Disc wind or disc line? The extraordinary Fe-K feature of Mrk 1513

TL;DR

This paper analyzes the unusual Fe-K spectral feature in Mrk 1513, suggesting it may be caused by either a broad absorption trough or a relativistic emission line, with evidence pointing towards a persistent disc-scale outflow.

Contribution

It presents the first detailed analysis of the Fe-K feature in Mrk 1513, proposing the presence of a persistent X-ray wind based on spectral features and comparisons across observations.

Findings

Spectral drop at ~7 keV interpreted as absorption or emission

Evidence of a P-Cygni-like profile in Fe-K band

Indications of a persistent disc-scale outflow in Mrk 1513

Abstract

We discuss the origin of a very unusual spectral structure observed in the Fe-K band of the Seyfert galaxy Mrk 1513, a local ($z$=0.063) active galactic nucleus (AGN) that is efficiently accreting matter onto its central supermassive black hole ($L_{\rm bol}/L_{\rm Edd}\sim$0.5). We consider the highest quality X-ray observation of this source available to date, performed in 2003 by XMM-Newton. The hard X-ray spectrum is characterised by a remarkable spectral drop at $\sim$7 keV, which can be interpreted as either the onset of a broad absorption trough or the blue wing of a relativistic emission line. Overall, this complex feature is significant at >5$\sigma$, and it is qualitatively reminiscent of a P-Cygni profile. A serendipitous spectrum of lower quality taken by XMM-Newton in 2015 qualitatively confirms the presence of similar Fe-K structures. Although it is not possible to distinguish between the two physical scenarios on sheer statistical grounds with the current data, several considerations lend weight to the possibility that Mrk 1513 is actually hosting a persistent outflow at accretion-disc scales, thus adding to the handful of known AGN in which a wide-angle X-ray wind has been identified so far.