Asymmetric supernova remnants generated by Galactic, massive runaway stars

Abstract

After the death of a runaway massive star, its supernova shock wave interacts\nwith the bow shocks produced by its defunct progenitor, and may lose energy,\nmomentum, and its spherical symmetry before expanding into the local\ninterstellar medium (ISM). We investigate whether the initial mass and space\nvelocity of these progenitors can be associated with asymmetric supernova\nremnants. We run hydrodynamical models of supernovae exploding in the\npre-shaped medium of moving Galactic core-collapse progenitors. We find that\nbow shocks that accumulate more than about 1.5 Mo generate asymmetric remnants.\nThe shock wave first collides with these bow shocks 160-750 yr after the\nsupernova, and the collision lasts until 830-4900 yr. The shock wave is then\nlocated 1.35-5 pc from the center of the explosion, and it expands freely into\nthe ISM, whereas in the opposite direction it is channelled into the region of\nundisturbed wind material. This applies to an initially 20 Mo progenitor moving\nwith velocity 20 km/s and to our initially 40 Mo progenitor. These remnants\ngenerate mixing of ISM gas, stellar wind and supernova ejecta that is\nparticularly important upstream from the center of the explosion. Their\nlightcurves are dominated by emission from optically-thin cooling and by X-ray\nemission of the shocked ISM gas. We find that these remnants are likely to be\nobserved in the [OIII] lambda 5007 spectral line emission or in the soft\nenergy-band of X-rays. Finally, we discuss our results in the context of\nobserved Galactic supernova remnants such as 3C391 and the Cygnus Loop.\n