MHD winds can emanate from both stars and surrounding disks. When the two systems are coupled by accretion, it is of interest to know which (if either) of the two dominates the outflow power. Recent observations lead us to consider how such coupled MHD winds may be operating in planetary nebulae (PN). In this context, we calculate the MHD wind power from a coupled disk and star, where the forme...

Title of Dissertation: Magnetic Fields Around Black Holes David A. G. Garofalo, Doctor of Philosophy, 2008 Dissertation directed by: Professor Christopher Stephen Reynolds Department of Astronomy Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and ...

A simple variational calculation is presented showing that a uniformly rotating barotropic fluid in an external potential attains a true energy minimum if and only if the rotation profile is everywhere subsonic. If regions of supersonic rotation are present, fluid variations exist that could take the sytem to states of lower energy. In any given system, these states may or may not be dynamicall...

NGC 205, a close satellite of the M31 galaxy, is our nearest example of a dwarf elliptical galaxy. Photometric and kinematic observations strongly suggest that NGC 205 is currently undergoing tidal distortion as a result of its interaction with M31. Despite earlier attempts, the orbit and progenitor properties of NGC 205 are not well known. In this paper, we present an optimized search for thes...

Magnetic fields play an important role in creating, driving, and in the evolution of outflows and jets from protostars and accretion disks. On the other hand, the temperature profile of the accretion disks may also affect the structure of the magnetic field and outflows. In this paper, we use the self-similar method in cylindrical coordinates to investigate the effect of the temperature profile...

We present 2D hydrodynamic simulations of circumstellar disks around protostars using a 'Piecewise Parabolic Method' (PPM) code. We include a point mass embedded within the disk and follow the migration of that point mass through the disk. Companions with masses Mc > ∼ 0.5M J can open a gap in the disk sufficient to halt rapid migration through the disk. Lower mass companions open gaps, but mig...

Existence of an exact solution of the Navier-Stokes equations representing swirling flow consisting of two fluid layers is proven. It is assumed that the fluid in the bottom layer is injected into the swirl from a rotating disk. This describes the case when a disk melts in an ambient fluid and the melted fluid is removed by rotation of the disk.

The Bardeen-Petterson effect around a rapidly-rotating compact object causes a tilted accretion disk to warp into the equatorial plane of the rotating body. Viscous forces cause the accretion flow to divide into two distinct regions an inner aligned accretion disk and an outer tilted accretion disk. The transition between these two occurs at a characteristic radius that depends on the mass and ...