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| DOI | 10.5194/ACP-15-3647-2015 | ||||
| Año | 2015 | ||||
| Tipo | artículo de investigación |
Citas Totales
Autores Afiliación Chile
Instituciones Chile
% Participación
Internacional
Autores
Afiliación Extranjera
Instituciones
Extranjeras
OH rotational temperatures are widely used to derive mesopause temperatures and their variations. Since most data sets are only based on a fixed set of lines of a single band, it is important to know possible systematic uncertainties related to the choice of lines. Therefore, a comprehensive study of as many OH bands as possible is desirable. For this purpose, astronomical echelle spectrographs at large telescopes are the most suitable instruments. They offer a wide wavelength coverage, relatively high spectral resolution, and high sensitivity. Moreover, since each ground-based astronomical observation has an imprint of the Earth's atmosphere, the data archives of large astronomical facilities are a treasure for atmospheric studies. For our project, we used archival data of the medium-resolution X-shooter echelle spectrograph operated by the European Southern Observatory at Cerro Paranal in Chile. The instrument can simultaneously observe all OH bands that are accessible from ground. We reduced and analysed a set of 343 high-quality spectra taken between 2009 and 2013 to measure OH line intensities and to derive rotational and vibrational temperatures of 25 bands between 0.58 and 2.24 mu m. We studied the influence of the selected line set, OH band, upper vibrational level nu', and the molecular data on the derived level populations and temperatures. The rotational temperature results indicate differences by several degrees depending on the selection. The temperatures for bands of even and odd nu' show deviations which increase with nu'. A study of the temporal variations revealed that the nocturnal variability pattern changes for nu' from 2 to 9. In particular, the spread of temperatures tends to increase during the night, and the time of the min- imum temperature depends on nu'. The vibrational temperatures depend on the range of nu' used for their determination, since the higher vibrational levels from 7 to 9 seem to be overpopulated compared to the lower levels. The vibrational temperature tends to increase during the night, while the intensity decreases. Our results support the assumption that the OH emission altitude depends on nu'. Moreover, the emission layer appears to rise in the course of the night, which makes the OH thermalisation less efficient. The derived rotational temperatures and their change with nu' seem to be significantly affected by non- equilibrium populations.
| Ord. | Autor | Género | Institución - País |
|---|---|---|---|
| 1 | Noll, Stefan | Hombre |
Univ Innsbruck - Austria
University of Innsbruck - Austria Universität Innsbruck - Austria |
| 2 | Kausch, Wolfgang | Hombre |
Univ Innsbruck - Austria
Univ Vienna - Austria University of Innsbruck - Austria Universität Wien - Austria Universität Innsbruck - Austria |
| 3 | Kimeswenger, Stefan | Hombre |
Univ Innsbruck - Austria
Universidad Católica del Norte - Chile University of Innsbruck - Austria Universität Innsbruck - Austria |
| 4 | Unterguggenberger, S. | Mujer |
Univ Innsbruck - Austria
University of Innsbruck - Austria Universität Innsbruck - Austria |
| 5 | HERNANDEZ-TOLEDO, HECTOR M. | Hombre |
Univ Innsbruck - Austria
Max Planck Inst Astrophys - Alemania University of Innsbruck - Austria Max Planck Institute for Astrophysics - Alemania Universität Innsbruck - Austria |
| Agradecimiento |
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| This project made use of the ESO Science Archive Facility. X-shooter spectra from different observing programmes of the period from October 2009 to March 2013 were used. We thank the two anonymous referees for their detailed and very helpful comments. This publication is supported by the Austrian Science Fund (FWF). S. Noll and S. Unterguggenberger receive funding from FWF project P26130. W. Kausch is funded by project IS538003 (Hochschulraumstrukturmittel) provided by the Austrian Ministry for Research (bmwfw), which also supports A. M. Jones via project BMWF-10.490/0008-II/3/2011. |