Stars, neutron

Neutron stars. Neutron stars are compact Cns 0.3) relativistic objects. They can participate to the emission of gravitational waves following different mechanisms, either alone or in binary systems. 

Coalescing neutron star binaries. Coalescing of neutron stars (or black holes) is foreseen to be the the most powerful source of detectable gw. The frequency of such events is estimated to be ly D/200 Mpc) and their amplitude will allow detection of sources as far as 50 Mpc. We are thus waiting for about one event every 60 years with the current sensitivity of detectors. 

Black holes. One great achievement of gravitational wave astronomy would be the first detection of a signal coming directly from a black hole. Just like with neutron stars, black holes can emit gw either alone or in binary systems. 

Coalescence of black holes. The coalescence of two black holes will generate even more gravitational waves than neutron stars coalescence, and coalescence of two lOM black holes will be detectable up to 500 Mpc... 

Proc. of the International summer school on Experimental physics of gravitational waves, (Barone, M. et al. Eds., World Scientihc, London 2000). Contains a valuable chapter on General relativity by P. Tourrenc (contains a precise description of the various coordinates systems and their use, OBLIGATORY), a chapter by S. Bonazzola and E. Gourgoulhon on compact sources, in particular neutron stars, and a chapter by Jean-Yves Vinet on numerical simulations of interferometric gw detectors. 

The composition of the Earth was determined both by the chemical composition of the solar nebula, from which the sun and planets formed, and by the nature of the physical processes that concentrated materials to form planets. The bulk elemental and isotopic composition of the nebula is believed, or usually assumed to be identical to that of the sun. The few exceptions to this include elements and isotopes such as lithium and deuterium that are destroyed in the bulk of the sun s interior by nuclear reactions. The composition of the sun as determined by optical spectroscopy is similar to the majority of stars in our galaxy, and accordingly the relative abundances of the elements in the sun are referred to as "cosmic abundances." Although the cosmic abundance pattern is commonly seen in other stars there are dramatic exceptions, such as stars composed of iron or solid nuclear matter, as in the case with neutron stars. The... 

This is an extremely small quantity, which combined with the also extremely small interaction of gravitational waves (GWs) with matter makes it impossible to generate and detect GW on earth. Fast conversions of solar-size masses are required to produce signals with amplitudes that could be detectable. Astrophysical sources are for instance supernova explosions or a collision of two neutron stars or black holes. 

Low (<1 solar mass) Middle (5-10 solar masses) High (>20 solar masses) Protostar — pre-main sequence — main sequence — red giant — planetary nebula — white dwarf — black dwarf Protostar - main sequence — red giant — planetary nebula or supernova —> white dwarf or neutron star Protostar — main sequence —> supergiant — supernova — neutron star... 

Neutron star A very compact dense stellar remnant that is stabilised with respect to collapse by the degenerate neutron gas composition of the star. 

The result of all these processes is that the Sun was bom 4.6 Gyr ago with mass fractions X 0.70, Y 0.28, Z 0.02. These abundances (with perhaps a slightly lower value of Z) are also characteristic of the local ISM and young stars. The material in the solar neighbourhood is about 15 per cent gas (including dust which is about 1 per cent by mass of the gas) and about 85 per cent stars or compact remnants thereof these are white dwarfs (mainly), neutron stars and black holes. 

Degeneracy, white dwarfs and neutron stars 5.4.1 Introduction... 

The site of the r-process is also not clear, but it seems that the conditions needed to reproduce Solar-System r-process abundances may hold in the hot bubble caused by neutrino winds in the immediate surroundings of a nascent neutron star in the early stages of a supernova explosion (see Fig. 6.10). Circumstantial evidence from Galactic chemical evolution supports an origin in low-mass Type II supernovae, maybe around 10 M (Mathews, Bazan Cowan 1992 Pagel Tautvaisiene 1995). Another possibility is the neutrino-driven wind from a neutron star formed by the accretion-induced collapse of a white dwarf in a binary system (Woosley Baron 1992) leading to a silent supernova (Nomoto 1986). In stars with extreme metal-deficiency, the heavy elements sometimes display an abundance pattern characteristic of the r-process with little or no contribution from the s-process, and the... 

The question of upper mass limits to stars which explode as SN II and leave neutron-star remnants is discussed by Maeder (1992,1993) and by Brown, Bruenn and Wheeler (1992) it is highly controversial. (Note that Koppen and Arimoto (1991) when referring to the Scalo IMF use the version with b T) = 1, as I have done, whereas Maeder (1993) uses the version with b (T) = 0.48, corresponding to yields that are 3 times higher )... 

Discovery of the neutron (Chadwick) and positron (Dirac, Anderson). First nuclear reaction induced in an accelerator (7Li(/ , a) Cockcroft and Walton). Baade and Zwicky suggest a neutron star may be created as residue of a supernova explosion. 

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

We report on a new force that acts on cavities (literally empty regions of space) when they are immersed in a background of non-interacting fermionic matter fields. The interaction follows from the obstructions to the (quantum mechanical) motions of the fermions in the Fermi sea caused by the presence of bubbles or other (heavy) particles immersed in the latter, as, for example, nuclei in the neutron sea in the inner crust of a neutron star. 

This topic is relevant to the physics of neutron stars (nuclei or quark bubbles embedded in a neutron gas), to dilute Bose-Einstein-condensate bubbles inside the background of a Fermi-Dirac condensate, to buckyballs in liquid mercury and to superconducting droplets in a Fermi liquid. 

The investigation of bubbles inside a Fermi gas background is also of relevance for the inner core of neutron stars namely, under the assumption that quark droplets will form, there exists a similar pattern with the quark droplet phase taking over the role of the embedded nuclei. 

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