Other
Scientific paper
Sep 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........11l&link_type=abstract
Ph.D. Thesis Wisconsin Univ., Madison.
Other
17
Binary Stars, Mass Ratios, Pre-Main Sequence Stars, Star Formation, Stellar Models, Mathematical Models, Stellar Luminosity, Stellar Spectra
Scientific paper
This thesis is to test the calibrations of theoretical pre-main-sequence (PMS) evolutionary models. We compare the theoretical masses and ages of the components of five double-lined pre-main-sequence binaries with the dynamical mass ratios and the assumption of coeval formation of binary components. The spectral types and luminosity ratios of the components are derived from comparisons of selected lines in the observed spectra with synthetic binary spectra created from spectral standards. These are based on echelle observations obtained during 1989-1990. Theoretical masses and ages of the components are obtained by comparing with the theoretical evolutionary models of Mazzitelli and VandenBerg. All five binaries have components with theoretical masses and ages consistent with the dynamical mass ratios and the assumption of coeval formation. We find no substantial problems with the relative mass calibrations of the theoretical tracks, nor the assumption of coeval formation of binary components. These hold for binaries with ages ranging from approximately 106 yr to few times 106 yr. Assuming coeval formation of binary components, we compare the ranges of both the theoretical mass ratios and the dynamical mass ratios with the detectable range of dynamical mass ratios. The results show that the ranges of theoretical mass ratios and the dynamical mass ratio are small subsets of the detectable range of dynamical mass ratios. This finding indicates that this analysis is a significant test of the relative mass calibrations of the PMS tracks of Mazzitelli and VandenBerg. The binary P1540 with age of approximately 105 yr is the youngest in our sample. The maximum age difference for the solutions that have theoretical mass ratios consistent with the dynamical mass ratio is only a few times 105 yr. This is small compared to the ages of few times 106 yr of the other binaries in the sample. This indicates it is possible that processes such as disk accretions have little effects on the evolution of the binaries after approximately 105 yr.
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