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首页> 外文期刊>The Astrophysical journal >M33’s Variable A: A Hypergiant Star More Than 35 YEARS in Eruption
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M33’s Variable A: A Hypergiant Star More Than 35 YEARS in Eruption

机译:M33的变数A:爆发超过35年的超巨星

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Variable A in M33 is a member of a rare class of highly luminous, evolved stars near the upper luminosity boundary that show sudden and dramatic shifts in apparent temperature due to the formation of optically thick winds in high mass loss episodes. Recent optical and infrared spectroscopy and imaging reveal that its "eruption," begun in ~1950, has ended, having lasted ≈45 yr. Our current observations show major changes in its wind from a cool, dense envelope to a much warmer state surrounded by low-density gas with rare emission lines of Ca II, [Ca II], and K I. Its spectral energy distribution has unexpectedly changed, especially at the long wavelengths, with a significant decrease in its apparent flux, while the star remains optically obscured. We conclude that much of its radiation is now escaping out of our line of sight. We attribute this to the changing structure and distribution of its circumstellar ejecta, corresponding to the altered state of its wind as the star recovers from a high mass loss event.
机译:M33中的变量A是稀有类别的高亮度,演化的恒星附近的成员,这些恒星在高光度边界附近显示出明显的温度突然变化,这是由于在高质量损失事件中形成了光学上较厚的风。最近的光学和红外光谱和成像显示,它的“喷发”始于1950年,已经结束了,持续了大约45年。我们目前的观察表明,风从冷的致密包层转变为由低密度气体包围的非常温暖的状态,并伴有Ca II,[Ca II]和K I的稀有发射谱线。 ,尤其是在长波长时,其视在通量显着下降,而恒星仍被光学遮挡。我们得出的结论是,它的大部分辐射现在正在逃离我们的视线。我们将其归因于其恒星喷射的结构和分布的变化,这与恒星从高质量损失事件中恢复时风的变化状态相对应。

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