A search for rapid optical variability in radio-quiet quasars

¹ Physics Department, University College, Dublin 4, Ireland
² Applied Physics and Instrumentation Department, Regional Technical College, Cork, Ireland

Received: 5 May 1997
Accepted: 7 October 1997

Abstract

The detection of rapid variability on a timescale of hours in radio-quiet quasars (RQQSOs) could be a powerful discriminator between starburst, accretion disc and relativistic jet models of these sources. This paper contains an account of a dedicated search for rapid optical variability in RQQSOs. The technique used differential photometry between the RQQSO and stars in the same field of view of the CCD. The 23 RQQSOs that were observed all have high luminosities (), and 22 of these sources are at redshifts . The total amount of observation time was about 60 hours and these observations are part of an ongoing programme, started in September 1990, to search for rapid variability in RQQSOs. No evidence for short-term variability greater than about 0.1 magnitudes was detected in any of the 23 sources, however long-term variability was recorded for the radio-quiet quasar PG 2112+059. The finding charts are included here because they identify the RQQSO and the reference stars used in the photometry, and hence are available for use by other observers. The unusual properties of two RQQSOs that were not included in our source list are noted. X-ray results reveal that PG 1416-129 is variable on a timescale of days and that the remarkable source IRAS 13349+2438 varied by a factor of two on a timescale of a few hours. The latter source displayed blazar type behaviour in X-rays and implies that relativistic beaming may occur in at least some RQQSOs. Radio results also indicate the presence of jets in at least some RQQSOs.