Assessing black hole spin in deep Suzaku observations of Seyfert 1 AGN

TL;DR

This study uses deep Suzaku X-ray observations to analyze the spectra of nearby Seyfert 1 AGN, aiming to measure black hole spins and assess the presence of relativistic disk emission, finding most black holes are not maximally spinning.

Contribution

It provides the first comprehensive broadband spectral analysis of multiple Seyfert 1 AGN with high S/N data, constraining black hole spins and the significance of relativistic Fe K emission.

Findings

Maximal black hole spins are ruled out at 90% confidence.

Relativistic Fe K emission is marginal or not required in some AGN.

Black hole spin estimates vary, with some indicating moderate spins.

Abstract

We present a broad-band analysis of deep Suzaku observations of nearby Seyfert 1 AGN: Fairall 9, MCG--6-30-15, NGC 3516, NGC 3783 and NGC 4051. The use of deep observations (exposures >200 ks) with high S/N allows the complex spectra of these objects to be examined in full, taking into account features such as the soft excess, reflection continuum and complex absorption components. After a self-consistent modelling of the broad-band data (0.6-100.0 keV, also making use of BAT data from Swift), the subtle curvature which may be introduced as a consequence of warm absorbers has a measured affect upon the spectrum at energies >3 keV and the Fe K region. Forming a model (including absorption) of these AGN allows the true extent to which broadened diskline emission is present to be examined and as a result the measurement of accretion disc and black hole parameters which are consistent over the full 0.6-100.0 keV energy range. Fitting relativistic line emission models appear to rule out the presence of maximally spinning black holes in all objects at the 90% confidence level, in particular MCG--6-30-15 at >99.5% confidence. Relativistic Fe K line emission is only marginally required in NGC 3516 and not required in NGC 4051, over the full energy bandpass. Nonetheless, statistically significant broadened 6.4 keV Fe K alpha emission is detected in Fairall 9, MCG--6-30-15 and NGC 3783 yielding black hole spin estimates of a=0.67(+0.10,-0.11), a=0.4(+0.20,-0.12) and a<-0.04 respectively, when fitted with disc emission models.