A search for intra-night optical variability in radio-quiet QSOs

Abstract

We report results from a new program, using the 2.34-m Vainu Bappu Telescope, to search for intra-night optical variability in five QSOs which are radio-quiet but optically bright and luminous. Our limited data show mild indications of microvariability for some of the sources, but in no case has the reality of the fluctuations been clearly established. Additional observations of these and other QSOs could provide a powerful means of discriminating between various theoretical mechanisms proposed for the origin of optical microvariability in active galactic nuclei. Clear detections of microvariability in radio-quiet QSOs would favor models in which flares on accretion discs are responsible for the microvariability, while a demonstration that such fluctuations are extremely rare would support models based on shocks propagating down the relativistic jets which are only associated with radio-loud active galactic nuclei.