Critical phenomena in neutron stars: II. Head-on collisions

Thorsten Kellerman (1) , Luciano Rezzolla (1, 2) , David Radice (1)

1 AEI - Max-Planck-Institut für Gravitationsphysik ( Albert-Einstein-Institut )
2 Department of Physics and Astronomy

We consider the head-on collision of equal-mass neutron stars boosted towards each other and we study the behavior of such systems near the threshold of black-hole formation. In particular, we confirm the previous findings by [ 1 ] that a type-I critical phenomenon can be observed by fine-tuning the initial mass of the two neutron stars. At the same time, we argue against the interpretation that the critical solution is not a perturbed spherical star and show instead that the metastable star corresponds to a (perturbed) equilibrium solution on the unstable branch of the equilibrium configurations. As a result, the head-on collision of two neutron stars near the critical threshold can be seen as a transition in the space of configurations from an initial stable solution over to a critical metastable one which can either migrate to a stable solution or collapse to a black hole. The critical exponent for this process shows a fine structure which was already observed in the case of the critical collapse of scalar fields but never before for perfect fluids.

Mots clés: 04.25.Dm; 04.40.Dg; 04.70.Bw; 95.30.Lz; 97.60.Jd

Thorsten Kellerman, Luciano Rezzolla, David Radice. Critical phenomena in neutron stars: II. Head-on collisions. Classical and Quantum Gravity, 2010, 27 (23), pp.235016. ⟨10.1088/0264-9381/27/23/235016⟩. ⟨hal-00649075⟩