Crystalline silicate dust around evolved stars - II. The crystalline silicate complexes

By F. Molster, L. Waters, A. Amsterdam, G. I. O. Technology, Atlanta, K. Leuven, Sron, Groningen, presently at Estecesa. 2002

174 citations recorded by the source corpus.

This is the second paper in a series of three in which we present an exhaustive inventory of the solid state emission bands observed in a sample of 17 oxygen-rich dust shells surrounding evolved stars. The data were taken with the Short and Long Wavelength Spectrographs on board of the Infrared Space Observatory (ISO) and cover the 2 to 200 m wavelength range. Apart from the broad 10 and 18 m bands that can be attributed to amorphous silicates, at least 49 narrow bands are found whose position and width indicate they can be attributed to crystalline silicates. Most of these emission bands are concentrated in well dened spectral regions (called complexes). We dene 7 of these complexes; the 10, 18, 23, 28, 33, 40 and 60 micron complex. We derive average properties of the individual bands. Almost all of these bands were not known before ISO. Comparison with laboratory data suggests that both olivines (Mg2xFe(2 2x)SiO4) and pyroxenes (MgxFe(1 x)SiO3) are present, with x close to 1, i.e. the minerals are very Mg-rich and Fe-poor. This composition is similar to that seen in disks surrounding young stars and in the solar system comet Hale-Bopp. A signicant fraction of the emission bands cannot be identied with either olivines or pyroxenes. Possible other materials that may be the carriers of these unidentied bands are briefly discussed. There is a natural division into objects that show a disk-like geometry (strong crystalline silicate bands), and objects whose dust shell is characteristic of an outflow (weak crystalline silicate bands). In particular, stars with the 33.5 m olivine band stronger than about 25 percent over continuum are invariably disk sources. Likewise, the 60 m region is dominated by crystalline silicates in the disk sources, while it is dominated by crystalline H2O ice in the outflow sources. We show that the disk and outflow sources have signicant dierences in the shape of the emission bands. This dierence must be related to the composition or grain shapes of the dust particles. The incredible richness of the crystalline silicate spectra observed by ISO allows detailed studies of the mineralogy of these dust shells, and is the origin and history of the dust.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a63a6c30882acd84247f12e533e922af6a0165dc

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. A. Andersen
2. J. Hjorth
3. C. Gall
4. G. Blake
5. F. Ménard
6. C. Pinte
7. Th. Henning
8. K. Pontoppidan

Citations in the corpus

• INTERSTELLAR DUST GRAINS (2003, background): “In all cases thus far the crystalline silicate material appears to be very Mg-rich and Fe-poor, consistent with pure forsterite and enstatite (Tielens et al. 1998, Molster et al. 2002a).”
• Probing dust grain evolution in IM Lupi's circumstellar disc. Multi-wavelength observations and mo (2008, background): “O bending mode), other features are visible in the spectrum that we attribute to crystalline forsterite (Mg– rich end member of the olivine group) and crystalline enstatite (Mg–rich pyroxene, Koike et al. 2000; Molster et al. 2002).”
• Steps toward interstellar silicate mineralogy - VII. Spectral properties and crystallization behaviour of magnesium silicates produced by the sol-gel method (2003, background): “The main dust component in different astronomical environments, though, remains amorphous magnesium-iron silicates (Molster et al. 1999; Demyk et al. 1999; Bouwman et al. 2001; Molster et al. 2002a,b).”
• Production of dust by massive stars at high redshift (2011, background): “Such grains are consistent with observed features in infrared (IR) spectra of cool giants (Molster et al, 2002a,b,c).”
• Composition and quantities of dust produced by AGB-stars and returned to the interstellar medium (2006, background): “Observationally it is known that crystalline silicate grains are formed in some circumstellar dust shells (see Molster et al. 2002a,b,c), but this is neglected in this paper.”