Neutron stars are some of the densest manifestations of massive objects in the universe. They are ideal astrophysical laboratories for testing theories of dense matter physics and provide connections among nuclear physics, particle physics, and astrophysics. Neutron stars may exhibit conditions and phenomena not observed elsewhere, such as hyperon-dominated matter, deconfined quark matter, superfluidity and superconductivity with critical temperatures near 10 10 kelvin, opaqueness to neutrinos, and magnetic fields in excess of 10 13 Gauss. Here, we describe the formation, structure, internal composition, and evolution of neutron stars. Observations that include studies of pulsars in binary systems, thermal emission from isolated neutron stars, glitches from pulsars, and quasi-periodic oscillations from accreting neutron stars provide information about neutron star masses, radii, temperatures, ages, and internal compositions.

https://arxiv.org/pdf/astro-ph/0405262.pdf

The physics of neutron stars

Neutron Stars 1: Equation of State and Structure

Isospin asymmetry in nuclei and neutron stars

The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

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Physics of Neutron Star Crusts

Astrophysical methods to constrain axions and other novel particle phenomena

The neutrons inside neutron stars are almost certainly superfluid below a critical temperature T/subc/approx.10/sup 10/ K. Below T/subc/, pairs of excited neutron quasiparticles may recombine, resulting, if weak neutral currents exist, in the emission of neutrino-antineutrino pairs. We calculate the emissivity associated with this process and compare it with other neutrino emissivities. For neutron star interior temperatures in the range 10/sup 9/-10/sup 10/ K the recombination emissivity can dominate all others. (AIP)

Neutrino pair emission from finite-temperature neutron superfluid and the cooling of young neutron stars

We consider the astrophysical implications of, and limits on, possible weak neutral-tensor-current interactions. Such interactions give the neutrino dipole moments that permit it to couple directly to photons. Photons in an astrophysical plasma, with q/sup 2/ not-equal 0, then decay into ..nu..nu-bar pairs. We discuss astrophysical limits, based on a comparison of stellar evolution theory and observations, that can be set on the strength of this modified plasma neutrino-energy loss rate. We find that the best limit is probably set by a comparison of degenerate dwarf cooling times with observations of hot white dwarfs. We deduce that G/subT//G/subF/ approximately-less-than 1/15, where G/subT/ is the coupling constant for neutral tensor currents and G/subF/ is the Fermi coupling constant. (AIP)

Astrophysical Limitations on Possible Tensor Contributions to Weak Neutral Current Interactions

In the dense collapsing core of a star undergoing a supernova, electron-type neutrinos are produced by neutronization, and neutrino-antineutrino pairs of all types are produced by thermal processes. At some time the core plus an overlying mantle may become opaque to neutrinos, and large number densities of these particles may build up. Then scattering processes in which neutrinos can exchange energy are important for determing the energy distribution functions and the loss rates for the low-energy neutrinos which have smaller opacities. We calculate ..nu../sub e/-..nu../sub e/, ..nu../sub e/-nu-bar/sub e/, and ..nu../sub e/-..nu../sub mu/ scattering rates. We find that all three rates are comparable to that for ..nu../sub e/-e scattering and hence they also may play an important role. (AIP)

Neutrino-neutrino scattering and supernovae.

A diamond as big as the ritz

In neutron star matter over the density range 4.3×1011<-ϱ≤4×1014 g cm−3 there are both free neutrons and neutron-rich nuclei. If there is a weak neutral current interaction between neutrinos and neutrons, as suggested by recent experiments, then when neutrons scatter off nuclei they may emit\(v\bar v\) pairs as bremsstrahlung radiation. We calculate the associated emissivity for degenerate (but not superfluid) neutrons and uncorrelated (not crystallized) nuclei. We find that, under these conditions. this emissivity can under some conditions compare with that calculated by Festa and Ruderman for\(v\bar v\) bremsstrahlung in electron-nucleus collisions.

Elliott G. Flowers

Papers

Neutrino pair emission from finite-temperature neutron superfluid and the cooling of young neutron stars

Astrophysical Limitations on Possible Tensor Contributions to Weak Neutral Current Interactions

Neutrino-neutrino scattering and supernovae.

A diamond as big as the ritz

Neutrino-pair bremsstrahlung in collisions between neutrons and nuclei in neutron star matter