Abstract
We suggest a generalization of the standard Chandrasekhar model for degenerate dwarfs. We apply an equation of state for a degenerate ideal electron gas in the form of a Sommerfeld expansion in the parameter k B T(r)/m 0 c 2. The radial temperature distribution T(r) is modeled taking into account the presence of the isothermal core. The model has four dimensionless parameters, two microscopic (the relativistic parameter at the stellar center x 0 and the chemical-composition parameter µ e = A/Z) and two macroscopic (the dimensionless temperature T 0 * = k B T c /m 0 c 2 and dimensionless radius ξ 0 = R c /R of the core, where R c and R are the radii of the core and dwarf). We found x 0, µ e , and T 0 * for about 3000 DA white dwarfs, based on their masses, radii, and effective temperatures from the Sloan Digital Sky Survey Data Release 4; ξ 0 was treated as a free parameter. The influence of temperature effects on the macroscopic characteristics is analyzed, in particular, the minimum mass and maximum radii of the stars. Based on our computed energy-radius dependence, we suggest an interpretation of the observed radius distribution for these dwarfs.
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