THE MICROVARIABILITY OF SELECTED RADIO-QUIET AND RADIO-LOUD QSOS

A selected sample of radio-quiet and radio-loud quasi-stellar objects has been optically monitored in an effort to test-some of the prominen t theoretical mechanisms proposed for the origin of optical microvaria bility in active galactic nuclei. Two out of 10 radio-quiet QSOs and 6 out of 7 radio-loud QSOs observed show evidence for microvariations. This apparent contrast in microvariations between radio-quiet and radi o-loud QSOs implies substantial support for models based on propagatin g shocks on relativistic jets as the process probably responsible for producing most of the microvariations observed in AGN. (C) 1997 Americ an Astronomical Society.