CDROM/APJ/V490/P328     "Mass Discrepancy" for Massive Stars (Burkholder+ 1997)
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The "Mass Discrepancy" for Massive Stars: Tests of Models Using Spectroscopic
Binaries
        Valorie Burkholder, Philip Massey, and Nidia Morrell
        <1997, ApJ, 490, 328>
        =1997ApJ...490..328B
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Abstract:
     Stellar evolutionary models are often used to infer a star's mass
  via its luminosity, but empirical checks on the accuracy of the
  theoretical mass-luminosity relation for very massive stars have been
  lacking.  This is of particular concern given that modern atmosphere
  models yield systematically smaller masses for massive stars than do
  evolutionary models, with the discrepancy a factor of two for Of
  stars.  We attempt to resolve this mass discrepancy by obtaining new,
  high-resolution optical data on seven early-type spectroscopic
  binaries: V453 Cyg, HD 191201, V382 Cyg, Y Cyg, HD 206267, DH Cep, and
  AH Cep.  Our study produces improved spectral substypes for the
  components of these systems, crucial for evaluating their luminosities
  and locations in the H-R diagram.  Our radial velocity study utilizes
  a measuring method which explicitly accounts for the effects of
  pair-blending.  We combine our new orbit solutions with existing data
  on inclinations and distances when available to compare the orbital
  masses with evolutionary models, and we find good agreement in all
  cases where the stars are non-interacting. (The components of V382 Cyg
  and DH Cep fill their Roche lobes, and in both cases we find masses
  substantially lower than the masses inferred from evolutionary tracks,
  suggesting that significant material has been lost rather than
  transferred.  We confirm that this same trend exists for other systems
  drawn from the literature.)  Our own data extends to only 15 Msun,
  although photometric inclination determinations for HD 191201 and HD
  206267 should prove possible, and will provide examples of higher mass
  systems.  We briefly discuss suitable systems from the literature, and
  conclude that orbit solutions provide good agreement with the
  evolutionary models to 25 Msun. Beyond this, most known binaries
  either fill their Roche lobes or have other complications.  We also
  discuss five systems for which our improved data and analysis failed
  to yield acceptable orbit solutions: EO Aur, IU Aur, V640 Mon
  (Plaskett's star), LY Aur, and 29 UW CMa all remained intractable,
  despite improved data.

Keywords:  binaries: spectroscopic -- stars: early-type --
  stars: evolution -- stars: fundamental parameters


File Summary:
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File Name     Lrecl     Records     Explanations
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table2.dat      62        143       Radial velocities
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Byte-by-byte Description of file: table2.dat
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   Bytes Format  Units       Label      Explanations
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   1-10   A10    ---         ID         Star identification
  11-20   D10.3  JD          HJD        Heliocentric Julian Date
  21-26   F6.2   ---         Phase      Orbital phase
  27-33   F7.0   km/s        RVp        Radial velocity of the primary, RV(p)
  34-40   F7.1   km/s        O-Cp       Obs. RV(p) minus calculated orbital vel.
  41-44   F4.1   ---         WTp       *Weight given RV(p) in computing orbit
  45-51   F7.0   km/s        RVs        Radial velocity of the secondary, RV(s)
  52-58   F7.1   km/s        O-Cs       Obs. RV(s) minus calculated orbital vel.
  59-62   F4.1   ---         WTs       *Weight given RV(s) in computing orbit
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Notes for file: table2.dat
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WTp, WTs:
  The weight given the primary's, or secondary's, radial velocity
  in computing the orbit, usually sqrt(number of lines measured).
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(End)                                            Lee E. Brotzman [ADS] 27-Jul-97