Evolution of massive stars with semiconvective diffusion

Evolutionary sequences at constant mass are presented for Pop I stars of 15 and 30 solar masses until the onset of core carbon burning. A time-dependent diffusion model based on a vibrational instability analysis is adopted in order to describe mixing of layers having a gradient of mean molecular we...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 1985-04, Vol.145 (1), p.179-191
Main Authors: LANGER, N, EL EID, M. F, FRICKE, K. J
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
Star formation
Stars
Stellar characteristics and properties
Online Access:Get full text
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Summary:Evolutionary sequences at constant mass are presented for Pop I stars of 15 and 30 solar masses until the onset of core carbon burning. A time-dependent diffusion model based on a vibrational instability analysis is adopted in order to describe mixing of layers having a gradient of mean molecular weight (semiconvection). The fully-convective layers are determined according to the Ledoux criterion. For comparison, evolutionary sequences are also calculated for the same masses without assuming semiconvection but using the Schwarzschild criterion for convective instability. It is found that the vibrational instability does not establish the Schwarzschild-Haerm criterion for semiconvection during the fast phases of evolution, such as shell hydrogen burning. The modification of the chemical profile by semiconvection during this phase does strongly affect the evolutionary tracks in the H-R diagram during core helium burning. The results are discussed in comparison to earlier calculations of massive star evolution with and without inclusion of semiconvection.
ISSN:0004-6361
1432-0746