BROAD ABSORPTION LINE VARIABILITY ON MULTI-YEAR TIMESCALES IN A LARGE QUASAR SAMPLE
Author
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Filiz, N.
Author
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Brandt, W. N.
es_CL
Author
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Hall, P. B.
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Author
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Schneider, D. P.
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Author
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Anderson, S. F.
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Author
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Hamann, F.
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Author
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Lundgren, B. F.
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Author
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Myers, Adam D.
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Author
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Pâris, I.
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Author
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Petitjean, P.
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Author
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Ross, Nicholas P.
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Author
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Shen, Yue
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Author
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York, Don
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Admission date
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2014-01-07T18:28:28Z
Available date
dc.date.available
2014-01-07T18:28:28Z
Publication date
dc.date.issued
2013
Cita de ítem
dc.identifier.citation
The Astrophysical Journal, 777:168 (29pp), 2013 November 10
en_US
Identifier
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doi:10.1088/0004-637X/777/2/168
Identifier
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https://repositorio.uchile.cl/handle/2250/126008
General note
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Artículo de publicación ISI
en_US
Abstract
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We present a detailed investigation of the variability of 428 C iv and 235 Si iv broad absorption line (BAL) troughs
identified in multi-epoch observations of 291 quasars by the Sloan Digital Sky Survey-I/II/III. These observations
primarily sample rest-frame timescales of 1–3.7 yr over which significant rearrangement of the BAL wind is
expected. We derive a number of observational results on, e.g., the frequency of BAL variability, the velocity
range over which BAL variability occurs, the primary observed form of BAL-trough variability, the dependence of
BAL variability upon timescale, the frequency of BAL strengthening versus weakening, correlations between BAL
variability and BAL-trough profiles, relations between Civ and Si iv BAL variability, coordinated multi-trough
variability, and BAL variations as a function of quasar properties. We assess implications of these observational
results for quasar winds. Our results support models where most BAL absorption is formed within an order-ofmagnitude
of the wind-launching radius, although a significant minority of BAL troughs may arise on larger scales.
We estimate an average lifetime for aBALtrough along our line-of-sight of a fewthousand years.BAL disappearance
and emergence events appear to be extremes of general BAL variability, rather than being qualitatively distinct
phenomena. We derive the parameters of a random-walk model for BAL EW variability, finding that this model
can acceptably describe some key aspects of EW variability. The coordinated trough variability of BAL quasars
with multiple troughs suggests that changes in “shielding gas” may play a significant role in driving general BAL
variability.