The peculiar symbiotic star CH Cyg – a bright counterpart of cataclysmic variables?

Extract

CH Cyg has begun to show symbiotic features only since 1963. Up to now four outbursts of CH Cyg have been recorded, the fifth going on at the present time. CH Cyg reveals a lot of peculiarities as compared to ‘normal’ symbiotic stars (extended inactive periods between the ‘symbiotic’ periods; the most extended active period in 1977–1986 including the ejection of bipolar radio jets; a stage of increased activity since 1992, with peculiar profiles of the Balmer emission lines etc.); see Mikolajewski, Mikolajewska & Khudyakova (1990) for further references.

Classical models for explaining the outbursts of symbiotic stars (e.g. Mikolajewska & Kenyon 1992) are unable to account for the behaviour of CH Cyg. The magnetic rotator model has been proposed and developed by Mikolajewski & Mikolajewska (1988, 1996). The model includes a wind accreting, magnetic (B ~ 10⁷ G), rapidly rotating (P ~ 8 m) white dwarf (WD) as the hot component of the symbiotic system. A strong magnetic field prevents matter from the red giant’s wind being accreted onto the WD surface in the usual way. Instead, three stages of accretion could be considered: inactive, propeller and accretor state.