Extreme Relativistic Reflection in the Active Galaxy ESO 033-G002

TL;DR

This study presents a detailed broadband X-ray analysis of the Seyfert galaxy ESO 033-G002, revealing extreme relativistic reflection, a compact corona, and a rapidly rotating black hole, advancing understanding of AGN inner regions.

Contribution

First high signal-to-noise broadband X-ray spectrum of ESO 033-G002, disentangling complex absorption and reflection components, and constraining black hole spin and corona properties.

Findings

Extreme disc reflection with high reflection fraction (~5).

Compact corona within ~2 gravitational radii of the black hole.

Rapid black hole spin with a* > 0.96.

Abstract

We present the first high signal-to-noise broadband X-ray spectrum of the radio-quiet type-2 Seyfert ESO 033-G002, combining data from $XMM$-$Newton$ and $NuSTAR$. The nuclear X-ray spectrum is complex, showing evidence for both neutral and ionised absorption, as well as reflection from both the accretion disc and more distant material, but our broadband coverage allows us to disentangle all of these different components. The total neutral column during this epoch is $N_{\rm{H}} \sim 5-6 \times 10^{22}$ cm$^{-2}$, consistent with the optical classification of ESO 033-G002 as a type-2 Seyfert but not so large as to prevent us from robustly determining the properties of the innermost accretion flow. The ionised absorption - dominated by lines from Fe XXV and Fe XXVI - reveals a moderately rapid outflow ($v_{\rm{out}} \sim 5400$ km s$^{-1}$) which has a column comparable to the neutral absorption. We find the disc reflection from the innermost regions to be extreme, with a reflection fraction of $R_{\rm{frac}} \sim 5$. This requires strong gravitational lightbending and, in turn, both an extremely compact corona (within $\sim$2 $R_{\rm{G}}$ of the black hole) and a rapidly rotating black hole ($a^* > 0.96$). Despite this tight size constraint, with a temperature of $kT_{\rm{e}} = 40-70$ keV the X-ray corona in ESO 033-G002 appears similar to other AGN in terms of its placement in the compactness-temperature plane, consistent with sitting close to the limit determined by runaway pair production. Finally, combining X-ray spectroscopy, timing and updated optical spectroscopy, we also estimate the mass of the black hole to be $\log[M_{\rm{BH}} / M_{\odot}] \sim 7.0 - 7.5$.