A metric and optimization scheme for microlens planet searches

OGLE III and MOA-II are discovering 600-1000 Galactic bulge microlens events each year. This stretches the resources available for intensive follow-up monitoring of the light curves in search of anomalies caused by planets near the lens stars. We advocate optimizing microlens planet searches by using an automatic prioritization algorithm based on the planet detection zone area probed by each new data point. This optimization scheme takes account of the telescope and detector characteristics, observing overheads, sky conditions and the time available for observing on each night. The predicted brightness and magnification of each microlens target are estimated by fitting to available data points. The optimization scheme then yields a decision on which targets to observe and which to skip, and a recommended exposure time for each target, designed to maximize the planet detection capability of the observations. The optimal strategy maximizes detection of planet anomalies, and this must be coupled with rapid data reduction to trigger continuous follow-up of anomalies that are thereby found. A web interface makes the scheme available for use by human or robotic observers at any telescope. We also outline a possible self-organizing scheme that may be suitable for coordination of microlens observations by a heterogeneous telescope network.