XMM-Newton and Swift Observations of the Seyfert 1 AGN NGC 5940

TL;DR

This study analyzes XMM-Newton and Swift observations of the Seyfert 1 galaxy NGC 5940, focusing on its soft X-ray excess, and finds that thermal Comptonisation is the most likely explanation among several models.

Contribution

It provides a detailed spectral analysis of NGC 5940, comparing multiple models for the soft X-ray excess and favoring thermal Comptonisation based on observational evidence.

Findings

Soft X-ray excess observed below 2 keV in NGC 5940.

Thermal Comptonisation model is favored for the soft excess.

Other models like ionised partial covering and blurred reflection are less supported.

Abstract

Probing the physics of the accretion flow around active galactic nuclei (AGN) is crucial to understanding their emission mechanisms as well as being able to constrain the geometrical and variability properties of the different regions around them. The soft X-ray excess -- usually observed below $\sim2\,\mathrm{keV}$ in excess of the dominant X-ray powerlaw continuum -- is one prominent feature that is commonly seen in type 1 Seyfert AGN and therefore readily provides a useful diagnostic of the accretion flow mechanism around these systems. NGC 5940 is a Seyfert 1 AGN which reveals strong, prominent soft X-ray excess below $\sim2\,\mathrm{keV}$ as seen in both its XMM-Newton and Swift observations. Model fit to the data revealed that this feature could be equally well explained by the ionised partial covering, the thermal Comptonisation and the blurred reflection models. Although the other models cannot be decisively ruled out with the data at hand, the lack of significant broad iron $K_{\alpha}$ as well as any significant emission/absorption line features in the reflection grating spectrometer (RGS) data tend to favour the thermal Comptonisation origin for the soft X-ray excess in NGC 5940.