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McGraw, S. M.; Brandt, W. N.; Grier, C. J.; Ak, N. Filiz; Hall, P. B.; Schneider, D. P.; Anderson, S. F.; Green, P. J.; Hutchinson, T. A.; Macleod, C. L.; Vivek, M.
{ "DOI": "10.1093/mnras/stx1063", "abstract": "We investigate broad absorption line (BAL) disappearance and emergence using a 470 BAL-quasar sample over <= 0.10-5.25 rest-frame years with at least three spectroscopic epochs for each quasar from the Sloan Digital Sky Survey. We identify 14 disappearing BALs over <= 1.73-4.62 rest-frame years and 18 emerging BALs over <= 1.46-3.66 rest-frame years associated with the C IV lambda 1548,1550 and/or Si IV lambda lambda 1393,1402 doublets, and report on their variability behaviour. BAL quasars in our data set exhibit disappearing/emerging C IV BALs at a rate of 2.3(-0.7)(+0.9) and 3.0(-0.8)(+1.0) per cent, respectively, and the frequency for BAL to non-BAL quasar transitions is 1.7(-0.6)(+0.8) per cent. We detect four re-emerging BALs over <= 3.88 rest-frame years on average and three re-disappearing BALs over <= 4.15 rest-frame years on average, the first reported cases of these types. We infer BAL lifetimes along the line of sight to be nominally less than or similar to 100-1000 yr using disappearing C IV BALs in our sample. Interpretations of (re-) emerging and (re-) disappearing BALs reveal evidence that collectively supports both transverse-motion and ionization-change scenarios to explain BAL variations. We constrain a nominal C IV/Si IV BAL-outflow location of less than or similar to 100 pc from the central source and a radial size of greater than or similar to 1x 10(-7) pc (0.02 au) using the ionization-change scenario, and constrain a nominal outflow location of less than or similar to 0.5 pc and a transverse size of similar to 0.01 pc using the transverse-motion scenario. Our findings are consistent with previous work, and provide evidence in support of BALs tracing compact flow geometries with small filling factors.", "author": [ { "family": "McGraw", "given": " S. M." }, { "family": "Brandt", "given": " W. N." }, { "family": "Grier", "given": " C. J." }, { "family": "Ak", "given": " N. Filiz" }, { "family": "Hall", "given": " P. B." }, { "family": "Schneider", "given": " D. P." }, { "family": "Anderson", "given": " S. F." }, { "family": "Green", "given": " P. J." }, { "family": "Hutchinson", "given": " T. A." }, { "family": "Macleod", "given": " C. L." }, { "family": "Vivek", "given": " M." } ], "container_title": "MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY", "id": "45141", "issue": "3", "issued": { "date-parts": [ [ 2017, 1, 1 ] ] }, "page": "3163-3184", "title": "Broad absorption line disappearance and emergence using multiple-epoch spectroscopy from the Sloan Digital Sky Survey", "type": "article-journal", "volume": "469" }
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