Optical and UV Investigation of the Envelope of AG Carinae

  • Roberto Viotti
  • Aldo Altamore
  • Corinne Rossi
  • Angelo Cassatella
Conference paper
Part of the Astrophysics and Space Science Library book series (ASSL, volume 157)


The galactic LBV object AG Car is unique for assembling several interesting features: (i) a light curve typical of Hubble-Sandage variables, (ii) a largely variable P Cygni-type spectrum, (iii) a strong IR excess, and especially (iv) a small ring nebula. Caputo and Viotti (1970) found that during 1949-59 the AG Car spectrum varied between Al and BO equivalent spectral types. A dramatic evolution occurred in recent years, when the visual magnitude gradually faded from V=6 in 1981 to V=8 in 1985, followed by a rise of the line excitation from Aeq in 1981 (Wolf and Stahl 1982), to Be£ in 1983 (Viotti et al. 1984), and to 0fpe/WN9 in January 1985 (Stahl 1986). This behaviour has represented a unique chance to follow a LBV in different spectral ranges during its major photometric and spectral changes. In the following we present the results of a long term monitoring of the star and of its nebula in the optical and UV. We propose thatAG Car evolved in recent times from a red supergiant phase, and that the present LBV phase is characterized by a critical structure of the stellar atmosphere.


Light Curve Stellar Atmosphere Visual Magnitude Strong Fell Unique Chance 
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Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • Roberto Viotti
    • 1
  • Aldo Altamore
    • 2
  • Corinne Rossi
    • 2
  • Angelo Cassatella
    • 3
  1. 1.Istituto Astrofisica Spaziale, CNRFrascatiItaly
  2. 2.Istituto AstronomicoUniversita’ La SapienzaRomaItaly
  3. 3.IUE Observatory, ESAMadridSpain

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