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

Bright, Stacey N.; Chesneau, O.; Clayton, Geoffrey C.; Marco, Orsola De; Leão, I. C.; Nordhaus, Jason; Gallagher, J.

doi:10.1111/j.1365-2966.2011.18449.x

Cited by 12 publications

(19 citation statements)

References 52 publications

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“…Recent results from investigations of R CrB stars (Jeffers et al 2012) indicate the presence of dust clouds with different grain-sizes. Nevertheless, Bright et al (2011) did not detect any differential phase signature for these objects, arguing that the signatures of dust clumps are not strong enough to induce significant spectral signatures like the one we observed. This might not be the case for AGB stars because R CrB stars are much hotter and H-deficient (i.e.…”

Section: Discussionmentioning

confidence: 56%

“…On the other hand, these obscuration events have similarities with those observed for R Coronae Borealis stars (R CrB; Clayton et al 2012). In the latter case, the third and the fourth scenario would be more likely explanations (Bright et al 2011;Jeffers et al 2012 This Letter presents high angular resolution observations in the mid-infrared that allow us to probe the dust-forming region of the nearby AGB star R For. Observations close in time, with different position angles and baseline lengths, the differential phase information, and the comparison with geometric models can help to distinguish possible deviations from a spherical structure.…”

Section: Introductionmentioning

confidence: 99%

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Detection of an asymmetry in the envelope of the carbon Mira R Fornacis using VLTI/MIDI

Paladini

Sacuto

Klotz

et al. 2012

A&A

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Aims. We present a study of the envelope morphology of the carbon Mira R For with VLTI/MIDI. This object is one of the few asymptotic giant branch (AGB) stars that underwent a dust-obscuration event. The cause of such events is still a matter of discussion. Several symmetric and asymmetric scenarios have been suggested in the literature. Methods. Mid-infrared interferometric observations were obtained separated by two years. The observations probe different depths of the atmosphere and cover different pulsation phases. The visibilities and the differential phases were interpreted using GEM-FIND, a tool for fitting spectrally dispersed interferometric observations with the help of wavelength-dependent geometric models. Results. We report the detection of an asymmetric structure revealed through the MIDI differential phase. This asymmetry is observed at the same baseline and position angle two years later. The observations are best simulated with a model that includes a uniform-disc plus a Gaussian envelope plus a point-source. The geometric model can reproduce both the visibilities and the differential phase signatures. Conclusions. Our MIDI data favour explanations of the R For obscuration event that are based on an asymmetric geometry. We clearly detect a photocentre shift between the star and the strongly resolved dust component. This might be caused by a dust clump or a substellar companion. However, the available observations do not allow us to distinguish between the two options. The finding has strong implications for future studies of the geometry of the envelope of AGB stars: if this is a binary, are all AGB stars that show an obscuration event binaries as well? Or are we looking at asymmetric mass-loss processes (i.e. dusty clumps) in the inner part of a carbon-rich Mira?

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Section: Discussionmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Detection of an asymmetry in the envelope of the carbon Mira R Fornacis using VLTI/MIDI

Paladini

Sacuto

Klotz

et al. 2012

A&A

View full text Add to dashboard Cite

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“…Models of the mergers have been carried out with 3D hydrodynamic codes (Staff et al, 2012), which in turn were used as inputs to 1D stellar structure codes (Menon et al, 2013) to determine the nucleosynthetic properties of the merger. The relationship between the dust activity and the merger past remains unclear (Bright et al, 2011). The prevalence of close binaries amongst massive stars (Kiminki & Kobulnicky, 2012;Sana et al, 2012a, Section 2.1) leads us to the inevitable conclusion that many will interact and merge (de Mink et al, 2014).…”

Section: Stripped Stellar Cores and Mergersmentioning

confidence: 99%

Dawes Review 6: The Impact of Companions on Stellar Evolution

Marco

Izzard

2017

Publ. Astron. Soc. Aust.

187

136

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Astrophysicists are increasingly taking into account the effects of orbiting companions on stellar evolution. New discoveries have underlined the role of binary star interactions in a range of astrophysical events, including some that were previously interpreted as being due uniquely to single stellar evolution. We review classical binary phenomena, such as type Ia supernovae, and discuss new phenomena, such as intermediate luminosity transients, gravitational wave-producing double black holes, and the interaction between stars and their planets. Finally, we reassess well-known phenomena, such as luminous blue variables, in light of interpretations that include both single and binary stars. At the same time we contextualise the new discoveries within the framework of binary stellar evolution. The last decade has seen a revival in stellar astrophysics as the complexity of stellar observations is increasingly interpreted with an interplay of single and binary scenarios. The next decade, with the advent of massive projects such as the Square Kilometre Array, the James Webb Space Telescope, and increasingly sophisticated computational methods, will see the birth of an expanded framework of stellar evolution that will have repercussions in many other areas of astrophysics such as galactic evolution and nucleosynthesis.

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“…The HST and ExPo images clearly show a dust cloud at a detection signal-to-noise of 33 sigma. Observations of another R CrB star RY Sgr (de Laverny & Mékarnia 2004;Bright et al 2011) show many dust clouds likely to be randomly ejected from the stellar surface. As noted by de Laverny & Mékarnia (2004) over the last 50 years the number of brightness declines for R CrB is much greater than that of RY Sgr, implying that we should be seeing many more dust clouds in the circumstellar environment of R CrB.…”

Section: Dust Cloudsmentioning

confidence: 99%

“…This is notably the closest observed dust cloud around an R CrB star. More recently Bright et al (2011) also used VLTI/MIDI to probe the circumstellar environments of RY Sgy, V CrA and V854 Cen at very small spatial scales (50 mas/400 R ). They find that their observations are consistent with a scenario of random dust ejection around the star, which over time creates a halo of dust.…”

Section: Introductionmentioning

confidence: 99%

Direct imaging of a massive dust cloud around R Coronae Borealis

Jeffers¹,

Min²,

Waters³

et al. 2012

A&A

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We present recent polarimetric images of the highly variable star R CrB using ExPo and archival WFPC2 images from the HST. We observed R CrB during its current dramatic minimum where it decreased more than 9 mag due to the formation of an obscuring dust cloud. Since the dust cloud is only in the line-of-sight, it mimics a coronograph allowing the imaging of the star's circumstellar environment. Our polarimetric observations surprisingly show another scattering dust cloud at approximately 1.3 or 2000 AU from the star. We find that to obtain a decrease in the stellar light of 9 mag and with 30% of the light being reemitted at infrared wavelengths (from R CrB's SED) the grains in R CrB's circumstellar environment must have a very low albedo of approximately 0.07%. We show that the properties of the dust clouds formed around R CrB are best fitted using a combination of two distinct populations of grains size. The first are the extremely small 5 nm grains, formed in the low density continuous wind, and the second population of large grains (∼0.14 μm) which are found in the ejected dust clouds. The observed scattering cloud, not only contains such large grains, but is exceptionally massive compared to the average cloud.

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

Cited by 12 publications

References 52 publications

Detection of an asymmetry in the envelope of the carbon Mira R Fornacis using VLTI/MIDI

Detection of an asymmetry in the envelope of the carbon Mira R Fornacis using VLTI/MIDI

Dawes Review 6: The Impact of Companions on Stellar Evolution

Direct imaging of a massive dust cloud around R Coronae Borealis

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