Session 104 - Accretion-Powered X-Ray Sources.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

## [104.08] Precession of Accretion Disks in X-Ray Binaries

R. C. Iping (University of Guam), J. A. Petterson (Georgia Tech Research Institute)

An increasing number of stellar close Binary systems, especially X-Ray Binaries is found to display a "long-term periodicity" with a period which is typically one to two orders of magnitude larger than the system's binary period. Nearly all massive X-ray binaries may turn out to have a long-term period, caused by a regular feature, common to all X-ray binaries. It is argued that the possession of an accretion disk, which precesses, driven by tidal interaction, is the most likely candidate for the long-term periodicity. If one assumes tidal interaction responsible for the precession, systems with a known long-term periodicity allow an independent estimate for the mass at the center of the accretion disk. It is indeed possible to make a crude independent estimate of the mass at the center of the disk if one assumes disk-precession driven tidally. This independent mass estimate indicates a massive blackhole for CygX-1. However other causes for long-term periods in X-ray binaries, such as the \dotM variations remain possible.