EDP Sciences
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Volume 439, Number 2, August IV 2005
Page(s) 427 - 432
Section Astrophysical processes
DOI http://dx.doi.org/10.1051/0004-6361:20042263

A&A 439, 427-432 (2005)
DOI: 10.1051/0004-6361:20042263

Neutrino emission rates in highly magnetized neutron stars revisited

M. Riquelme1, A. Reisenegger1, O. Espinosa2 and C. O. Dib2

1  Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
    e-mail: areisene@astro.puc.cl
2  Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile

(Received 27 October 2004 / Accepted 2 April 2005)

Magnetars are a subclass of neutron stars whose intense soft-gamma-ray bursts and quiescent X-ray emission are believed to be powered by the decay of a strong internal magnetic field. We reanalyze neutrino emission in such stars in the plausibly relevant regime in which the Landau band spacing $\Delta
E$ of both protons and electrons is much larger than kT (where k is the Boltzmann constant and T is the temperature), but still much smaller than the Fermi energies. Focusing on the direct Urca process, we find that the emissivity oscillates as a function of density or magnetic field, peaking when the Fermi level of the protons or electrons lies about ~3 kT above the bottom of any of their Landau bands. The oscillation amplitude is comparable to the average emissivity when $\Delta
E$ is roughly the geometric mean of kT and the Fermi energy (excluding mass), i.e., at fields much weaker than required to confine all particles to the lowest Landau band. Since the density and magnetic field strength vary continuously inside the neutron star, there will be alternating surfaces of high and low emissivity. Globally, these oscillations tend to average out, making it unclear whether there will be any observable effects.

Key words: dense matter -- neutrinos -- stars: magnetic fields -- stars: neutron

© ESO 2005