2001ApJ...549..891W

We present a detailed analysis of iron Kα line variabilities in NGC 4151 using long ASCA observation data obtained in 1995 May. Despite the relatively small amplitude variations in the continuum flux, the iron Kα line flux and profile show dramatic variations. Particularly, the line profile changes from a single peak to what appears to be double peaks and back in timescales of a few times 10⁴ s. The apparently double-peaked profiles can be well interpreted as line emission from a Keplerian ring around a massive black hole. An absorption line at around 5.9 keV is also marginally detected. We discuss current Fe K line models, but none of them can well explain the observed line and continuum variations.