Continuum reverberation mapping in a z = 1.41 radio-loud quasar

TL;DR

This study uses multi-wavelength monitoring of a gravitationally lensed quasar at z=1.41 to investigate the structure of its accretion disk and the nature of its central irradiating source.

Contribution

It provides new insights into the radial structure of the accretion disk and the central irradiation mechanism in a high-redshift radio-loud quasar.

Findings

Evidence of a centrally irradiated, standard accretion disk.

Detection of significant intrinsic brightness variations.

Multi-wavelength light curves support accretion disk models.

Abstract

Q0957+561 was the first discovered gravitationally lensed quasar. The mirage shows two images of a radio-loud quasar at redshift z = 1.41. The time lag between these two images is well established around one year. We detected a very prominent variation in the optical brightness of Q0957+561A at the beginning of 2009, which allowed us to predict the presence of significant intrinsic variations in multi-wavelength light curves of Q0957+561B over the first semester of 2010. To study the predicted brightness fluctuations of Q0957+561B, we conducted an X-ray, NUV, optical and NIR monitoring campaign using both ground-based and space-based facilities. The continuum NUV-optical light curves revealed evidence of a centrally irradiated, standard accretion disk. In this paper, we focus on the radial structure of the standard accretion disk and the nature of the central irradiating source in the distant radio-loud active galactic nucleus (AGN).