Letter to the Editor Infrared emission of hot water in the atmosphere of Mira
نویسندگان
چکیده
The ISO/SWS spectrum of o Cet taken at its maximum exhibits an absorption-like feature between 3.5 and 4.0 μm. We present evidence that the feature is due to emission of H2O and SiO molecules, in a layer extended to about two stellar radii with an excitation temperature of 2000 K. These hot molecules are also observed in a spectrum of Z Cas near minimum, but this time in absorption. A simple plane-parallel model is used to fit the spectra of these two stars. The H2O column densities and excitation temperatures in the layers are found to be similar in both stars. The difference of the H2O band is thus primarily due to the layer size. The H2O layers seem to be more extended at visual maximum, probably related to the stellar pulsation. The estimated lower limit to the local gas density in the layers of ∼ 1011 cm−3 is in good agreement with theoretical predictions from dynamical model atmospheres.
منابع مشابه
The time variation in infrared water - vapour bands in Mira variables ⋆
The time variation in the water-vapour bands in oxygen-rich Mira variables has been investigated using multi-epoch ISO/SWS spectra of four Mira variables in the 2.5–4.0 µm region. All four stars show H2O bands in absorption around minimum in the visual light curve. At maximum, H2O emission features appear in the ∼3.5– 4.0 µm region, while the features at shorter wavelengths remain in absorption...
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تاریخ انتشار 1999