Temperature and luminosity of hot components in symbiotic stars.

Typical radiation temperatures and luminosities are derived for the hot component of a representative sample of symbiotic systems by adapting the Zanstra method to the special requirements of symbiotic stars. Temperatures are derived by comparing the He II 1640 nebular recombination line with the underlying continuum. Particle-bounded and radiation-bounded nebulae are differentiated by comparing the continuum flux at 1640 A with the nebular Balmer continuum at the long end of the IUE wavelength range. Interstellar extinctions are determined as well. Mass-loss rates for the red giants are determined where the binary periods are known. It is inferred that the hot components in symbiotic systems lie on the post-red-giant track. In some cases this may be a white dwarf; in others it may be closer to the central star of a planetary nebula, and in still others it is a white dwarf in a slow nova-like outburst, which may last for decades.