2024ApJ...963...38L

Iron Kα (Fe Kα) emission is observed ubiquitously in active galactic nuclei (AGN), and it is a powerful probe of their circumnuclear environment. Examinations of the emission line play a pivotal role in understanding the disk geometry surrounding black holes. It has been suggested that the torus and the broad-line region (BLR) are the origins of emission. However, there is no universal location for the emitting region relative to the BLR. Here, we present an analysis of the narrow component of the Fe Kα line in the Seyfert AGN MCG-5-23-16, one of the brightest AGN in X-rays and in Fe Kα emission, to localize the emitting region. Spectra derived from Chandra/HETGS observations show asymmetry in the narrow Fe Kα line, which has only been confirmed before in the AGN NGC 4151. Models including relativistic Doppler broadening and gravitational redshifts are preferred over simple Gaussians and measure radii consistent with R ≃ 200-650 r_g. These results are consistent with those of NGC 4151 and indicate that the narrow Fe Kα line in MCG-5-23-16 is primarily excited in the innermost part of the optical BLR, or X-ray BLR. Characterizing the properties of the narrow Fe Kα line is essential for studying the disk geometries of the AGN population and mapping their innermost regions.