A long-term survey of a sample of high luminosity (-27<MV<-30) and medium to high redshift (0.466<z<4.7) radio-quiet quasars was undertaken, in order to search for short and long term optical variability on timescales of hours to years. A large sample of 23 RQQSOs was observed, with a total observation time of about 60 hours spread over a period of several years. Long-term variability was detected in the RQQSO PG 2112+059 when it varied by 0.18 magnitudes in the V-band between 1992 and 1996. No rapid variability was observed in any of the sources in this sample of RQQSOs. The finding charts are included because they identify the RQQSO and the reference stars used in the photometry and hence are available to other observers.
There have been a few reports of rapid optical variability in a number of RQQSOs but these reports are not in conflict with the results presented here because such small variability would not have been detected in many of the sources monitored in this survey. The unusual properties of two sources are highlighted. These sources were not monitored in this survey but have recently been added to the list of sources for study. The remarkable source IRAS 13349+2438 combines some of the properties of blazars and radio quiet quasars and hence further observations may elucidate the nature of this hybrid source. The two unusual sources have R values near the top of the range for RQQSOs and also have unusual radio spectra that may signify the presence of several source components. Further observations with VLA and VLBI should reveal new and enlightening views on the radio properties of these sources.
Acknowledgements
The Jacobus Kapteyn Telescope on the island of La Palma is operated by the Royal Greenwich Observatory at the Spanish Observatorio del Roque de los Muchachos of the Institato de Astrofisica de Canarias. We are grateful to Catherine Handley and Matt Delaney for their help in the preparation of this paper.