Imaging the circumstellar envelope of OH 26.5+0.6

Fong, D.; Justtanont, K.; Meixner, M.; Campbell, M. T.

doi:10.1051/0004-6361:20021272

Cited by 20 publications

(21 citation statements)

References 23 publications

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“…This model was refined in Fong et al (2002), where OH 26.5 was mapped in the CO J = 1-0 line with the BIMA interferometer, and where the ISO SWS and LWS spectrum were used as well to constrain the SED modelling. Pure silicate grains and silicate core water-ice mantle grains were used.…”

Section: Radiative Transfer Modellingmentioning

confidence: 99%

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An extension of the DUSTY radiative transfer code and an application to OH 26.5 and TT Cygni

Groenewegen

2012

A&A

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For the best-studied nearby Galactic asymptotic giant branch (AGB) stars a wealth of observational data is typically available in the form of photometry, often extending into the sub-mm, spectra covering a wide wavelength range, and often also visibility curves. Almost 100 AGB stars and red super giants have been imaged as part of the MESS Herschel guaranteed time key program. This does not only add photometry points between 60 and 500 micron, but also intensity profiles at these wavelengths. Dust radiative transfer models are often used to analyse these types of datasets, but there are very many input parameters and therefore it is not straightforward how to derive a best fit. In order to facilitate this, the publicly available one-dimensional (1D) dust radiative transfer code DUSTY was modified and extended, and included as a subroutine in a minimazation code. The code allows a certain parameter set (typically luminosity, dust optical depth, dust temperature at the inner radius and slope of the density law) to be minimised against photometric and spectroscopic data, visibility curves and 1D intensity profiles as constraints. The code is described and first results are presented on the MESS targets OH 26.5 and TT Cyg. For OH26.5 previous findings regarding a two-component wind are confirmed, but with a smaller drop in mass loss (a factor of 5) than previously suggested. For TT Cyg it proved difficult to fit the Herschel intensity profiles and spectral energy distribution simultaneously. The best fits are obtained for density profiles that deviate strongly from r −2 and are more like r +3−+3.5 . This is qualitatively consistent with hydrodynamical models that simulate the interaction of the stellar wind with the interstellar medium.

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Section: Radiative Transfer Modellingmentioning

confidence: 99%

“…Such a small outer radius can in fact be excluded. Fong et al (2002) mapped CO and detected it to 7 × 10 17 cm correspoding to about 3.3 . This should correspond to the CO photodissociation radius, and the outer radius of the dust should extent beyond this.…”

Section: Appendix B: Oh 265mentioning

confidence: 99%

An extension of the DUSTY radiative transfer code and an application to OH 26.5 and TT Cygni

Groenewegen

2012

A&A

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“…For instance, the mass loss rate estimate by the IR method for AFGL 3068 (Le Bertre 1997) is ∼3 times larger than by the CO method (G02). Another possible example, OH/IR 26.5+0.6, has been studied by Justtanont et al (1996) and Fong et al (2002) who find evidence for a sudden increase of the mass loss rate, by a factor ≥50, about 200 years ago. Other cases of deficiency of CO emission as compared to the IR energy distribution have been identified among OH/IR sources by Heske et al (1990).…”

Section: Iras Nameṁṁṁmentioning

confidence: 99%

Galactic mass-losing AGB stars probed with the IRTS. II

Bertre

Tanaka

Yamamura

et al. 2003

A&A

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Abstract.We are using the 2002 data-release from the Japanese space experiment IRTS to investigate the spatial distribution of galactic mass-losing (>2 × 10 −8 M yr −1 ) AGB stars and the relative contribution of C-rich and O-rich ones to the replenishment of the ISM. Our sample contains 126 C-rich and 563 O-rich sources which are sorted on the basis of the molecular bands observed in the range 1.4-4.0 µm, and for which we estimate distances and mass loss rates from near-infrared photometry (K and L ). There is a clear dependence on galactocentric distance, with O-rich sources outnumbering C-rich ones for r GC < 8 kpc, and the reverse for r GC > 10 kpc. The contribution to the replenishment of the ISM by O-rich AGB stars relative to C-rich ones follows the same trend. Although they are rare (∼10% in our sample), sources with 10 −6 M yr −1 <Ṁ < 10 −5 M yr −1 dominate the replenishment of the ISM by contributing to ∼50% of the total of the complete sample. We find 2 carbon stars at more than 1 kpc from the Galactic Plane, that probably belong to the halo of our Galaxy.

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“…For OH 26.5+0.6, Suh & Kwon (2013) could reproduce the observed image at 8.7 µm obtained by Chesneau et al (2005) using the dust model image of R out = 3 × 10 4 AU. However, the CO(J=1-0) image size of the object is much smaller (4700 AU; Fong et al 2002). This may mean that the gas mass-loss is not as effective as the dust mass-loss for high mass-loss rate OH/IR stars.…”

Section: 2ṁ -Color Diagramsmentioning

confidence: 99%

Mass-Loss Rates of Oh/Ir Stars

Suh¹,

Kwon²

2013

Journal of The Korean Astronomical Society

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We compare mass-loss rates of OH/IR stars obtained from radio observations with those derived from the dust radiative transfer models and IR observations. We collect radio observational data of OH maser and CO line emission sources for a sample of 1533 OH/IR stars listed in Suh & Kwon (2011). For 1259 OH maser, 76 CO(J=1-0), and 55 CO(J=2-1) emission sources, we compile data of the expansion velocity and mass-loss rate. We use a dust radiative transfer model for the dust shell to calculate the mass-loss rate as well as the IR color indices. The observed mass-loss rates are in the range predicted by the theoretical dust shell models corresponding toṀ = 10 −8 M /yr -10 −4 M /yr. We find that the dust model using a simple mixture of amorphous silicate and amorphous Al 2 O 3 (20% by mass) grains can explain the observations fairly well. The results indicate that the dust radiative transfer models for IR observations generally agree with the radio observations. For high mass-loss rate OH/IR stars, the mass-loss rates obtained from radio observations are underestimated compared to the mass-loss rates derived from the dust shell models. This could be because photon momentum transfer to the gas shell is not possible for the physical condition of high mass-loss rates. Alternative explanations could be the effects of different dust-to-gas ratios and/or a superwind.

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Imaging the circumstellar envelope of OH 26.5+0.6

Cited by 20 publications

References 23 publications

An extension of the DUSTY radiative transfer code and an application to OH 26.5 and TT Cygni

An extension of the DUSTY radiative transfer code and an application to OH 26.5 and TT Cygni

Galactic mass-losing AGB stars probed with the IRTS. II

Mass-Loss Rates of Oh/Ir Stars

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