Variability of Active Galactic Nuclei
نویسنده
چکیده
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.
منابع مشابه
The Variability of "Normal" Galactic Nuclei
The Variability of "Normal" Galactic Nuclei Jacob Nelson Department of Physics and Astronomy Bachelor of Science It is likely that the nuclei of all galaxies contain black holes. If matter falls in toward the black hole, some of it can be heated an ejected creating an active nucleus. Astronomers monitor the infall and estimate black hole masses by measuring variations in the brightness of the n...
متن کاملTesting the X-ray variability of active galactic nuclei with the nonlinear prediction method
The analysis of eight EXOSAT X-ray lightcurves of six active galactic nuclei by nonlinear prediction methods indicates that the observed variability is truly stochastic and is not caused by deterministic chaos. This result favors X-ray emission models with mutliple centers of production of hot, possibly relativistic electrons.
متن کاملVariability-selected low luminosity AGNs in the SA57 and in the CDFS
Low Luminosity Active Galactic Nuclei (LLAGNs) are contaminated by the light of their host galaxies, thus they cannot be detected by the usual colour techniques. For this reason their evolution in cosmic time is poorly known. Variability is a property shared by virtually all active galactic nuclei, and it was adopted as a criterion to select them using multi epoch surveys. Here we report on two...
متن کاملSUPERMASSIVE BLACK HOLES IN GALACTIC NUCLEI Observational Evidence and Some Astrophysical Consequences
Abstract. I review the status of observational determinations of central masses in nearby galactic nuclei. Results from a variety of techniques are summarized, including ground-based and space-based optical spectroscopy, radio VLBI measurements of luminous water vapor masers, and variability monitoring studies of active galactic nuclei. I will also discuss recent X-ray observations that indicat...
متن کاملX-ray Variability of Active Galactic Nuclei and the Flare Model
Short-term variability of X-ray spectra has been reported for several Active Galactic Nuclei. Significant X-ray flux variations are observed within time scales down to 10—10 seconds. We discuss short variability time scales in the framework of the X-ray flare model, which assumes the release of a large hard X-ray flux above a small portion of the accretion disk. The resulting observed X-ray spe...
متن کامل