Discovery of the Transition of a Mini-Broad Absorption Line into Broad
  Absorption in the SDSS Quasar J115122.14+020426.3
  We present the detection of a rare case of dramatic strengthening in the UV
absorption profiles in the spectrum of the quasar J115122.14+020426.3 between
observations ~2.86 years apart in the quasar rest-frame. A 2001 spectrum from
the Sloan Digital Sky Survey (SDSS) shows a CIV "mini-broad" absorption line
(FWHM=1,220 km/s) with a maximum blueshift velocity ~9,520 km/s, while a later
spectrum from the Very Large Telescope (VLT) shows significantly broader and
stronger absorption line, with a maximum blueshift velocity of ~12,240 km/s,
that qualifies as a broad absorption line. A similar variability pattern is
observed in two additional systems at lower blueshifted velocities and in the
Lya and NV transitions as well. One of the absorption systems appears to be
resolved and shows evidence for partial covering of the quasar continuum source
(Cf~0.65), indicating a transverse absorber size of, at least, ~6 x 10^(16) cm.
In contrast, a cluster of narrower CIV lines appears to originate in gas that
fully covers the continuum and broad emission line sources. There is no
evidence for changes in the centroid velocity of the absorption troughs. This
case suggests that, at least some of the absorbers that produce "mini-broad"
and broad absorption lines in quasar spectra do not belong to intrinsically
separate classes. Here, the "mini-broad" absorption line is most likely
interpreted as an intermediate phase before the appearance of a broad
absorption line due to their similar velocity. While the current observations
do not provide enough constraints to discern among the possible causes for this
variability, future monitoring of multiple transitions at high resolution will
help achieve this goal.
