Gravitational Microlensing of a Reverberating Quasar Broad Line Region - I. Method and Qualitative Results

TL;DR

This paper presents a combined microlensing and reverberation mapping method to study quasar broad line regions, demonstrating that microlensing can produce observable effects that aid in understanding BELR properties.

Contribution

It introduces a novel approach combining microlensing with reverberation mapping and provides qualitative analysis of its potential to reveal BELR characteristics.

Findings

Microlensing effects can produce observable spectral changes.

Different BELR models show distinct microlensing signatures.

The method offers new insights into BELR structure and kinematics.

Abstract

The kinematics and morphology of the broad emission line region (BELR) of quasars are the subject of significant debate. The two leading methods for constraining BELR properties are microlensing and reverberation mapping. Here we combine these two methods with a study of the microlensing behaviour of the BELR in Q2237+0305, as a change in continuum emission (a "flare") passes through it. Beginning with some generic models of the BELR - sphere, bicones, disk - we slice in velocity and time to produce brightness profiles of the BELR over the duration of the flare. These are numerically microlensed to determine whether microlensing of reverberation mapping provides new information about the properties of BELRs. We describe our method and show images of the models as they are flaring, and the unlensed and lensed spectra that are produced. Qualitative results and a discussion of the spectra are given in this paper, highlighting some effects that could be observed. Our conclusion is that the influence of microlensing, while not strong, can produce significant observable effects that will help in differentiating the properties of BELRs.