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J/A+A/289/101   Orion OB1 association. I.                         (Brown+, 1994)
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The Orion OB1 association. I. Stellar content
     Brown A.G.A., de Geus E.J., de Zeeuw P.T.
     <Astron. Astrophys. 289, 101 (1994)>
     =1994A&A...289..101B    (SIMBAD/NED Reference)
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ADC_Keywords: Associations, stellar; Populations, stellar; Stellar distribution
Keywords:  stars: fundamental parameters - Hertzsprung-Russel diagram -
           open clusters and associations: general, individual: Orion OB1 -
           ISM: bubbles - stars: luminosity function, mass function

Abstract:
    Walfraven photometry of established and probable members of the Orion OB1 
    association is presented. Effective temperature, surface gravity, 
    luminosity and mass are derived for all stars, using atmosphere model by 
    Kurucz (1979). Absolute magnitudes are calculated using the Straizys and 
    Kuriliene (1981) tables. Distance moduli and visual extinctions are 
    determined. A comparison of the visual extinctions to IRAS 100 micrometers
    data shows that the near edge of the Orion A and B clouds lies at a 
    distance of approximately 320 pc, while the far edge is at approximately 
    500 pc. A method for deriving the ages of the subgroups by comparing 
    theoretical isochrones to the observations in the log g, log Teff plane is
    presented. The derived ages suggest, contrary to earlier studies, that 
    subgroup 1b is younger than 1c, which can possibly be explained by past 
    geometries of the system of stars and gas. The initial mass function for 
    Orion OB1 is derived with the aid of the Kolmogorov-Smirnoff test. Through 
    extensive simulations, we show that it is very difficult to derive 
    accurately the Initial Mass Function (IMF) from the available data. To 
    within somewhat weak limits the IMF is found to be of the form 
    xi(log M) = AM-1.7 +/- 0.2 for all subgroups. The energy output of the 
    subgroups in the form of stellar winds and supernovae is calculated and 
    compared to the observed size and expansion velocity of the Orion-Eridanus
    bubble. It is shown that the energy output of the association can account 
    for the morphology and kinematics of the interstellar medium (ISM). 

File Summary:
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 FileName    Lrecl    Records    Explanations
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ReadMe          80          .    This file
table1a        104        311    Subgroup 1a stars derived physical parameters
table1b        104        139    Subgroup 1b stars derived physical parameters
table1c        104        350    Subgroup 1c stars derived physical parameters
table1d        104         14    Subgroup 1d stars derived physical parameters
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Byte-by-byte Description of file: table1a, table1b, table1c, table1d
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   Bytes Format  Units   Label    Explanations
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   1-  5  I5     ---     IN       Internal number of star in proposal 141 for
                                   the HIPPARCOS mission (1)
   8- 18  A11    ---     HD       HD or BD designation
  21- 25  A5     ---     HIC      Hipparcos Input Catalogue number
  28- 40  A13    ---     Name     Name of the star
  43- 46  F4.2   [K]    log(Teff) Logarithm of effective temperature
  49- 52  F4.2  [cm/s2]  log(g)   Logarithm of surface gravity
  55- 57  F3.1  [solLum] log(L)   Logarithm of luminosity
  60- 64  F5.2   mag     mv       Visual magnitude
  67- 70  F4.1   mag     Mv       Absolute visual magnitude
  73- 77  F5.2   mag     Av       Visual extinction
  80- 83  F4.1   mag     DM       Distance modulus
  86- 87  A2     ---     Mem.     Indication of membership:
                                                           blank: member
                                                           PM: possible member
                                                           NM: non-member
      90  A1     ---     n        [+*] Note:
                                    * : the star is included in fig. 6a of paper
                                    + : the star is included in fig. 6b of paper
  93-104  A12    ---     MK       Spectral type
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Note (1): This number is also listed in: 
     de Geus, E.J., Lub, J., van de Grift, E., 1990, A&AS 85, 915
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(End)                                           Patricia Bauer [CDS] 08-Apr-1994