Search for companion stars to the Mira variables s Leonis and U Cancri

Document Type


Publication Date



Spectra of the Mira variables S Leo and U Cnc were taken near minimum light to search for faint companions. The spectra were expected to show an increase in flux in the blue continuum of the spectrum (wavelengths shortward of 5,000 Å), if a hot, faint companion exists. The spectrum of S Leo does not show a rise in the blue end of its spectrum which suggests that it does not have a hot, faint companion. The spectrum of U Cnc has very weak Ca II K and H lines, and the continuum appears uniform shortward of 5,000 Å. This suggests that U Cnc may have a companion. The blue continuum of the spectrum of U Cnc can be fit with a 10,000 K, and a 0.01R⊙ blackbody. The temperature is a lower limit and the radius is an upper limit. The temperature and radius of the possible companion are similar to the temperature and radius of a white dwarf star. However, if a white dwarf companion exists, its apparent magnitude would be too faint to significantly contribute to the spectra of U Cnc. So we are left with the possibility of a companion, but its nature remains questionable. In addition to the search for companions, the spectra are used for classification of S Leo and U Cnc at minimum. S Leo is found to be similar to an M4e-M5e type star and U Cnc is found to be similar to an M5e-M6e type star. These classifications are consistent with their average spectral types.