IUE and the search for a lukewarm corona

The use of the International Ultraviolet Explorer (IUE) to search for stars having neither a hot corona nor a cool outer atmosphere, but a lukewarm corona is outlined. An interactive computer system permits extensive analysis of the data immediately after transmission to earth, allowing the results of one exposure to influence the taking of subsequent exposures. The observation program is illustrated for the star HR 1099, noting that observations were taken while previous spectra were being analyzed. Observations of many stars of spectral types G and K lead to the construction of a border region on the Hertzsprung-Russell diagram between stars with hot coronas and those with cool outer atmospheres. Stars lying near this border region were then observed, however none with lukewarm coronas were found. The interactive control facility in the satellite control room is considered an important factor in the efficient implementation of the search procedure.