Implementation of a goodness-of-fit test for finding optimal concurrent radio and {\gamma}-ray pulsar light curves

Abstract

Since the launch of the Fermi Large Area Telescope in 2008 the number of known ${\gamma}$-ray pulsars has increased immensely to over 200, many of which are also visible in the radio and X-ray bands. Seyffert et al. (2011) demonstrated how constraints on the viewing geometries of some of these pulsars could be obtained by comparing their observed radio and ${\gamma}$-ray light curves by eye to light curves from geometric models. While these constraints compare reasonably well with those yielded by more rigorous single-wavelength approaches, they are still a somewhat subjective representation of how well the models reproduce the observed radio and ${\gamma}$-ray light curves. Constructing a more rigorous approach is, however, made difficult by the large uncertainties associated with the ${\gamma}$-ray light curves as compared to those associated with the radio light curves. Naively applying a ${\chi}^{2}$-like goodness-of-fit test to both bands invariably results in constraints dictated by the radio light curves. A number of approaches have been proposed to address this issue. In this paper we investigate these approaches and evaluate the results they yield. Based on what we learn, we implement our own version of a goodness-of-fit test, which we then use to investigate the behaviour of the geometric models in multi-dimensional phase space.