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Critical phenomena in neutron stars. II: Head-on collisions. (English) Zbl 1207.85009

Summary: We consider the head-on collision of equal-mass neutron stars boosted towards each other and we study the behaviour of such systems near the threshold of black-hole formation. In particular, we confirm the previous findings by K. J. Jin et al. [Phys. Rev. Lett. 98, 131101 (2007)] 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.
[For Part I, see the authors, ibid., Article ID 235015, 17 p. (2010; Zbl 1207.85010).]

MSC:

85A15 Galactic and stellar structure
76Y05 Quantum hydrodynamics and relativistic hydrodynamics
83C55 Macroscopic interaction of the gravitational field with matter (hydrodynamics, etc.)

Citations:

Zbl 1207.85010

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