Asteroseismic determination of stellar angular momentum

Theoretical Astrophysics Center (TAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade, 8000 Århus C, Denmark

Corresponding author: F. P. Pijpers, fpp@phys.au.dk

Received: 29 November 2002
Accepted: 14 February 2003

Abstract

The total angular momentum of stars is an important diagnostic for testing theories of formation of stars. Angular momentum can also play a decisive role in the evolution of stars, in particular towards the higher masses. Asteroseismology can play an important role in providing measurement of this parameter. The spectrum of stellar oscillations is affected by rotation in a way similar to the splitting of spectral lines through the magnetic Zeeman effect. It is shown here that this can be used to determine accurately the total angular momentum of stars, taking full differential rotation into account, and without any dependence of inclination angle of rotation axis with respect to the line of sight. All aspects of this technique are addressed, including the issue of mode identification, determination of the moment of inertia, and the influence of the reference model on the seismic inference. It is a realistic prospect to do asteroseismogyrometry with planned space satellite missions such as MOST, MONS, COROT, and Eddington.