K. Ivarsen, D. Reichart, J. Haislip, A. LaCluyze, R. Egger, A. Foster, J.
Moore, A. Oza, M. Schubel, A. Trotter, J. A. Crain, and M. Nysewander
Skynet observed the Swift/BAT localization of GRB 100423A (Stroh et al.,
GCN 10651) with four of the 16" PROMPT telescopes at CTIO beginning 49
seconds after the trigger in BVRI.
We detect the afterglow (Filgas et al., GCN 10652) in all filters.
At 51 seconds after the trigger, its magnitude is R = 15.81 +0.12 -0.11
(calibrated to 13 SDSS stars, transformed using Jester et al., 2005, ApJ,
Until about 8 minutes after the trigger, the afterglow faded with a
power-law index of about -0.5. Afterward, it steepened. Between 30 and 90
minutes after the trigger, the afterglow faded with a power-law index of
Skynet's most recent BVRI light curve, calibrated to SDSS stars, can be