A SEARCH FOR RAPID OPTICAL VARIABILITY IN RADIO-QUIET QUASARS

The detection of rapid variability on a timescale of hours in radio-qu iet quasars (RQQSOs) could be a powerful discriminator between starbur st, accretion disc and relativistic jet models of these sources. This paper contains an account of a dedicated search for rapid optical vari ability in RQQSOs. The technique used differential photometry between the RQQSO and stars in the same field of view of the CCD, The 23 RQQSO s that were observed all have high luminosities (-27 < M-V < -30), and 22 of these sources are at redshifts z > 1. The total amount of obser vation time was about 60 hours and these observations are part of an o ngoing programme, started in September 1990, to search for rapid varia bility in RQQSOs. No evidence for short-term variability greater than about 0.1 magnitudes was detected in any of the 23 sources, however lo ng-term variability was recorded for the radio-quiet quasar PG 2112+05 9. The finding charts are included here because they identify the RQQS O and the reference stars used in the photometry, and hence are availa ble for use by other observers. The unusual properties of two RQQSOs t hat were not included in our source list are noted. X-ray results reve al that PG 1416-129 is variable on a timescale of days and that the re markable source IRAS 13349+2438 varied by a factor of two on a timesca le of a few hours. The latter source displayed blazar type behaviour i n X-rays and implies that relativistic beaming may occur in at least s ome RQQSOs. Radio results also indicate the presence of jets in at lea st some RQQSOs.