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Photometry of R Coronae Borealis Stars during the Recovery Phase of their Declines

Published online by Cambridge University Press:  05 March 2013

Lj. Skuljan ,
P. L. Cottrell ,
A. C. Gilmore  and
P. M. Kilmartin
Lj. Skuljan
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand; l.skuljan@phys.canterbury.ac.nz
P. L. Cottrell
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand; p.cottrell@phys.canterbury.ac.nz
A. C. Gilmore
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand; a.gilmore@phys.canterbury.ac.nz
P. M. Kilmartin
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand; p.kilmartin@phys.canterbury.ac.nz
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Abstract

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The photometric observations (UBVRI) of nine cool R Coronae Borealis (RCB) stars have been collected at Mt John University Observatory, New Zealand, over a period of twelve years. The analysis of the magnitude–colour and colour–colour diagrams for the recovery phase demonstrates that all declines exhibit a similar asymptotic approach to their normal brightness. Declines return to maximum brightness along a line with essentially the same slope that does not depend on the star or the depth of the decline. Assuming a uniform obscuration of the photosphere by the dust cloud during the recovery phase, the extinction properties of the material were determined. The ratio of total to selective extinction (RV) for the RCB stars in our sample is in the range 2.5 to 4.6, indicating that the obscuring dust has extinction properties similar to that of the interstellar dust. Observations have been compared with the theoretical extinction curves for different sorts of grains.

Keywords

stars: variables: R Coronae Borealismethods: data analysis
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 20 , Issue 2 , 2003 , pp. 159 - 164
Copyright
Copyright © Astronomical Society of Australia 2003

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