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II/180          uvby-beta photometry of metal-poor stars (Schuster+ 1989)
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uvby-beta photometry of high-Velocity and metal-poor stars
    Schuster W.J., Nissen P.E.
    <Astron. Astrophys. 222, 69 (1989)>
    =1989A&A...222...69S
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ADC_Keywords: Stars, high-velocity ; Stars, metal-deficient
Keywords: Galaxy: evolution - Galaxy: halo - stars: metallicity - stars: ages

Description:
    Using the calibrations derived by Schuster and Nissen
    (=1989A&A...221...65S), the interstellar color excesses, E(b-y), and
    the metallicities, [Fe/H], have been determined for the 711 high
    velocity and metal-poor stars in the catalogue of uvby-beta photometry
    (=1988A&AS...73..225S). 220 of these listed in table1 turn out to be
    halo stars according to the criterion [Fe/H] <= -1.0. About 15% of
    the halo stars have colors that are significantly affected by
    interstellar reddening, i.e. E(b-y) > 0.025.

    The distributions in the c0-(b-y)0 diagram of the halo stars grouped
    according to [Fe/H], have well defined turn-off points. From the Teff
    values of these points a minimum age of 18-20 Gyr for the halo stars
    is determined. However, this age may be 2-3 Gyr too high due to a
    possible systematic error in Teff for the stellar models used.

    Relative ages of 77 halo stars in the turn-off region of the c0-(b-y)0
    diagram are derived using the isochrones VandenBerg and Bell
    (=1985ApJS...58..561V). Assuming that the O/Fe abundance ratio is
    constant in halo stars, evidence of a cosmic age scatter of
    +/-2.5Gyr at a given metallicity is found. Furthermore, the mean age
    of the halo stars is found to decrease smoothly by about 3 Gyr from
    [Fe/H]= -2.0 to -1.0. These results suggest that a pressure-supported
    slow uniform collapse controlled the formation and early evolution of
    the Galaxy. However, the scenario of Searle and Zinn
    (=1978ApJ...225..357S) is also compatible with the results.

See also:
    J/A+AS/97/951 : a second catalogue by Schuster et al.  =1993A&AS...97..951S

File Summary:
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 FileName       Lrecl       Records    Explanations
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ReadMe             80             .    This file
table1.dat         73           220    The Catalogue
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Byte-by-byte Description of file: table1.dat
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   Bytes Format  Units   Label    Explanations
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   3- 12  A10    ---     Name     Star designation (HD/DM/Giclas)
  15- 16  I2     h       RAh      Right Ascension 1950
  18- 19  I2     min     RAm      Right Ascension 1950
  21- 24  F4.1   s       RAs      Right Ascension 1950
      27  A1     ---     DE-      Declination 1950 Sign
  28- 29  I2     deg     DEd      Declination 1950
  31- 32  I2     arcmin  DEm      Declination 1950
  34- 35  I2     arcsec  DEs      Declination 1950
  38- 43  F6.3   mag     E(b-y)   ? Interstellar reddening
      45  A1     ---     l_[Fe/H] '<' if [Fe/H] metallicity is an upper limit
  46- 50  F5.2   Sun     [Fe/H]   [-3.5/-1[ Metallicity (relative to Sun)
  53- 56  F4.1   Ga      Age      ? Age in Giga-years
  59- 61  F3.1   Ga      e_Age    ? rms error on Age
  64- 73  A10    ---     Notes    Remarks (1)
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Note (1): the following symbols are used in the remarks:
     AGB    = asymptotic giant branch
     D      = two stars in the diaphragm
     PHV    = photometrically variable
     RHB    = red horizontal branch
     RV-var = radial velocity variable
     SB-CL  = spectroscopic binary (Carney + Latham, 1987, AJ 93, 116)
     SG     = subgiant
     BS?    = possible blue straggler
     *        See Individual Notes
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Individual Notes:
    G 266-060: common proper motion with G 226-061.
    HD  23439: double, component B is SB-CL, orbital elements by
                Latham et al.                           (=1988AJ.....96..567L).
    G 088-010: orbital elements by Latham et al.        (=1988AJ.....96..567L).
    G 089-014: orbital elements by Latham et al.        (=1988AJ.....96..567L).
    G 114-026: orbital elements by Latham et al.        (=1988AJ.....96..567L).
    HD 103095: double, orbital elements by
                Beardsley et al.                        (=1974ApJ...194..637B).
    G 065-022: orbital elements by Latham et al.        (=1988AJ.....96..567L).
    HD 134439: common proper motion with HD 134440.
    G 141-019: orbital elements by Latham et al.        (=1988AJ.....96..567L).
    G 206-034: orbital elements by Latham et al.        (=1988AJ.....96..567L).
    G 026-009: double lined SB, orbital elements by
                Peterson et al.                         (=1980ApJ...239...50R).
    G 126-062: orbital elements by Latham et al.        (=1988AJ.....96..567L).


Acknowledgements:
    We thank Dr Poul E. Nissen for having supplied a copy of Table1.

Historical Notes:
  * 09-Sep-1992: table supplied by Poul E. Nissen <pen@obs.aau.dk>
  * 04-Jan-1993: First documentation at CDS (Francois Ochsenbein)
  * 03-Nov-1995: Documentation standardized at CDS, and notes added
                 (Francois Ochsenbein)
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(End)                                     Francois Ochsenbein [CDS]  03-Nov-1995