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A&A Supplement Series, Vol. 126, November II 1997, 91-103

Received July 25, 1996; accepted March 3, 1997

Spectroscopic and photometric behaviour of the FU Orionis variable Z Canis Majoris

M. Teodoranitex2html_wrap1879 - L. Erricotex2html_wrap1879 - A.A. Vittonetex2html_wrap1879 - F. Giovannellitex2html_wrap1885 - C. Rossitex2html_wrap1887

Send offprint request: A.A. Vittone
tex2html_wrap535 Osservatorio Astronomico di Capodimonte , Via Moiariello 16, I-80131 Napoli, Italy
tex2html_wrap535  Istituto di Astrofisica Spaziale, CNR, Via E.Fermi 21, C.P. 67, I-00044 Frascati (Roma), Italy
tex2html_wrap537  Istituto Astronomico, Universita' "La Sapienza" di Roma, Via Lancisi 29, I-00161 Roma, Italy


We present optical and IR photometry, optical multi-dispersion spectroscopy, and IR spectrophotometry of the FU Ori variable Z Canis Majoris, obtained in the years 1984, 1985, 1989 and 1996. A comparison of data obtained in 1984 and 1985 confirms that in 1985 Z CMa underwent a low-power eruption. The enhancement of tex2html_wrap_inline1857 emission line, the transition of tex2html_wrap_inline1859 and FeII lines from pure absorption to emission with or without a P Cygni profile, the appearance of the HeI 6678Å absorption line, a radial velocity increase of about 30% of the P Cygni absorption components, and finally a 0.2-0.3 mag increase of IR luminosity, were all dinstinctive characteristics of this state. Further observations in 1996 show that Z CMa is in a low-luminosity state at V = 10.24 while the appearance of a double-peaked tex2html_wrap_inline1857 emission, with the blue component much weaker than the red one, is the most significant spectroscopic variation. Energy distributions in the range tex2html_wrap_inline1867, obtained during 1984 and 1985 observational runs, are also presented.

keywords: stars: individual: Z CMa -- stars: pre-main-sequence -- stars: Be -- stars: variables: other

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