Tracking the spectral properties of ESO 511-G030 across different epochs

Abstract

The Type 1 active galactic nucleus (AGN) ESO 511-G030, a formerly bright and soft excess dominated source, was observed in 2019 in the context of a multi-wavelength monitoring campaign. In the new exposures, the source was found to be in a flux state approximately ten times lower than archival exposures and without any trace of the soft excess. Interestingly, the X-ray weakening observed in the 2019 data corresponds to a comparable fading of the UV flux, suggesting a strong link between these two components. The UV-X-ray spectral energy distribution (SED) of ESO 511-G030 shows remarkable variability. We tested both phenomenological and physically motivated models on the data, finding that the overall emission spectrum of ESO 511-G030 in this extremely low flux state is due to the superposition of a power-law-like continuum (Γ ∼ 1.7) and two reflection components emerging from hot and cold matter. Both the primary X-ray continuum and relativistic reflection are produced in the inner regions close to the supermassive black hole. The prominent variability of ESO 511-G030 and the lack of a soft excess can be explained by the dramatic change in the observed accretion rate, which dropped from an L/LEdd of 2% in 2007 to one of 0.2% in 2019. The X-ray photon index also became harder during the low flux observations from 2019, perhaps as a result of a photon starved X-ray corona.