Iron K and K lines in active galactic nuclei (AGNs). Evidence of the existence of the Cerenkov line-like radiation

The update observation of XMM-Newton shows that, except for the iron K line at~ 6.4keV, there is also an apparent iron K line at~7.0keV in Seyfert 1 galaxy NGC 3783 with intensity markedly higher than that predicted by the traditional fluorescence emission. The observed ratio of the equivalent widths EW K/ EW K 3.43 is difficult to understand from the photoelectric absorption-fluorescence emission' mechanism. In this paper, we argue that the new Cerenkov line-like radiation mechanism suggested by You et al. can provide a solution for the puzzle of EW K/ EW K.We present a detailed model consideration and theoretical calculation. Our calculated result shows that, except for the fluorescence emission, there coexists a Cerenkov line-like radiation mechanism in AGNs, which gives a significant contribution to the iron K-line emission, even moderately higher than the former.