Variable oxygen emission from the accretion disk of Mrk 110

TL;DR

This study analyzes six XMM-Newton observations of Mrk 110, revealing a variable broad OVII emission line originating from the accretion disk, with flux correlated to the continuum, providing insights into the disk's structure and emission properties.

Contribution

First detection of variable broad OVII emission line in Mrk 110's accretion disk, with inferred disk parameters and flux correlation to the continuum.

Findings

Broad OVII line modeled with a face-on disk profile

Inner radius of emission between 20-100 gravitational radii

Significant correlation between OVII flux and continuum flux

Abstract

Six XMM-Newton observations of the bright narrow line Seyfert 1, Mrk 110, from 2004-2020, are presented. The analysis of the grating spectra from the Reflection Grating Spectrometer (RGS) reveals a broad component of the He-like Oxygen (OVII) line, with a full width at half maximum (FWHM) of $15900\pm1800$ km s$^{-1}$ measured in the mean spectrum. The broad OVII line in all six observations can be modelled with a face-on accretion disk profile, where from these profiles the inner radius of the line emission is inferred to lie between about 20-100 gravitational radii from the black hole. The derived inclination angle, of about 10 degrees, is consistent with studies of the optical Broad Line Region in Mrk 110. The line also appears variable and for the first time, a significant correlation is measured between the OVII flux and the continuum flux from both the RGS and EPIC-pn data. Thus the line responds to the continuum, being brightest when the continuum flux is highest, similar to the reported behaviour of the optical HeII line. The density of the line emitting gas is estimated to be $n_{\rm e}\sim10^{14}$ cm$^{-3}$, consistent with an origin in the accretion disk.