The Cerenkov iron Kα line in Active Galactic Nuclei - Calculation in the optically thin case

In this paper we continue the research on the Cerenkov origin of the iron Kα line in AGNs. We claim again that the newly recognized line emission mechanism, Cerenkov line-like radiation, could be significantly responsible for the observed iron K-lines of AGNs. We give a new model calculation of the luminosity of the iron Kα line in the optically thin condition, which is an important extension of our previous calculation in the optically thick case. The new calculation is also comparable to the typical observed luminosity of iron Kα line, thus confirming the effectiveness of the new mechanism. Besides, we analyze a possible negative influence of the hydrogen-dominated plasma upon the efficiency of Cerenkov line-like radiation in detail, which was ignored in our previous paper (You et al. 2003). We conclude that such a negative effect of the plasma oscillation is unimportant and can be neglected.