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The WR/LBV system HD 5980: wind-velocity – brightness correlations

Published online by Cambridge University Press:  12 July 2011

Gloria Koenigsberger
Affiliation:
Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico, email: gloria@astro.unam.mx
Leonid Georgiev
Affiliation:
Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, México D.F. 04510, Mexico, email: georgiev@astro.unam.mx
D. John Hillier
Affiliation:
Department of Astronomy, 3941 O'Hara Street, University of Pittsburg, Pittsburg, PA 15260, USA, email: djh@rosella.phyast.pitt.edu
Nidia Morrell
Affiliation:
Las Campanas Observatory, The Carnegie Observatories, Colina El Pino s/n, Casillas 601, La Serena, Chile, email: nmorrell@lco.cl
Rodolfo Barbá
Affiliation:
Departamento de Física, Universidad de la Serena, Benavente 980, La Serena, Chile; ICATE-CONICET, San JuanArgentina, email: rbarba@dfuls.cl
Roberto Gamen
Affiliation:
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Box and Instituto de Astrofísica de La Plata (CCT La Plata-CONICET), Paseo del Bosque S/N, B1900FWA, La Plata, Argentina, email: rgamen@gmail.com
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Abstract

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The massive eclipsing system HD 5980 in the Small Magellanic Cloud presented sudden ~1–3 mag eruptive events in 1993-1994, the nature of which is still unexplained. We recently showed that these brief eruptions occurred at the beginning of an extended high state of activity which is characterized by large emission-line intensities and that this high state is currently ending (Koenigsberger et al. 2010). Star A, the more massive member of the 19-day binary, is responsible for the spectacular spectral variations observed over the past 3 decades (see Figure 1). It has a He-enriched stellar wind and is over-luminous for its mass, implying an advanced evolutionary state (Koenigsberger et al. 1998). Data obtained over the past 3 decades show that Star A's wind speed slowed down as the system brightened. Also present in these data is a correlated increase in emission-line strength, visual and UV brigthness. The latter suggests that the high activity state in HD 5980 may be attributed to a bolometric luminosity increase, consistent with the results of Drissen et al. (2001). Hence, HD 5980 may be providing the important clues needed for understanding the behavior of other luminous blue variables and for understainding the evolutionary transition between massive O-type stars and Wolf-Rayet stars.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2011

References

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