X-ray view of four high-luminosity Swift/BAT AGN: Unveiling obscuration and reflection with Suzaku

TL;DR

This study uses Suzaku X-ray observations to analyze four luminous Swift/BAT AGN, revealing details about obscuration, reflection, and variability, and identifying a candidate Compton-thick AGN among them.

Contribution

It provides detailed X-ray spectral analysis of four high-luminosity AGN, highlighting the properties of obscuration and reflection, and identifying a potential Compton-thick AGN candidate.

Findings

3C 452 is a likely Compton-thick AGN candidate.

3C 105 shows significant long-term variability.

The sample confirms high X-to-[OIII] luminosity ratios.

Abstract

The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10^-11 erg cm^-2 s^-1 and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 < Log L(BAT) < 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (<0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density, X-ray luminosity and radio morphology, but shows a strong long-term variability in flux and scattering fraction, consistent with the soft emission being scattered from a distant region (e.g., the narrow emission line region). The sample presents high (>100) X-to-[OIII] luminosity ratios, confirming the [OIII] luminosity to be affected by residual extinction in presence of mild absorption, especially for "buried" AGN such as 3C 452. Three of our targets are powerful FRII radio galaxies, making them the most luminous and absorbed AGN of the BAT Seyfert survey despite the inversely proportional N_H - L_X relation.