SIMBAD references

We study the transient (i.e. emerging or disappearing) Civ broad absorption line (BAL) components in 50 radio-detected QSOs using multi-epoch spectra available in Sloan Digital Sky Survey Data Release-10. We report the detection of six BALQSOs having at least one distinct transient Civ absorption component. Based on the structure function analysis of optical light curves, we suggest that the transient absorption is unlikely to be triggered by continuum variations. Transient absorption components usually have low Civ equivalent widths (<8 Å), high ejection velocities (>10 000 km/s) and typically occur over rest-frame time-scales >800 d. The detection rate of transient Civ absorption seen in our sample is higher than that reported in the literature. Using a control sample of QSOs, we show that this difference is most likely due to the longer monitoring time-scale of sources in our sample while the effect of small number statistics cannot be ignored. Thus, in order to establish the role played by radio jets in driving the BAL outflows, we need a larger sample of radio-detected BALs monitored over more than 3 yr in the QSO's rest frame. We also find that the transient phenomenon in radio-detected and radio-quiet BALs does not depend on any of the QSO properties, i.e. the Eddington ratio, black hole mass, bolometric luminosity and optical-to-IR colours. All this suggests that transient BAL phenomenon is simply the extreme case of BAL variability.