Iron line profiles in Suzaku spectra of bare Seyfert galaxies

TL;DR

This study models Suzaku spectra of six 'bare' Seyfert galaxies to analyze Fe K line profiles, revealing common ionized emission lines, moderate relativistic broadening, and constraints on black hole spins, improving understanding of AGN accretion physics.

Contribution

It provides a detailed, physically motivated analysis of Fe K lines in bare Seyferts, including new spin measurements and the impact of ionized lines on relativistic modeling.

Findings

Ionized lines at 6.7 and 6.97 keV are common.

Moderately broad emission originates from tens of Rg.

Black holes are not maximally spinning, with specific spin constraints for Mrk 335 and NGC 7469.

Abstract

We methodically model the broad-band Suzaku spectra of a small sample of six 'bare' Seyfert galaxies: Ark 120, Fairall 9, MCG-02-14-009, Mrk 335, NGC 7469 and SWIFT J2127.4+5654. The analysis of bare Seyferts allows a consistent and physical modelling of AGN due to a weak amount of any intrinsic warm absorption, removing the degeneracy between the spectral curvature due to warm absorption and the red-wing of the Fe K region. Through effective modelling of the broad-band spectrum and investigating the presence of narrow neutral or ionized emission lines and reflection from distant material, we obtain an accurate and detailed description of the Fe K line region using models such as laor, kerrdisk and kerrconv. Results suggest that ionized emission lines at 6.7 keV and 6.97 keV (particularly Fe XXVI) are relatively common and the inclusion of these lines can greatly affect the parameters obtained with relativistic models i.e. spin, emissivity, inner radius of emission and inclination. Moderately broad components are found in all objects, but typically the emission originates from tens of Rg, rather than within <6Rg of the black hole. Results obtained with kerrdisk line profiles suggest an average emissivity of q~2.3 at intermediate spin values with all objects ruling out the presence of a maximally spinning black hole at the 90% confidence level. We also present new spin constraints for Mrk 335 and NGC 7469 with intermediate values of a=0.70(+0.12,-0.01) and a=0.69(+0.09,-0.09) respectively.