**AAS 198th Meeting, June 2001**

*Session 37. Gravitational Lenses, Relativistic Astrophysics*

Display, Tuesday, June 5, 2001, 10:00am-6:30pm, Exhibit Hall
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## [37.06] Self-similar Relativisitic Disks revisted

*M. J. Cai, F. H. Shu (U. C. Berkeley)*

We revisit the rotating self-similar disk first studied by
Lynden-Bell and Pineault and extend it to include pressure.
A two-parameter family of solutions is constructed
numerically. These disks are parameterized by the constant
linear rotation velocity v, and the isothermal sound speed
\gamma^{1/2}. For sufficiently high velocities, an ergo
region develops in the form of the exterior of a cone. For
each value of \gamma, there is a maximum velocity v_{c}
above which there is no equilibrium solutions. For this
solution the frame dragging is infinite and the ergo cone
closes on the rotation axis. The null geodesic equations are
also integrated numerically. Due to the infinite extend and
mass of the system, all photon trajectories are focused
towards the disk. The behavior of equatorial photons orbits
is qualitatively the same as that of cold disks.

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