We present 21 examples of C IV Broad Absorption Line (BAL) trough
disappearance in 19 quasars selected from systematic multi-epoch observations
of 582 bright BAL quasars (1.9 < z < 4.5) by the Sloan Digital Sky Survey-I/II
(SDSS-I/II) and SDSS-III. The observations span 1.1-3.9 yr rest-frame
timescales, longer than have been sampled in many previous BAL variability
studies. On these timescales, ~2.3% of C IV BAL troughs disappear and ~3.3% of
BAL quasars show a disappearing trough. These observed frequencies suggest that
many C IV BAL absorbers spend on average at most a century along our line of
sight to their quasar. Ten of the 19 BAL quasars showing C IV BAL disappearance
have apparently transformed from BAL to non-BAL quasars; these are the first
reported examples of such transformations. The BAL troughs that disappear tend
to be those with small-to-moderate equivalent widths, relatively shallow
depths, and high outflow velocities. Other non-disappearing C IV BALs in those
nine objects having multiple troughs tend to weaken when one of them
disappears, indicating a connection between the disappearing and
non-disappearing troughs, even for velocity separations as large as 10000-15000
km/s. We discuss possible origins of this connection including disk-wind
rotation and changes in shielding gas.
Description
[1208.0836] Broad Absorption Line Disappearance on Multi-Year Timescales in a Large Quasar Sample
%0 Generic
%1 ak2012broad
%A Ak, N. Filiz
%A Brandt, W. N.
%A Hall, P. B.
%A Schneider, D. P.
%A Anderson, S. F.
%A Gibson, R. R.
%A Lundgren, B. F.
%A Myers, A. D.
%A Petitjean, P.
%A Ross, Nicholas P.
%A Shen, Yue
%A York, D. G.
%A Bizyaev, D.
%A Brinkmann, J.
%A Malanushenko, E.
%A Oravetz, D. J.
%A Pan, K.
%A Simmons, A. E.
%A Weaver, B. A.
%D 2012
%K BAL absorption line quasar
%T Broad Absorption Line Disappearance on Multi-Year Timescales in a Large
Quasar Sample
%U http://arxiv.org/abs/1208.0836
%X We present 21 examples of C IV Broad Absorption Line (BAL) trough
disappearance in 19 quasars selected from systematic multi-epoch observations
of 582 bright BAL quasars (1.9 < z < 4.5) by the Sloan Digital Sky Survey-I/II
(SDSS-I/II) and SDSS-III. The observations span 1.1-3.9 yr rest-frame
timescales, longer than have been sampled in many previous BAL variability
studies. On these timescales, ~2.3% of C IV BAL troughs disappear and ~3.3% of
BAL quasars show a disappearing trough. These observed frequencies suggest that
many C IV BAL absorbers spend on average at most a century along our line of
sight to their quasar. Ten of the 19 BAL quasars showing C IV BAL disappearance
have apparently transformed from BAL to non-BAL quasars; these are the first
reported examples of such transformations. The BAL troughs that disappear tend
to be those with small-to-moderate equivalent widths, relatively shallow
depths, and high outflow velocities. Other non-disappearing C IV BALs in those
nine objects having multiple troughs tend to weaken when one of them
disappears, indicating a connection between the disappearing and
non-disappearing troughs, even for velocity separations as large as 10000-15000
km/s. We discuss possible origins of this connection including disk-wind
rotation and changes in shielding gas.
@misc{ak2012broad,
abstract = {We present 21 examples of C IV Broad Absorption Line (BAL) trough
disappearance in 19 quasars selected from systematic multi-epoch observations
of 582 bright BAL quasars (1.9 < z < 4.5) by the Sloan Digital Sky Survey-I/II
(SDSS-I/II) and SDSS-III. The observations span 1.1-3.9 yr rest-frame
timescales, longer than have been sampled in many previous BAL variability
studies. On these timescales, ~2.3% of C IV BAL troughs disappear and ~3.3% of
BAL quasars show a disappearing trough. These observed frequencies suggest that
many C IV BAL absorbers spend on average at most a century along our line of
sight to their quasar. Ten of the 19 BAL quasars showing C IV BAL disappearance
have apparently transformed from BAL to non-BAL quasars; these are the first
reported examples of such transformations. The BAL troughs that disappear tend
to be those with small-to-moderate equivalent widths, relatively shallow
depths, and high outflow velocities. Other non-disappearing C IV BALs in those
nine objects having multiple troughs tend to weaken when one of them
disappears, indicating a connection between the disappearing and
non-disappearing troughs, even for velocity separations as large as 10000-15000
km/s. We discuss possible origins of this connection including disk-wind
rotation and changes in shielding gas.},
added-at = {2012-08-07T09:01:55.000+0200},
author = {Ak, N. Filiz and Brandt, W. N. and Hall, P. B. and Schneider, D. P. and Anderson, S. F. and Gibson, R. R. and Lundgren, B. F. and Myers, A. D. and Petitjean, P. and Ross, Nicholas P. and Shen, Yue and York, D. G. and Bizyaev, D. and Brinkmann, J. and Malanushenko, E. and Oravetz, D. J. and Pan, K. and Simmons, A. E. and Weaver, B. A.},
biburl = {https://www.bibsonomy.org/bibtex/2fa2c95ffb494ce8f7c7dd6766e48800a/miki},
description = {[1208.0836] Broad Absorption Line Disappearance on Multi-Year Timescales in a Large Quasar Sample},
interhash = {d58353ac238164ff6137b3d4df8069d2},
intrahash = {fa2c95ffb494ce8f7c7dd6766e48800a},
keywords = {BAL absorption line quasar},
note = {cite arxiv:1208.0836},
timestamp = {2012-08-07T09:01:55.000+0200},
title = {Broad Absorption Line Disappearance on Multi-Year Timescales in a Large
Quasar Sample},
url = {http://arxiv.org/abs/1208.0836},
year = 2012
}