2017MNRAS.468.3607K

Ton 34 recently transitioned from non-absorbing quasar into a broad absorption line quasi-stellar object. Here, we report new HST-STIS observations of this quasar. Along with C IV absorption, we also detect absorption by NV+Lyα and possibly O VI+Lyβ. We follow the evolution of the C IV BAL, and find that, for the slower outflowing material, the absorption trough varies little (if at all) on a rest-frame time-scale of ∼2 yr. However, we detect a strong deepening of the absorption in the gas moving at larger velocities (-20 000 to -23 000 km s^–1). The data is consistent with a multistreaming flow crossing our line of sight to the source. The transverse velocity of the flow should be ∼ few thousand km s^–1, similar to the rotation velocity of the BLR gas (≃2 600 km s^–1). By simply assuming Keplerian motion, these two components must have similar locations, pointing to a common outflow forming the BLR and the BAL. We speculate that BALs, mini-BALs and NALs are part of a common, ubiquitous, accretion-disc outflow in AGN, but become observable depending on the viewing angle towards the flow. The absorption troughs suggest a wind covering only ∼20 per cent of the emitting source, implying a maximum size of 10^–3 pc for the clouds forming the BAL/BLR medium. This is consistent with constraints of the BLR clouds from X-ray occultations. Finally, we suggest that the low excitation broad emission lines detected in the spectra of this source lie beyond the wind, and this gas is probably excited by the shock of the BAL wind with the surrounding medium.