It has been shown that effective chiral hadronic models can satisfactorily describe nuclear matter, properties of finite nuclei as well as the structure of neutron stars1. While most of the approaches are based on variations of the linear sigma model or its non-linear realization, in the approach discussed here the scalar sigma meson serves to split the nucleon and its chiral partner (particle ...

Recent observations suggest that neutron stars in low-mass X-ray binaries rotate within a narrow range of spin frequencies clustered around 300Hz. A proposed explanation for this remarkable fact is that gravitational radiation from a steady-state r-mode oscillation in the neutron star’s core halts the spin-up due to accretion. For the neutron star transients, balancing the time-averaged accreti...

The nearby isolated neutron stars are a group of seven relatively slowly rotating neutron stars that show thermal X-ray spectra, most with broad absorption features. They are interesting both because they may allow one to determine fundamental neutron-star properties by modeling their spectra, and because they appear to be a large fraction of the overall neutron-star population. Here, we descri...

9 Black holes and neutron stars are fascinating objects with great potential for testing physical theories in extreme conditions. The gravitational fields near these objects provide an opportunity for tests of General Relativity in the strong-field limit and the properties of matter at the remarkably high densities that exist within neutron stars are unknown. While many of these objects are in ...

Among a dozen known magnetar-candidates there are no binary objects. As an estimate of a fraction of binary neutron stars is about 10% it is reasonable to address the question of solitarity of magnetars, to estimate theoretically the fraction of binary objects among them, and to mark out the most probable companions. We present population synthesis calculations of binary systems. Our goal is to...

We report on the detailed modelling of the X-ray spectra of three likely neutron stars. The neutron stars, observed with XMM-Newton are found in three quiescent X-ray binaries in the globular clusters: ω Cen, M 13 and NGC 2808. Whether they are accreting at very low rates or radiating energy from an accretion heated core, their X-ray spectra are expected to be those of a hydrogen atmosphere. We...

ROSAT has discovered a new group of isolated neutron stars characterized by soft blackbody like spectra (kT ∼ 50-120 eV), apparent absence of radio emission and no association with supernovae remnants. So far only six such sources are known. A small fraction of these stars exhibit X-ray pulsations with relatively long periods of the order of 10 sec. Two very different mechanisms may be envisage...

The current status of the problem of whether neutron stars can form, in close binary systems, by accretion{induced collapse (AIC) of white dwarfs is examined. We nd that, in principle, both initially cold C+O white dwarfs in the high{mass tail of their mass distribution in binaries and O+Ne+Mg white dwarfs can produce neutron stars. Which fractions of neutron stars in diierent types of binaries...

Strange stars that are entirely made of strange quark matter (SQM) have been long ago proposed as an alternative to neutron stars (e.g., [1, 2]). The possible existence of strange stars is a direct consequence of the conjecture that SQM composed of roughly equal numbers of up, down, and strange quarks plus a smaller numbers of electrons (to neutralize the electric charge of the quarks) may be t...

I review attempts made to determine the properties of neutron stars. I focus on constraints on the maximum mass that a neutron star can have, and on attempts to measure neutron-star radii. So far, there appears to be only one neutron star for which there is strong evidence that its mass is above the canonical 1.4 M ⊙ , viz., Vela X-1, for which a mass close to 1.9 M ⊙ is found. Prospects for pr...