Critical Phenomena in Head-on Collisions of Neutron Stars

TL;DR

This paper demonstrates that critical collapse phenomena can occur in head-on neutron star collisions modeled with a polytropic EOS, without ultra-relativistic assumptions or fine-tuning, suggesting possible collapse in astrophysical processes like cooling.

Contribution

It shows that critical collapse can happen due to EOS changes alone, expanding understanding of neutron star stability without initial data fine-tuning.

Findings

Critical collapse observed in neutron star collisions with polytropic EOS.

Collapse can occur due to EOS changes, not just initial conditions.

Potential for neutron stars to undergo collapse during cooling processes.

Abstract

We found type I critical collapses of compact objects modeled by a polytropic equation of state (EOS) with polytropic index $\Gamma=2$ without the ultra-relativistic assumption. The object is formed in head-on collisions of neutron stars. Further we showed that the critical collapse can occur due to a change of the EOS, without fine tuning of initial data. This opens the possibility that a neutron star like compact object, not just those formed in a collision, may undergo a critical collapse in processes which slowly change the EOS, such as cooling.