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 ( R star), whereas 29SiO was distributed in the accelerated wind beyond 5 R star 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.
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机译：恒星辐射会加速渐近巨型分支（AGB）恒星周围形成的尘埃，从而驱动恒星风，这将新合成的核素提供给银河系。硅酸盐是空间中主要的尘埃物种，但据认为约40％的富氧AGB恒星具有相当数量的氧化铝尘埃。然而，人们对这些富氧恒星周围的尘埃形成和驱动机制知之甚少。我们基于阿塔卡马大毫米/亚毫米阵列获得的观测结果，报告了富含氧化铝的M型AGB星W Hydrae周围AlO和 29 SiO分子的空间分布。仅在三个星半径（R star ）内观察到AlO分子，而 29 SiO分布在加速风中超过5 R star 消耗。这有力地表明，凝结的氧化铝粉尘在加速恒星风和防止W Hydrae周围有效形成硅酸盐粉尘方面起着关键作用。
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