Analysis of the warm absorber in NGC 6814

Abstract

NGC 6814, a Seyfert 1.5 Active Galactic Nucleus (AGN) at redshift z = 0.00522, is a compelling object to study due to its high X-ray variability and the presence of photoionized gas outflows. In 2016, a rapid occultation event, indicative of the presence of a highly ionized absorbing gas, was detected in NGC 6814, presenting a unique opportunity to investigate the properties, size, and location of the eclipsing gas. The primary objective of this work is to probe the warm absorber in NGC 6814 using high-resolution spectra from 2021, comparing the properties of the warm absorber with those from the obscuring gas observed in 2016. This analysis aims to unveil insights into the origin of the eclipsing gas and provide further details on the properties and kinematics of the central region of NGC 6814. This work reveals that two warm absorbing models with similar velocities but varying ionisations and densities are statistically required to fit the absorption features in the spectrum, with some features remaining unfitted. A picture can be drawn of the warm absorption system in NGC 6814, where both warm absorbing clouds are a part of the same medium moving outwards at a velocity of ≈ 2500 km s^−1, or that the two warm absorbers are describing an ionisation and density gradient within the same cloud.