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J/A+AS/115/75  Optical astrometry of Benchmark radio sources. III (Costa+, 1996)
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Optical astrometry of Benchmark radio sources. III. Positions of 35
southern extragalactic radio sources with respect to the International
Reference Stars catalogue.
     Costa E., Loyola P.
    <Astron. Astrophys. Suppl. Ser. 115, 75 (1996)>
    =1996A&AS..115...75C      (SIMBAD/NED BibCode)
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ADC_Keywords: Radio sources ; QSOs
Keywords: astrometry - radio continuum: stars - reference system -
          quasar: Q0523-570

Description:
    Optical positions, relative to the International Reference Stars
    catalogue (IRS), and therefore in the system of the FK5, have been
    obtained for the optical counterparts of 35 extragalactic radio
    sources south of {delta}~+3deg.
    Many of these sources are being considered as possible
    Benchmark objects for the establishment of a quasi-inertial unified
    radio/optical reference frame. Precision levels better than 0.2" in
    both coordinates were achieved. A comparison with VLBI radio
    positions available for these sources is presented. We give evidence
    for a possible offset in RA between the radio and optical reference
    frames.

File Summary:
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  FileName      Lrecl  Records   Explanations
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ReadMe             80        .   This file
table1             79       35   Optical positions in the FK5 system of
                                 35 extragalactic radio sources
table2             40       15   Comparison in the FK5 system with the radio
                                 positions of the NRL/USNO Survey
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Byte-by-byte Description of file: table1
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   Bytes Format  Units      Label    Explanations
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   4- 11  A8     ---        IAU      IAU designation of the source
  17- 18  I2     h          RAh      Right ascension (2000)
  20- 21  I2     min        RAm      Right ascension (2000)
  23- 28  F6.3   s          RAs      Right ascension (2000)
  32- 35  F4.2   arcsec   e_RAs      ? Error on right ascension:
                                     {sigma}({alpha}cos{delta}) (1)
      40  A1     ---        DE-      Declination sign
  41- 42  I2     deg        DEd      Declination (2000)
  44- 45  I2     arcmin     DEm      Declination (2000)
  47- 51  F5.2   arcsec     DEs      Declination (2000)
  55- 58  F4.2   arcsec   e_DEs      ? Error on declination:
                                     {sigma}(cos{delta})(1)
  63- 70  A8   "DD/MM/YY"   Date     Epoch of observation
  75- 78  A4     ---        Notes    Notes
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Note (1): Determined as described in Costa and Loyola 1992
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Byte-by-byte Description of file: table2
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   Bytes Format Units   Label     Explanations
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   1-  8  A8    ---     IAU       IAU designation of the source
  24- 28  F5.2  arcsec  DeltaRA   Difference with the VLBI radio position
                                  from the NRL/USNO Survey (Fey et al. 1994);
                                  NRL-CL (CL=this paper);
                                  Delta {alpha} cos {delta}
  36- 40  F5.2  arcsec  DeltaDE   Difference with the VLBI radio position
                                  from the NRL/USNO Survey (Fey et al. 1994);
                                  NRL-CL (CL=this paper); Delta {delta}
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Table 2 (continued):
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   Mean residual          -0.24        0.04
   Sigma                   0.27        0.22
   Standard error          0.07        0.06
   Nx of common objects           15
   ------------------------------------------
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References:
   Costa E. and Loyola P. 1992, A&AS 96, 183               =1992A&AS...96..183C
   Fey A.L., Russell J.L., de Vegt C. et al. 1994, AJ 107, 385
                                                           =1994AJ....107..385F
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(End)                                             Simona Mei [CDS]   06-Sep-1995