Violent stellar interactions

Abstract

Core-collapse supernovae give birth to neutron stars with a natal "kick", which is the linear motion given due to asymmetries in the explosion. A large fraction of core-collapse supernova explosions are expected to occur in the presence of a close-by companion star. Due to the stochastic nature of the kicks, the direction is considered to be random, and could sometimes be shot into the companion star. There has been surprisingly little work on the consequence of collisions between normal stars and neutron stars, mainly because it has been considered that it would lead to immediate mergers. However, in some situations the neutron star may penetrate the companion's envelope, creating interesting phenomena. In this talk, I will present results of 3D hydrodynamical simulations of collisions between new-born neutron stars and stellar companions in binary systems. We discovered three possible interesting outcomes especially when the neutron star can penetrate the companion envelope. First, it can create hypervelocity stars with velocities exceeding the classical limit. Second, the neutron star can carry away material from the companion star, which can eventually form protoplanetary disks to host pulsar planets. Third, part of the carried away matter can accrete onto the neutron star, creating observable features. I will discuss how these scenarios may be able to resolve some conflicts between some observed objects and theoretical models for their origin.