Journal Article

Very Large Telescope Interferometer observations of the dust geometry around R Coronae Borealis stars*

S. N. Bright, O. Chesneau, G. C. Clayton, O. De Marco, I. C. Leão, J. Nordhaus and J. S. Gallagher

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 2, pages 1195-1206
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18449.x
Very Large Telescope Interferometer observations of the dust geometry around R Coronae Borealis stars*

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We are investigating the formation and evolution of dust around the hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars. We aim to determine the connection between the probable merger past of these stars and their current dust-production activities.

We carried out high angular resolution interferometric observations of three RCB stars, namely RY Sgr, V CrA and V854 Cen, with the mid-infrared interferometer (MIDI) on the Very Large Telescope Interferometer (VLTI), using two telescope pairs. The baselines ranged from 30 to 60 m, allowing us to probe the dusty environment at very small spatial scales (∼50 mas or 400R). The observations of the RCB star dust environments were interpreted using both geometrical models and one-dimensional radiative transfer codes.

From our analysis, we find that asymmetric circumstellar material is apparent in RY Sgr, may also exist in V CrA and is possible for V854 Cen. Overall, we find that our observations are consistent with dust forming in clumps ejected randomly around the RCB star so that over time they create a spherically symmetric distribution of dust. However, we conclude that the determination of whether there is a preferred plane of dust ejection must wait until a time series of observations are obtained.

Keywords: techniques: high angular resolution; techniques: interferometric; stars: individual: RY Sgr; stars: individual: V CrA; stars: individual: V854 Cen; stars: mass-loss

Journal Article.  8759 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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