About the Proper Choice of the Characteristic Length in the Convection Theory
Abstract
It is known that convection sets in rather abruptly for stars with Teff < Tb, where Tb depends on the luminosity. The boundary line Tb(L) goes through the H-R diagram from late A or early F main-sequence stars to late F or early G supergiants. In the mixing length approach to the theory of convection the exact theoretical position of this boundary temperature depends on the assumptions about the size of the mixing length 1. We make the assumption that the red boundary of the Cepheid instability strip agrees with the line Tb(L). If we also assume 1 = n pressure scale height H, with n being the same constant for all stars, we find 1 H to give the correct Tb(L). If we assume the region of large instability to determine 1, the relation 1 R2 also gives approximately the correct Tb(L). We do not think, however, that the latter relation has any physical significance. Subject headings: convection - stars: Cepheids - stars: chromosphere - stars: interiors
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1976
- DOI:
- 10.1086/154883
- Bibcode:
- 1976ApJ...210..741B