Fundamental X-ray Corona Parameters of Swift/BAT AGN

TL;DR

This study analyzes X-ray spectra of 33 AGN to determine fundamental coronal parameters, revealing correlations with physical properties and demonstrating the importance of high-energy data for accurate modeling.

Contribution

It provides the first comprehensive set of coronal parameters for a sizable AGN sample using combined Swift/BAT, XMM-Newton, and NuSTAR data, highlighting new correlations and the impact of high-energy observations.

Findings

Seyfert 2 AGN have lower Eddington ratios and photon indices than Seyfert 1-1.9.

A known correlation between photon index and reflection coefficient is confirmed.

Including Swift BAT data reduces uncertainties in spectral parameters.

Abstract

While X-ray emission from active galactic nuclei (AGN) is common, the detailed physics behind this emission is not well understood. This is in part because high quality broadband spectra are required to precisely derive fundamental parameters of X-ray emission such as the photon index, folding energy, and reflection coefficient. Here we present values of such parameters for 33 AGN observed as part of the 105 month Swift/BAT campaign and with coordinated archival XMM-Newton and NuSTAR observations. We look for correlations between the various coronal parameters in addition to correlations between coronal parameters and physical properties such as black hole mass and Eddington ratio. Using our empirical model, we find good fits to almost all of our objects. The folding energy was constrained for 30 of our 33 objects. When comparing Seyfert 1 - 1.9 to Seyfert 2 galaxies, a K-S test indicates that Seyfert 2 AGN have lower Eddington ratios and photon indices than Seyfert 1 - 1.9 objects with p-values of $5.6 \times 10^{-5}$ and $7.5 \times 10^{-3}$ respectively. We recover a known correlation between photon index and reflection coefficient as well as the X-ray Baldwin effect. Finally, we find that the inclusion of the high energy Swift BAT data significantly reduces the uncertainties of spectral parameters as compared to fits without the BAT data.