SIMBAD references

We present orfeus spectra of the OVI λλ1032,1038 emission lines in the symbiotic stars AG Dra, V1016 Cyg, RR Tel, CD-43° 14304, AG Peg and Z And. The OVI emission lines can convert into broad and highly polarized emission lines at λ6825 and λ7082 in a Raman scattering process by neutral hydrogen. From a comparison of direct and Raman scattered radiation we extract new information on the scattering geometry in symbiotic systems. The nebular OVI emission lines are in all objects redshifted by about +40km/s. This can be explained as a radiative line transfer effect in a slowly expanding emission region. A comparable redshift is measured in the Raman scattered OVI lines. In AG Peg the OVI emissions show beside a narrow nebular line a broad component from a fast stellar wind outflow. Many interstellar absorption lines of molecular hydrogen are detected, particularly near the OVI λ1038 component. With model calculations we investigate their impact on the OVI lines. From the dereddened line fluxes of the direct and Raman scattered OVI lines we derive the scattering efficiency, which is defined as photon flux ratio N_Raman/N_OVI. The efficiencies derived for RR Tel, V1016 Cyg and Z And indicate that about 30% of the released OVI λ1032 photons interact with the neutral scattering region. The efficiencies for AG Dra and CD-43 14304 are much higher, which may suggest that the OVI nebulosity is embedded in a H⁰-region. The D-type system RR Tel shows strong line profile differences between the direct OVI emission, which is single-peaked, and the Raman scattered emission, which is double-peaked. This indicates that the neutral scattering region in RR Tel ``sees'' different OVI line profiles, implying that the OVI nebulosity is far from spherically symmetric. In a tentative model we suggest for RR Tel an OVI flow pattern where material streams from the cool giant towards the hot component, which further accelerates the gas radially. For the S-type systems AG Dra, CD-43 14304 and Z And the line profile differences between the direct and the Raman scattered OVI emissions are less pronounced. This may suggest that the OVI profiles depend less on the emission direction than in the D-type system RR Tel. For AG Peg we detect for the first time the Raman scattered emission at λ6825. The Raman line shows a narrow, nebular component as the OVI line, but no equivalent emission to the broad OVI wind component. The higher conversion efficiency for the narrow component indicates that the nebular OVI emission is significantly closer to the cool giant than the hot, mass losing component, and strongly supports previous colliding wind models for this object.