The shape of the relativistic iron K-alpha line from MCG6--6-30-15 measured with the Chandra HETGS and RXTE

TL;DR

This paper confirms the relativistic broadening of the iron K-alpha line in MCG6--6-30-15 using Chandra and RXTE data, revealing details about the line profile, narrow components, and their variability, which informs models of the accretion disk.

Contribution

It provides the first simultaneous high-resolution and broad-band observations confirming the relativistic iron line profile and constrains the contribution from distant material.

Findings

Relativistically broadened iron K-alpha line confirmed.

Narrow component with velocity width ~4700 km/s observed.

Stringent limit on narrow line equivalent width of 16 eV.

Abstract

We confirm the detection of the relativistically broadened iron K-alpha emission at 6.4 keV with simultaneous Chandra HETGS and RXTE PCA observations. Heavily binned HETGS data show a disk line profile with parameters very similar to those previously seen by ASCA. We observe a resolved narrow component with a velocity width ~4700 km/s (FWHM ~ 11,000 km/s), that is most prominent, and narrower (FWHM ~ 3600 km/s) when the continuum flux is high. It plausibly is just the blue wing of the broad line. We obtain a stringent limit on the equivalent width of an intrinsically narrow line in the source of 16 eV, indicating little or no contribution due to fluoresence from distant material such as the molecular torus. Variability studies of the narrow component show a constant iron line flux and variable width indicating the line may be originating from different kinematic regions of the disk.