Measurements of the circumstellar shell geometry in IRC + 10216

Dyck, H. M.; Zuckerman, B.; Howell, R. R.; Beckwith, S.

doi:10.1086/131960

Cited by 27 publications

(20 citation statements)

References 15 publications

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“…24-27, we compare the model with available near-IR visibilities obtained by Mariotti et al (1983), Dyck et al (1987), , Weigelt et al (1998a), and Osterbart et al (2000). The model visibility is plotted for only two orthogonal directions, parallel (PA ≈ 20…”

Section: Near-infrared Visibilitiesmentioning

confidence: 96%

“…Polarimetric imaging by Tamura et al (1988) detected an extended envelope also in highly polarized light. A weakly-bipolar reflection nebula (Kastner & Weintraub 1994) or a geometrically thick disk (Dyck et al 1987) or a dusty torus (Skinner et al 1998) must be significantly inclined toward an observer. A complex, clumpy subarcsecond structure in the near IR is changing on time scales of a few years, as has been demonstrated by interferometric observations of Weigelt et al (1998a) and .…”

Section: Properties Of the Envelopementioning

confidence: 99%

See 1 more Smart Citation

Structure and physical properties of the rapidly evolving dusty envelope of IRC + 10216 reconstructed by detailed two-dimensional radiative transfer modeling

Men’shchikov

Balega²,

Blöcker³

et al. 2001

A&A

116

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Abstract. We present the first detailed, two-dimensional radiative transfer model of the dusty envelope around the carbon star IRC +10 216. Our goal was to find a self-consistent model of the star and its envelope which takes into account as many observational constraints as possible. The model reproduces very well the entire beam-matched spectral energy distribution of IRC +10 216 from optical to centimeter wavelengths (at several phases of stellar luminosity), observed intensity profiles of the object at 1.25, 2.2, 10.5, 50, 100 µm, and 1.3 mm, a 10.5 µm lunar occultation intensity profile, our high-resolution J, H, K, and H −K bispectrum speckle-interferometry images, and visibilities in J, H, K, L, M , and N bands. For the adopted distance of 130 pc, the model of IRC +10 216 implies that the object changes its luminosity between 13 000 and 5200 L , its effective temperature between 2800 and 2500 K, and its radius between 500 and 390 R . There is a dense non-spherical dust shell around the star, with outflow cavities at position angle PA ≈ 20• . The southern cavity with a full opening angle of 36• is tilted toward us by 40• from the plane of sky, causing the observed bipolar appearance of the object on a subarcsecond scale. If the envelope's outflow velocity of 15 km s −1 applies to the material making up the dense core, then just ∼ 15 years ago the star was losing mass at a rate of 9 10 −5 M yr −1 . Dust exists in the envelope of IRC +10 216 everywhere from the stellar photosphere up to a distance of 3 pc from the star. The total mass of the envelope lost by the central star is 3 M and the dust-to-gas mass ratio is 0.004. The total optical depth τV toward the star in the visual is 40, in the polar cavities it is 10. The innermost parts of the envelope are optically thick even at 10.7 µm due to a strong resonance absorption of silicon carbide grains at that wavelength. In addition to SiC dust, the model contains inhomogeneous grains made of a mixture of SiC and incompletely amorphous carbon with thin [Mg0.5Fe0.5]S mantles. This is the simplest dust mixture required to fit all observations of IRC +10 216 and to correctly interpret the well-known 11.3 µm and 27 µm emission bands. The dust model found in this study can also be successfully applied to many other carbon stars exhibiting broad emission features in the 10.3-12.6 µm and 25-37 µm wavelength regions. An important and firm result of our modeling is that the brightest compact peak observed in IRC +10 216 is not the direct light from the underlying central star. In contrast to previous suggestions, the brightest southern component, labeled A in our high-resolution near-infrared images (Weigelt et al. 1998a,b;Osterbart et al. 2000), is only the radiation emitted and scattered in the optically thinner southern cavity of the bipolar dense shell moving away from the central star. The carbon star is at the position of the fainter component B in our H and K images, which is 0. 21 away from A along the symmetry axis. Direct stellar light (component B) is not se...

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Section: Near-infrared Visibilitiesmentioning

confidence: 96%

Section: Properties Of the Envelopementioning

confidence: 99%

Structure and physical properties of the rapidly evolving dusty envelope of IRC + 10216 reconstructed by detailed two-dimensional radiative transfer modeling

Men’shchikov

Balega²,

Blöcker³

et al. 2001

A&A

116

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“…Evidence was provided from optical and near-infrared data for an equatorial density enhancement in the form of a geometrically thick disk (Dyck et al 1987) or dusty torus (Skinner et al 1998;Murakawa et al 2005;Jeffers et al 2014) seen almost edge-on. Beyond 1 , multiple almost concentric shells (or arcs) are detected on top of the smooth extended envelope (Mauron & Huggins 1999Leão et al 2006;Dinh-V-Trung & Lim 2008;Fong et al 2003;Decin et al 2011).…”

