An independent distance estimate to CW Leonis

Groenewegen, M. A. T.; Barlow, M. J.; Blommaert, J. A. D. L.; Cernicharo, J.; Decin, L.; Gomez, Haley Louise; Hargrave, Peter Charles; Kerschbaum, F.; Ladjal, D.; Lim, T.; Matsuura, M.; Olofsson, G.; Sibthorpe, B.; Swinyard, Bruce; Ueta, Toshiya; Yates, J.

doi:10.1051/0004-6361/201219604

Cited by 57 publications

(62 citation statements)

References 34 publications

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“…For some Galactic targets, large grains have proven necessary when near-IR visibility data are available, because they provide an additional scattering component. Examples include IRC +10 216 and OH 26.5, which were fitted with MoD code by Groenewegen et al (2012) and Groenewegen (2012), respectively. Recently, Norris et al (2012), Scicluna et al (2015), and Ohnaka et al (2016) found evidence for grains in the range 0.3-0.5 µm, and 0.1-1 µm grains are advocated to drive the outlow around oxygen-rich stars (Höfner 2008, Bladh & Höfner 2012).…”

Section: Dust Grain Propertiesmentioning

confidence: 99%

Luminosities and mass-loss rates of Local Group AGB stars and red supergiants

Groenewegen

Sloan

2018

A&A

Self Cite

102

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Context. Mass loss is one of the fundamental properties of asymptotic giant branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking. Aims. We aim to investigate mass loss and luminosity in a large sample of evolved stars in several Local Group galaxies with a variety of metalliticies and star-formation histories: the Small and Large Magellanic Cloud, and the Fornax, Carina, and Sculptor dwarf spheroidal galaxies (dSphs). Methods. Dust radiative transfer models are presented for 225 carbon stars and 171 oxygen-rich evolved stars in several Local Group galaxies for which spectra from the Infrared Spectrograph on Spitzer are available. The spectra are complemented with available optical and infrared photometry to construct spectral energy distributions. A minimization procedure was used to determine luminosity and mass-loss rate (MLR). Pulsation periods were derived for a large fraction of the sample based on a re-analysis of existing data. Results. New deep K-band photometry from the VMC survey and multi-epoch data from IRAC (at 4.5 µm) and AllWISE and NEOWISE have allowed us to derive pulsation periods longer than 1000 days for some of the most heavily obscured and reddened objects. We derive (dust) MLRs and luminosities for the entire sample. The estimated MLRs can differ significantly from estimates for the same objects in the literature due to differences in adopted optical constants (up to factors of several) and details in the radiative transfer modelling. Updated parameters for the super-AGB candidate MSX SMC 055 (IRAS 00483−7347) are presented. Its current mass is estimated to be 8.5 ± 1.6 M ⊙ , suggesting an initial mass well above 8 M ⊙ in agreement with estimates based on its large Rubidium abundance. Using synthetic photometry, we present and discuss colour-colour and colour-magnitude diagrams which can be expected from the James Webb Space Telescope.

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Section: Dust Grain Propertiesmentioning

confidence: 99%

Luminosities and mass-loss rates of Local Group AGB stars and red supergiants

Groenewegen

Sloan

2018

A&A

Self Cite

102

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“…Combining several sparsely sampled epochs, they found that some lines of spatially extended species such as the SiCC and low-J CO lines showed little variation, while some other molecular lines such as high-J CO, CS, SiO, SiS, HCN, CCH N=6-5, and H 2 O lines all show evident variability. Particularly, the varying CCH N=6-5 line was argued to be emitted from an extended region in the CSE which, together with the far infrared (IR) variability of dust emission found by Groenewegen et al (2012), demonstrated the importance of IR excitation/heating of dust and gas in the outer parts of the CSE.…”

Section: Introductionmentioning

confidence: 96%

Monitor Variability of Millimeter Lines in IRC+10216

Dinh-V-Trung

Hasegawa

2017

ApJ

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A single dish monitoring of millimeter maser lines SiS J=14-13 and HCN ν 2 = 1 f J=3-2 and several other rotational lines is reported for the archetypal carbon star IRC +10216. Relative line strength variations of 5%∼30% are found for eight molecular line features with respect to selected reference lines. Definite line-shape variation is found in limited velocity intervals of the SiS and HCN line profiles. The asymmetrical line profiles of the two lines are mainly due to the varying components. Their dominant varying components of the line profiles have similar periods and phases as the IR light variation, although both quantities show some degree of velocity dependence; there is also variability asymmetry between the blue and red line wings of both lines. Combining the velocities and amplitudes with a wind velocity model, we suggest that the line profile variations are due to SiS and HCN masing lines emanating from the wind acceleration zone. The possible link of the variabilities to thermal, dynamical and/or chemical processes within or under this region is also discussed.

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“…CW Leo (also known as IRC +10216) is the nearest carbon-rich asymptotic giant branch (AGB) star at a distance of about 120 to 150 pc (Men'shchikov et al 2001;Groenewegen et al 2012, and reference therein). During the AGB phase, the evolution is determined by mass loss, with the mass-loss rate being significantly higher than the rate at which mass is comsumed by nuclear burning (Lagadec et al 2008).…”

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

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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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An independent distance estimate to CW Leonis

Cited by 57 publications

References 34 publications

Luminosities and mass-loss rates of Local Group AGB stars and red supergiants

Luminosities and mass-loss rates of Local Group AGB stars and red supergiants

Monitor Variability of Millimeter Lines in IRC+10216

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

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