To be published in "The Starburst-AGN Connection" 2001.
astro-ph/0109495


VARIABILITY OF ACTIVE GALACTIC NUCLEI

Bradley M. Peterson


Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
E-mail: peterson@astronomy.ohio-state.edu


Abstract. Continuum and emission-line variability of active galactic nuclei provides a powerful probe of microarcsecond scale structures in the central regions of these sources. In this contribution, we review basic concepts and methodologies used in analyzing AGN variability. We develop from first principles the basics of reverberation mapping, and pay special attention to emission-line transfer functions. We discuss application of cross-correlation analysis to AGN light curves. Finally, we provide a short review of recent important results in the field.


Table of Contents

INTRODUCTION

BACKGROUND AND BASIC PHENOMENOLOGY
Basic Characteristics of Variability
Origin of the Variations
Blazar Variability
Emission-Line Variability
The First Monitoring Programs
Spectrophotometric Flux Calibration
Requirements for a Successful Monitoring Program

THEORY OF REVERBERATION MAPPING
Reverberation Mapping Assumptions
The Transfer Equation
Isodelay Surfaces
Transfer Functions for a Variety of Simple Models
Transfer Function Recovery

CROSS-CORRELATION ANALYSIS
Fundamentals
Relationship to the Transfer Function
Discrete Correlation Methods
Computational Issues
Uncertainties in Cross-Correlation Lags

OBSERVATIONAL RESULTS
Size of the Broad-Line Region
AGN Black-Hole Masses
Emission-Line Transfer Functions
Emission-Line Profile Variability
Multiwavelength Continuum Variability
Conclusion

REFERENCES

For a postscript version of the article, click here.

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