Constraints on Galaxy Density Profiles from Strong Gravitational Lensing: The Case of B1933+503

We consider a wide range of parametric mass models for B~1933+503, a ten-image radio lens, and identify shared properties of the models with the best fits. The approximate rotation curve varies by less than 7% from the average value between the innermost and the outermost image (1.5h⁻¹ kpc to 4.1h⁻¹ kpc) for models within 1 \σ of the best fit, and the radial dependence of the shear strength and angle also have common behavior for the best models. The time delay between images 1 and 6, the longest delay between the radio cores, is \Δ t = (11.0 \± 1.7)h⁻¹ days (\Ω_0=0.3, \λ_0=0.7) including all the modeling uncertainties. Deeper infrared observations, to more precisely register the lens galaxy with the radio images and to measure the properties of the Einstein ring image of the radio source's host galaxy, would significantly improve the model constraints and further reduce the uncertainties in the time delay.