Reprocessing Models for the Optical Light Curves of Hypervariable Quasars from the Sloan Digital Sky Survey Reverberation Mapping Project

TL;DR

This study models the optical light curves of 17 hypervariable quasars using different reprocessing geometries, revealing that most are best described by hemisphere or thick-disk models, advancing understanding of quasar inner environments.

Contribution

Introduces and applies reprocessing models with novel geometries to hypervariable quasars, providing a framework for understanding their inner structures.

Findings

Most quasars fit hemisphere or thick-disk models

Reprocessing models explain some, but not all, variability

Classification scheme for quasar geometries is proposed

Abstract

We explore reprocessing models for a sample of 17 hypervariable quasars, taken from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project, which all show coordinated optical luminosity hypervariability with amplitudes of factors $\gtrsim 2$ between 2014 and 2020. We develop and apply reprocessing models for quasar light curves in simple geometries that are likely to be representative of quasar inner environments. In addition to the commonly investigated thin-disk model, we include the thick-disk and hemisphere geometries. The thick-disk geometry could, for instance, represent a magnetically-elevated disk, whereas the hemisphere model can be interpreted as a first-order approximation for any optically-thick out-of-plane material caused by outflows/winds, warped/tilted disks, etc. Of the 17 quasars in our sample, eleven are best-fit by a hemisphere geometry, five are classified as thick disks, and both models fail for just one object. We highlight the successes and shortcomings of our thermal reprocessing models in case studies of four quasars that are representative of the sample. While reprocessing is unlikely to explain all of the variability we observe in quasars, we present our classification scheme as a starting point for revealing the likely geometries of reprocessing for quasars in our sample and hypervariable quasars in general.