SPECTROSCOPIC AND PHOTOMETRIC BEHAVIOR OF THE FU ORIONIS VARIABLE Z-CANIS-MAJORIS

We present optical and IR photometry, optical multi-dispersion spectro scopy, and IR spectrophotometry of the FU Ori variable Z Canis Majoris , obtained in the years 1984, 1985, 1989 and 1996. A comparison of dat a obtained in 1984 and 1985 confirms that in 1985 Z CMa underwent a lo w-power eruption. The enhancement of Ha emission line, the transition of H beta and Fe II lines from pure absorption to emission with or wit hout a P Cygni profile, the appearance of the He I 6678 Angstrom absor ption line, a radial velocity increase of about 30% of the P Cygni abs orption components, and finally a 0.2 - 0.3 mag increase of IR luminos ity, were all dinstinctive characteristics of this state. Further obse rvations in 1996 show that Z CMa is in a low-luminosity state at V = 1 0.24 while the appearance of a double-peaked H alpha emission, with th e blue component much weaker than the red one, is the most significant spectroscopic variation. Energy distributions in the range 0.4 - 5 mu m, obtained during 1984 and 1985 observational runs, are also present ed.