The Evolving Shapes of<i>o</i>Ceti and R Leonis

Tatebe, K.; Wishnow, Edward H.; Ryan, Cornelius; Hale, David; Griffith, R. L.; Townes, C. H.

doi:10.1086/592679

Cited by 8 publications

(12 citation statements)

References 28 publications

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“…Such a variability in the size of R Leo is detected by several authors in the near-IR (Perrin et al 1999;Chagnon et al 2002;Mennesson et al 2002;Fedele et al 2005;Woodruff et al 2008Woodruff et al , 2009, with the star being largest at visual minimum as already predicted by pulsation models; none of these models, however, can reproduce the pulsation amplitude of R Leo (Ireland et al 2004a). Such variability was also detected in the optical (Burns et al 1998) and mid-infrared (Tatebe et al 2006(Tatebe et al , 2008. Mennesson et al (2002) mention that such changes may be caused by variations in the spatial extent and/or in the opacity of the outer atmospheric layers.…”

Section: Appendix A3: R Leomentioning

confidence: 74%

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The VLTI/MIDI view on the inner mass loss of evolved stars from theHerschelMESS sample

Paladini

Klotz

Sacuto

et al. 2017

A&A

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Context. The mass-loss process from evolved stars is a key ingredient for our understanding of many fields of astrophysics, including stellar evolution and the chemical enrichment of the interstellar medium (ISM) via stellar yields. Nevertheless, many questions are still unsolved, one of which is the geometry of the mass-loss process. Aims. Taking advantage of the results from the Herschel Mass loss of Evolved StarS (MESS) programme, we initiated a coordinated effort to characterise the geometry of mass loss from evolved red giants at various spatial scales. Methods. For this purpose we used the MID-infrared interferometric Instrument (MIDI) to resolve the inner envelope of 14 asymptotic giant branch stars (AGBs) in the MESS sample. In this contribution we present an overview of the interferometric data collected within the frame of our Large Programme, and we also add archive data for completeness. We studied the geometry of the inner atmosphere by comparing the observations with predictions from different geometric models. Results. Asymmetries are detected for the following five stars: R Leo, RT Vir, π 1 Gruis, omi Ori, and R Crt. All the objects are O-rich or S-type, suggesting that asymmetries in the N band are more common among stars with such chemistry. We speculate that this fact is related to the characteristics of the dust grains. Except for one star, no interferometric variability is detected, i.e. the changes in size of the shells of non-mira stars correspond to changes of the visibility of less than 10%. The observed spectral variability confirms previous findings from the literature. The detection of dust in our sample follows the location of the AGBs in the IRAS colour-colour diagram: more dust is detected around oxygen-rich stars in region II and in the carbon stars in region VII. The SiC dust feature does not appear in the visibility spectrum of the U Ant and S Sct, which are two carbon stars with detached shells. This finding has implications for the theory of SiC dust formation.

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Section: Appendix A3: R Leomentioning

confidence: 74%

“…Ellipticity. Reports of an elliptical shape of the CSE of R Leo are reported in the optical (Lattanzi et al 1997) mid-infrared (Tatebe et al 2008). On the other hand, several other studies do not find any signs of ellipticity (e.g.…”

Section: Appendix A3: R Leomentioning

confidence: 99%

The VLTI/MIDI view on the inner mass loss of evolved stars from theHerschelMESS sample

Paladini

Klotz

Sacuto

et al. 2017

A&A

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“…At ϕ = 0.5, the uniform-disc diameter between 1.0 and 4.0 µm was observed to vary between ∼ 27 mas and ∼ 55 mas (Woodruff et al 2009). Observations by Tatebe et al (2008) at 11.15 µm indicated a uniform-ellipse size (31.81 ± 0.15) × (30.67 ± 0.22) (ϕ = 0.6 to 0.8). At 43 GHz, Reid & Menten (2007) measured the size of R Leo to be (61 ± 10) × (39 ± 6) (ϕ ∼ 0.55), while Matthews et al (2018) reported (54 ± 3) × (45 ± 2) mas (ϕ ∼ 0.23).…”

Section: R Leomentioning

confidence: 97%

Resolving the extended stellar atmospheres of asymptotic giant branch stars at (sub)millimetre wavelengths

