2013MNRAS.434.3275C

In this paper, we report on two Civ narrow absorption systems emerging from the spectrum of the quasar SDSS J095254.10+021932.8, which are located at zabs = 2.0053 and zabs = 1.8011, respectively. These features have velocity offsets of ∼ 13800 and ∼ 34700kms-1 with respect to the quasar, and show obviously partial coverage to the background emission sources. The two Civ 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 1186.4d 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.