Electron-positron and photon wind from the surface of a strange star |
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| Authors: | A G Aksenov |
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| Institution: | (1) Institute for Theoretical and Experimental Physics, ul. Bol'shaya Cheremushkinskaya 25, Moscow, 117259, Russia |
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| Abstract: | We consider the problem of strange-star (SS) radiation. The bare quark SS surface and electrons on the stellar surface generate an electric field that is strong enough for electron-positron pairs to be produced from a vacuum at a nonzero temperature. The luminosity in pairs is assumed to be within ?1049 erg s?1 from a surface with a characteristic radius of 10 km. We consider the energy transfer from pairs to photons by taking into account the well-studied reactions between e, e +, γ and obtain a change in the photon spectrum with luminosity. Our analysis is restricted to the spherically symmetric case. The magnetic field is disregarded. To solve the problem, we developed a new numerical method of integrating the Boltzmann kinetic equations for pairs and photons. This method is used to calculate the problem up to a luminosity of 1042 erg s?1 This region is difficult to investigate when the optical path for pairs or photons is considerably larger than unity but the two optical depths are not simultaneously much larger than unity (when hydrodynamics with heat conduction is applicable). It turns out that the mean photon energy is approximately equal to $\bar \in _\gamma \approx m_e c^2$ (the annihilation line for pairs) at a modest luminosity, L?1×1037 erg s?1, and decreases to ≈210 keV at L?1038 erg s?1. Hydrodynamic estimates point to an increase in the mean energy $\bar \in _\gamma$ to 1 MeV as the luminosity further increases to L?1049 erg s?1. Our calculations may prove to be useful in interpreting soft gamma repeaters (SGRs) and are of methodological interest. |
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| Keywords: | neutron stars γ -ray radiation radiation mechanism |
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