||Dust formation and wind acceleration around the aluminum oxide–rich AGB star W Hydrae
Takigawa, Aki ,
Kamizuka, Takafumi ,
Tachibana, ShogoYamamura, Issei
2017-11-01 , American Association for the Advancement of Science (AAAS)
死にゆく星からの恒星風の加速、酸化アルミニウム形成が引き金 --アルマ望遠鏡が明かすケイ酸塩に乏しい質量放出星の謎--. 京都大学プレスリリース. 2017-11-02.
Dust grains, formed around asymptotic giant branch (AGB) stars, are accelerated by stellar radiation to drive stellar winds, which supply freshly synthesized nuclides to the Galaxy. Silicate is the dominant dust species in space, but ~40% of oxygen-rich AGB stars are thought to have comparable amounts of aluminum oxide dust. Dust formation and the wind-driving mechanism around these oxygen-rich stars, however, are poorly understood. We report on the spatial distributions of AlO and 29SiO molecules around an aluminum oxide–rich M-type AGB star, W Hydrae, based on observations obtained with the Atacama Large Millimeter/submillimeter Array. AlO molecules were only observed within three stellar radii (Rstar), whereas 29SiO was distributed in the accelerated wind beyond 5 Rstar without significant depletion. This strongly suggests that condensed aluminum oxide dust plays a key role in accelerating the stellar wind and in preventing the efficient formation of silicate dust around W Hydrae.