Temperature and luminosity of hot components in symbiotic stars.

Abstract

The nature of the hot component in symbiotic binaries is still controversial. The existence of a hot radiative source is inferred from the presence of a photoionized nebula. The nebular spectrum points to typical radiation temperatures of T * ≃100 000 K. The bulk of the ionizing radiation is therefore emitted below 1200 A, the effective short end of IUE (International Ultraviolet Explorer). We set ourselves the task of deriving temperatures and luminosities for the hot component of a representative sample of symbiotic systems. For that purpose the Zanstra method is adapted to the special requirements of symbiotic stars. T * is basically derived by comparing the nebular recombination line HeII λ1640 with the underlying continuum.