Broad absorption line disappearance/emergence in multiple ions in a weak
  emission-line quasar
  We report the discovery of disappearance of Mg ii, Al iii, C iv, and Si iv
broad absorption lines (BALs) at the same velocity, accompanied by a new Civ
BAL emerging at a higher velocity, in the quasar J0827+4252 at z = 2.038. This
is the first report of BAL disappearance (i) over Mg ii, Al iii, C iv, and Si
iv ions and (ii) in a weak emission-line quasar (WLQ). The discovery is based
on four spectra from the SDSS and one follow-up spectrum from HET/LRS2. The
simultaneous Civ BAL disappearance and emergence at different velocities,
together with no variations in the CRTS light curve, indicate that ionization
changes in the absorbing material are unlikely to cause the observed BAL
variability. Our analyses reveal that transverse motion is the most likely
dominant driver of the BAL disappearance/emergence. Given the presence of
mildly relativistic BAL outflows and an apparently large C iv emission-line
blueshift that is likely associated with strong bulk outflows in this WLQ,
J0827+4252 provides a notable opportunity to study extreme quasar winds and
their potential in expelling material from inner to large-scale regions.
