NICER observation list: Target ID 453401

Challenges to the standard model of the circumnuclear environment in AGN were found in recent observations of local AGN. The narrow Fe K line in X-rays is a powerful probe of these environments. Recent observations of the brightest Fe K line in NGC 4151 enabled the emission region to be localized using the line asymmetry and the reverberation delay. It was found that a significant fraction of the line is emitted in a region smaller than the BLR. This is a new powerful tool to probe the circumnuclear environment of the black hole. Here, we propose to monitor MCG-5-23-16 for 100 ks over a six months period to track the Fe K line variability and search for time delays. The unique monitoring capability of NICER will allow unprecedented view of the line emitting region and its location.