The Nature of LS 5039

The number of gammaray binary candidates has been increasing in recent years,yet we are still far from understanding the physical processes that take placein these extreme systems. In most cases we even cannot differentiate between aNS and a BH. We propose contemporaneous XMMNewton and NuSTAR observationsaround the superior conjunction phase of the gammaray microquasar LS 5039. Withthe outstanding timing resolution of EPICPN in Timing mode and the acquiredcontemporaneous softtohard Xray spectrum, we can search for pulsar or BHsignatures using timing and spectral information. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]