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arXiv 1708.06372astro-ph.SR
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红超巨星仙女座中的剧烈大气运动

Vigorous atmospheric motion in the red supergiant star Antares

K. Ohnaka, G. Weigelt, K. -H. Hofmann

摘要:

红超巨星代表了质量超过9个太阳质量的恒星演化的晚期阶段,在此阶段,它们发展出复杂的、多成分的大气。利用干涉成像技术在红超巨星的大气层中探测到了亮点。在红超巨星的光球层之上,分子外层大气延伸到大约两个恒星半径。此外,红超巨星的热色球层(5,000至8,000开尔文)和冷气体(小于3,500开尔文)在大约三个恒星半径处共存。这种复杂大气的动力学已经通过紫外光谱和光学光谱进行了探测。然而,最直接的方法是测量恒星图像上每个位置的气体速度,就像观测太阳一样。在这里,我们报告的速度场映射的表面和大气附近的红超巨星仙女座。从我们的近红外光谱干涉成像获得的二维速度场图显示了几个巨大的气体团在大气中以大约每秒-20至+20公里的速度剧烈上升和下降运动,延伸到大约1.7个恒星半径。对流本身不能解释观测到的湍流运动和大气扩展,这表明一个未知的过程正在扩展的大气中运行。

英文摘要:

Red supergiant stars represent a late stage of the evolution of stars more massive than about nine solar masses, in which they develop complex, multi-component atmospheres. Bright spots have been detected in the atmosphere of red supergiants using interferometric imaging. Above the photosphere of a red supergiant, the molecular outer atmosphere extends up to about two stellar radii. Furthermore, the hot chromosphere (5,000 to 8,000 kelvin) and cool gas (less than 3,500 kelvin) of a red supergiant coexist at about three stellar radii. The dynamics of such complex atmospheres has been probed by ultraviolet and optical spectroscopy. The most direct approach, however, is to measure the velocity of gas at each position over the image of stars as in observations of the Sun. Here we report the mapping of the velocity field over the surface and atmosphere of the nearby red supergiant Antares. The two-dimensional velocity field map obtained from our near-infrared spectro-interferometric imaging reveals vigorous upwelling and downdrafting motions of several huge gas clumps at velocities ranging from about -20 to +20 kilometres per second in the atmosphere, which extends out to about 1.7 stellar radii. Convection alone cannot explain the observed turbulent motions and atmospheric extension, suggesting that an unidentified process is operating in the extended atmosphere.

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