Crystalline silicate dust around evolved stars. III. A correlations study of crystalline silicate features

By F. Molster, L. Waters, A. Tielens, C. Koike, H. Amsterdam, G. I. O. Technology, Atlanta, K. Leuven, Sron, Groningen and 3 more. 2002

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We have carried out a quantitative trend analysis of the crystalline silicates observed in the ISO spectra of a sample of 14 stars with dierent evolutionary backgrounds. We have modeled the spectra using a simple dust radiative transfer model and have correlated the results with other known parameters. We conrm the abundance dierence of the crystalline silicates in disk and in outflow sources, as found by Molster et al. (1999a). We found some evidence that the enstatite over forsterite abundance ratio diers, it is slightly higher in the outflow sources with respect to the disk sources. It is clear that more data is required to fully test this hypothesis. We show that the 69.0 micron feature, attributed to forsterite, may be a very suitable temperature indicator. We found that the enstatite is more abundant than forsterite in almost all sources. The temperature of the enstatite grains is about equal to that of the forsterite grains in the disk sources but slightly lower in the outflow sources. Crystalline silicates are on average colder than amorphous silicates. This may be due to the dierence in Fe content of both materials. Finally we nd an indication that the ratio of ortho to clino enstatite, which is about 1:1 in disk sources, shifts towards ortho enstatite in the high luminosity (outflow) sources.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/60921ee32538ccd977761b11a6f2a15e8297d346

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Citations in the corpus

• ISO Spectroscopy of Gas and Dust: From Molecular Clouds to Protoplanetary Disks (2004, background): “%) found in the envelopes around evolved stars (e.g., 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).”
• The Cosmic Energy Inventory (2004, background): “It is known (Draine 2003) that & 90% of silicon atoms in interstellar matter are condensed into grains, probably dominantly in the forms of enstatite (MgSiO3) and forsterite (Mg2SiO4) with the former likely three to four times more abundant (Molster et al. 2002).”
• 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).”
• 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.”
• ISO spectroscopy of disks around Herbig Ae/Be stars , (2004, background): “51 Oph and MWC 300 were also removed from the list; these are probably evolved objects and not HAEBEs (van den Ancker et al. 2001; Molster et al. 2002, respectively).”
• Characterization of Presolar Silicate and Oxide Grains in Primitive Carbonaceous Chondrites (2007, background): “Spectra of circumstellar environments indicate the presence of both amorphous and crystalline silicates, where the crystalline silicates contain on average <10 wt.% Fe and amorphous silicates contain more Fe (Molster et al. 1999, 2002; Demyk et al. 2000).”