VLTI observations of the dust geometry around R Coronae Borealis stars

Abstract

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-IR interferometer, MIDI on the 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 400 stellar radii). 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.

Accepted for publication in MNRAS; 14 pages, 10 figures, 6 tables

References in corpus (4)

• High spatial resolution mid-infrared observations of the low-mass young star TW Hya
• The circumbinary disc around the J-type C-star IRAS 18006-3213
• Asymmetric silicate dust distribution toward the silicate carbon star BM Gem
• A snapshot of the inner dusty regions of a RCrB-type variable

Cited by in corpus (10)

• The impact of companions on stellar evolution
• The Circumstellar Environment of R Coronae Borealis: White Dwarf Merger or Final Helium Shell Flash?
• The Dust Properties of Two Hot R Coronae Borealis Stars and a Wolf-Rayet Central Star of a Planetary Nebula: in Search of a Possible Link
• Dust around R Coronae Borealis stars: I. Spitzer/IRS observations
• Direct imaging of a massive dust cloud around R Coronae Borealis
• Detection of an asymmetry in the envelope of the carbon Mira R Fornacis using VLTI/MIDI
• The Double Dust Envelopes of R Coronae Borealis Stars
• R Coronae Borealis: Radial-velocity and other observations, 1950-2007
• ROAD and K2 photometry of V348 Sgr: probing the pulsation dust connection
• The RCB star V854 Cen is surrounded by a hot dusty shell