A further argument for the iron lines in active galactic nuclei arising from cerenkov line-like radiation - Calculation for an optically thin case

Confronted by observations, the difficulties to explain the formation of the iron Kα lines in active galactic nuclei (AGNs) in the context of the current “reflection disk-photoelectric absorption-fluorescence line” model are discussed in detail, and it is further pointed out that a newly recognized line emission mechanism - the Cerenkov line-like radiation could be the dominant mechanism to produce the AGN iron Kα line. The negative effect of the hydrogen plasma on the refractive index is proved to be negligible. The Cerenkov iron Kα line emission is calculated for the optically thin case and compared with the observations. The reasonableness of this new mechanism is verified, thus providing a new scenario for the physical situation around a black hole.