J/A+A/525/A37 Variability indexes of QSOs in SDSS Stripe 82 (Meusinger+, 2011)
Spectral variability of quasars from multi-epoch photometric data in the Sloan
Digital Sky Survey Stripe 82.
Meusinger H., Hinze A., de Hoon A.
<Astron. Astrophys. 525, A37 (2011)>
=2011A&A...525A..37M 2011A&A...525A..37M
ADC_Keywords: Active gal. nuclei ; Photometry, SDSS ; QSOs
Keywords: galaxies: active - quasars: general - quasars: emission lines
Description:
We identified 8744 quasars in the Light-Motion Curve Catalogue
(LMCC; Bramich et al., 2008MNRAS.386..887B 2008MNRAS.386..887B,
http://das.sdss.org/value_added/stripe_82_variability/SDSS_82_public/)
for the stripe 82 of the Sloan Digital Sky Survey (SDSS). The light
curves were used, after correction for photometric outliers, to
compute individual noise-corrected first-order structure functions
(variance as a function of time-lag) binned into rest frame time-lag
intervals. The mean value of the corrected structure function at rest
frame time-lags from 300 to 600 days is found to be a useful
variability index for the statistical investigation of quasar samples
with redshifts up to ∼3. For each quasar, the variability indexes for
the five SDSS bands are given along with the equatorial coordinates,
redshift, mean g band magnitude, absolute i band magnitude, and a
remark on spectral peculiarities.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 83 8744 Variability indexes of quasars
--------------------------------------------------------------------------------
See also:
J/ApJS/186/233 : Variable point sources in SDSS stripe 82. I. (Bhatti+, 2010)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq Running number
6- 15 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
17- 25 F9.6 deg DEdeg Declination in decimal degrees (J2000)
27- 31 F5.3 --- z Redshift (spectroscopic)
33 I1 --- zFlag [0,1] Redshift Flag (0: ok, 1: uncertain)
35- 40 F6.3 mag gmag Mean apparent g band magnitude
42- 47 F6.2 mag iMAG Absolute i band magnitude (1)
49- 53 F5.3 mag+2 Vu Variability index in the u band (2)
55- 59 F5.3 mag+2 Vg Variability index in the g band (2)
61- 65 F5.3 mag+2 Vr Variability index in the r band (2)
67- 71 F5.3 mag+2 Vi Variability index in the i band (2)
73- 77 F5.3 mag+2 Vz Variability index in the z band (2)
79- 83 A5 --- Remark ? Remark about the spectrum (3)
--------------------------------------------------------------------------------
Note (1): computed following Kennefick and Bursick (2008AJ....136.1799K 2008AJ....136.1799K)
with Galactic foreground extinction from the "Galactic Dust Extinction
Service" of the NASA/IPAC Infrared Science Archive.
Note (2): The index is actually created to compare the variability (e.g.,
between different quasars with each other or between different
passbands of the same quasar) but is not apt to measure the
significance of the variability. On the one hand, a variability index
of "0" means no significant variability. However, non-variable quasars
can have also a finite (small) value but there is no critical value
for such an index to clearly separate between variables and
non-variables. (In the paper, we have shown that more than ∼90% of the
quasars are significantly variable in the ugri bands.)
Note (3): Remarks use the following abbreviations:
w_l = Weak emission lines
s_bal = Strong broad absorption lines
x_bal = Extreme broad absorption lines
myst = Mysterious spectrum
--------------------------------------------------------------------------------
References:
Bramich et al., Light-Motion Curve Catalogue, 2008MNRAS.386..887B 2008MNRAS.386..887B,
http://das.sdss.org/value_added/stripe_82_variability/SDSS_82_public/
(End) Helmut Meusinger [TLS, Germany], Patricia Vannier [CDS] 27-Oct-2010