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J/AJ/121/1872       FIRST radio-selected QSOs                (Helfand+, 2001)
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Long-term optical variability of radio-selected quasars from the FIRST survey.
    Helfand D.J., Stone R.P.S., Willman B., White R.L., Becker R.H., Price T.,
    Gregg M.D., McMahon R.G.
   <Astron. J. 121, 1872 (2001)>
   =2001AJ....121.1872H
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ADC_Keywords: QSOs ; Photometry ; Redshifts
Keywords: methods: statistical - quasars: general - surveys

Abstract:
    We have obtained single-epoch optical photometry for 202 quasars,
    taken from the FIRST Bright Quasar Survey (FBQS), which span a wide
    range in radio loudness. Comparison with the magnitudes of these
    objects on the POSS-I plates provides by far the largest sample of
    long-term variability amplitudes for radio-selected quasars yet
    produced. We find the quasars to be more variable in the blue than in
    the red band, consistent with work on optically selected samples. The
    previously noted trend of decreasing variability with increasing
    optical luminosity applies only to radio-quiet objects. Furthermore,
    we do not confirm a rise in variability amplitude with redshift, nor
    do we see any dependence on radio flux or luminosity. The variability
    over a radio-optical flux ratio range spanning a factor of 60000 from
    radio-quiet to extreme radio-loud objects is largely constant,
    although there is a suggestion of greater variability in the extreme
    radio-loud objects. We demonstrate the importance of Malmquist bias in
    variability studies and develop a procedure to correct for the bias in
    order to reveal the underlying variability properties of the sample.

File Summary:
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 FileName      Lrecl  Records   Explanations
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ReadMe            80        .   This file
table2.dat       134      201   FIRST Variable Quasar Catalog
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See also:
   IX/15   : Einstein EMSS Survey (Gioia+ 1990, Stocke+ 1991)
   VIII/59 : the FIRST Survey, version 1999Jul (White+ 1999)

Byte-by-byte Description of file: table2.dat
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   Bytes Format Units      Label    Explanations
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   1-  2  I2    h          RAh      FIRST radio Right Ascension (J2000)
   4-  5  I2    min        RAm      FIRST radio Right Ascension (J2000)
   7- 11  F5.2  s          RAs      FIRST radio Right Ascension (J2000)
      13  A1    ---        DE-      Sign of the Declination (J2000)
  14- 15  I2    deg        DEd      FIRST radio Declination (J2000)
  17- 18  I2    arcmin     DEm      FIRST radio Declination (J2000)
  20- 23  F4.1  arcsec     DEs      FIRST radio Declination (J2000)
  25- 32  F8.3  yr         Obs1     Year of POSS-I observation
  34- 41  F8.3  yr         Obs2     Year of CCD observation
      43  A1    ---      f_Bmag     [*] Indicates a source with too few CCD
                                     calibration stars to recalibrate the POSS-I
                                     magnitudes
  45- 49  F5.2  mag        Bmag     Extinction-corrected B band magnitude
  51- 55  F5.2  mag        Omag     Extinction-corrected POSS-I O band magnitude
  57- 61  F5.2  mag        B-O      The (B-O) color
  63- 67  F5.2  mag        Rmag     Extinction-corrected R band magnitude
  69- 73  F5.2  mag        Emag     Extinction-corrected POSS-I E band magnitude
  75- 79  F5.2  mag        R-E      The (R-E) color
  81- 88  F8.2  mJy        P20cm    The peak 20cm (1.5GHz) flux density
  90- 97  F8.2  mJy        I20cm    The integrated 20cm (1.5GHz) flux density
  99-103  F5.3  ---        z        Redshift
 105-109  F5.1  mag        BMag     The absolute B band magnitude
 111-114  F4.1 [mW/m2/Hz]  logLum   Log of the radio luminosity in
                                      erg/cm^2^/s/Hz (1)
 116-120  F5.2  ---        logR     Log of the K-corrected 5GHz radio to
                                      2500{AA} optical luminosity (2)
 122-133  A12   ---        Morph    Radio morphology (3)
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Note (1): At a rest-frame frequency of 5 GHz, assuming spectral index
          {alpha}=-0.5(F_{nu}_ {propto} {nu}^{alpha}^).
Note (2): Using the definition of Stocke et al. (1991, Cat. <IX/15>).
Note (3): Categories are FRII (double, with approximate separation in
          arcseconds), core-jet (with approximate core-jet length in
          arcseconds), and complex.  Objects with no notation are symmetrical,
          isolated sources.
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History:
    From electronic version of the journal
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(End)                    Greg Schwarz [AAS], Patricia Bauer [CDS]    08-Jun-2001