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J/MNRAS/268/305     Variability of optically selected quasars (Hook+ 1994)
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The variability of optically selected quasars
      Hook I.M., McMahon R.G., Boyle B.J., Irwin M.J.
     <Mon. Not. R. Astron. Soc. 268, 305 (1994)>
     =1994MNRAS.268..305H      (SIMBAD/NED BibCode)
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ADC_Keywords: QSOs ; Redshifts ; Magnitudes
Keywords: quasars: general

Abstract:
    The variability properties of a sample of ~300 optically selected
    quasars near the South Galactic Pole (SGP) have been studied over a
    baseline of 16 years using a series of twelve UK Schmidt Telescope
    B_J_ plates at seven epochs. In this sample there is a correlation
    between variability and both quasar luminosity and redshift, at
    greater than the 99 per cent significance level. Quasars of high
    luminosity show significantly less variability than those with low
    luminosity, the rms variation ranging from about 0.25mag at M_B_=-23
    to 0.1mag at M_B_=-28. The observed trends can be explained by an
    intrinsic dependence of quasar variability on luminosity combined with
    the effects of time dilation, and have implications for quasar samples
    selected by variability or multicolour techniques. The change in the
    slope of the n(m) relation at the break can be less pronounced in
    variability-selected samples. Our results can be used to test models
    for the origin and reprocessing of the continuum emission in quasars.

File Summary:
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  FileName    Lrecl  Records   Explanations
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ReadMe           80        .   This file
tablea1.dat      47      332   Positions, redshifts, mean apparent Bj magnitudes
                                and variability index for the SGP sample
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Byte-by-byte Description of file: tablea1.dat
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   Bytes Format Units   Label     Explanations
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       1  I1    h       RAh       Right ascension (1950.0)
   3-  4  I2    min     RAm       Right ascension (1950.0)
   6- 10  F5.2  s       RAs       Right ascension (1950.0)
      12  A1    ---     DE-       Declination sign
  13- 14  I2    deg     DEd       Declination (1950.0)
  16- 17  I2    arcmin  DEm       Declination (1950.0)
  19- 22  F4.1  arcsec  DEs       Declination (1950.0)
  24- 27  F4.2  ---     z         Redshift
  29- 33  F5.2  mag     Bj        Mean apparent B_J_ magnitude
  35- 38  F4.2  ---     sigmaV    Variability index sigma_V_ (1)
  40- 41  I2    ---     Ref       Reference (2)
  43- 47  A5    ---     Note      Notes (3)
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Note (1): sigma_v_=1/(Ne-1)*[sum(i=1 to Ne)(|m_i_-<m>|)]*sqr(pi/2)
           where Ne is the number of epochs at which the quasar was visible
           on the plate and m_i_ the magnitude of the quasar at the epoch i
Note (2): References:
          1: Boyle et al., 1985MNRAS.216..623B
          2: Boyle et al., 1990, Cat. <J/MNRAS/243/1>
          3: Burbidge et al., 1977ApJ...218....1B
          4: Campusano, 1986IAUS..119...49C
          5: Campusano, 1991AJ....102..502C
          6: Hazard et al., 1986Natur.322...38H
          7: Hazard et al., 1986MNRAS.223...87H
          8: Hazard et al., 1987ApJ...323..263H
          9: Hazard & McMahon, in prep.
         10: Jauncey et al., 1984ApJ...286..498J
         11: Morris et al., 1991AJ....102.1627M
         12: Pocok et al., 1984MNRAS.210..373P
         13: Savage et al., 1985MNRAS.213..485S
         14: Smith et al., 1981MNRAS.195..437S
         15: Trew et al., 1982MNRAS.200..785T
         16: Wampler, 1985ApJ...296..416W
         17: Warren et al., 1987Natur.330..453W
         18: Warren et al., 1987Natur.325..131W
         19: Warren et al., 1991, Cat. <J/ApJS/76/23>
Note (3): a: z < 0.3
          b: <m> > 21.0
          c: <M_B_> > -23.0
          d: classified as non-stellar by APM
          e: merged with another image on reference plate
          f: object appeared at fewer than 5 independent epochs
          g: photometry on plate J14545 affected by fireball
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History: Prepared via OCR at CDS.
         Corrections made on 21-Jul-1997:
         In line 297: "1  1 11.81" corrected in "1  1 01.81"
         In line 298: "1  1 14.08" corrected in "1  1 04.08"
         In line 299: "1  1 18.24" corrected in "1  1 08.24"
         In line 303: "1  1 20.67" corrected in "1  2 00.67"
         In line 304: "1  1 23.81" corrected in "1  2 03.81"
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(End)                           James Marcout, Patricia Bauer [CDS]  07-Mar-1997