Surface composition of magnetic neutron stars |
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Authors: | Leonard C Rosen A G W Cameron |
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Institution: | (1) Department of Physics and Astronomy, Dartmouth College, Hanover, N.H., USA;(2) Belfer Graduate School of Science, Yeshiva University, New York, N.Y., USA;(3) Goddard Institute for Space Studies, NASA, New York, N.Y., USA |
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Abstract: | The relative abundances of seven constitutent nuclei, He4, C12, O16, Ne20, Mg24, Si28 and Fe56, are calculated as a function of time for neutron star atmospheres within which exist magnetic fields of the order of 1013G. The opacity, equation of state of the electrons, and cooling rate of the magnetic star are discussed, and it is shown to be a reasonable approximation to assume an atmosphere to be isothermal. The effects of particle diffusion are included in the nuclear reaction network. Computations are performed both for a constant mass atmosphere and for an atmosphere in which mass is being ejected. It is found that the final abundances are model independent as long as the initial model contains predominantly He4. The relative abundances are compared to the cosmic ray spectrum. For both the constant mass and mass loss atmospheres, nucleosynthesis proceeds virtually completely to Fe56. However the outermost layers of the envelope, in which no mass is being ejected, are composed almost entirely of He4 with trace amounts of Fe56. After the loss of about 1021 g, only Fe56 is ejected from atmospheres expelling mass.A portion of the research on which this paper was based was performed while L. C. Rosen was present at the Lawrence Radiation Laboratory, Livermore, California. |
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