GCN Circular 650
N. Mirabal, J. P. Halpern (Columbia U.), R. M. Wagner (Ohio State U.) report on behalf of the MDM Observatory GRB follow-up team: "We reobserved the suggested afterglow candidate for GRB 000418 (Klose et al., GCN #645) in the R-band using the MDM 2.4m telescope. The object at position (J2000) RA 12:25:19.30, Dec. +20:06:11.1 has faded to R = 22.59 +/- 0.23 on April 27.26 UT from our previous detection at R = 21.52 +/- 0.12 on April 21.15 UT (Mirabal et al., GCN #646). The second measurement was made with a non-standard broad R filter. Both magnitudes are referenced to the same USNO star at (J2000) RA 12:25:25.62, Dec +20:04:57.8 which is listed as R = 15.4. The corresponding power-law decay index would be -0.84 +/- 0.20. The magnitude of the decline and its rate are plausible for a GRB afterglow, but further confirmation is desired. This message may be cited."