We analyze the long-term ( rest-frame 3–30 yr ) X-ray variability of eleven broad absorption line ( BAL ) quasars , mainly to constrain the variation properties of the X-ray absorbing shielding gas that is thought to play a critical role in BAL wind launching .
Our BAL quasar sample has coverage with multiple X-ray observatories including Chandra , XMM-Newton , BeppoSAX , ASCA , ROSAT , and Einstein ; 3–11 observations are available for each source .
For seven of the eleven sources we have obtained and analyzed new Chandra observations suitable for searching for any strong X-ray variability .
We find highly significant X-ray variability in three sources ( PG 1001 + 054 , PG 1004 + 130 , and PG 2112 + 059 ) .
The maximum observed amplitude of the 2–8 keV variability is a factor of 3.8 \pm 1.3 , 1.5 \pm 0.2 , and 9.9 \pm 2.3 for PG 1001 + 054 , PG 1004 + 130 , and PG 2112 + 059 , respectively , and these sources show detectable variability on rest-frame timescales down to 5.8 , 1.4 , and 0.5 yr. For PG 1004 + 130 and PG 2112 + 059 we also find significant X-ray spectral variability associated with the flux variability .
Considering our sample as a whole , we do not find that BAL quasars exhibit exceptional long-term X-ray variability when compared to the quasar population in general .
We do not find evidence for common strong changes in the shielding gas owing to physical rearrangement or accretion-disk rotation , although some changes are found ; this has implications for modeling observed ultraviolet BAL variability .
Finally , we report for the first time an X-ray detection of the highly polarized and well-studied BAL quasar IRAS 14026+4341 in its new Chandra observation .