Sui Chi Woo, David A. Turnshek, Carles Badenes, Steven Bickerton
We examine the variability of the high-ionization Ly\alpha \lambda 1216 broad emission line (BEL) in a sample of 61 high-luminosity, high-redshift quasars observed at two epochs by the Sloan Digital Sky Survey (SDSS). These bright objects lie in the redshift interval z = [2.5, 4.3] and have luminosities greater than \lambda L~2.7x10^45erg/s at 1300A. Utilizing improved spectrophotometric flux calibrations relative to nearby compact stars observed simultaneously, we are able to measure the flux changes in Ly\alpha and the nearby continuum at two epochs. We find 20 objects that exhibit Ly\alpha BEL flux variability at a significance level greater than 5\sigma on time scales ranging from days to years in the quasar rest frame. The results show that, despite some early work in which no significant Ly\alpha BEL flux changes were detected, variability is present and readily observable. We also consider the CIV \lambda 1549 BEL. The lack of a strong correlation between Ly\alpha BEL variability and nearby continuum variability is consistent with the presence of a time lag between the variations, whereas the presence of a stronger correlation between Ly\alpha BEL variability and CIV BEL variability suggests that these BEL regions (BELRs) are at similar distances from the central ionizing source. Some interesting examples are high-lighted in the analysis, including a case where the flux of a Ly\alpha BEL increased by 26% in 14 days in the quasar rest frame, suggesting that the BELR has the shape of a disc, which is being observed face-on. This work demonstrates that future campaigns of spectrophotometric monitoring can improve our understanding of the structure of the BELRs of high-luminosity, high-redshift quasars.
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http://arxiv.org/abs/1305.4357
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