Change search
ReferencesLink to record
Permanent link

Direct link
Micron-sized forsterite grains in the pre-planetary nebula of IRAS 17150 3224 Searching for clues to the mysterious evolution of massive AGB stars
Stockholm University, Faculty of Science, Department of Astronomy.
Show others and affiliations
Number of Authors: 6
2015 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 576, A98Article in journal (Refereed) Published
Abstract [en]

Aims. We study the grain properties and location of the forsterite crystals in the circumstellar environment of the pre-planetary nebula (PPN) IRAS 17150 3224 in order to learn more about the as yet poorly understood evolutionary phase prior to the PPN. Methods. We use the best-fit model for IRAS 17150 3224 of Meixner et al. (2002, ApJ, 571, 936) and add forsterite to this model. We investigate different spatial distributions and grain sizes of the forsterite crystals in the circumstellar environment. We compare the spectral bands of forsterite in the mid-infrared and at 69 mu m in radiative transport models to those in ISO-SWS and Herschel/PACS observations. Results. We can reproduce the non-detection of the mid-infrared bands and the detection of the 69 mu m feature with models where the forsterite is distributed in the whole outflow, in the superwind region, or in the AGB-wind region emitted previous to the superwind, but we cannot discriminate between these three models. To reproduce the observed spectral bands with these three models, the forsterite crystals need to be dominated by a grain size population of 2 mu m up to 6 mu m. We also tested models where the forsterite is located in a torus region or where it is concentrated in the equatorial plane, in a disk-like fashion. These models show either absorption features that are too strong or a 69 mu m band that is too weak, respectively, so we exclude these cases. We observe a blue shoulder on the 69 mu m band that cannot be explained by forsterite and we suggest a possible population of micron-sized ortho-enstatite grains. We hypothesise that the large forsterite crystals were formed after the superwind phase of IRAS 17150 3224, where the star developed an as yet unknown hyperwind with an extremely high mass-loss rate (>= 10(3) M-circle dot/yr). The high densities of such a hyperwind could be responsible for the efficient grain growth of both amorphous and crystalline dust in the outflow. Several mechanisms are discussed that might explain the lower-limit of similar to 2 mu m found for the forsterite grains, but none are satisfactory. Among the mechanisms explored is a possible selection effect due to radiation pressure based on photon scattering on micron-sized grains.

Place, publisher, year, edition, pages
2015. Vol. 576, A98
Keyword [en]
radiative transfer, stars: winds, outflows, planetary nebulae: general, stars: AGB and post-AGB, stars: evolution, stars: mass-loss
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-119766DOI: 10.1051/0004-6361/201424843ISI: 000357274600033OAI: diva2:848601
Available from: 2015-08-25 Created: 2015-08-24 Last updated: 2015-08-25Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
de Vries, Bernard L.
By organisation
Department of Astronomy
In the same journal
Astronomy and Astrophysics
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 9 hits
ReferencesLink to record
Permanent link

Direct link