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Published online by Cambridge University Press: 12 April 2016
Pre-Main-Sequence contracting objects, post-Main-Sequence expanding stars and mass-losing components of semi-detached systems all occupy more or less the same region in the conventional H-R-diagram. We make a transformation to variables Δ (logL) and Δ (log Te), where Δ is the difference between the observed quantity, log L or log Te, and the value of that quantity which a star of the same mass would have on the empirical Main Sequence. It is demonstrated that a plot between the new variables clearly separates the mass-losing stars from other objects which is essentially an effect of the increasing abundance of helium relative to hydrogen.
Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on ‘Double Stars: Physical Properties and Generic Relations', held at Bandung, Indonesia, 3-7 June, 1983.