X-ray reflection from the inner disk of the AGN Ton S180

TL;DR

This study analyzes X-ray data from the AGN Ton S180, finding that the soft excess is not due to relativistic reflection and that the black hole likely has a low spin, with a complex continuum model fitting better.

Contribution

It demonstrates that the soft excess in Ton S180 cannot be explained by relativistic reflection and supports a low black hole spin through combined spectral modeling.

Findings

Soft excess is not produced by relativistic reflection.

Relativistic reflection modeling favors low black hole spin (<0.4).

A two-component Comptonization plus reflection model fits the spectrum better.

Abstract

We analyse a long archival XMM-Newton observation of the narrow-line Seyfert 1 galaxy Ton S180, using the latest reflection models to explore the high quality X-ray spectrum. We find that the iron line is relatively narrow and sharp, and the soft excess is extremely smooth. We cannot find an acceptable reflection model that describes both components, and conclude that the soft excess cannot be produced by relativistic reflection. Fitting the 3-10 keV band with relativistic reflection to model the iron line strongly prefers low spin values (< 0.4), with the exact value depending on the model and not well constrained. We then model the broad- band spectrum with a two-component Comptonization continuum plus relativistic reflection. This gives a much better fit than a pure reflection model, which again prefers a low spin value. The photon index of the reflection component is intermediate between the two Comptoniza- tion components, suggesting that both illuminate the disk a similar amount and therefore both contribute to the reflection.