Neutron Stars. II. Neutrino-Cooling and Observability

Abstract

Calculations of the rates of the cooling reactions n+n→n+p+e-+νe and n+π-→n+e-+νe are presented; the rates of the closely related muon-producing reactions and the four inverse processes are also given. Several different arguments are used to obtain estimates of the relavant matrix elements. The nucleons are assumed to form a normal Fermi fluid with a continuous excitation spectrum. The calculated cooling rates indicate that a neutron star containing quasifree pions would cool within a few days to a temperature so low that the star would be unobservable. The surface of a star that does not contain quasifree pions would cool to 107 °K in a few months and would reach 4×10^6 °K in about 100 years. The calculated cooling rates strongly indicate that the discrete x-ray sources located in the direction of the galactic center are not neutron stars.

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