## Constraining pulsar magnetospheric electrodynamics via joint radio and gamma-ray light curve fitting

**Albertus Seyffert**

(C Venter, AK Harding, C Kalapotharakos, on behalf of the Fermi LAT Collaboration)

**Abstract:**

To date the Fermi Large Area Telescope (LAT) has detected at least 216 pulsars, many of which also pulsate in the radio band. This wealth of dual-band data has stimulated the development of sophisticated models of the pulsar magnetosphere, e.g., the force-free and force free inside dissipative outside (FIDO) models. Emission models based upon such magnetospheres yield concurrent radio and gamma-ray light curve predictions that can, in principle, constrain pulsar viewing geometries and electrodynamics via statistical goodness-of-fit testing. However, when concurrent fits are attempted via the Pearson's Chi-Squared test a clear bias toward the radio data emerges arising from the large disparity between the radio and gamma-ray relative light curve errors. To overcome this bias we have developed the Scaled-Flux Normalised Chi-Squared test statistic. The main difference between this and the traditional Chi-Squared test statistic is that it redefines the units in which the goodness-of-fit value for a single-band fit is expressed, allowing us to assign each concurrent dual-band fit a score between 0 and 1 with an associated Monte-Carlo-derived uncertainty. The goodness-of-fit values thus obtained can now be sensibly compared across both models and pulsars. As a first test of this new statistic we investigate the correlation between magnetospheric conductivity and pulsar spin-down luminosity uncovered by Brambilla et al. (2015) based on spectral fitting using the FIDO model. We will search for this trend by comparing predicted light curves from the FIDO-based model to observed radio and gamma-ray light curves of 16 young and millisecond pulsars.