Suzaku observation of IRAS 00521-7054, a peculiar type-II AGN with a very broad feature at 6 keV

TL;DR

This study analyzes Suzaku X-ray data of IRAS 00521-7054, a peculiar type-II AGN with an extremely broad Fe Kα line, exploring models involving ionized absorption and blurred reflection to explain its spectral features.

Contribution

It provides the first detailed analysis of IRAS 00521-7054's X-ray spectrum, proposing two viable models involving ionized absorption and relativistic reflection.

Findings

Confirmed a strong Fe Kα excess at 6 keV with EW ~800 eV

Both absorption and reflection models fit the data well

The source may be an obscured narrow-line Seyfert 1

Abstract

IRAS 00521$-$7054 is the first Seyfert 2 in which the presence of an extremely large Fe K$\alpha$ line has been claimed. We report here on the analysis of a 100 ks Suzaku observation of the source. We confirm the existence of a very strong excess over the power-law X-ray continuum at $E\sim6$ keV ($EW\simeq 800$ eV), extending down to $\sim 4.5$ keV, and found that the X-ray spectrum of the source can be explained by two different models. i) An absorption scenario, in which the X-ray source is obscured by two fully-covering ionized absorbers, with a strong reflection component from neutral material ($R\sim 1.7$), a black body component and four narrow Gaussian lines (corresponding to Fe K$\alpha$, Fe K$\beta$, Fe xxv and Fe xxvi). ii) A reflection scenario, in which the X-ray spectrum is dominated by an obscured ($\log N_{\rm\,H}\sim 22.9$) blurred reflection produced in an ionized disk around a rotating supermassive black hole with a spin of $a \geq 0.73$, and affected by light-bending ($R\sim 2.7$), plus two narrow Gaussian lines (corresponding to Fe K$\alpha$ and Fe K$\beta$). The narrow Fe K$\alpha$ and K$\beta$ lines are consistent with being produced by ionized iron, and in particular by Fe xiv-Fe xvi and Fe xii-Fe xvi for the absorption and reflection scenario, respectively. While the X-ray continuum varies significantly during the observation, the intensity of the broad feature appears to be constant, in agreement with both the absorption and reflection scenarios. For both scenarios we obtained a steep power-law emission ($\Gamma\sim 2.2-2.3$), and we speculate that the source might be an obscured narrow-line Seyfert 1.