Exploring the complex X-ray spectrum of NGC 4051

Archival XMM–Newton data on the nearby Seyfert galaxy NGC 4051, taken in relatively high‐ and low‐flux states, offer a unique opportunity to explore the complexity of its X‐ray spectrum. We find the hard X‐ray band to be significantly affected by reflection from cold matter, which can also explain a non‐varying, narrow Fe K fluorescent line. We interpret major differences between the high‐ and low‐flux hard X‐ray spectra in terms of the varying ionization (opacity) of a substantial column of outflowing gas. An emission‐line spectrum in the low‐flux state indicates an extended region of photoionized gas. A high‐velocity, highly ionized outflow seen in the high‐flux state spectrum can replenish the gas in the extended emission region over ∼103 yr, while having sufficient kinetic energy to contribute significantly to the hard X‐ray continuum.