Detection of a stellar prominence of the K supergiant 32 Cyg.

Abstract

Light curves at various UV wavelengths have been determined from a sequence of high resolution IUE spectra taken around the 1981 eclipse of 32 Cyg B. Attention is given to the first detection of a stellar prominence of the K supergiant, seen as a transient absorption of the B star continuum flux whose mechanism is probably Rayleigh scattering at the HI ground state which follows from the wavelength dependence of optical depths. The prominence has a typical density of 10 to the 12th/cu cm, while the density contrast relative to the surrounding chromosphere is of the order of a factor of 10. In the case where magnetic fields balance the excess prominence pressure, a field of about 4 Gauss would be required.