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| Paper: |
How Do Massive Asymptotic Giant Branch Stars Lose All Their Mass? |
| Volume: |
497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time |
| Page: |
351 |
| Authors: |
de Vries, B. L.; Blommaert, J. A. D. L.; Waters, L. B. F. M.; Waelkens, C.; Min, M.; Lombaert, R.; Van Winckel, H. |
| Abstract: |
Recent studies have made it increasingly clear that oxygen-rich and
massive (≥5 M☉) asymptotic giant branch (AGB) stars go
through only one, short, superwind. Although the superwind was
originally introduced for the star to lose enough mass to reach that
of a white dwarf, evidence is now building that the superwind lasts
too short a time for it to be sufficiently efficient. The integrated
mass lost during the whole superwind is not enough to remove the
remaining H-rich envelope and terminate the AGB.
Studies presented at the conference have shown, from methods based on
both gas and dust, that the superwind lasts only ≲1200 years.
The analysis of solid-state spectral bands of crystalline olivine
(Mg2–2xFe2xSiO4) in the spectra of massive OH/IR stars
is a powerful way to determine the extent of the superwind.
De Vries, Blommaert, Waters et al. (2014)
show that the temperature indicated by the observed
69μm band of crystalline olivine can only be reproduced by models
with a geometrically compact superwind
(RSW ≲ 2500 AU = 1400 R*).
The way by which a star loses its remaining mass after the superwind
is unknown. During the conference this problem was discussed and the
most likely hypothesis would be a short but very strong phase after
the superwind. This hyperwind would have a mass-loss rate
of ≳10–3 M☉/yr. |
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