A Bayesian algorithm for model selection applied to caustic-crossing binary-lens microlensing events

摘要

We present a full Bayesian algorithm designed to perform automated searchesof the parameter space of caustic-crossing binary-lens microlensing events.This builds on previous work implementing priors derived from Galactic modelsand geometrical considerations. The geometrical structure of the priors dividesthe parameter space into well-defined boxes that we explore with multiple MonteCarlo Markov Chains. We outline our Bayesian framework and test our automatedsearch scheme using two data sets: a synthetic lightcurve, and the observationsof OGLE-2007-BLG-472 that we analysed in previous work. For the synthetic data,we recover the input parameters. For OGLE-2007-BLG-472 we find that while\chi^2 is minimised for a planetary mass-ratio model with extremely longtimescale, the introduction of priors and minimisation of BIC, rather than\chi^2, favours a more plausible lens model, a binary star with components of0.78 and 0.11 M_Sun at a distance of 6.3 kpc, compared to our previous resultof 1.50 and 0.12 M_Sun at a distance of 1 kpc.