http://arxiv.org/abs/1706.09371
We study radial oscillations of hybrid non-rotating neutron stars composed by a quark matter core and hadronic external layers. At first, we deduce the junction conditions that should be imposed between two any phases in these systems when perturbations take place. Then we compute the spectrum exhibited by the radial oscillations of hybrid neutron stars focusing on the effects of slow and rapid phase conversions at the quark-hadron interface. For the quark matter core, we use a generic MIT bag model that allows the inclusion of the effects of finite quark masses, strong interactions and color superconductivity. For the hadronic phase, we use a relativistic mean field theory widely used to describe hadronic matter in neutron stars. In the case of rapid transitions we report the presence of a new mode, that could be either the fundamental mode or the first excited one, depending on the equation of state parametrizations. We show that the speed of the phase conversion at the hybrid interface plays a key role on the stability of the star as a whole. The static stability condition $\partial M/\partial \rho_c\geq 0$, where $\rho_c$ is the central density of a star whose total mass is $M$, remains always true for rapid phase transitions but breaks down in general for slow phase transitions. In fact, we find that the frequency of the fundamental mode can be a real number (indicating stability) even for some branches of stellar models that verify $\partial M/\partial \rho_c \leq 0$. This may lead to the existence of twin or even triplet stars with the same gravitational mass but different radii which, if observed, could reveal the nature of reactions in stars and by consequence their hybrid nature and aspects of their innermost phases.
J. Pereira, C. Flores and G. Lugones
Thu, 29 Jun 17
1/44
Comments: 14 figures
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