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GCN Circular 650

Subject
GRB 000418, Optical Observation
Date
2000-04-27T09:28:28Z (24 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
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."
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