NuSTAR and Suzaku X-ray Spectroscopy of NGC 4151: Evidence for Reflection from the Inner Accretion Disk

TL;DR

This study uses simultaneous NuSTAR and Suzaku X-ray observations to analyze the inner accretion disk and corona of NGC 4151, providing evidence for relativistic reflection and a rapidly spinning black hole.

Contribution

It presents the first detailed spectral analysis combining NuSTAR and Suzaku data to confirm relativistic reflection and measure black hole spin in NGC 4151.

Findings

Strong relativistic reflection from the inner accretion disk.

Black hole spin estimated to be greater than 0.9.

Spectral variability driven by coronal and disk flux changes.

Abstract

We present X-ray timing and spectral analyses of simultaneous 150 ks Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku X-ray observations of the Seyfert 1.5 galaxy NGC 4151. We disentangle the continuum emission, absorption, and reflection properties of the active galactic nucleus (AGN) by applying inner accretion disk reflection and absorption-dominated models. With a time-averaged spectral analysis, we find strong evidence for relativistic reflection from the inner accretion disk. We find that relativistic emission arises from a highly ionized inner accretion disk with a steep emissivity profile, which suggests an intense, compact illuminating source. We find a preliminary, near-maximal black hole spin a>0.9 accounting for statistical and systematic modeling errors. We find a relatively moderate reflection fraction with respect to predictions for the lamp post geometry, in which the illuminating corona is modeled as a point source. Through a time-resolved spectral analysis, we find that modest coronal and inner disk reflection flux variation drives the spectral variability during the observations. We discuss various physical scenarios for the inner disk reflection model, and we find that a compact corona is consistent with the observed features.