**34th Meeting of the AAS Division on Dynamical Astronomy, May 2003**

* 11 Disks*

Oral, Wednesday, May 7, 2003, 8:30-10:30am,
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## [11.06] Instabilities of Stellar Disks

*M. A. Jalali, C. Hunter (Dept. of Mathematics, Florida State U.)*

We investigate the instabilities of the flat isochrone and
Kuzmin-Toomre disks using Kalnajs's matrix method. For the
unperturbed disks in equilibrium, we introduce a new class
of anisotropic distribution functions (DF) in the form
f(E,L_{z})=f_{0}(E)+f_{1}(E,L_{z}). At first, we prescribe
f_{1}(E,L_{z}), determine its corresponding surface density
and subtract it from the model density. We then reproduce
the remainder density by the isotropic part of the DF,
f_{0}(E). The DFs that we generate, enable us to control the
population of circular, radial and rosette orbits. We
investigate how the populations of these orbits influence
the instability of our axisymmetric disks. To compute the
matrix elements of Kalnajs's method, we choose orbital
frequencies as the integration variables and regularize
resonance singularities using the Legendre functions of the
second kind. The response of the disk, and its unstable
modes are then computed through an iterative scheme.

The author(s) of this abstract have provided an email address
for comments about the abstract:
mjalali@math.fsu.edu

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Bulletin of the American Astronomical Society, **35** #4

© 2003. The American Astronomical Soceity.