 |
 |
 |
 |
 |
 |
|
|
|
|
|
|
Chin, C.-W., and R. Stothers, 1971: Low-mass white dwarfs and the cooling sequences in the Hyades cluster. Astrophys. J., 163, 555-565.
Detailed evolutionary sequences have been constructed for models of white dwarfs with very low mass (0.1,0.2, and 0.3 M☉) and with a variety of chemical compositions. Convection near the surface is taken fully into account in the models with hydrogen envelopes. Down to a luminosity of at least log (L/L☉) = -3.3, the basic properties of the models are not affected significantly by the presence of convection in the hydrogen-rich layers. All the models with envelopes assumed to be in radiative equilibrium are insensitive to the choice of chemical composition of the envelope, at least as long as the mass of the envelope encompasses 1 percent, or less, of the total mass.
The color-magnitude diagram of the white dwarfs in the Hyades has been reinterpreted. Two major mass sequences are isolated: a "blue" sequence at ~1 M☉ and a probable "red" sequence at ~0.1 M☉, with a scatter of intermediate-mass stars. The observed luminosity functions seem to be in good agreement with the theoretical ones. If the red sequence is real, then the bifurcation of the white-dwarf masses occurs at a parent mass of 2.4×0.4 M☉. A speculative picture is presented of the origin of the whitedwarf sequences.
|
|
|
