Computing Gravity Modes for Rotating Stellar Models: A Progress Report
Abstract
The slowly rotating B stars and the lineprofile variables on the upper main sequence are now believed to involve nonradial gravity modes of high radial order (n>15) and be driven by the ionization zones of the iron group metals. This paper is the second progress report on efforts to compute the eigenfunctions of these particular modes for rapidly rotating stars. This is a very challenging numerical problem especially in the observationally relevant, long period limit where the gmode spectrum in so rich or dense that it is very difficult to separate and identify the solutions. For this reason, numerical fitting methods which require an initial trial eigenfunction (and iteration to convergence) fail at high radial order. In this paper, I report on a superior, implicit finitedifference scheme which doesn't require an initial trial solution. One can simply scan eigenfrequency space and extract solutions as they appear. Identifying the modes, however, is not a trivial task because rotation mixes spherical harmonics Y_{l}(m) of different angular order l. The most interesting result so far is that rapid rotation forces all the modes to adopt a sectorial geometry; that is, the displacement amplitude is greatly enhanced in the equatorial regions at the expense of the polar ones. This makes one question the apparent sectorial nature of the observed modes (i.e., l =~ m). We may be seeing just the effects of rotation.
 Publication:

American Astronomical Society Meeting Abstracts #190
 Pub Date:
 May 1997
 Bibcode:
 1997AAS...190.2613C