Oxygen VI in stellar winds.

Abstract

A review of observational evidence for five-times ionized oxygen (OVI) in stars and new high-resolution spectral scans obtained with Copernicus satellite are presented to show how this phenomenon varies with spectral type. The region of the OVI resonance doublet was observed in nine stars with the Copernicus spectrometer, and P Cygni profiles or shifted absorption lines indicating mass flow were found in seven stars. However, no OVI was seen in rho Leo or gamma Ara. The OVI profiles show a variety not correlated with spectral type. Zeta Pup has a broad emission and deep absorption ranging over all velocities to about -2800 km/sec, while HD 151804 has only a narrow absorption from -1060 to -1660 km/sec and 15 Mon has a narrower feature from -1700 to -2100 km/sec. Absorptions in 10 Lac, tau Sco, zeta Orph and nu Ori are discussed, and it is concluded that the ionization appears to increase outward in 15 Mon and 10 Lac, decrease outward in tau Sco and be independent of distance in the supergiants and zeta Orph.