Fe K Emission and Absorption in the XMM-EPIC Spectrum of the Seyfert Galaxy IC 4329a

Abstract

We present a detailed analysis of the XMM-Newton long-look of the Seyfert galaxy IC 4329a. The Fe K bandpass is dominated by two resolved peaks at 6.4 and 7.0 keV, consistent with neutral or near-neutral Fe Kα and Kβ emission. There is a prominent redward asymmetry in the 6.4 keV line, which could indicate emission from a Compton shoulder. Alternatively, models using dual relativistic disk lines are found to describe the emission profile well. A low-inclination, moderately relativistic dual disk-line model is possible if the contribution from narrow components, due to distant material, is small or absent. A high-inclination, moderately relativistic profile for each peak is possible if there are roughly equal contributions from both the broad and narrow components. Combining the XMM-Newton data with RXTE monitoring data, we explore the time-resolved spectral behavior on timescales from hours to 2 years. We find no strong evidence for variability of the Fe K line flux on any timescale, likely due to the minimal level of continuum variability. We detect, at high significance, a narrow absorption line at 7.68 keV. This feature is most likely due to Fe XXVI Kα absorption blueshifted to ~0.1c relative to the systemic velocity, suggesting a high-velocity, highly ionized outflow component. As is often the case with similar outflows seen in high-luminosity quasars, the power associated with the outflow represents a substantial portion of the total energy budget of the AGN. The outflow could arise from a radiatively driven disk wind, or it may be in the form of a discrete, transient blob of ejected material.