Vlemmings

Khouri

Olofsson

2019

A&A

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Context. The initial conditions for mass loss during the asymptotic giant branch (AGB) phase are set in their extended atmospheres, where, among others, convection and pulsation driven shocks determine the physical conditions. Aims. High resolution observations of AGB stars at (sub)millimetre wavelengths can now directly determine the morphology, activity, density, and temperature close to the stellar photosphere. Methods. We used Atacama Large Millimeter/submillimeter Array (ALMA) high angular resolution observations to resolve the extended atmospheres of four of the nearest AGB stars: W Hya, Mira A, R Dor, and R Leo. We interpreted the observations using a parameterised atmosphere model. Results. We resolve all four AGB stars and determine the brightness temperature structure between 1 and 2 stellar radii. For W Hya and R Dor we confirm the existence of hotspots with brightness temperatures > 3000 to 10000 K. All four stars show deviations from spherical symmetry. We find variations on a timescale of days to weeks, and for R Leo we directly measure an outward motion of the millimetre wavelength surface with a velocity of at least 10.6 ± 1.4 km s −1 . For all objects but W Hya we find that the temperatureradius and size-frequency relations require the existence of a (likely inhomogeneous) layer of enhanced opacity. Conclusions. The ALMA observations provide a unique probe of the structure of the extended AGB atmosphere. We find highly variable structures of hotspots and likely convective cells. In the future, these observations can be directly compared to multi-dimensional chromosphere and atmosphere models that determine the temperature, density, velocity, and ionisation structure between the stellar photosphere and the dust formation region. However, our results show that for the best interpretation, both very accurate flux calibration and near-simultaneous observations are essential.

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“…Observations of such small structures near evolved stars can only be performed with the use of high-angular resolution techniques like the infrared Very Large Telescope Interferometer (VLTI), i.e. planetary nebulae (Chesneau et al , 2007Lagadec et al 2006); VLTP star (Chesneau et al 2009); Mira stars (Tatebe et al 2006(Tatebe et al , 2007(Tatebe et al , 2008; carbon stars (Ohnaka & Boboltz 2008;Sacuto et al 2011;Deroo et al 2007b); OH/IR stars (Deroo et al 2007a,b;Chesneau et al 2005b); post-AGB stars (Deroo et al 2006;Matsuura et al 2006); proto-planetary nebulae (Murakawa et al 2008;Ohnaka et al 2006). Two of the best-studied examples of elongated and axisymmetric bipolar planetary nebulae are M2-9 and Menzel 3.…”

Section: Introductionmentioning

confidence: 99%

A disc inside the bipolar planetary nebula M2-9

Lykou

Chesneau

Zijlstra

et al. 2011

A&A

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Aims. Bipolarity in proto-planetary and planetary nebulae is associated with events occurring in or around their cores. Past infrared observations have revealed the presence of dusty structures around the cores, many in the form of discs. Characterising those dusty discs provides invaluable constraints on the physical processes that govern the final mass expulsion of intermediate mass stars. We focus this study on the famous M2-9 bipolar nebula, where the moving lighthouse beam pattern indicates the presence of a wide binary. The compact and dense dusty core in the centre of the nebula can be studied by means of optical interferometry. Methods. M2-9 was observed with VLTI/MIDI at 39-47 m baselines with the UT2-UT3 and UT3-UT4 baseline configurations. These observations are interpreted using a dust radiative transfer Monte Carlo code. Results. A disc-like structure is detected perpendicular to the lobes, and a good fit is found with a stratified disc model composed of amorphous silicates. The disc is compact, 25 × 35 mas at 8 μm and 37 × 46 mas at 13 μm. For the adopted distance of 1.2 kpc, the inner rim of the disc is ∼15 AU. The mass represents a few percent of the mass found in the lobes. The compactness of the disc puts strong constraints on the binary content of the system, given an estimated orbital period 90-120 yr. We derive masses of the binary components between 0.6-1.0 M for a white dwarf and 0.6-1.4 M for an evolved star. We present different scenarios on the geometric structure of the disc accounting for the interactions of the binary system, which includes an accretion disc as well.

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The Evolving Shapes ofoCeti and R Leonis

Cited by 8 publications

References 28 publications

The VLTI/MIDI view on the inner mass loss of evolved stars from theHerschelMESS sample

The VLTI/MIDI view on the inner mass loss of evolved stars from theHerschelMESS sample

Resolving the extended stellar atmospheres of asymptotic giant branch stars at (sub)millimetre wavelengths

A disc inside the bipolar planetary nebula M2-9

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