Stars pulsars

The high-density phases of QCD at low temperatures can be realized in rotating compact stars - pulsars. Therefore, the observational data from pulsars could provide potentially important information on the state of matter at super-nuclear densities, in particular the superconducting quark matter. 

Figure 8.6 A spinning neutron star (pulsar) appears from Earth to flash with a bright pulse of radiation that matches the period of its rotation. Charged particles near the star s surface rotate with the magnetic field and give off electromagnetic radiation.

Rapidly rotating neutron stars (pulsars) tend to be axisym-metric however, they must break this symmetry in order to radiate gravitationally. Several mechanisms may lead to deformations of the star, or to precession of its rotation axis, and hence to gravitational wave emission. The characteristic amplitude of gravitational waves from neutron stars at 10 kpc distance scales as... 

BINARY Stars Galactic Structure and evolution Geomagnetism Interstellar matter Neutron Stars Pulsars Solar System, Magnetic AND Electric Fields Stellar Structure and Evolution... 

Discovery of first pulsar (i.e. neutron star) announced (A. Hewish, J. Bell et al.). 

This represents an upper limit for the dimensions of the nucleus. Compared with the estimates for the size of the atom, obtained from kinetic theory calculations on gases, which are typically 4x10 9 m. we can see that the nucleus is very small indeed compared to the atom as a whole - a radius ratio of 10-5, or a volume ratio of 10 15, which supports Rutherford s observation that most of an atom consists of empty space. We can also conclude that the density of the nucleus must be extremely high - 1015 times that encountered in ordinary matter, consistent with density estimates in astronomical objects called pulsars or neutron stars. 

The problem of rotation of neutron stars in the framework of General Relativity Theory was solved before the discovery of pulsars and the important contribution of the Armenian scientists in this work is well documented. With all... 

Abstract From the earliest measurements of the masses of binary pulsars, observations of neutron stars have placed interesting constraints on the properties of high-density matter. The last few years have seen a number of observational developments that could place strong new restrictions on the equilibrium state of cold matter at supranuclear densities. We review these astronomical constraints and their context, and speculate on future prospects. 

The commonly accepted pulsar model is a neutron star of about one solar mass and a radius of the order of ten kilometers. A neutron star consists of a crust, which is about 1 km thick, and a high-density core. In the crust free neutrons and electrons coexist with a lattice of nuclei. The star s core consists mainly of neutrons and a few percents of protons and electrons. The central part of the core may contain some exotic states of matter, such as quark matter or a pion condensate. Inner parts of a neutron star cool up to temperatures 108iT in a few days after the star is formed. These temperatures are less than the critical temperatures Tc for the superfluid phase transitions of neutrons and protons. Thus, the neutrons in the star s crust and the core from a superfluid, while the protons in the core form a superconductor. The rotation of a neutron superfluid is achieved by means of an array of quantized vortices, each carrying a quantum of vorticity... 

In section I we consider the dynamics of rotation of a two-component neutron star and obtain the relaxation solutions for spin-down rate of the star. In section II we compare our solutions for the relaxation process with the observation data from the Vela pulsar. 

Figure 1. The dependence of AO + AQ,S on the radius of the star for the first glitch of Vela pulsar.

Alpar, A. (2003), Accretion models for young neutron stars , in Pulsars, AXPs and SGRs observed with BeppoSAX and other observatories . Edited by G. Cusumano, E. Massaro, T. Mineo. p. 197 [astro-ph/0306179]. 

Colpi, M., Wasserman, I. (2002), Formation of an evanescent proto-neutron star binary and the origin of pulsar kicks , ApJ 581, 1271. 

Hobbs, G. Manchester, R. Teoh, A. Hobbs, M. (2003), The ATNF Pulsar Catalogue , in Proc. of IAU Symp. 218 Young neutron stars and their environment [astro-ph/0309219]. 

Lai, D., Chernoff, D.F. Cordes, J.M. (2001), Pulsar jets implications for neutron star kicks and initial spins , ApJ 549, 1111. 

Nice, D.J., Splaver, E.M. (2003), Heavy neutron stars A status report on Arecibo timing of four pulsar - white dwarf systems , astro-ph/0311296. 

Neutron and quark stars are natural laboratories to investigate the interplay of strong, electro-weak and gravitational interaction. Many theoretically determined properties of these astrophysical objects were tested by the observed properties of pulsars, and detailed calculations exist for these stars[ 1 —4. ... 

In Fig. 5, we show the limiting mass Mum calculated in the case of the GMl+Bag model (dashed line) and in the case of the GM3+Bag model (continuous line) as a function of the bag constant B. In the same figure, we compare our theoretical determination for Mnm with some of the measured masses of compact stars in radio pulsar binaries (Thorsett Chakrabarty 1999) and for the compact stars VelaX-1 (Quaintrell et al. 2003) and Cygnus X-2 (Orosz Kuulkers 1999). 

Figure 5. The limiting (gravitational) mass Mum, according to generalized definition given in the present work, is plotted as a function of the Bag constant. Solid (dashed) lines show the results for the GM3+Bag (GMl+Bag) model. In both cases we take a = 30 MeV/fm2. The values of some measured masses of compact stars in radio pulsars and in Vela X-l and Cygnus X-2 are also reported for comparison.

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