Does the upper main sequence extend across the whole H-R diagram

Journal Article · Sat Jan 01 04:00:00 EST 1977 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/154919· OSTI ID:7130716

Stothers, R; Chin, C

The effect of using Carson's new radiative opacities in evolutionary sequences of stellar models has been studied over the mass range 7--60 M/sub sun/. The new opacities are very large in the outer part of the envelope, and induce such enormous radii for masses grater than approx. 30 M/sub sun/(Z/sub e/=0.02) or approx. 20 M/sub sun/(Z/sub e/=0.04) that the evolutionary tracks during the phase of core hydrogen burning extend across the whole H-R diagram. The choice of the Schwarzschild or Ledoux criterion for convection makes very little difference for the behavior of the tracks. Evolution through the effective-temperature range log T/sub e/ = 3.6--4.0 occurs in all cases on a rapid (secular) time scale. Core helium burning takes place exclusively in the red-supergiant configuration for stellar masses >8 M/sub sun/(Z/sub e/=0.02) or >6 M/sub sun/(Z/sub e/=0.04). The new stellar models seem to be in significantly better agreement with the observed distribution of bright stars on the H-R diagram than are the older models based on the Cox--Stewart opacities. It can be inferred that a large envelope opacity (e.g., Carson's) exists and that substantial mass loss takes place in very massive late-type supergiants. (AIP)

• Research Organization: Institute for Space Studies, Goddard Space Flight Center, NASA, New York
• OSTI ID: 7130716
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 211:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CONVECTION
DIAGRAMS
ENERGY TRANSFER
GIANT STARS
HEAT TRANSFER
HERTZSPRUNG-RUSSELL DIAGRAM
MAIN SEQUENCE STARS
MATHEMATICAL MODELS
NUCLEOSYNTHESIS
OPACITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
STAR EVOLUTION
STAR MODELS
STARS
SUPERGIANT STARS