From Dust Astrophysics Towards Dust Mineralogy – A Historical Review

Dorschner, J.

doi:10.1007/978-3-642-13259-9_1

Cited by 9 publications

(7 citation statements)

References 220 publications

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“…Features due to SiC (at 11.3 µm) and possibly MgS ("the 30 µm feature") dust are present (Lombaert et al 2012;Messenger et al 2013), but not the sharper features seen in O-CSEs. For historic overviews on studies of dust in CSEs, see, e.g., Dorschner (2010) and Molster et al (2010).…”

Section: Basic Properties Of Circumstellar Envelopesmentioning

confidence: 99%

Mass loss of stars on the asymptotic giant branch

Höfner

Olofsson

2018

Astron Astrophys Rev

475

376

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As low-and intermediate-mass stars reach the asymptotic giant branch (AGB), they have developed into intriguing and complex objects that are major players in the cosmic gas/dust cycle. At this stage, their appearance and evolution are strongly affected by a range of dynamical processes. Large-scale convective flows bring newlyformed chemical elements to the stellar surface and, together with pulsations, they trigger shock waves in the extended stellar atmosphere. There, massive outflows of gas and dust have their origin, which enrich the interstellar medium and, eventually, lead to a transformation of the cool luminous giants into white dwarfs. Dust grains forming in the upper atmospheric layers play a critical role in the wind acceleration process, by scattering and absorbing stellar photons and transferring their outward-directed momentum to the surrounding gas through collisions. Recent progress in high-angularresolution instrumentation, from the visual to the radio regime, is leading to valuable new insights into the complex dynamical atmospheres of AGB stars and their windforming regions. Observations are revealing asymmetries and inhomogeneities in the photospheric and dust-forming layers which vary on time-scales of months, as well as more long-lived large-scale structures in the circumstellar envelopes. High-angularresolution observations indicate at what distances from the stars dust condensation occurs, and they give information on the chemical composition and sizes of dust grains in the close vicinity of cool giants. These are essential constraints for building B Susanne Höfner

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Section: Basic Properties Of Circumstellar Envelopesmentioning

confidence: 99%

Mass loss of stars on the asymptotic giant branch

Höfner

Olofsson

2018

Astron Astrophys Rev

475

376

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“…where Ω = α and f (ξ, β) = δ(α) 6 . The dichroic polarization efficiency is defined by the ratio of the polarization cross-section (factor) to the extinction one…”

Section: Interpretation: Particles and Alignmentmentioning

confidence: 99%

“…For an extended consideration of the properties of dust in different astronomical objects see [1,2,3,4,5]. Excellent historical reviews on dust astrophysics are given by Dorschner [6] and Li [7].…”

Section: Introductionmentioning

confidence: 99%

Interstellar extinction and interstellar polarization: Old and new models

Вощинников

2012

Journal of Quantitative Spectroscopy and Radiative Transfer

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The review contains an analysis of the observed and model curves of the interstellar extinction and polarization. The observations mainly give information on dust in diffuse and translucent interstellar clouds. The features of various dust grain models including spherical/non-spherical, homogeneous/inhomogeneous particles are discussed. A special attention is devoted to the analysis of the grain size distributions, alignment mechanisms and magnetic field structure in interstellar clouds. It is concluded that the interpretation of interstellar extinction and polarization is not yet complete.

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“…Mid-IR spectra of AGB stars give valuable insights into the complex dust chemistry in the circumstellar envelopes (see e.g. Dorschner 2010;Molster et al 2010, for an overview). For determining which grains may contribute to wind acceleration, however, important constraints come from the visual and near-infrared wavelength regions which are crucial for the energy and momentum budget of the atmosphere since the radiative flux maximum of the star is at about 1−2 μm.…”

Section: Introductionmentioning

confidence: 99%

Exploring wind-driving dust species in cool luminous giants

Bladh

Höfner

Aringer

et al. 2015

A&A

137

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Context. Stellar winds observed in asymptotic giant branch (AGB) stars are usually attributed to a combination of stellar pulsations and radiation pressure on dust. Shock waves triggered by pulsations propagate through the atmosphere, compressing the gas and lifting it to cooler regions which creates favourable conditions for grain growth. If sufficient radiative acceleration is exerted on the newly formed grains through absorption or scattering of stellar photons, an outflow can be triggered. Strong candidates for wind-driving dust species in M-type AGB stars are magnesium silicates (Mg 2 SiO 4 and MgSiO 3 ). Such grains can form close to the stellar surface, they consist of abundant materials and, if they grow to sizes comparable to the wavelength of the stellar flux maximum, they experience strong acceleration by photon scattering. Aims. The purpose of this study is to investigate if photon scattering on Mg 2 SiO 4 grains can produce realistic outflows for a wide range of stellar parameters in M-type AGB stars. Methods. We use a frequency-dependent radiation-hydrodynamics code with a detailed description for the growth of Mg 2 SiO 4 grains to calculate the first extensive set of time-dependent wind models for M-type AGB stars. This set includes 139 solar-mass models, with three different luminosities (5000 L , 7000 L , and 10 000 L ) and effective temperatures ranging from 2600 K to 3200 K. The resulting wind properties, visual and near-IR photometry and mid-IR spectra are compared with observations. Results. We show that the models can produce outflows for a wide range of stellar parameters. We also demonstrate that they reproduce observed mass-loss rates and wind velocities, as well as visual and near-IR photometry. However, the current models do not show the characteristic silicate features at 10 and 18 μm as a result of the cool temperature of Mg 2 SiO 4 grains in the wind. Including a small amount of Fe in the grains further out in the circumstellar envelope will increase the grain temperature and result in pronounced silicate features, without significantly affecting the photometry in the visual and near-IR wavelength regions. Conclusions. Outflows driven by photon scattering on Mg 2 SiO 4 grains are a viable wind scenario for M-type AGB stars, given the success of the current models in reproducing observed mass-loss rates, wind velocities, and photometry. Both synthetic and observed photometry suggest that the dusty envelopes of M-type AGB stars are quite transparent at visual and near-IR wavelengths, otherwise the variations in visual flux would not be dominated by molecular features.

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From Dust Astrophysics Towards Dust Mineralogy – A Historical Review

Cited by 9 publications

References 220 publications

Mass loss of stars on the asymptotic giant branch

Mass loss of stars on the asymptotic giant branch

Interstellar extinction and interstellar polarization: Old and new models

Exploring wind-driving dust species in cool luminous giants

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