Multi-epoch X-ray observations of the Seyfert 1.2 galaxy Mrk 79: bulk motion of the illuminating X-ray source

TL;DR

This study analyzes eight years of multi-epoch X-ray spectra of Mrk 79, revealing a black hole spin of approximately 0.7 and suggesting that the X-ray source moves at mildly relativistic speeds, affecting observed reflection features.

Contribution

It provides the first detailed multi-epoch X-ray spectral analysis of Mrk 79, indicating the bulk motion of the X-ray source and constraining the black hole spin.

Findings

Black hole spin estimated at a = 0.7+/-0.1.

Reflection component weaker than simple models predict.

No significant evidence for light bending effects.

Abstract

Multi-epoch X-ray spectroscopy (0.3-25 keV) of the Seyfert 1.2 galaxy Mrk 79 (UGC 3973) spanning nearly eight years and a factor of three in broadband flux are analysed. The data are obtained at seven epochs with either XMM-Newton or Suzaku. Comparison with contemporaneous RXTE monitoring indicate that all flux states of Mrk 79 are represented by the data. The spectra are fitted in a self-consistent manner adopting a power law and ionised reflection to describe the broadband continuum. Modification of the spectra by a distant photoionised medium, seen predominantly in emission, are also included. Under the assumption that the inner disk is at the innermost stable circular orbit, our blurred reflection models give a spin of a = 0.7+/-0.1. The reflection component in each spectrum is weaker than predicted by simple reflection models. If the illuminating X-ray emission is produced by flares above the disk that move at mildly relativistic velocities, however, diminished reflection is expected. Light bending due to strong gravity near black holes can influence how the illuminating and reflected flux are observed; variations in Mrk 79 do not suggest that light bending is important in this source.