Spectral classification, HR diagram and distribution of symbiotic stars

Abstract

45 symbiotic stars observed in the direction of the galactic bulge are classified in spectral type using TiO 6180 Å, 7100 Å and VO λ 6865 Å, absorption feature indices and visual comparation. The effective temperatures obtained are used together with K data from the literature to estimate the bolometric luminosity of the giant components, and the corresponding HR Diagram is plotted together with evolutionary tracks for intermediate mass stars. Statistical distances to the known galactic symbiotic stars are also derived from the calibration of the bolometric luminosities of galactic bulge symbiotic giants. The results are used to gain insight on the mass and evolutionary status of both S- and D- type symbiotic giants, as well as their spatial distribution and position in the stellar populations scheme of our galaxy. The importance of the ST-Teff relation is also addressed.