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Astron. Astrophys. 343, 1009-1024 (1999)

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Neutrino-pair bremsstrahlung by electrons in neutron star crusts

A.D. Kaminker 1, C.J. Pethick 2,3, A.Y. Potekhin 1, V. Thorsson 2,4 and D.G. Yakovlev 1

1 Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St.-Petersburg, Russia
2 Nordita, Blegdamsvej 17, DK-2100 Copenhagen O, Denmark
3 Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, USA
4 Department of Physics, University of Washington, Box 351560, Seattle, Washington 98195-1560, USA

Received 9 September 1998 / Accepted 10 December 1998


Neutrino-pair bremsstrahlung by relativistic degenerate electrons in a neutron-star crust at densities [FORMULA] g cm-3 [FORMULA] g cm-3 is analyzed. The processes taken into account are neutrino emission due to Coulomb scattering of electrons by atomic nuclei in a Coulomb liquid, and electron-phonon scattering (the phonon contribution) and Bragg diffraction (the static-lattice contribution) in a Coulomb crystal. The static-lattice contribution is calculated including the electron band-structure effects for cubic Coulomb crystals of different types and also for the liquid crystal phases composed of rod- and plate-like nuclei near the bottom of the neutron-star crust ([FORMULA] g cm[FORMULA] g cm-3). The phonon contribution is evaluated with proper treatment of the multi-phonon processes which removes a jump in the neutrino bremsstrahlung emissivity at the melting point obtained in previous works. Generally, bremsstrahlung in the solid phase does not differ significantly from that in the liquid. At [FORMULA] g cm-3, the results are rather insensitive to the nuclear form factor, but results for the solid state near the melting point are affected significantly by the Debye-Waller factor and multi-phonon processes. At higher densities the Debye-Waller factor and multi-phonon processes become less important but the nuclear form factor becomes more significant. With growing [FORMULA], the phonon contribution becomes smaller. Near the bottom of the neutron star crust bremsstrahlung becomes less efficient due to the reduction of the effective electron-nucleus matrix element by the electron band-structure effects and the nuclear form factor. A comparison of the various neutrino generation mechanisms in neutron star crusts shows that electron bremsstrahlung is among the most important ones.

Key words: dense matter – stars: neutron

Present address: Department of Molecular Biotechnology, University of Washington, Box 357350, Seattle, Washington 98195-7350, USA

Send offprint requests to: C.J. Pethick (pethick@nordita.dk)

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999