Emergences of C IV narrow absorption troughs in the quasar SDSS
  J095254.10+021932.8
  In this paper, we report on two C IV narrow absorption systems emerging from
the spectrum of the quasar SDSS J095254.10 +021932.8, which are located at
$z_{\rm abs}=2.0053$ and $z_{\rm abs}=1.8011$, respectively. These features
have velocity offsets of $\rm \sim 13,800$ and $\rm \sim 34,700~km~s^{-1}$ with
respect to the quasar, and show obviously partial coverage to the background
emission sources. The two C IV absorption systems are imprinted on the spectrum
obtained by the Sloan Digital Sky Survey (SDSS) III on 2011 March 25, which
cannot be observed from the spectrum obtained by SDSS-I/II on 2000 December 30.
The time interval of the two SDSS observations is 1186.4 d at the quasar rest
frame. Because the continuum radiation, broad emission lines and mass accretion
rate are stable for the two observations, together with the time interval of
observations, we believe that the observed spectral variations are less likely
to be caused by the changes in the ionization states of the absorbing gas or by
a new outflow, arising from the situation where there was previously no outflow
at all. Instead, they probably arise from the motions of multiple streaming gas
across the sightline of the quasar.
