Constraints on the absorption-dominated model for the X-ray spectrum of MCG-6-30-15

TL;DR

This paper evaluates the absorption-dominated model for MCG-6-30-15's X-ray spectrum, finding it over-predicts iron line flux unless restrictive conditions are met, thus favoring the relativistic reflection interpretation.

Contribution

It critically assesses the absorption-dominated model by considering fluorescent emission, demonstrating its limitations compared to the relativistic reflection model.

Findings

Absorption-dominated model over-predicts iron line flux.

Geometric constraints are required for the absorption model to be viable.

Relativistic reflection model is favored due to fewer restrictive conditions.

Abstract

Complexities in the X-ray spectrum of the nearby Seyfert 1.2 galaxy MCG-6-30-15 are commonly interpreted in terms of a broad iron line and the associated Compton reflection hump from the innermost relativistic regions of an accretion disk around a rapidly spinning black hole. However, an alternative model has recently been proposed in which these spectral features are caused entirely by complex (ionized and partial-covering) absorption. By considering the fluorescent emission that must accompany photoelectric absorption, we show that the absorption-dominated model over-predicts the 6.4keV iron line flux unless the marginally Compton-thick absorber responsible for the hard X-ray hump satisfies very restrictive geometric constraints. In the absence of a specific model that both obeys these geometrical constraints and is physically-plausible, the relativistic-reflection model is favoured.