Observations were obtained with the International Ultraviolet Explorer (IUE) of four symbiotic stars. The UV spectra of YY Her, SY Mus, CL Sco, and BX Mon are characterized by varying degrees of thermal excitation. We have analyzed these low resolution spectra in terms of line-blanketed model atmospheres of early A, B, and F type stars in order to identify the nature of the hot companion in these systems. The expected emission from early main sequence stars does not fully explain the observed distribution of UV continuum energy over the entire IUE spectral range (1200-3200 A). More likely the observed continuum may be originating from an accretion disk and/or hot subdwarf that photoionizes circumstellar material, and gives rise to the high excitation lines we have detected. The Bowen fluorescent excited lines of 0 III in SY Mus exhibit slightly broadened profiles that suggest possible turbulent motions in an extended circumstellar cloud with characteristic velocities ~ 300 km s^-1.
Michalitsianos, A.G., Kafatos, M., Feibelman, W.A., Hobbs, R.W. (1982) Ultraviolet Observations of Four Symbiotic Stars, Astrophysical Journal, 253: 735-744. doi: 10.1086/159674