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**Session 26 - Stars in the Visible & IR.**

*Display session, Tuesday, June 10*

*South Main Hall, *

## [26.13] Computing Gravity Modes for Rotating Stellar Models: A Progress Report

*M. J. Clement (U.Toronto)*
The slowly rotating B stars and the line-profile 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 g-mode 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
finite-difference 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_\ell^m of different angular order \ell. 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., \ell \simeq m).
We may be seeing just the effects of rotation.

**Program
listing for Tuesday**