Interactions of Primordial Black Hole with Neutron Star

Several recent studies show that constraints can be put on primordial black holes (PBHs) as a candidate for dark matter by considering their capture by neutron stars (NSs). If a PBH is captured by a NS, the NS is accreted onto the PBH and eventually collapses. A related scenario arises from asymmetric dark matter particles collecting in the center of NS, and eventually forming a small BH. In this work, we study such systems where a small BH has formed in the center of a NS, and follow the dynamics as the small BH consumes the NS from inside. We solve numerically the coupled system of equations formed by the Einstein equations and hydrodynamics under spherical symmetry. Using numerical simulations, we examine the time scale for the NS to collapse into the PBH, and the possible unbounded material from the NS.