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Observations and Interpretation of Luminous Blue Variables

Published online by Cambridge University Press:  12 April 2016

Henny J.G.L.M. Lamers
Henny J.G.L.M. Lamers*
Affiliation:
Astronomical Institute and SRON Laboratory for Space Research, Princetonplein 5, NL-3584 CA Utrecht, The Netherlandshennyl@sron.ruu.nl

Abstract

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The different types of variations of LBVs are discussed. The “typical LBV variations” have amplitudes of ΔV ≃ 0.5 to 2.0 magnitudes and irregular time-scales of months to years. This is due to changes in the stellar radius and the effective temperature. Modelling of this variability for one star, S Dor, shows that the radius of the star varies between 100 and 380 R⊙, the effective temperature between 20,000 and 9,000 K, and the luminosity between log L* = 6.10 to 5.9. The variation of the radius is not an apparent variation of the effective radius of the wind due to a variable mass loss rate (which has often been assumed) but it is a true variation of the radius of the star itself. The changes in L* suggest that about 10−3 to 10−2M* takes part in the expansion of the star. The irregular microvariations with amplitudes of about ΔV ≃ 0.2m on timescales of weeks are probably due to non-adiabatic pulsations with mode-interaction. We argue that LBVs are close to their effective Eddington Limit and discuss a qualitative scenario to explain their location in the HR-diagram.

Type
Part 1. The Scientific Programme
Information
International Astronomical Union Colloquium , Volume 155 , 1995 , pp. 176 - 191
Copyright
Copyright © Astronomical Society of the Pacific 1995

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