THE BINARY-SYSTEM OF THE BE STAR MX ANDROMEDAE

New high S/N ratio observations of the Be binary KX And made it possib le to display the secondary's spectrum from the near IR up to the H ga mma region. The radial velocity curve of the secondary is obtained ove r half a period. The photospheric HeI line lambda 6678 Angstrom is fou nd to be disturbed by a variable red emission, the HeI lambda 4471 Ang strom is probably disturbed in a similar manner. No radial velocity cu rve of the primary star can therefore be derived from photospheric lin es provided by our data. The H alpha line is strongly in emission with V/R < 1. Its strength has been increasing from 1983 to 1993. The seco ndary's spectrum as well as the estimated dilution coefficient are con sistent with the presence of a cool giant companion (K0II) filling its Roche lobe. The sudden decrease of metallic shell lines belonging to the primary's envelope at the phase (phi = 0.19 can be explained by a partial eclipse of the envelope by the cool giant secondary.