Jets and MHD Flows Associated with Symbiotic Stars
Symbiotic stars are evolved systems consisting of a binary containing a late-type star (M-type, red giant or in some cases long-period variable) and a hot subdwarf or white dwarf secondary. These systems are classified as either S-type (showing the presence of a hot stellar continuum) or D-type (dust-type and showing no hot star continuum). D-type symbiotics are associated with long-period variables or Miras. Symbiotics have been studied at a variety of wavelengths, most recently and most successfully at far UV wavelengths using the International Ultraviolet Explorer (IUE) and even at soft X-rays using ROSAT. Observational results and overall properties of the components in symbiotics stars are presented. These systems show evidence of high ionization lines such as He II, C IV and N V as well as a number of semi-forbidden lines such as 0 IV], 0 III], N III], C III], and C II] and forbidden lines such as [Ne V] and [O II]. The lines arise in nebular regions surrounding the system, accretion disks and even jets. A number of systems show directed outflow, often in the form of individual jet parcels. Although the exact nature of the outflow process is not determined, it is likely to involve an accretion disk which may be magnetized. in the D-type symbiotics, ejection may be facilitated by radiation pressure onto grains. These jets provide opportunities to study the entire physics of jet phenomena for objects at close distances to the solar system. Some observational results of two jet prototypes are presented, R Aquarii (D-type) and CH Cygni (S-type). R Aqr is the nearest astrophysical jet and affords great opportunities to study these phenomena. ROSAT observations of these systems indicate that the soft X-ray emission is probably anslng in “hot spots” which may be MHD-related. A new magnetized accretion model for R Aqr is presented.
KeywordsAccretion Disk Radiation Pressure White Dwarf Stellar Wind Hubble Space Telescope
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