On the Steady Nature of Line-Driven Disk Winds
Abstract
We perform an analytic investigation of the steady nature of line-driven disk winds, independent of hydrodynamic simulations. Our motive is to determine whether line-driven disk winds can account for the wide/broad UV resonance absorption lines seen in cataclysmic variables (CVs) and quasi-stellar objects (QSOs). In both CVs and QSOs, observations generally indicate that the absorption arising in the outflowing winds has a steady velocity structure on timescales exceeding years (for CVs) and decades (for QSOs). However, published results from hydrodynamic simulations of line-driven disk winds are mixed, with some researchers claiming that the models are inherently unsteady, while other models produce steady winds. The analytic investigation presented here shows that the line-driven disk winds can be steady if the accretion disk is steady and capable of locally supplying the corresponding mass flow. In particular, we show that a gravitational force initially increasing along the wind streamline, which is characteristic of disk winds, does not imply an unsteady wind. The steady nature of line-driven disk winds is consistent with the one-dimensional streamline disk wind models of Murray and collaborators and the 2.5-dimensional time-dependent models of Pereyra and collaborators. This paper emphasizes the underlying physics behind the steady nature of line-driven disk winds using mathematically simple models that mimic the disk environment.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2004
- DOI:
- 10.1086/386320
- arXiv:
- arXiv:astro-ph/0311268
- Bibcode:
- 2004ApJ...608..454P
- Keywords:
-
- Accretion;
- Accretion Disks;
- Hydrodynamics;
- Stars: Novae;
- Cataclysmic Variables;
- Galaxies: Quasars: Absorption Lines;
- Astrophysics
- E-Print:
- Astrophys.J.608:454-469,2004