A Chandra-HETG VIEW OF MCG +8-11-11

TL;DR

This study uses Chandra HETG and Suzaku data to analyze the X-ray spectrum of MCG +8-11-11, finding no warm absorption but evidence of distant neutral reprocessing and a soft excess, challenging previous claims.

Contribution

First detailed broadband spectral analysis of MCG +8-11-11 combining Chandra HETG and Suzaku data, clarifying the nature of absorption and reflection features.

Findings

Warm absorption not required by data

Detection of neutral Fe Kα emission line

Consistent with a distant, Compton-thick torus

Abstract

We present a spectral analysis of the 118 ks High Energy Transmission Gratings (HETG) observation of the X-ray bright Seyfert 1.5 galaxy MCG +8-11-11, in conjunction with 100 ks of archival Suzaku data, aimed at investigating the signatures of warm absorption and Compton reflection reported from previous Suzaku and XMM-Newton studies of the source. Contrary to previous results, we find that warm absorption is not required by the data. Instead, we report upper limits on absorption lines that are below previous (marginal) detections. Fe Ka line emission is clearly detected and is likely resolved with sigma ~ 0.02 keV with the HETG data. We applied self-consistent, broadband spectral-fitting models to the HETG and Suzaku data to investigate this and other signatures of distant absorption and reflection. Utilizing in particular the MYTorus model, we find that the data are consistent with reprocessing by a distant, neutral torus that is Compton thick and out of the line-of-sight. However, we do not find compelling evidence of a relativistically-broadened Fe-K emission line, which is often expected from type 1 AGN. This is consistent with some, although not all, previous studies of MCG +8-11-11. A well-measured edge is identified by the HETG near 0.5 keV, indicating neutral absorption in the line of sight that is consistent with galactic absorption; however, the absorption may be partially intrinsic to the source. The HETG data are consistent with the presence of a soft excess, a feature that may be missed by considering the Suzaku data alone.