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 \sim 2.86 years apart in the quasar rest-frame .
A 2001 spectrum from the Sloan Digital Sky Survey ( SDSS ) shows a C iv “ mini-broad ” absorption line ( FWHM= 1 , 220 km s ^ { -1 } ) with a maximum blueshift velocity \sim 9 , 520 km s ^ { -1 } , while a later spectrum from the Very Large Telescope ( VLT ) shows significantly broader and stronger absorption line , with a maximum blueshift velocity of \sim 12 , 240 km s ^ { -1 } , that qualifies as a broad absorption line .
A similar variability pattern is observed in two additional systems at lower blueshifted velocities and in the Ly \alpha and N v transitions as well .
One of the absorption systems appears to be resolved and shows evidence for partial covering of the quasar continuum source ( C _ { f } \sim 0.65 ) , indicating a transverse absorber size of , at least , \sim 6 \times 10 ^ { 16 } cm .
In contrast , a cluster of narrower C iv 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 .