The structure of white dwarf stars

Abstract

A FORTRAN code to compute the structure of white dwarf Stars has been written. It is assumed that a good model for the matter in white dwarf stars is the free Fermi gas of electrons at zero temperature, treated with relativistic kinematics. The code written essentially solves numerically the two coupled first-order differential equations that determined the structure of the star for the given equation of state. The variation of mass density with distance from the center of the star is found to be directly proportional to the assigned density at the center of the dwarf and the value of the parameter which characterizes the chemical composition of the dwarf, but inversely proportional to the distance from the center of the star. In general, the density decreases with increase in the distance. For a given central density, the radius of the hydrogen white dwarf is greater than that of the helium, carbon, or oxygen which are equal and greater than that of iron. Thus the radius increases with the parameter . The so called Chandrasekhar mass limit has been found to be 1.144 × 10³⁴ gm for hydrogen white dwarf, 2.861 × 10³³ gm for helium, carbon, and oxygen white dwarf, and 2.464 × 10³³ gm for iron white dwarf.

Journal of the Nigerian Association of Mathematical Physics, Volume 15 (November, 2009), pp 237 - 246