The rate at which mass is lost during the red supergiant (RSG) evolutionary stage may strongly influence how the star appears. Though there have been many studies discussing how RSGs appear in the mid- and far-infrared (IR) as a function of their mass-loss rate, to date, there have been no such investigations at optical and near-IR wavelengths. In a preliminary study, we construct model atmospheres for RSGs that include a wind, and use these models to compute synthetic spectra from the optical to the mid-IR. The inclusion of a wind has two important effects. First, higher mass-loss rates result in stronger absorption in the TiO bands, causing the star to appear as a later spectral type despite its effective temperature remaining constant. This explains the observed relation between spectral type, evolutionary stage, and mid-IR excess, as well as the mismatch between temperatures derived from the optical and IR. Secondly, the wind mimics many observed characteristics of a ‘MOLsphere’, potentially providing an explanation for the extended molecular zone inferred to exist around nearby RSGs. Thirdly, we show that wind fluctuations can explain the spectral variability of Betelgeuse during its recent dimming, without the need for dust.

中文翻译：

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风对红超巨星光谱外观的影响

红超巨星（RSG）演化阶段质量损失的速度可能会强烈影响恒星的出现方式。尽管有许多研究讨论了 RSG 如何在中远红外 (IR) 中作为其质量损失率的函数出现，但迄今为止，还没有在光学和近红外波长上进行此类研究。在一项初步研究中，我们为包含风的 RSG 构建了模型大气，并使用这些模型来计算从光学到中红外的合成光谱。包含风有两个重要的影响。首先，较高的质量损失率导致二氧化钛波段的吸收更强，导致恒星出现为较晚的光谱类型，尽管其有效温度保持不变。这解释了观察到的光谱类型、进化阶段和中红外过量之间的关系，以及来自光学和红外的温度之间的不匹配。其次，风模仿了“MOLsphere”的许多观察到的特征，可能为推断存在于附近 RSG 周围的扩展分子区提供了解释。第三，我们表明风的波动可以解释参宿四在最近变暗期间的光谱变化，而不需要灰尘。