Time Delays in the Gravitational Lens CLASS B1608+656: Results from Second and Third Seasons of VLA Monitoring

The gravitational lens CLASS B1608+656 is one of the most promising lens systems for the measurement of H0. The three independent time delays between the four lensed images have been measured, and the extended lensed optical emission holds the promise for a very well-constrained model. The current time delay measurements are based on the first season of VLA monitoring, in which the background source varied by only 5% in flux density. The small level of variation leads to relatively large uncertainties in the determination of the time delays (10-20%). Two more seasons of monitoring have now been completed and the source flux density has changed by ~30% during that time. We will present the results of the continued VLA monitoring and the resulting time-delay analysis. The new data can be used to reduce the uncertainties on the time delays and, hence, on the resulting determination of H0 from this system