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Justtanont, K.; Yamamura, I.; Jong, T. de; Cami, J.; Waters, L. B. F. M.

doi:10.1023/a:1001504311386

Cited by 82 publications

(158 citation statements)

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“…As very simple it may seem, such a two-layer model turned out to be successful in interpreting infrared molecular spectra obtained with ISO/SWS. For example, Yamamura et al (1999) and Matsuura et al (2002) could reproduce H 2 O spectra of Mira variables obtained with ISO/SWS using a two-layer model, although their two-layer model consists of a stack of plane-parallel slabs, instead of spherical layers as adopted in the present work.…”

Section: Modeling Of the Warm Water Vapor Envelopementioning

confidence: 99%

Warm water vapor envelope in Mira variables and its effects on the apparent size from the near-infrared to the mid-infrared

Ohnaka

2004

A&A

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Abstract.We present a possible interpretation for the increase of the angular diameter of the Mira variables o Cet, R Leo, and χ Cyg from the K band to the 11 µm region revealed by the recent interferometric observations using narrow bandpasses where no salient spectral feature is present (Weiner et al. 2003a,b). A simple two-layer model consisting of hot and cool H 2 O layers for the warm water vapor envelope, whose presence in Mira variables was revealed by previous spectroscopic observations, can reproduce the angular diameters observed with Infrared Spatial Interferometer as well as the high-resolution TEXES spectra obtained in the 11 µm region. The warm water vapor layers are optically thick in the lines, and therefore, strong absorption due to H 2 O can be expected from such a dense water vapor envelope. However, the absorption lines are filled in by emission from the extended part of the envelope, and this results in the high-resolution 11 µm spectra which exhibit only weak, fine spectral features, masking the spectroscopic evidences of the dense, warm water vapor envelope. On the other hand, the presence of the warm water vapor envelope manifests itself as the larger angular diameters in the 11 µm region as compared to those measured in the near-infrared. Furthermore, comparison of the visibilities predicted in the near-infrared (1.5-3.8 µm) with observational results available in the literature demonstrates that our two-layer model for the warm water vapor envelope can also reproduce the observed near-infrared visibilities and angular diameters, and suggests that the wavelength dependence of the angular size of Mira variables in the infrared largely reflects the H 2 O opacity. The radii of the hot H 2 O layers in the three Mira variables are derived to be 1.5-1.7 R with temperatures of 1800-2000 K and H 2 O column densities of (1−5) × 10 21 cm −2 , while the radii of the cool H 2 O layers are derived to be 2.2-2.5 R with temperatures of 1200-1400 K and H 2 O column densities of (1−7) × 10 21 cm −2 .

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Section: Modeling Of the Warm Water Vapor Envelopementioning

confidence: 99%

Warm water vapor envelope in Mira variables and its effects on the apparent size from the near-infrared to the mid-infrared

Ohnaka

2004

A&A

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“…The atmospheres are affected by the pulsation of the interior creating shocks in the outer layers. Because of the third dredge-up, the AGB stars may have C/O > 1 (Iben & Renzini 1983) and therefore their spectra maybe dominated by features of carbon species such as C 2 , C 2 H 2 , C 3 , CN, and HCN (Goebel et al 1981;Joyce 1998;Lançon et al 2000;Loidl et al 2001;Yamamura & de Jong 2000). These are the classical carbon stars.…”

Section: Introductionmentioning

confidence: 99%

Interferometric properties of pulsating C-rich AGB stars

Paladini¹,

Aringer²,

Hron³

et al. 2009

A&A

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Aims. On the basis of a set of dynamic model atmospheres of C-rich AGB stars, we present the first theoretical study of centre-to-limb variation (CLV) properties and relative radius interpretation on narrow and broad-band filters. We computed visibility profiles and the equivalent uniform disc (UD) radii to investigate the dependence of these quantities on the wavelength and pulsation phase. Methods. After an accurate morphological analysis of the visibility and intensity profiles determined in narrow and broad-band filters, we fitted our visibility profiles with a UD function simulating the observational approach. The UD-radii were computed using three different fitting-methods to investigate the influence of the visibility sampling profile: single point, two points and a least squares method. Results. The intensity and visibility profiles of models characterises by mass loss show a behaviour very different from a UD. We found that UD-radii are wavelength dependent and that this dependence is stronger if mass loss is present. Strong opacity contributions from C 2 H 2 affect all radius measurements at 3 μm and in the N-band, resulting in higher values for the UD-radii. In the case of models with mass loss the predicted behaviour of UD-radii versus phase is complicated, while the radial changes are almost sinusoidal for models without mass loss. Compared to the M-type stars, for the C-stars no windows are available for measuring the pure continuum.

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“…The most commonly detected molecules in the near-IR to mid-IR range are H 2 O, OH, CO, CO 2 , SiO and SO 2 (see e.g. Cami et al 1997;Justtanont et al 1998;Ryde et al 1998;Duari, Cherchneff & Willacy 1999;Yamamura et al 1999a;Yamamura, de Jong & Cami 1999b;Jørgensen et al 2001;Matsuura et al 2002;Blommaert et al 2005), and most of those are also prominently present in our Spitzer spectra (see Fig. 4).…”

Section: Molecular Bands: Inventorymentioning

confidence: 59%

“…This band has been detected in the ISO/SWS spectra of some oxygen-rich AGB stars (Yamamura et al 1999a), and can appear in absorption or in emission. Even at the low resolution of our observations, a close inspection of the spectra in Fig.…”

Section: Molecular Bands: Inventorymentioning

confidence: 81%

“…Water opacity plays a key role in our targets. It has been shown (Yamamura et al 1999b;Cami 2002) that at least two layers containing water vapour are required to properly reproduce the observations, owing to the high opacity of water and temperature gradients in the photosphere and the circumstellar environment. We thus include two water layers in our models.…”

Section: Molecular Bands: Modelsmentioning

confidence: 99%

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