Department of Astronomy: Quasars and Active Galaxies

Quasars & Active Galaxies

Variability of AGN and QSO

Active Galactic Nuclei (AGN) are among the most luminous objects we know in the universe. Located in the center of a galaxy they can emit a comparable amount of energy or even more as the entire host galaxy. One characterizing feature of an AGN is the variability of the continuum flux over the entire electromagnetic spectrum and of the broad emission lines on times scales from minutes to years.

Intensive multiwavelength monitoring campaigns have shown that variability studies provide an excellent tool to investigate the innermost region of active galactic nuclei (AGNs). Detailed studies of the continuum and emission-line variations have revealed new insights about the size, structure, and dynamics of the broad-line region (BLR) in these sources (see Peterson 1993 or Netzer & Peterson 1997 for a review).

Over the last decade, a number of large space-based and ground-based AGN monitoring programs have been undertaken by the International AGN Watch consortium (Alloin et al. 1994) on several Seyfert galaxies, including programs on NGC 3783, NGC4051, NGC 4151, NGC 5548, NGC 7469, Mkn279, Mkn509, Akn564, Fairall 9, and 3C390.3

With the new generation of 10m class telescopes and instruments in earth's orbit it will be possible to address more specific questions and applying more sophisticated methodes like reverberation mappping to data of higher quality.

Variation of the optical spectrum of 3C390.3 from Oct 1994 (low state) until Oct 1995 (high state).

Variability of the optical continuum flux (F5100) and of the broad H-beta emission line flux of NGC5548 from late 1988 until 1996.

This page created by Matthias Dietrich
Questions or comments should be sent to: Matthias Dietrich

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