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首页> 外文期刊>The Astrophysical journal >WATER ON THE EARLY M SUPERGIANT STARS α ORIONIS AND μ CEPHEI
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WATER ON THE EARLY M SUPERGIANT STARS α ORIONIS AND μ CEPHEI

机译：上M个上恒星α猎户座和μCEPHEI上的水

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摘要

We reanalyze the spectra of α Ori (M2 Iab) and μ Cep (M2 Ia) observed with the balloon-borne telescope Stratoscope II more than 35 years ago, and we confirm the presence of water in these early M supergiant stars. This identification was first proposed by the Stratoscope observers themselves (Woolf, Schwarzschild, and Rose in 1964; and Danielson, Woolf, and Gaustad in 1965), but this important discovery was overlooked for a long time without any follow-up observation. Consequently, this finding has so far had little influence on the theory of the atmosphere of red supergiant stars. A reason for this may be due to an early criticism by Wing and Spinrad, who suggested CN instead of H_2O for the spectral features observed by Stratoscope II. This alternative proposition has more easily been accepted since CN has widely been observed from the Sun to red supergiants, while H_2O has been observed only in very cool stars such as Mira variables. In fact, we confirm that the self-consistent photospheric model of the early M supergiants shows CN bands but no H_2O band in the near-infrared. Nevertheless, we find that the contribution of CN is only minor and that H_2O should be the dominant absorber for the 1.4 and 1.9 μm features on the Stratoscope spectra of α Ori and μ Cep, a conclusion opposite to that of Wing and Spinrad. The observed spectra can best be interpreted by the water gas with the column density of the order of 10~(20) cm~(-2) and temperature about 1500 ± 500 K, but they cannot be originating in the photosphere. We suggest a possible presence of a gaseous component not as hot as the chromosphere but warmer than the cool expanding envelope. On the other hand, we notice that the mid-infrared pure-rotation lines of H_2O recently discovered on Betelgeuse (α Ori) and Antares (α Sco) by Jennings and Sada may partly be originating in the photosphere, even though the larger part should again be non-photospheric in origin. Thus, the presence of water possibly originating in the outer atmosphere of Betelgeuse is confirmed by the independent observation in the mid-infrared region. We now conclude that water should be an important new probe on the atmosphere of the early M supergiant stars, for which water has not been recognized as such until recently.
机译：我们重新分析了35年前用气球望远镜Stratoscope II观测到的αOri（M2 Iab）和μCep（M2 Ia）的光谱，并且我们确认了这些M超巨型恒星中存在水。这种识别最初是由Stratoscope观察者自己提出的（Woolf，Schwarzschild和Rose在1964年； Danielson，Woolf和Gaustad在1965年），但是很长时间以来，这一重要发现被忽略了，而没有任何后续观察。因此，迄今为止，这一发现对红色超巨型恒星的大气理论影响不大。造成这种情况的原因可能是Wing和Spinrad的早期批评，他们对Stratoscope II观察到的光谱特征建议使用CN而不是H_2O。由于从太阳到红色超巨星已广泛观测到CN，而H_2O仅在非常凉爽的恒星（如Mira变星）中观测到，因此更容易接受这种替代性命题。实际上，我们确认了早期M超巨星的自洽光球模型在近红外波段显示CN波段，但没有H_2O波段。然而，我们发现CN的贡献很小，并且H_2O应该是αOri和μCep的Stratoscope光谱上1.4和1.9μm特征的主要吸收体，这一结论与Wing和Spinrad的结论相反。观察到的光谱可以最好地由具有约10〜（20）cm〜（-2）的柱密度和约1500±500 K的温度的水气来解释，但是它们不能起源于光球。我们建议可能存在一种气体成分，该气体成分不如色球层那么热，但比冷膨胀的包膜要热。另一方面，我们注意到詹宁斯和萨达最近在Betelgeuse（αOri）和Antares（αSco）上发现的H_2O的中红外纯自转谱线可能部分起源于光球，即使较大的部分应该再次起源于非光球。因此，通过在中红外区域的独立观察证实了可能存在于Betelgeuse外部大气中的水的存在。现在我们得出结论，水应该是对M超巨星早期大气的重要新探测，直到最近才认识到水。

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