1ES 1927+654: a bare Seyfert 2

TL;DR

This study investigates the unusual properties of 1ES 1927+654, an AGN with a Seyfert 2 optical spectrum but minimal X-ray obscuration, revealing insights into its accretion and outflow mechanisms.

Contribution

The paper provides a comprehensive analysis of 1ES 1927+654's X-ray and optical properties, proposing models that explain its atypical characteristics and challenging the standard AGN unification model.

Findings

X-ray spectrum consistent with a corona around a standard accretion disc

High-velocity outflow (~0.3c) with significant kinetic luminosity

Edge-on view with a tenuous torus explaining optical and X-ray features

Abstract

1ES 1927+654 is an active galactic nucleus (AGN) that appears to defy the unification model. It exhibits a type-2 optical spectrum, but possesses little X-ray obscuration. XMM-Newton and Suzaku observations obtained in 2011 are used to study the X-ray properties of 1ES 1927+654. The spectral energy distribution derived from simultaneous optical-to-X-ray data obtained with XMM-Newton shows the AGN has a typical Eddington ratio (L/L_Edd = 0.014-0.11). The X-ray spectrum and rapid variability are consistent with originating from a corona surrounding a standard accretion disc. Partial covering models can describe the x-ray data; however, the narrow Fe Ka emission line predicted from standard photoelectric absorption is not detected. Ionized partial covering also favours a high-velocity outflow (v ~ 0.3c), which requires the kinetic luminosity of the wind to be >30 per cent of the bolometric luminosity of the AGN. Such values are not unusual, but for 1ES 1927+654 it requires the wind is launched very close to the black hole (~ 10 Rg). Blurred reflection models also work well at describing the spectral and timing properties of 1ES 1927+654 if the AGN is viewed nearly edge-on, implying that an inner accretion disc must be present. The high inclination is intriguing as it suggests 1ES 1927+654 could be orientated like a Seyfert 2, in agreement with its optical classification, but viewed through a tenuous torus.