A study of UV spectra of zeta Aur/VV CEP stars. IV. System parametersand mass-loss of delta Sge.

Abstract

The orbital elements of the Delta Sge system were improved using new radial velocity measurements. A distance of 170 pc is determined with the assumption that the companion is a mainsequence star with Te = 10,500 K (ca. B9) as found from IUE fluxes. Combining the mass-function with the locations of the components in the HR-diagram, a mass-ratio of about 3 has been obtained. A comparison with speckle-interferometric measurements of the angular separation is given. Using cicumstellar Fe II absorption lines in the UV spectrum of the B star companion, a mass-loss rate of 2 x 10 to the -8th solar mass/yr has been found for the M2 II primary. Evidence for an accretion disk around the B star fed by the M giant wind and a shock front moving with the B star is briefly discussed.