The circumstellar envelope of IRC+10216 from milli-arcsecond to arcmin scales

Leão, I. C.; Laverny, P. de; Mékarnia, D.; Medeiros, J. R. De; Vandame, B.

doi:10.1051/0004-6361:20054577

Cited by 78 publications

(115 citation statements)

References 23 publications

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“…IRC+10216 could be a very interesting testcase to check if the clumps can produce a phase signature in carbon stars. Indeed, several dust clumps were detected in the atmosphere of this star (Haniff & Buscher 1998;Weigelt et al 1998Weigelt et al , 2002Leao et al 2006) at spatial scales comparable to the one we obtained with the GEM-FIND modelling (∼30 AU).…”

Section: Discussionsupporting

confidence: 80%

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: Discussionsupporting

confidence: 80%

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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“…The VLT-FORS raw images and calibration files were extracted from the ESO archive. The V-band image of IRC+10216 was first shown by Leao et al (2006). The HST data are from programs 9463 and 10185, PI: R. Sahai.…”

Section: Additional Observationsmentioning

confidence: 99%

Deep optical imaging of asymptotic giant branch circumstellar envelopes

Mauron

Huggins

Cheung

2013

A&A

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We report results of a program to image the extended circumstellar envelopes of asymptotic giant branch (AGB) stars in dust-scattered Galactic light. The goal is to characterize the shapes of the envelopes to probe the mass-loss geometry and the presence of hidden binary companions. The observations consist of deep optical imaging of 22 AGB stars with high mass loss rates: 16 with the ESO 3.6 m NTT telescope, and the remainder with other telescopes. The circumstellar envelopes are detected in 15 objects, with mass loss rates > ∼ 2 × 10 −6 M yr −1 . The surface brightness of the envelopes shows a strong decrease with Galactic radius, which indicates a steep radial gradient in the interstellar radiation field. The envelopes range from circular to elliptical in shape, and we characterize them by the ellipticity (E = major/minor axis) of iso-intensity contours. We find that ∼50% of the envelopes are close to circular with E < ∼ 1.1, and others are more elliptical with ∼20% with E > ∼ 1.2. We interpret the shapes in terms of populations of single stars and binaries whose envelopes are flattened by a companion. The distribution of E is qualitatively consistent with expectations based on population synthesis models of binary AGB stars. We also find that ∼50% of the sample exhibit small-scale, elongated features in the central regions. We interpret these as the escape of light from the central star through polar holes, which are also likely produced by companions. Our observations of envelope flattening and polar holes point to a hidden population of binary companions within the circumstellar envelopes of AGB stars. These companions are expected to play an important role in the transition to post-AGB stars and the formation of planetary nebulae.

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“…This is not surprising, as this nearby carbon star is subject to a high mass loss rate and is surrounded by a thick CSE. The circumstellar shell has been imaged at different wavelengths, in the visible by Mauron and Huggins (2000), in the NIR by Leão et al (2006), at 1.3 mm by Groenewegen et al (1997) and using CO lines by Huggins et al (1988) and Fong et al (2004).…”

Section: Cw Leomentioning

confidence: 99%

870 μm observations of evolved stars with LABOCA

Ladjal

Justtanont

Groenewegen

et al. 2010

A&A

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Context. During their evolution, asymptotic giant branch (AGB) stars experience a high mass loss which leads to the formation of a circumstellar envelope (CSE) of dust and gas. The mass loss process is the most important phenomenon during this evolutionary stage. In order to understand it, it is important to study the physical parameters of the CSE. The emission of the CSE in the (sub)millimetre range is dominated by the dust continuum. This means that (sub)millimetre observations are a key tool in tracing the dust and improving our knowledge of the mass loss process. Aims. The aim of this study is to use new submillimetre observations of a sample of evolved stars to constrain the CSE physical parameters. Methods. We used aperture photometry to determine the fluxes at 870 μm and to investigate the extended emission observed with the new APEX bolometer LABoCa. We computed the spectral energy distribution (SEDs) with the 1D radiative transfer code DUSTY, which we compared to literature data. Grain properties were calculated with both the spherical grains distribution and the continuous distribution of ellipsoids (CDE), and a comparison between the two is drawn. Synthetic surface brightness maps were derived from the modelling and were compared to the LABoCa brightness maps. Results. A sample of nine evolved stars with different chemistry was observed with LABoCa. We detected extended emission around four stars. Physical parameters of the circumstellar envelope were derived from SED modelling, like the dust chemical composition, the dust condensation temperature and the total mass of the envelope. It proved to be difficult to fit the SED and the intensity profile simultaneously however. The use of the CDE leads to "broad" SEDs when compared to spherical grains, and this results in steep density distributions (∝r −2.2 typically).

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The circumstellar envelope of IRC+10216 from milli-arcsecond to arcmin scales

Cited by 78 publications

References 23 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

Deep optical imaging of asymptotic giant branch circumstellar envelopes

870 μm observations of evolved stars with LABOCA

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