INTRANIGHT OPTICAL VARIABILITY IN OPTICALLY SELECTED QSOS

We report results from a continuing programme to search for intranight optical variability in one radio-moderate and six radio-quiet (but al l optically bright and luminous) quasi-stellar objects, using the 2.34 -m Vainu Bappu Telescope. Our data clearly show microvariability for t he radio-moderate QSO, 0838 + 359, and provide strong indications of m icrovariability for two of the radio-quiet QSOs, 0946 + 301 and 1049 - 006, and possibly also for a third, 1206 + 459. Additional observatio ns of these and other QSOs could provide a powerful means of discrimin ating among various theoretical mechanisms proposed for the energy sou rce and, in particular, the origin of optical microvariability in acti ve galactic nuclei. These apparent detections of microvariability in r adio-quiet QSOs seem to favour models where flares on accretion discs are responsible for the microvariability.