Update: PrecisionDsdecay constant from full lattice QCD using very fine lattices

We update our previous determination of both the decay constant and the mass of the Dₒ meson using the highly improved staggered quark formalism. We include additional results at two finer values of the lattice spacing along with improved determinations of the lattice spacing and improved tuning of the charm and strange quark masses. We obtain m₃ₒ=1. 9691 (32) GeV, in good agreement with experiment, and f₃ₒ=0. 2480 (25) GeV. Our result for f₃ₒ is 1. 6 lower than the most recent experimental average determined from the Dₒ leptonic decay rate and using V₂ₒ from Cabibbo-Kobayashi-Maskawa unitarity. Combining our f₃ₒ with the experimental rate we obtain a direct determination of V₂ₒ=1. 010 (22), or alternatively 0. 9900+0. 013-0. 016 using a probability distribution for statistical errors for this quantity which vanishes above 1. We also include an accurate prediction of the decay constant of the ₂, f₂=0. 3947 (24) GeV, as a calibration point for other lattice calculations.