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

It has been recently observed by XMM-Newton that besides the emission line of iron Kα at 6.4 keV there also exists in the Seyfert 1 galaxy NGC 3783 the very intense emission line of iron Kβ 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 EWKα/EWKβ 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.