Section: Introductionmentioning

confidence: 99%

ALMA data suggest the presence of spiral structure in the inner wind of CW Leonis

Decin

Richards

Neufeld

et al. 2015

A&A

121

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Context. Evolved low-mass stars lose a significant fraction of their mass through stellar winds. While the overall morphology of the stellar wind structure during the asymptotic giant branch (AGB) phase is thought to be roughly spherically symmetric, the morphology changes dramatically during the post-AGB and planetary nebula phase, during which bipolar and multi-polar structures are often observed. Aims. We aim to study the inner wind structure of the closest well-known AGB star CW Leo. Different diagnostics probing different geometrical scales have implied a non-homogeneous mass-loss process for this star: dust clumps are observed at milli-arcsec scale, a bipolar structure is seen at arcsecond-scale, and multi-concentric shells are detected beyond 1 . Methods. We present the first ALMA Cycle 0 band 9 data around 650 GHz (450 μm) tracing the inner wind of CW Leo. The fullresolution data have a spatial resolution of 0. 42 × 0. 24, allowing us to study the morpho-kinematical structure of CW Leo within ∼6 . Results. We have detected 25 molecular emission lines in four spectral windows. The emission of all but one line is spatially resolved. The dust and molecular lines are centered around the continuum peak position, which is assumed to be dominated by stellar emission. The dust emission has an asymmetric distribution with a central peak flux density of ∼2 Jy. The molecular emission lines trace different regions in the wind acceleration region and imply that the wind velocity increases rapidly from about 5 R , almost reaching the terminal velocity at ∼11 R . The images prove that vibrational lines are excited close to the stellar surface and that SiO is a parent molecule. The channel maps for the brighter lines show a complex structure; specifically, for the 13 CO J = 6-5 line, different arcs are detected within the first few arcseconds. The curved structure in the position-velocity (PV) map of the 13 CO J = 6-5 line can be explained by a spiral structure in the inner wind of CW Leo, probably induced by a binary companion. From modelling the ALMA data, we deduce that the potential orbital axis for the binary system lies at a position angle of ∼10-20• to the north-east and that the spiral structure is seen almost edge-on. We infer an orbital period of 55 yr and a binary separation of 25 au (or ∼8.2 R ). We tentatively estimate that the companion is an unevolved low-mass main-sequence star. Conclusions. A scenario of a binary-induced spiral shell can explain the correlated structure seen in the ALMA PV images of CW Leo. Moreover, this scenario can also explain many other observational signatures seen at different spatial scales and in different wavelength regions, such as the bipolar structure and the almost concentric shells. ALMA data hence for the first time provide the crucial kinematical link between the dust clumps seen at milli-arcsecond scale and the almost concentric arcs seen at arcsecond scale.

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“…This nebula was further modeled as an inclined bi-conical structure (Dyck et al 1987;Haniff & Buscher 1998). Upon examination of all archival Hubble Space Telescope (HST) images of IRC+10216ʼs core, we find that in 2011 the aforementioned bipolar nebula had disappeared and a different set of peaks appeared.…”

Section: Introductionmentioning

confidence: 99%

HST IMAGES REVEAL DRAMATIC CHANGES IN THE CORE OF IRC+10216

Kim

Lee

Mauron

et al. 2015

ApJ

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IRC+10216 is the nearest carbon star with a very high mass-loss rate. The existence of a binary companion has been hinted at by indirect observational evidence, such as the bipolar morphology of its nebula and a spiral-like pattern in its circumstellar material; however, to date, no companion has been identified. We have examined archival Hubble Space Telescope images of IRC+10216, and find that the images taken in 2011 exhibit dramatic changes in its innermost region from those taken at earlier epochs. The scattered light is more spread out in 2011. After proper motion correction, the brightest peak in 2011 is close to, but not coincident with, the dominant peak in previous epochs. A fainter point-like object was revealed at ∼0″ .5 from this brightest peak. We suggest that these changes at the core of IRC+10216 are caused by dissipation of intervening circumstellar dust, as indicated by the brightening trend in the light curve extracted from the Catalina photometric survey. We tentatively identify the brightest peak in 2011 as the primary star of IRC+10216 and the fainter point-like source as a companion. The cause of non-detections of the companion candidate in earlier epochs is uncertain. These identifications need to be verified by monitoring the core of IRC+10216 at high resolution in the future.

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Measurements of the circumstellar shell geometry in IRC + 10216

Cited by 27 publications

References 15 publications

Structure and physical properties of the rapidly evolving dusty envelope of IRC + 10216 reconstructed by detailed two-dimensional radiative transfer modeling

Structure and physical properties of the rapidly evolving dusty envelope of IRC + 10216 reconstructed by detailed two-dimensional radiative transfer modeling

ALMA data suggest the presence of spiral structure in the inner wind of CW Leonis

HST IMAGES REVEAL DRAMATIC CHANGES IN THE CORE OF IRC+10216

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