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J/PASP/107/32       uvby-hk photometry in M22             (Anthony-Twarog+ 1995)
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CN and Ca abundance variations among the giants in M 22
     Anthony-Twarog B.J., Twarog B.A., Craig J.
    <Publ. Astron. Soc. Pac. 107, 32 (1995)>
    =1995PASP..107...32A        (SIMBAD/NED BibCode)
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ADC_Keywords: Clusters, globular ; Photometry, K-line ; Photometry, uvby

Abstract:
    We have obtained uvbyCa data for over 300 giants and horizontal branch
    stars in  three fields of M22.  The spread in (b-y)  for the giant and
    horizontal   branches  is  consistent  with  a  spread  in  foreground
    reddening Delta-E(B-V) ~ 0.08.  Reanalysis  of the data  of Norris and
    Freeman (1983) indicates not only positive correlations between CH, CN
    and  a unimodal distribution for Ca. Our photometric indices, m_1, and
    hk, demonstrate a range in metallicity that persists to two magnitudes
    below the horizontal  branch,  and  confirm  the  correlation  between
    calcium  abundance  and  CN/CH.   We   infer   from   comparisons   to
    spectroscopic data that  m_1 is dominated  by the CN  and CH abundance
    and find  no independent evidence of a  range in [Fe/H]. The excessive
    ranges in m_1 and hk  also  suggest  the  influence  of  a  continuous
    opacity   source,  reminiscent  of  the   Bond-Neff  effect,  that  is
    correlated  with CNO abundance. The relative contributions of internal
    mixing and primordial variations for M22's giants are discussed.

Copyright: Astronomical Society of the Pacific

Objects:
   ---------------------------------
     RA (2000) DE    Name(s)
   ---------------------------------
   18 36.4   -23 54  M 22 = NGC 6656
   ---------------------------------

File Summary:
--------------------------------------------------------------------------------
 FileName    Lrecl    Records    Explanations
--------------------------------------------------------------------------------
ReadMe          80          .    This file
table3         124        396    uvbyCa photometry of stars in M22.
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See also:
    GCPD/81 : General Catalog of Photometric Data, CaII HK photometric system
    GCPD/04 : General Catalog of Photometric Data, uvby (Stromegren) system


Byte-by-byte Description of file: table3
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   Bytes Format Units   Label     Explanations
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   2-  6  I5    ---     ID        Designation of the star (1)
   8-  9  I2    ---     Pr        [0-99]?=-1 Probability of membership, from
                                    Peterson and Cudworth (1994ApJ...420..612P)
  11- 16  F6.1  arcsec  Xpos      X-position, increasing to positive R.A. (2)
  18- 23  F6.1  arcsec  Ypos      Y-position  north of field center (2)
  26- 31  F6.3  mag     Vmag      Johnson's V
  33- 38  F6.3  mag     b-y       Stroemgren index (see e.g. <GCPD/04>)
  40- 45  F6.3  mag     m1        Stroemgren index ((v - b) - (b - y))
  47- 52  F6.3  mag     c1        Stroemgren index ((u - v) - (v - b))
  54- 59  F6.3  mag     hk        index = (Ca-b)-(b-y) (see e.g. <GCPD/81>)
  62- 66  A5    ---     AM        Cross-identifications to Arp
                                    and Melbourne (1959AJ.....64...28A)
  68- 72  A5    ---     AL        Cross-identifications to Alcaino
                                    and Liller (1983AJ.....88.1330A)
  76- 80  F5.3  mag     e_Vmag    []?=0.000 Mean error on Vmag
  83- 87  F5.3  mag     e_b-y     []?=0.000 Mean error on b-y
  90- 94  F5.3  mag     e_m1      []?=0.000 Mean error on m1
  97-101  F5.3  mag     e_c1      []?=0.000 Mean error on c1
 104-108  F5.3  mag     e_hk      []?=0.000 Mean error on hk
     112  I1    ---     Ny        Number of y frames
     115  I1    ---     Nb        Number of b frames
     118  I1    ---     Nv        Number of v frames
     121  I1    ---     Nu        Number of u frames
     124  I1    ---     NCa       Number of Ca frames
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Note (1): the first digit denotes the CCD field:
          5 for NE, 2 for South, 4 for Southwest,
          3 for overlap between 2 and 4.
Note (2): Field center is at 18 33 21.5 -23 56 44 (1950).
                   in J2000: 18 36 24.6 -23 54 12
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Courtesy: Barbara J. Anthony-Twarog  <ANTHONY@kustar.phsx.ukans.edu>
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(End)                                     Francois Ochsenbein [CDS]  18-Aug-1995