AAS 202nd Meeting, May 2003
Session 13 Stars and Supernovae
Oral, Monday, May 26, 2003, 10:00-11:30am, 204

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[13.03] The S Dor phases of AG Carinae

C. Sterken (Astronomy Group, Vrije Universiteit Brussel, Belgium)

AG Car (HD 94910) is a Luminous Blue Variable (LBV) of the southern hemisphere. Its light curve displays episodes of fading and brightening with strongly variable amplitude, as is observed in S Doradus and some other LBVs or Hubble-Sandage variables. Van Genderen, Sterken & de Groot (1997) discussed all available photometric data covering more than one century, and introduced the concept S Dor phase: phases of brightening with a cyclic pattern of recurrence. In particular, they distinguish short S Dor phases superimposed on a much longer rhythm of brightening and fading. S Dor phases are recognised by a substantial reddening while the star migrates to the red side of the H-R diagram. Such changes, when strong, are not seldomly mistaken for eruptions.

In 1995, AG Car was in one of its brightest maxima since the early 1980s, and then faded again to a more quiescent state. Recently, the star started brightening again and has now Strömgren colour indices very similar to those of 1994, though the level of brightening is less strong. The current brightening corresponds to cycle 7 after the 1995 maximum and conforms to the cycle length of 371.4 days.

Financial support from the Belgian Fund for Scientific Research (FWO) and the Belgian Federal Office for Scientific, Technical and Cultural Affairs (IUAP-5/36) is acknowledged. Observing time at La Silla was provided by ESO and by the Danish Natural Science Research Council through the centre for Ground-Based Observational Astronomy.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.