Circumstellar Matter in the Accretion Model of Cosmic X-Ray Sources

概要

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Matter accretion onto compact stars has been considered as a likely process of X-ray emission from stellar X-ray sources. The accreting matter forms a circumstellar envelope that absorbs a part of X-rays emitted from the central star. The ionization equilibrium due to the photoionization by X-rays and the recombination with electrons is calculated, and the optical depth for X-ray absorption is obtained as a function of the mass and radius of the central star, the absolute luminosity and the spectrum of X-rays. The K-absorption of oxygen and the L-absorption of iron are found to be responsible for the reduction of the X-ray intensity in the energy range 0.9〜3 keV. This is not in favour of the interpretation of Sco X-1 in terms of the accretion model, whereas the circumstellar absorption explains the X-ray spectrum of Cen X-3, thus further supporting the model that Cen X-3 is a neutron star belonging to a close binary system.
1973-08-25