We consider the neutron matter quark matter phase transition along with possible existence of hybrid quark stars. The equation of state for neutron matter is obtained using a nonperturbative method with pion dressing of the neutron matter and an analysis similar to that of symmetric nuclear matter. The quark matter sector is treated perturbatively in the small distance domain. For bag constant ...

We consider the situation where a spin-induced wavy perturbation is present on disks of neutron-star low-mass X-ray binaries. By non-linearly coupling with the perturbation, some modes of disk oscillations resonantly interact with the disks. We examine the resonant conditions under the assumption that the disks are vertically isothermal. The results show that when the spin frequency has some pa...

Presolar SiC grains formed around Asymptotic Giant Branch (AGB) stars during their carbon-rich phase and contain heavy elements in trace amounts showing the signature of the slow neutron capture process (s process). Thanks to recent advances in analysis techniques, SiC data now provide extremely precise information on neutron capture cross sections and AGB models. For example, high-precision da...

Observations of thermonuclear (also called Type I) X-ray bursts from neutron stars in low mass X-ray binaries (LMXB) with the Rossi X-ray Timing Explorer (RXTE) have revealed large amplitude, high coherence X-ray brightness oscillations with frequencies in the 300 600 Hz range. Substantial spectral and timing evidence point to rotational modulation of the X-ray burst flux as the cause of these ...

We analyze several aspects of the recently noted neutron star collapse instability in close binary systems. We utilize (3+1) dimensional and spherical numerical general relativistic hydrodynamics to study the origin, evolution, and parametric sensitivity of this instability. We derive the modified conditions of hydrostatic equilibrium for the stars in the curved space of quasi-static orbits. We...

Quasi-periodic oscillations (QPOs) at frequencies near 1000 Hz were recently discovered in several x-ray binaries containing neutron stars. Two sources show no correlation between QPO frequency and source count rate (Berger et al. 1996, Zhang et al. 1996). We suggest that the QPO frequency is determined by the Keplerian orbital frequency near the marginally stable orbit predicted by general rel...

The origin of the magnetic fields in neutron stars, and the physical differences between magnetars and strongly magnetised radio pulsars are still under vigorous debate. It has been suggested that the properties of the progenitors of neutron stars (the massive OB stars), such as rotation, magnetic fields and mass, may play an important role in the outcome of core collapse leading to type II SNe...

Recent models based on General Relativity attribute important spectral features of some accreting neutron stars to their surfaces and ”gap accretion” while observations of x-ray novae indicate a surprising lack of distinguishing spectral characteristics between these neutron stars and black hole candidates. The shared spectral characteristics strongly suggest that both have surfaces without eve...

The work of J. A. Wheeler in the mid 1960’s showed that for smooth equations of state no stable stellar configurations with central densities above that corresponding to the limiting mass of ‘neutron stars’ (in the generic sense including hybrids) were stable. Accordingly, there has been no reason to expect that a stable degenerate family of stars with higher density than the known white dwarfs...

Context. Many thermally emitting, isolated neutron stars have magnetic fields that are larger than 1013 G. A realistic cooling model that includes the presence of high magnetic fields should be reconsidered. Aims. We investigate the effects of an anisotropic temperature distribution and Joule heating on the cooling of magnetized neutron stars. Methods. The 2D heat transfer equation with anisotr...