Doublet 2800 MgII in close binary systems

The origin of the intercomponent ultraviolet emission from binary radio stars is discussed following an examination of observed emission parameters. Observations are used to consider four arguments which suggest that the Mg emission originates in the space between the components of the binary and not in the chromosphere. Parameters examined include the ratio of Mg emission to that of other binaries, the direct variation of emission with brightness strength, the derivation and nature of the radial velocity, and comparisons of absolute luminosities. Emission (A) and absorption (B) streams or clouds generate the emission, and the observed wavelength distortions are caused by B. An examination of the nature of the emission yields both qualitative and quantitative criteria, including the notion of weak ionization of the hydrogen atoms in B clouds relative to the ionization in A clouds.