A global optimization technique for the fitting of color, magnitude diagrams

We present a new technique to analyze color-magnitude diagrams, such as those of stellar clusters, based on the cross-entropy global-optimization procedure. The method uses theoretical isochrones available in the literature and minimizes an objective function that describes the quality of a fit to the color-color and color-magnitude diagrams. The objective function is based on the two-dimensional distances of the points in the color-magnitude and color-color diagrams to the theoretical curves and is modified by weights that take into account the stellar distance to the observed cluster center, observed magnitude uncertainties and the King profile of the cluster, among others. The parameters determined simultaneously are distance, reddening, age and metalicity. The method uses a Monte Carlo approach to obtain uncertainties on the determined parameters for the cluster. We present results for 10 well-studied open clusters and show that the results are consistent with previous studies.