Pulsar

Perhaps the most remarkable object in the sample of known gamma-ray-emitting pulsars is Geminga. For 

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M. Ryle and A, Hewish (Cambridge) pioneering research in radioastrophysics Ryle for his observations and inventions, in particular of the aperture-synthesis technique, and Hewish for his decisive role in the discovery of pulsars. 

R. A. Hulse and J. H. Taylor (Princeton) discovery of a new type of pulsar, that has opened up new possibilities for the study of gravitation. 

Keywords gravitational waves, PSR1913+16 pulsar, relativistic objects, gravitational wave... 

The binary pulsar PSR1913+16. In 1974 Russell Hulse and Joseph Taylor discovered a very special pulsar PSR1916+13. A striking feature that was revealed just after its discovery was a large shift of the pulses rate with a period of a few hours. This was explained by Doppler shift, so PSR1916-H13 is in fact a binary system in which a pulsar orbits about the center of mass of the system. Thanks to the presence of this very stable local clock, Hulse and Taylor were able to obtain all the orbital parameters of this system. By studying the variations of those parameters over nearly twenty years, they... 

Determination of Mass Transfer Coefficient (kLa) in a Municipal Wastewater Treatment Plant (with PULSAR aerators)... 

The PULSAR units are high efficiency static aerators that have been developed for municipal wastewater treatment plants and have successfully been used over extended periods of time without any operational problems such as unstable operation or plugging up during intermittent operation of the air pumps (Chourda-kis, 1999). Data have been collected from a pilot plant unit at the Wastewater Treatment plant of the Industrial Park (Herakleion, Crete). A series of experiments were conducted for the determination of the mass transfer coefficient (kLa) and are shown in Figure 17.4. The data are also available in tabular form as part of the parameter estimation input files provided with the enclosed CD. 

Figure 17.4 PULSAR Measurements of Dissolved Oxygen (DO) Concentration During a Dynamic Gassing-in/Gassing-out Experiment.

Figure 17.5 PULSAR Determination of Oxygen Uptake Rate by Simple Linear Least Squares During the Gassing-out Period...

Table 17.7 PULSAR Reduction of the LS Objective Function and Convergence to the Optimum (Three Parameters)...

Chourdakis, A., "PULSAR Oxygenation System", Operation Manual, Herakleion, Crete (1999). 

Fig. 1.18 General view of the Pulsar system. Each applicator is connected to one or two microwave generators set in both side parts of the equipment (courtesy of MES company).

Until now, no certain evidence of the existence of GWs has been found. However Hulse and Taylor, studying the PSR 1913+13 binary system of pulsars, found that experimental data were fully coherent with the hypothesis that part of the system energy was lost through gravitational radiation [52-54],... 

R.A. Hulse The discovery of the binary pulsar, Les Prix Nobel 1993, 58-79. The Nobel Foundation (1994)... 

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

T. Gold identifies spin-down of central pulsar as energy source for Crab Nebula. 

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... 

Several theories were proposed in the past to describe the postglitch relaxation of pulsars angular velocity. Each physical model considers the spin-down of the superfluid in a different way. Alpar et al. [3, 4] suggest that the crustal superfluid is responsible for the glitches and postglitch relaxation they describe the dynamical properties of the crust superfluid in terms of a thermal... 

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. 

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