Exploring the spectral variability of the Seyfert 1.5 galaxy Markarian 530 with Suzaku

TL;DR

This study analyzes Suzaku data of Seyfert 1.5 galaxy Markarian 530, revealing two independent spectral variability modes and exploring physical models to explain the spectral changes and features.

Contribution

It identifies two distinct spectral variability modes and evaluates three physical models, providing insights into the spectral behavior of Markarian 530.

Findings

Spectral transition from soft to hard states

Rapid variability confined to 1-3 keV band

Fe K-alpha emission from distant torus

Abstract

A 2012 Suzaku observation of the Seyfert 1.5 galaxy Markarian 530 was analysed and found to exhibit two distinct modes of variability, which were found to be independent from one another. Firstly, the spectrum undergoes a smooth transition from a soft to a hard spectrum. Secondly, the spectrum displays more rapid variability seemingly confined to a very narrow energy band (~ 1-3 keV). Three physical models (blurred reflection, partial covering, and soft Comptonisation) were explored to characterise the average spectrum of the observation as well as the spectral state change. All three models were found to fit the average spectrum and the spectral changes equally well. The more rapid variability appears as two cycles of a sinusoidal function, but we cannot attribute this to periodic variability. The Fe K-alpha band exhibits a narrow 6.4 keV emission line consistent with an origin from the distant torus. In addition, features blueward of the neutral iron line are consistent with emission from He-like and H-like iron that could be originating from the highly ionised layer of the torus, but a broad Gaussian profile at ~ 6.7 keV also fits the spectrum well.