The Infrared Continuum Spectrum of VY Canis Majoris

Harwit, Martin; Malfait, K.; Decin, L.; Waelkens, Christoffel; Feuchtgruber, H.; Melnick, Gary J.

doi:10.1086/321684

Cited by 34 publications

(46 citation statements)

References 33 publications

(63 reference statements)

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“…The presence of metallic Fe in the CSE of VY CMa was postulated by Harwit et al (2001) and is also used to explain the SEDs of OH/IR stars (Kemper et al 2002). Moreover, metallic Fe is a product of the O-rich condensation sequence.…”

Section: A Continuum Opacity Sourcementioning

confidence: 88%

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The dust condensation sequence in red supergiant stars

Verhoelst

Zypen²,

Hony

et al. 2009

A&A

130

146

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Context. Red supergiant (RSG) stars exhibit significant mass loss by means of a slow, dense wind. They are often considered to be the more massive counterparts of Asymptotic Giant Branch (AGB) stars. While AGB mass loss is related to their strong pulsations, the RSG are often only weakly variable. This raises the question of whether their wind-driving mechanism and the dust composition of the wind are the same. Aims. We study the conditions at the base of the wind by determining the dust composition of a sample of RSG. The dust composition is assumed to be sensitive to the density, temperature, and acceleration at the base of the wind. We compare the derived dust composition with the composition measured in AGB star winds. Methods. We compile a sample of 27 RSG infrared spectra (ISO-SWS) and supplement these with photometric measurements to derive the full spectral energy distribution (SED). These data are modelled using a dust radiative-transfer code, taking into account the optical properties of the relevant candidate materials to search for correlations between mass-loss rate, density at the inner edge of the dust shell, and stellar parameters. Results. We find strong correlations between the dust composition, mass-loss rate, and the stellar luminosity, roughly in agreement with the theoretical dust condensation sequence. We identify the need for a continuous (near-)IR dust opacity and tentatively propose amorphous carbon, and we note significant differences with AGB star winds in terms of the presence of PAHs, absence of "the" 13 μm band, and a lack of strong water bands. Conclusions. Dust condensation in RSG is found to experience a freeze-out process that is similar to that in AGB stars. Together with the positive effect of the stellar luminosity on the mass-loss rate, this suggests that radiation pressure on dust grains is an important ingredient in the driving mechanism. Still, differences with AGB stars are manifold and thus the winds of RSG should be studied individually in further detail.

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Section: A Continuum Opacity Sourcementioning

confidence: 88%

“…VY CMa is an RSG experiencing extreme mass loss, which produces an optically thick circumstellar environment (CSE). The detailed analysis required to derive reliable dust-composition parameters for VY CMa is beyond the scope of this paper, and we refer to Harwit et al (2001) for a study of its ISO-SWS spectrum.…”

Section: The Samplementioning

confidence: 99%

The dust condensation sequence in red supergiant stars

Verhoelst

Zypen²,

Hony

et al. 2009

A&A

130

146

View full text Add to dashboard Cite

show abstract

“…Therefore the origin of the radio continuum is certainly not entirely photospheric. Indeed, models of the spectral energy distribution of VY CMa (e.g., Harwit et al 2001) suggest that at the observed frequencies the total flux is almost entirely reprocessed dust radiation, with the direct photospheric flux constituting of only a few percent of the total emission. Our measured flux of 0.6 Jy at 320 GHz is consistent with those models.…”

Section: Localization and Abundances Of The Tio And Tio 2 Gasmentioning

confidence: 99%

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris

Kamiński

Gottlieb

Menten

et al. 2013

A&A

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We report the first detection of pure rotational transitions of TiO and TiO 2 at (sub-)millimeter wavelengths towards the red supergiant VY CMa. A rotational temperature, T rot , of about 250 K was derived for TiO 2 . Although T rot was not well constrained for TiO, it is likely somewhat higher than that of TiO 2 . The detection of the Ti oxides confirms that they are formed in the circumstellar envelopes of cool oxygen-rich stars and may be the "seeds" of inorganic-dust formation, but alternative explanations for our observation of TiO and TiO 2 in the cooler regions of the envelope cannot be ruled out at this time. The observations suggest that a significant fraction of the oxides is not converted to dust, but instead remains in the gas phase throughout the outflow.

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“…A proper identification of the type of silicates would also require the observation of the 18 μm band. The flux ratio F ν,E /F ν,W ∼ 0.4 (instead of unity) at the "continuum" wavelengths of 8.5 and 13 μm indicates achromatic attenuation, which is most likely due to metallic Fe, a crucial ingredient in the SED modelling of OH/IR stars and obscured RSG (Kemper et al 2002;Harwit et al 2001). The observed absorption towards 8 μm can be attributed to amorphous silicates, but only through scattering by fairly large grains.…”

Section: The Spectramentioning

confidence: 99%

A dam around the Water Fountain Nebula?

Verhoelst

Waters

Verhoeff

et al. 2009

A&A

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Context. Bipolar morphologies in planetary nebulae (PNe) are believed to be closely linked to binary central stars. Either by collimating a fast stellar wind or by driving a jet via accretion in the central system, dusty torii or stable disks may be crucial ingredients for the shaping of PNe. Aims. We study the dust distribution in the very young proto-planetary nebula (PPN) IRAS16342-3814, also known as the Water Fountain Nebula, which is known to show strong bipolar characteristics in the shape of two reflection lobes, and high-velocity collimated molecular outlfows. Methods. We use the new mid-infrared (MIR) instrument VISIR on the Very Large Telescope (VLT) both in imaging and spectroscopy mode at wavelengths from 8 to 13 μm. Results. We present the first spatially resolved MIR observations of a dusty evolved star obtained with VISIR and find that the improved spatial resolution contradicts previous claims of an elliptical brightness distribution at the heart of IRAS16342: we find the waist region to be dark even in the MIR. We show that the filling angle of the obscuring dust lane, which is made mostly of amorphous silicates, is very large, possibly even close to a spherically symmetric superwind as seen in OH/IR stars. Conclusions. We conclude that, in contrast to the multitude of recent dusty-disk detections in post-AGB stars and PNe, IRAS16342 does not show this extreme equatorial density enhancement, at least not on the scale of the dusty environment which lends the object its IR appearance. Rather, it appears that the observed precessing jets are shaping the bipolar nature in the remains of a spherically symmetric AGB superwind.

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The Infrared Continuum Spectrum of VY Canis Majoris

Cited by 34 publications

References 33 publications

The dust condensation sequence in red supergiant stars

The dust condensation sequence in red supergiant stars

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris

A dam around the Water Fountain Nebula?

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The Infrared Continuum Spectrum of VY Canis Majoris

Cited by 34 publications

References 33 publications

The dust condensation sequence in red supergiant stars

The dust condensation sequence in red supergiant stars

Pure rotational spectra of TiO and TiO2in VY Canis Majoris

A dam around the Water Fountain Nebula?

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Product

Resources

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Pure rotational spectra of TiO and TiO₂in VY Canis Majoris