Further Investigation of the Time Delay, Magnification Ratios, and Variability in the Gravitational Lens 0218+357

High precision VLA flux density measurements for the lensed images of0218+357 yield a time delay of 10.1(+1.5-1.6)days (95% confidence). This isconsistent with independent measurements carried out at the same epoch (Biggset al. 1999), lending confidence in the robustness of the time delaymeasurement. However, since both measurements make use of the same features inthe light curves, it is possible that the effects of unmodelled processes, suchas scintillation or microlensing, are biasing both time delay measurements inthe same way. Our time delay estimates result in confidence intervals that aresomewhat larger than those of Biggs et al., probably because we adopt a moregeneral model of the source variability, allowing for constant and variablecomponents. When considered in relation to the lens mass model of Biggs et al.,our best-fit time delay implies a Hubble constant of H_o = 71(+17-23) km/s-Mpcfor Omega_o=1 and lambda_o=0 (95% confidence; filled beam). This confidenceinterval for H_o does not reflect systematic error, which may be substantial,due to uncertainty in the position of the lens galaxy. We also measure the fluxratio of the variable components of 0218+357, a measurement of a small regionthat should more closely represent the true lens magnification ratio. We findratios of 3.2(+0.3-0.4) (95% confidence; 8 GHz) and 4.3(+0.5-0.8) (15 GHz).Unlike the reported flux ratios on scales of 0.1", these ratios are notstrongly significantly different. We investigate the significance of apparentdifferences in the variability properties of the two images of the backgroundactive galactic nucleus. We conclude that the differences are not significant,and that time series much longer than our 100-day time series will be requiredto investigate propagation effects in this way.