Discovering Gravitational Lenses through Measurements of Their Time Delays

We consider the possibility that future wide-field time domain optical imaging surveys may be able to discover gravitationally lensed quasar pairs through serendipitous measurements of their time delays. We discuss the merits such a discovery technique would have relative to conventional lens searches. Using simulated quasar light curves, we demonstrate that in a survey that observes objects several times each lunar cycle over the course of five years it is possible, through the use of time delay selection, to significantly improve the efficiency of a gravitational lens search relative to that of an equivalent search that does not take advantage of time delay information. We show that window function effects associated with the length of the observing season are more important than the total number of data points in determining the effectiveness of this method. We also qualitatively discuss several complications that might be relevant to a real-time delay search.