Polycyclic Aromatic Hydrocarbons Orbiting HD 233517, an Evolved Oxygen-rich Red Giant

Jura, M.; Bohac, C. J.; Sargent, B.; Forrest, W. J.; Green, J.; Watson, D. M.; Sloan, G. C.; Kemper, F.; Chen, C. H.; Najita, J.

doi:10.1086/500429

Cited by 32 publications

(37 citation statements)

References 44 publications

(66 reference statements)

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“…Such a scenario was proposed by Jura et al (2006) to explain PAH features observed in the oxygen-rich giant HD 233517. The spectrum of MACHO 81.9728.14 does not show any other features due to C-rich or O-rich dust species, such as SiC or silicates, although it cannot be ruled out that these features are present at longer wavelengths, for which no Spitzer-IRS spectrum is available unfortunately.…”

Section: Macho 81972814mentioning

confidence: 77%

Chemical depletion in the Large Magellanic Cloud: RV Tauri stars and the photospheric feedback from their dusty discs

Gielen

Winckel

Reyniers

et al. 2009

A&A

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Aims. By studying the photospheric abundances of 4 RV Tauri stars in the LMC, we test whether the depletion pattern of refractory elements, seen in similar Galactic sources, is also common for extragalactic sources. Since this depletion process probably only occurs through interaction with a stable disc, we investigate the circumstellar environment of these sources. Methods. A detailed photospheric abundance study was performed using high-resolution UVES optical spectra. To study the circumstellar environment we use photometric data to construct the spectral energy distributions of the stars, and determine the geometry of the circumstellar environment, whereas low-resolution Spitzer-IRS infrared spectra are used to trace its mineralogy. Results. Our results show that, also in the LMC, the photospheres of RV Tauri stars are commonly affected by the depletion process, although it can differ significantly in strength from source to source. From our detailed disc modelling and mineralogy study, we find that this process, as in the Galaxy, appears closely related to the presence of a stable Keplerian disc. The newly studied extragalactic objects have similar observational characteristics as Galactic post-AGB binaries surrounded by a dusty disc, and are therefore also believed to be part of a binary system. One source shows a very small infrared excess, atypical for a disc source, but still has evidence for depletion. We speculate this could point to the presence of a very evolved disc, similar to debris discs seen around young stellar objects.

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Section: Macho 81972814mentioning

confidence: 77%

Chemical depletion in the Large Magellanic Cloud: RV Tauri stars and the photospheric feedback from their dusty discs

Gielen

Winckel

Reyniers

et al. 2009

A&A

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“…Sloan et al (2007) report on the detection of class-C PAH features in HD 100764, a carbon-rich red giant with evidence of a circumstellar disc. Jura et al (2006) also report on the detection of class-C PAH features in a circumstellar disc around the oxygen-rich K-giant HD 233517. Two young objects, the T Tauri star SU Aur (Furlan et al 2006) and the Herbig Ae/Be source HD 135344 (Sloan et al 2005), also show PAH spectra of class C, although in HD 135344 the PAH features seem to be somewhat more in between B and C. This source is also slightly hotter than other class C sources.…”

Section: Pah Featuresmentioning

confidence: 95%

“…Since HD 233517 is an oxygen-rich star, it is remarkable that the disc shows features of carbon-rich chemistry. Jura et al (2006) propose a scenario in which the PAHs could be formed inside the disc due to Fischer-Tropsch (FT) catalysis on the surface of solid iron grains. These FT reactions can convert CO and H 2 into water and hydrocarbons (Willacy 2004), these hydrocarbons could then be converted in into PAHs.…”

Section: Pah Featuresmentioning

confidence: 99%

“…Some examples include Herbig Ae stars, or AGB stars, such as J-type carbon stars with silicate dust emission (Little-Marenin 1986;Lloyd Evans 1990). Others are red giants, for example HD 233517, an evolved O-rich red giant with PAHs in a circumstellar disc (Jura et al 2006). Other examples are planetary nebulae (PNe) with evidence of silicates and PAHs (Kemper et al 2002;Gutenkunst et al 2008), or the hydrogen-poor [WC] central stars of PNe Article published by EDP Sciences Note: Listed are the name, equatorial coordinates α and δ(J2000), effective temperature T eff , surface gravity log g, and metallicity [Fe/H] of our sample stars.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the infrared spectra of the peculiar post-AGB stars EP Lyrae and HD 52961

