Change search
ReferencesLink to record
Permanent link

Direct link
Dusty wind of W Hydrae Multi-wavelength modelling of the present-day and recent mass loss
Show others and affiliations
Number of Authors: 8
2015 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 577, A114Article in journal (Refereed) Published
Abstract [en]

Context. Low- and intermediate-mass stars go through a period of intense mass-loss at the end of their lives, during the asymptotic giant branch (AGB) phase. While on the AGB a significant part, or even most, of their initial mass is expelled in a stellar wind. This process controls the final stages of the evolution of these stars and contributes to the chemical evolution of galaxies. However, the wind-driving mechanism of AGB stars is not yet well understood, especially so for oxygen-rich sources. Characterizing both the present-day mass-loss rate and wind structure and the evolution of the mass-loss rate of such stars is paramount to advancing our understanding of this processes. Aims. We study the dusty wind of the oxygen-rich AGB star W Hya to understand its composition and structure and shed light on the mass-loss mechanism. Methods. We modelled the dust envelope of W Hya using an advanced radiative transfer code. We analysed our dust model in the light of a previously calculated gas-phase wind model and compared it with measurements available in the literature, such as infrared spectra, infrared images, and optical scattered light fractions. Results. We find that the dust spectrum of W Hya can partly be explained by a gravitationally bound dust shell that probably is responsible for most of the amorphous Al2O3 emission. The composition of the large (similar to 0.3 mu m) grains needed to explain the scattered light cannot be constrained, but probably is dominated by silicates. Silicate emission in the thermal infrared was found to originate from beyond 40 AU from the star. In our model, the silicates need to have substantial near-infrared opacities to be visible at such large distances. The increase in near-infrared opacity of the dust at these distances roughly coincides with a sudden increase in expansion velocity as deduced from the gas-phase CO lines. The dust envelope of W Hya probably contains an important amount of calcium but we were not able to obtain a dust model that reproduces the observed emission while respecting the limit set by the gas mass-loss rate. Finally, the recent mass loss of W Hya is confirmed to be highly variable and we identify a strong peak in the mass-loss rate that occurred about 3500 years ago and lasted for a few hundred years.

Place, publisher, year, edition, pages
2015. Vol. 577, A114
Keyword [en]
scattering, stars: AGB and post-AGB, stars: individual: W Hydrae, stars: winds, outflows, radiative transfer, solid state: refractory
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-119762DOI: 10.1051/0004-6361/201425092ISI: 000357345900066OAI: diva2:848616
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, B. 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: 14 hits
ReferencesLink to record
Permanent link

Direct link