Radio-Variability in Radio-Quiet Quasars and Low-Luminosity AGN
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We report on two surveys of radio-weak AGN to look for radio variability. We find significant variability with an RMS of 10-20% on a timescale of months in radio-quiet and radio-intermediate quasars. This exceeds the variability of radio cores in radio-loud quasars (excluding blazars), which vary only on a few percent level. The variability in radio-quiet quasars confirms that the radio emission in these sources is indeed related to the AGN. The most extremely variable source is the radio-intermediate quasar III Zw 2 which was recently found to contain a relativistic jet. In addition we find large amplitude variabilities (up to 300% peak-to-peak) in a sample of nearby low-luminosity AGN, Liners and dwarf-Seyferts, on a timescale of 1.5 years. The variability could be related to the activity of nuclear jets responding to changing accretion rates. Simultaneous radio/optical/X-ray monitoring also for radio-weak AGN, and not just for blazars, is therefore a potentially powerful tool to study the link between jets and accretion flows.
9 pages, 4 figures, to appear in "Probing the Physics of Active Galactic Nuclei by Multiwavelength Monitoring", eds. B.M. Peterson, R.S. Polidan, and R.W. Pogge, ASP Conf. Ser., also available at http://www.mpifr-bonn.mpg.de/staff/hfalcke/publications.html#llagnvar
9 pages, 4 figures, to appear in "Probing the Physics of Active Galactic Nuclei by Multiwavelength Monitoring", eds. B.M. Peterson, R.S. Polidan, and R.W. Pogge, ASP Conf. Ser., also available at http://www.mpifr-bonn.mpg.de/staff/hfalcke/publications.html#llagnvar