The problem of matching observed number ratios of blue to red supergiants (B/R) is examined within the framework of a single star-evolution model which undergoes helium ignition in the blue and is self-consistent with respect to mass loss. It is shown that the completeness of surveys of luminous blue and red supergiants has improved in the past few years by a factor of at least two. However, B/R ratios are still uncertain due to selection effects, uncertainties in the bolometric correction, and temperature conversions in hot stars. At low bolometric luminosities, M(bol) less than about 7.5 AGB stars may be contaminating the massive red supergiant sample. Observed B/R ratios for lower-metallicity regions of the Galaxy and the Magellanic Clouds, may still show significant incompleteness effects. In addition, the presence of Wolf-Rayet (W-R) stars and binaries may also contribute to the uncertainty. Methods for adjusting the mass loss rates estimates in order to reproduce the observed distribution of stars between the ZAMS and the Hertzsprung gap are described.
No takes yet. Share an insight, caveat, or question.
Brunish et al. (1986) studied this question.