Gielen¹,

Winckel²,

Matsuura

et al. 2009

A&A

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Aims. We aim to study in detail the peculiar mineralogy and structure of the circumstellar environment of two binary post-AGB stars, EP Lyr and HD 52961. Both stars were selected from a larger sample of evolved disc sources observed with Spitzer and show unique solid-state and gas features in their infrared spectra. Moreover, they show a very small infrared excess in comparison with the other sample stars. Methods. The different dust and gas species are identified on the basis of high-resolution Spitzer-IRS spectra. We fit the full spectrum to constrain grain sizes and temperature distributions in the discs. This, combined with our broad-band spectral energy distribution and interferometric measurements, allows us to study the physical structure of the disc, using a self-consistent 2D radiative-transfer disc model. Results. We find that both stars have strong emission features due to CO 2 gas, dominated by 12 C 16 O 2 , but with clear 13 C 16 O 2 and even 16 O 12 C 18 O isotopic signatures. Crystalline silicates are apparent in both sources but proved very hard to model. EP Lyr also shows evidence of mixed chemistry, with emission features of the rare class-C PAHs. Whether these PAHs reside in the oxygen-rich disc or in a carbon-rich outflow is still unclear. With the strongly processed silicates, the mixed chemistry and the low 12 C/ 13 C ratio, EP Lyr resembles some silicate J-type stars, although the depleted photosphere makes nucleosynthetic signatures difficult to probe. We find that the disc environment of both sources is, to a first approximation, well modelled with a passive disc, but additional physics such as grain settling, radial dust distributions, and an outflow component must be included to explain the details of the observed spectral energy distributions in both stars.

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“…Based on the peak-wavelength, BZ CMa is the only one that shows the B class PAHs resembling PNe, Herbig Ae/Be stars, and red supergiants (Tielens 2008). The other three stars can be classified as rare class C sources resembling some of the PAHs found in post-AGB stars (Gielen et al 2009), the carbon-rich red giant HD 100764 and in a disk around the oxygen-rich K giant HD 233517 (Jura et al 2006).…”

Section: Hydrocarbon Emissionmentioning

confidence: 97%

TheSpitzerspectroscopic survey of S-type stars

Smolders

Neyskens

Blommaert

et al. 2012

A&A

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Context. S-type AGB stars are thought to be in the transitional phase between M-type and C-type AGB stars. Because the composition of the circumstellar environment reflects the photospheric abundances, one may expect a strong influence of the stellar C/O ratio on the molecular chemistry and the mineralogy of the circumstellar dust. Aims. In this paper, we present a large sample of 87 intrinsic galactic S-type AGB stars, observed at infrared wavelengths with the Spitzer Space Telescope, and supplemented with ground-based optical data. Methods. On the one hand, we derive the stellar parameters from the optical spectroscopy and photometry, using a grid of model atmospheres. On the other, we decompose the infrared spectra to quantify the flux-contributions from the different dust species. Finally, we compare the independently determined stellar parameters and dust properties. Results. For the stars without significant dust emission features, we detect a strict relation between the presence of SiS absorption in the Spitzer spectra and the C/O ratio of the stellar atmosphere. These absorption bands can thus be used as an additional diagnostic for the C/O ratio. For stars with significant dust emission, we define three distinct groups, based on the relative contribution of certain dust species to the infrared flux. We find a strong link between group-membership and C/O ratio. Furthermore, we show that these groups can be explained by assuming that the dust-condensation can be cut short before silicates are produced, while the remaining free atoms and molecules can then be used to form the observed magnesium sulfides or the carriers of the unidentified 13 µm and 20 µm features. Finally, we present the detection of emission features attributed to molecules and dust characteristic to C-type stars, such as molecular SiS, hydrocarbons and magnesium sulfide grains. We show that we often detect magnesium sulfides together with molecular SiS and we propose that it is formed by a reaction of SiS molecules with Mg.

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Polycyclic Aromatic Hydrocarbons Orbiting HD 233517, an Evolved Oxygen-rich Red Giant

Cited by 32 publications

References 44 publications

Chemical depletion in the Large Magellanic Cloud: RV Tauri stars and the photospheric feedback from their dusty discs

Chemical depletion in the Large Magellanic Cloud: RV Tauri stars and the photospheric feedback from their dusty discs

Analysis of the infrared spectra of the peculiar post-AGB stars EP Lyrae and HD 52961

TheSpitzerspectroscopic survey of S-type stars

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