On the Structure of the Upper HRD of Humphreys
The observational HR diagram of luminous galactic stars, compiled by Humphreys (1978) Is a benchmark In the study of these objects. The diagram was considered as resulting from continuous star formation, and has been used by many authors to put constraints on the evolution of massive stars (Bertelll et al., Maeder: this conference; Bressan et al., 1981; Doom, 1982a). However, there is a puzzling characteristic of this HRD: there are too many stars outside the main sequence band.
KeywordsStar Formation Massive Star Main Sequence Puzzling Characteristic Stellar Density
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- Bertelli, G.; Bressan, A.G.; Chiosi, C.: 1983: Astron. Astrophys. (in press).Google Scholar