IUE observations of two late-type stars Bx Mon (M + pec) and TV Gem (M1 Iab)

The IUE observations of two late type stars BX Mon and TV Gem that reveal the emission properties in the ultraviolet of subluminous companions are discussed. Analysis of the continuum emission observed from BX Mon suggests the companion, is a middle A III star. High excitation emission lines observed between 1200 A and 2000 A that generally do not typify emission observed in either late M type variables or A type stars are also detected. It is suggested that these strong high excitation lines arise in a large volume of gas heated by nonradiation processes that could be the result of tidal interaction and mass exchange in the binary system. In contrast to stars such as BX Mon, the luminous M1 supergiant TV Gem shows unexpected intense UV continuum throughout the sensitivity range of IUE. The UV spectrum of TV Gem is characterized by intense continuum with broad absorption features detected in the short wavelength range. The analysis shows that the companion could be a B9 or A1 III-IV star. Alternate suggestions are presented for explaining the UV continuum in terms of an accretion disk in association with TV Gem.