2-dimensional models of rapidly rotating stars I. Uniformly rotating zero age main sequence stars
Astronomy Unit, Queen Mary, University of London, Mile End Road, London E1 4NS, UK e-mail: I.W.Roxburgh@qmul.ac.uk
2 LESIA, Observatoire de Paris, Place Jules Janssen, 92195 Meudon Cedex, France
Accepted: 6 August 2004
We present results for 2-dimensional models of rapidly rotating main sequence stars for the case where the angular velocity Ω is constant throughout the star. The algorithm used solves for the structure on equipotential surfaces and iteratively updates the total potential, solving Poisson's equation by Legendre polynomial decomposition; the algorithm can readily be extended to include rotation constant on cylinders. We show that this only requires a small number of Legendre polynomials to accurately represent the solution. We present results for models of homogeneous zero age main sequence stars of mass with a range of angular velocities up to break up. The models have a composition and were computed using the OPAL equation of state and OPAL/Alexander opacities, and a mixing length model of convection modified to include the effect of rotation. The models all show a decrease in luminosity L and polar radius Rp with increasing angular velocity, the magnitude of the decrease varying with mass but of the order of a few percent for rapid rotation, and an increase in equatorial radius Re. Due to the contribution of the gravitational multipole moments the parameter can exceed unity in very rapidly rotating stars and can exceed 1.5.
Key words: stars: interiors / stars: rotation
© ESO, 2004