Quasar J152645.61+193006.7 ( z _ { e } = 2.5771 ) was observed by the Sloan Digital Sky Survey ( SDSS ) on 2006 May 31 , and again on 2011 April 9 .
The time interval of the SDSS two observations is 497.4 days at the quasar rest frame .
From the spectra of this quasar , we detect a phenomenon of disappearance of a narrow Mg~ { } II~ { } \lambda \lambda 2796 , 2803 absorption system with a velocity up to 166 , 129 ~ { } km~ { } s ^ { -1 } with respect to the quasar .
This disappearance event can be caused by changes in the ionization state of absorbing gas or by the bulk motion of the absorbing gas across the quasar sightline .
The coverage fraction analysis shows that this absorber partially covers the background emission sources with an effective coverage fraction of C _ { f } = 0.40 \pm 0.06 .
The time variation analysis and the coverage fraction analysis imply that this absorber might be intrinsic to the quasar .
However , the scenario of a cosmologically separated foreground object located at z = 0.9170 accounting for the phenomenon can not be ruled out according to current available data .