A spectral energy distribution variability study of the eclipsing AGN NGC 6814

ABSTRACT The local Seyfert 1.5 active galactic nucleus, NGC 6814, is known to exhibit complex variability, eclipses, and even changing-look behaviour. In this work, we utilize optical-to-X-ray data obtained over 10 yr with the Neil Gehrels Swift Observatory to examine the short-term (i.e. daily) and long-term (yearly) variations in the spectral energy distribution (SED). This includes three epochs of high-cadence monitoring (2012, 2016, and 2022), as well as two single observations (2019 and 2021). Model-independent methods of examining the variability suggest that the three monitored epochs exhibit distinct behaviour. X-ray weakness in 2016 can be attributed to the previously studied eclipses, while similar behaviour in 2012 is associated with continuum changes and slight neutral absorption. The multi-epoch SED models are consistent with a black hole (${\log (M_{\rm BH}/\rm{\rm \, {\rm M}_{\odot }}{})\approx 7.6}$) that is accreting between $\dot{m}\approx 0.01-0.1$. While the corona (primary X-ray source) is compact, all epochs are better fit with an accretion disc inner radius that is much larger than the innermost stable circular orbit, implying the possibility of a non-standard accretion disc or central structure in NGC 6814.