INVESTIGADORES
GAMEN Roberto Claudio
artículos
Título:
Wind Structure and Luminosity Variations in the Wolf-Rayet/Luminous Blue Variable HD 5980
Autor/es:
GEORGIEV, L.; KOENIGSBERGER, G.; HILLIER, D. J.; MORRELL, N. I.; BARBÁ, R.; GAMEN, R. C.
Revista:
ASTRONOMICAL JOURNAL
Editorial:
IOP PUBLISHING LTD
Referencias:
Año: 2011 vol. 142 p. 191 - 211
ISSN:
0004-6256
Resumen:
Over the past 40 years, the massive luminous blue variable/Wolf-Rayet
system HD 5980 in the Small Magellanic Cloud (SMC) has undergone a
long-term S Doradus-type variability cycle and two brief and violent
eruptions in 1993 and 1994. In this paper we analyze a collection of UV
and optical spectra obtained between 1979 and 2009 and perform CMFGEN
model fits to spectra of 1994, 2000, 2002, and 2009. The results are as
follows: (1) the long-term S Dor-type variability is associated with
changes of the hydrostatic radius; (2) the 1994 eruption involved
changes in its bolometric luminosity and wind structure; (3) the
emission-line strength, the wind velocity, and the continuum luminosity
underwent correlated variations in the sense that a decreasing V
∞ is associated with increasing emission line and
continuum levels; and (4) the spectrum of the third star in the system
(Star C) is well fit by a T eff = 32 K model atmosphere with
SMC chemical abundances. For all epochs, the wind of the erupting star
is optically thick at the sonic point and is thus driven mainly by the
continuum opacity. We speculate that the wind switches between two
stable regimes driven by the "hot" (during the eruption) and the "cool"
(post-eruption) iron opacity bumps as defined by Lamers & Nugis and
Gräfener & Hamann, and thus the wind may undergo a bi-stability
jump of a different nature from that which occurs in OB stars.