I am Rajika Kuruwita, an Independant Postdoc Fellow
at the Heidelberg Institute for Theoretical Studies

Abstract: We carry out magnetohydrodynamical simulations with FLASH of the formation of a single, a tight binary (a ~2.5 AU) and a wide binary star (a ~45 AU). We study the outflows and jets from these systems to understand the contributions the circumstellar and circumbinary discs have on the efficiency and morphology of the outflow. In the single star and tight binary case we obtain a single pair of jets launched from the system, while in the wide binary case two pairs of jets are observed. This implies that in the tight binary case the contribution of the circumbinary disc on the outflow is greater than that in the wide binary case. We also find that the single star case is the most efficient at transporting mass, linear and angular momentum from the system, while the wide binary case is less efficient (~50%, ~33%, ~42% of the respective quantities in the single star case). The tight binary's efficiency falls between the other two cases (~71%, ~66%, ~87% of the respective quantities in the single star case). By studying the magnetic field structure we deduce that the outflows in the single star and tight binary star case are magnetocentrifugally driven, whereas in the wide binary star case the outflows are driven by a magnetic pressure gradient.

Movies: This animation shows side-on gas density projections of thickness 100AU for the single star(left), tight binary (middle) and wide binary (right) cases. In the single star case the projection is centred on the xz-plane. In the tight binary case the projections are orientated along the dense filament formed due to the initial density perturbation. In the wide binary case the projections are orientated along the separation axis of the binary. The thin lines show the magnetic field, and the arrows indicate the velocity field. Crosses show the position of the sink particles. The mass accreted by the sink particles in the simulations is indicated on the bottom left of each panel.

This animation shows top down density projections of thickness 100AU for the single star(left), tight binary (middle) and wide binary (right) cases. In all cases the projection is centred on the xy-plane. The thin lines show the magnetic field, and the arrows indicate the velocity field. Crosses show the position of the sink particles. The mass accreted by the sink particles in the simulations is indicated on the bottom left of each panel.

Acknowledgements: We thank the anonymous referee for the constructive feedback and comments that helped to improve the paper. R.K. would like to thank the Australian Government and the financial support provided by the Australian Postgraduate Award. C.F. gratefully acknowledges funding provided by the Australian Research Council's Discovery Projects (grants DP150104329 and DP170100603). The simulations presented in this work used high performance computing resources provided by the Leibniz Rechenzentrum and the Gauss Centre for Supercomputing (grants pr32lo, pr48pi and GCS Large-scale project 10391), the Partnership for Advanced Computing in Europe (PRACE grant pr89mu), the Australian National Computational Infrastructure (grant ek9), and the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia, in the framework of the National Computational Merit Allocation Scheme and the ANU Allocation Scheme. The simulation software FLASH was in part developed by the DOE-supported Flash Center for Computational Science at the University of Chicago.