Coronal properties of Swift/BAT-selected Seyfert 1 AGN observed with NuSTAR

TL;DR

This study analyzes the X-ray spectra of 46 Seyfert 1 AGN observed with NuSTAR to measure coronal properties, revealing most coronae are near pair production limits, which impacts understanding of coronal heating.

Contribution

It provides the first systematic measurement of high-energy cutoffs in a large sample of Seyfert 1 AGN, mapping their coronal temperature and compactness.

Findings

Most coronae are near the pair production boundary.

High-energy cutoffs suggest low coronal temperatures.

Implications for coronal heating and thermalization mechanisms.

Abstract

The NuSTAR observatory, with its high sensitivity in hard X-rays, has enabled detailed broadband modeling of the X-ray spectra of Active Galactic Nuclei (AGN), thereby allowing constraints to be placed on the high-energy cutoff of the X-ray coronal continuum. We investigate the spectral properties of a sample of 46 NuSTAR-observed Seyfert 1 AGN selected from the Swift/BAT 70-month hard X-ray survey. Our measurements of the high-energy cutoff of the continuum from modeling the NuSTAR X-ray spectra are used to map out the temperature - compactness ($\theta-l$) plane for AGN coronae. We find that most of the coronae lie clustered near the boundary for runaway pair production, suggesting that annihilation and pair production act to regulate the temperature of the corona. We discuss the implications of coronae whose high-energy cutoff may indicate a low coronal temperature on the heating and thermalization mechanisms in the corona.