Narrow Results

Recently, it has been shown by S. M. de Carvalho et al. (2014) that the deviations between the degenerate case and observations were already evident for 0.7-0.8 M${}_{\odot }$ white dwarfs. Such deviations were related to the neglected effects of finite temperatures on the structure of a white dwarf. Therefore, in this work by employing the Chandrasekhar equation of state taking into account the effects of temperature we show how the total pressure of the white dwarf matter depends on the mass density at different temperatures. Afterwards we construct equilibrium configurations of white dwarfs at finite temperatures. We obtain the mass-radius relations of white dwarfs for different temperatures by solving the Tolman-Oppenheimer-Volkoff equation, and compare them with the estimated masses and radii inferred from the Sloan Digital Sky Survey Data Release 4.

White dwarf stars are widely studied as being composed of an ion lattice embedded in a degenerate fermion gas. However, at the beginning of their lives these stars are subject to temperatures that can reach up to T = 10⁹K. In this limit there is no longer total degeneracy and a temperature-dependent equation of state (EOS) is needed to take in account the Fermi-Dirac occupation factor of fermion levels. In this article, we will study this regime, in particular the effect of positrons in the EOS and in the hot white dwarf structure.

We construct mass-radius relations of white dwarfs taking into account the effects of rotation and finite temperatures. We compare and contrast the theoretical mass-radius relations with observational data.

We consider the effects of rotation and temperature on the structure of white dwarfs in order to compare them with the estimated data from observations.