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J/A+A/325/167       Geneva photometry in NGC 6231 (Raboud+ 1997)
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Geneva photometry in the young open cluster NGC 6231
       Raboud D., Cramer N., Bernasconi P.A.
      <Astron. Astrophys. 325, 167 (1997)>
      =1997A&A...325..167R          (SIMBAD/NED BibCode)
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ADC_Keywords: Clusters, open ; Photometry, Geneva
Keywords: open clusters: individual: NGC 6231 - technique: photometry -
          stars: formation - stars: pre-main sequence

Abstract:
    We present photoelectric (127 stars) and CCD (168 stars) Geneva
    photometry for the very young open cluster NGC 6231. We have searched
    for new cluster members out to a distance of ~13arcmin, extending the
    Seggewiss area (~8arcmin), and we found at least 64 new probable
    members in this extended field. Differential reddening is clearly
    measured across the cluster area. We determine the cluster distance
    (1800pc) and age (3.8+/-0.6x10^6^yr). The probable presence of
    pre-main sequence stars and the consequence of this population on the
    cluster formation history is analysed. We also found that the O8.5III
    star S161 is a long term variable and we present its light curve
    extending over more than 20 years. Finally we discuss the existence of
    Ap stars in the cluster.
    For a description of the Geneva photometric system, see e.g. <GCPD/13>

Objects:
    ----------------------------------------------------------
       RA   (2000)   DE    Designation(s)
    ----------------------------------------------------------
     16 54.2      -41 48   NGC 6231
    ----------------------------------------------------------

File Summary:
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 FileName   Lrecl  Records   Explanations
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ReadMe         80        .   This file
table3        120      128   Member stars in the center
table4        121       44   Non-member stars
table5        116       64   Member stars in the corona
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See also:
   J/A+A/315/384 : Binarity among B-stars in NGC 6231 (Raboud, 1996)

Byte-by-byte Description of file: table?
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   Bytes Format Units        Label     Explanations
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   1-  4  A4    ---          Number    Star number
       7  I1    ---        n_Number    [1]? Note on Number (1)
  11- 12  A2    ---          Class     Classification
      13  A1    ---        u_Class     [?] Uncertainty flag on Class
  15- 19  F5.2  mag          Vmag      Apparent V magnitude
  23- 27  F5.2  mag          X         X parameter in Geneva photometry
  31- 35  F5.2  mag          Y         Y parameter in Geneva photometry
  39- 43  F5.2  mag          Z         Z parameter in Geneva photometry
  48- 51  F4.2  mag          Ebv       Colour excess
  55- 59  F5.2  mag          MVmag     ? Absolute V magnitude
  64- 67  F4.2  ---          U-B       U-B Geneva colour
  71- 75  F5.2  km/s         B-V       B-V Geneva colour
  78- 84  F7.2  pix          xpos      x coordinate centered on S289 (2)
  87- 93  F7.2  pix          ypos      y coordinate centered on S289 (2)
  97-116  A20   ---          SpT       Estimated photometric spectral type
                                        (for table3 and 5) or
                                       Rejection criteria (for table4)
     118  I1    ---        n_Class     ? Remark on classification. See Note (3)
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Note (1): 1: CCD measurement
Note (2): 1 pix = 1/16.4 arcmin
Note (3): 1: The star could be considered as non-member, following the
              proper motion values by Braes (1967BANS....2....1B)
          2: Likely non-member, following Raboud (1996, Cat. <J/A+A/315/384>)
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Acknowledgements: Didier Raboud <Didier.Raboud@obs.unige.ch>

References:
   Braes L.L.E. 1967, Bull. Astr. Inst. Neth. Suppl., 2, 1  =1967BANS....2....1B
   Raboud D. 1996, A&A, 315, 384 =1996A&A...315..384R, Cat. <J/A+A/315/384>
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(End)           Raboud [University of Lausanne]                       7-Mar-1997