The Seyfert 2 galaxy NGC 2110: hard X-ray emission observed by NuSTAR and variability of the iron K$\alpha$ line

TL;DR

This study analyzes NuSTAR and archival X-ray data of NGC 2110, revealing a high-energy cutoff above 210 keV, no significant Compton reflection, and variable iron Kα line components linked to different regions near the black hole.

Contribution

It provides the first detailed broadband X-ray spectral analysis of NGC 2110 with NuSTAR, identifying the nature of the iron line components and the absence of distant Compton-thick reflection.

Findings

High-energy cutoff >210 keV detected

No evidence of distant Compton-thick reflection

Iron Kα line has both constant and variable components

Abstract

We present NuSTAR observations of the bright Seyfert 2 galaxy NGC 2110 obtained in 2012, when the source was at the highest flux level ever observed, and in 2013, when the source was at a more typical flux level. We include archival observations from other X-ray satellites, namely XMM-Newton, Suzaku, BeppoSAX, Chandra and Swift. Simultaneous NuSTAR and Swift broad band spectra (in the 3-80 keV range) indicate a cutoff energy $E_{\rm c}>210$ keV, with no detectable contribution from Compton reflection. NGC 2110 is one of the very few sources where no evidence for distant Compton thick scattering is found and, by using temporal information collected over more than a decade, we investigate variations of the iron K$\alpha$ line on time scales of years. The Fe K$\alpha$ line is likely the sum of two components: one constant (originating from distant Compton-thick material) and the other one variable and linearly correlated with the source flux (possibly arising from Compton-thin material much closer to the black hole).