The 10 μm Infrared Band of Silicate Dust: A Laboratory Study Comparing the Aerosol and KBr Pellet Techniques

Tamanai, Akemi; Mutschke, H.; Blum, Jürgen; Meeus, G.

doi:10.1086/508164

Cited by 52 publications

(84 citation statements)

References 15 publications

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“…And yet, many uncertainties remain on the optical properties of these grains. For instance Tamanai et al (2006) showed the differences in band positions and band widths of the emissivity profiles for several species (crystalline forsterite and enstatite or amorphous Mg 2 SiO 4 ) when using two different laboratory techniques (KBr pellets versus aerosol measurements). These measured emissivity profiles are also different from absorption efficiencies calculated using optical constant measurements.…”

Section: The Dust Setupmentioning

confidence: 99%

“…As mentioned previously, these efficiencies suffer from uncertainties at different levels. Laboratory measurements are unfortunately subject to various environmental effects such as electromagnetic polarization of the embedding medium (KBr, CsI or PE) when using the pellet technique (see Tamanai et al 2006Tamanai et al , 2009. Additionally, when using the optical constant, scattering theories have their own caveats, as discussed for example in Min et al (2007) for the Mie and DHS theories.…”

Section: Forsterite and Crystalline Olivine Grainsmentioning

confidence: 99%

“…4 shows the peak positions for aerosol measurements for several emission features associated with crystalline olivine grains, as a function of the Fe content. Peak positions for aerosol measurements for synthesized forsterite (Tamanai et al 2006) are represented by black circles, while peak positions for Mg-and Ferich olivine grains (Tamanai & Mutschke 2010) are represented by red squares and green pentagons, respectively. The hatched areas in Fig.…”

Section: Forsterite and Crystalline Olivine Grainsmentioning

confidence: 99%

“…Peak positions of main emission features associated with crystalline olivine grains (9.8, 11, 16.2, 23-24, and 33 μm) as a function of the Fe fraction. Black circles, red squares, and green pentagons correspond to aerosol measurements of the pure forsterite, Mg-, and Fe-rich samples, respectively (Tamanai et al 2006;Tamanai & Mutschke 2010). Hatched regions correspond to the range of peak positions in the observed spectra of HD 69830, HD 113766 A, ID 8, and HD 169666. one can immediately see that the observed peak positions are better reproduced by Mg-or Fe-rich olivine grains, while synthesized forsterite does not seem to provide a good match (within a few tenths of μm).…”

Section: Forsterite and Crystalline Olivine Grainsmentioning

confidence: 99%

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Transient dust in warm debris disks

Olofsson

Juhász

Henning

et al. 2012

A&A

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Context. Debris disks trace remnant reservoirs of leftover planetesimals in planetary systems. In the past years, a handful of "warm" debris disks have been discovered in which emission in excess starts in the mid-infrared. An interesting subset of these warm debris disks shows emission features in mid-infrared spectra, which points towards the presence of μm-sized dust grains, with temperatures above hundreds K. Given the ages of the host stars, the presence of these small grains is puzzling, and raises questions about their origin and survival in time.Aims. This study focuses on determining the mineralogy of the dust around seven debris disks with evidence for warm dust, based on Spitzer/IRS spectroscopic data, to provide new insights into the origin of the dust grains. Methods. We developed and present a new radiative transfer code (Debra) dedicated to spectral energy distribution (SED) modeling of optically thin disks. The Debra code is designed such that it can simultaneously determine dust composition and disk properties. We used this code on the SEDs of seven warm debris disks, in combination with recent laboratory experiments on dust optical properties. Results. We find that most, if not all, debris disks in our sample are experiencing a transient phase, suggesting a production of small dust grains on relatively short timescales. Dust replenishment should be efficient on timescales of months for at least three sources. From a mineralogical point of view, we find that crystalline pyroxene grains (enstatite) have low abundances compared to crystalline olivine grains. The main result of our study is that we find evidence for Fe-rich crystalline olivine grains (Fe/[Mg + Fe] ∼ 0.2) for several debris disks. This finding contrasts with studies of gas-rich protoplanetary disks, where Fe-bearing crystalline grains are usually not observed. Conclusions. These Fe-rich olivine grains, and the overall differences between the mineralogy of dust in Class II disks compared to debris disks suggests that the transient crystalline dust in warm debris disk is of a new generation. We discuss possible crystallization routes to explain our results, and also comment on the mechanisms that may be responsible for the production of small dust grains.

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Section: The Dust Setupmentioning

confidence: 99%

Section: Forsterite and Crystalline Olivine Grainsmentioning

confidence: 99%

Section: Forsterite and Crystalline Olivine Grainsmentioning

confidence: 99%

Section: Forsterite and Crystalline Olivine Grainsmentioning

confidence: 99%

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Transient dust in warm debris disks

Olofsson

Juhász

Henning

et al. 2012

A&A

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“…Thus, measurements of infrared absorption spectra in the laboratory also have been carried out in the regime of Rayleigh scattering. The work of Tamanai et al (2006) is an experimental study of the dependency of the extrinsic properties of IR spectra. Using aerosol techniques, particles were well dispersed in air, and the structures of the particles can be analyzed by in situ microscopic imaging.…”

Section: Introductionmentioning

confidence: 99%

Shape and lattice distortion effects on infrared absorption spectra of olivine particles

Imai

Koike

Chihara

et al. 2009

A&A

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We prepared sub-micron olivine (Fo 92 ) particles of different shapes and different degrees of crystal lattice distortion, and studied both effects on the infrared absorption spectra experimentally. We found that the peak positions of the spectra shifted to short wavelength when the number fraction of spherical grains became large, consistent with spectral calculations using the continuous distributions of ellipsoids (CDE) model. We also found for the first time that the spectral features become broader by crystal lattice distortion. The peak intensities are affected by both effects. The peak intensity decreases with lattice distortion in general, but some peaks are largely affected by particle shape. The spectral difference of olivine measured in different laboratories can be explained by both the shape and lattice distortion effects through sample preparation methods. Broadening features in the infrared spectra of forsterite ejecta from comet Tempel 1 obtained in the Deep Impact mission, and forsterite crystals in circumstellar regions, suggest that forsterite crystals undergo lattice distortion.

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