Abstract:
In 1977, S. Tapia at the Univ. of Arizona discovered a short-period
binary system whose optical light is circularly polarized by as much
as 20%. The regime of magnetic accretion that was revealed by
this measurement has been a source of interest and excitement for
observers and theorists alike. Magnetic shocks, field-aligned flows,
turbulent coupling regions, funnels, and siphons are entertaining and
instructional ingredients of this remarkable picture, which continues
to reveal itself through discoveries using today's orbiting
observatories, deep optical surveys, and sensitive instrumentation
aboard large telescopes. The most recent discoveries may be the
oddest members of the family, with magnetic emission lines that can
be mistaken for those of QSOs, non-contact accretion, and
"bombardment" solutions to the hydrodynamic equations.