The iron emission lines Kα and Kβ in active galactic nuclei — A further piece of evidence for the Cerenkov line-like radiation*†

Abstract It has been recently observed by XMM-Newton that besides the emission line of iron K α at 6.4 keV there also exists in the Seyfert 1 galaxy NGC 3783 the very intense emission line of iron K β at 7.0 keV. Moreover, the ratio of equivalent widths (EWs) of these two lines can hardly be interpreted with the traditional mechanism of “photoelectric absorption — fluorescence emission”. By using the mechanism of Cerenkov line-like radiation proposed by YOU Jun-hian et al., the ratio of EW K α /EW K β may be reasonably interpreted by means of a detailed model theoretical computation. As shown by the results, the iron K lines in active galactic nuclei (AGNs) are formed not only by the fluorescence mechanism, but also by the Cerenkov line-like radiation. Both coexist in AGNs, with the latter playing the dominant role.