the candidate PSF does not appear extended (is consistent with a point source PSF). This suggests that the continuum emission is still dominated by the afterglow, or that the underlying host galaxy (cf. Bloom et al. GCN 661) is compact. This message may be cited."