PION: Simulations of Wind-Blown Nebulae
  We present an overview of PION, an open-source software project for solving
radiation-magnetohydrodynamics equations on a nested grid, aimed at modelling
asymmetric nebulae around massive stars. A new implementation of hybrid
OpenMP/MPI parallel algorithms is briefly introduced, and improved scaling is
demonstrated compared with the current release version. Three-dimensional
simulations of an expanding nebula around a Wolf-Rayet star are then presented
and analysed, similar to previous 2D simulations in the literature. The
evolution of the emission measure of the gas and the X-ray surface brightness
are calculated as a function of time, and some qualitative comparison with
observations is made.
