Neutron stars structure

Aguirre, R. M., De Paoli, A. L. (2002). Neutron star structure in a quark model with excluded volume correction. Phys.Rev.C68 055804. 

A more model-dependent way to constrain neutron star structure has to do with measurements of orbital frequencies in the accretion disk near the neutron star. Suppose that the frequency of some observed phenomenon could be identified with an orbital frequency vor >, and that this phenomenon lasted many cycles. The orbital radius f 0rb is clearly greater than the stellar radius R. In... 

In just the last year, several observations have allowed new constraints on neutron star structure (1) a mass of M > 1.6 M (at >95% confidence) has been measured for a neutron star (Nice et al. 2003) (2) the first surface redshift, 2 = 0.35, has been detected from a neutron star (Cottam et al. 2002), and (3) the first non-sinusoidal light curve has been measured from an accreting millisecond neutron star (Strohmayer et al 2003). These observations, along with many previously available data, hold out good hope for strong constraints on high-density matter in the next few years. 

NEUTRON STAR STRUCTURE WITH HYPERONS AND QUARKS... 

In the present article we review these issues and present our results for neutron star structure based on the resulting EOS of dense hadronic matter. 

Neutron Star Structure with Hyperons and Quarks... 

In order to study the effects of different TBF on neutron star structure, we have to calculate the composition and the EOS of cold, catalyzed matter. We require that the neutron star contains charge neutral matter consisting of neutrons, protons, and leptons (e, p ) in beta equilibrium. Using the various TBF discussed above, we compute the proton fraction and the EOS for charge neutral and beta-stable matter in the following standard way [23, 24] The Brueckner calculation yields the energy density of lepton/baryon matter as a function of the different partial densities,... 

The knowledge of the energy density allows then to compute EOS and neutron star structure as described before, now making allowance for the species... 

In this contribution we reported the theoretical description of nuclear matter in the BHF approach and its various refinements, with the application to neutron star structure calculation. We pointed out the important role of TBF at high density, which is, however, strongly compensated by the inclusion of hyperons. The resulting hadronic neutron star configurations have maximum masses of only about 1.3 M , and the presence of quark matter inside the star is required in order to reach larger values. 

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