The NuSTAR X-ray spectrum of the low-luminosity AGN in NGC 7213

TL;DR

This study analyzes NuSTAR X-ray data of NGC 7213, revealing a high-energy cut-off above 140 keV, no significant Compton reflection, and variability in iron line features, indicating a hot corona and complex circumnuclear environment.

Contribution

First detailed NuSTAR spectral analysis of NGC 7213 revealing high-energy properties and variability, with implications for the structure of the AGN's corona and surrounding gas.

Findings

High-energy cut-off Ec > 140 keV

No significant Compton reflection detected

Iron line variability over years

Abstract

We present an analysis of the 3-79 keV NuSTAR spectrum of the low-luminosity active galactic nucleus NGC 7213. In agreement with past observations, we find a lower limit to the high-energy cut-off of Ec > 140 keV, no evidence for a Compton-reflected continuum, and the presence of an iron Kalpha complex, possibly produced in the broad-line region. From the application of the MYTorus model, we find that the line-emitting material is consistent with the absence of a significant Compton reflection if arising from a Compton-thin torus of gas with a column density of 5.0(+2.0,-1.6) cm^-2. We report variability of the equivalent width of the iron lines on the time-scale of years using archival observations from XMM-Newton, Chandra and Suzaku. This analysis suggests a possible contribution from dusty gas. A fit with a Comptonization model indicates the presence of a hot corona with a temperature kTe > 40 keV and an optical depth tau < 1, assuming a spherical geometry.